app.py

import os
import logging
from typing import Dict, List, Optional
from functools import lru_cache
import re

import gradio as gr
try:
    from vector_db import VectorDatabase
except ImportError:
    print("Error: Could not import VectorDatabase from vector_db.py.")
    print("Please ensure vector_db.py exists in the same directory and is correctly defined.")
    exit(1)

try:
    from langchain_openai import ChatOpenAI
except ImportError:
    print("Error: langchain-openai not found. Please install it: pip install langchain-openai")
    exit(1)

from langchain.prompts import PromptTemplate
from langchain.chains import LLMChain

# Suppress warnings
import warnings
warnings.filterwarnings("ignore", category=SyntaxWarning)
warnings.filterwarnings("ignore", category=UserWarning, message=".*You are using gradio version.*")
warnings.filterwarnings("ignore", category=DeprecationWarning)

# Enhanced logging
logging.basicConfig(
    level=logging.INFO,
    format='%(asctime)s - %(levelname)s - [%(filename)s:%(lineno)d] - %(message)s'
)

# --- RAGSystem Class (Processing Logic - kept intact as requested) ---
class RAGSystem:
    def __init__(self, vector_db: Optional[VectorDatabase] = None):
        logging.info("Initializing RAGSystem")
        self.vector_db = vector_db if vector_db else VectorDatabase()
        self.llm = None
        self.chain = None
        self.prompt_template_str = """You are a legal assistant specializing in tenant rights and landlord-tenant laws. Your goal is to provide accurate, detailed, and helpful answers grounded in legal authority. Use the provided statutes as the primary source when available. If no relevant statutes are found in the context, rely on your general knowledge to provide a pertinent and practical response, clearly indicating when you are doing so and prioritizing state-specific information over federal laws for state-specific queries.
Instructions:
* Use the context and statutes as the primary basis for your answer when available.
* For state-specific queries, prioritize statutes or legal principles from the specified state over federal laws.
* Cite relevant statutes (e.g., (AS § 34.03.220(a)(2))) explicitly in your answer when applicable.
* If multiple statutes apply, list all relevant ones.
* If no specific statute is found in the context, state this clearly (e.g., 'No specific statute was found in the provided context'), then provide a general answer based on common legal principles or practices, marked as such.
* Include practical examples or scenarios to enhance clarity and usefulness.
* Use bullet points or numbered lists for readability when appropriate.
* Maintain a professional and neutral tone.
Question: {query}
State: {state}
Statutes from context:
{statutes}
Context information:
--- START CONTEXT ---
{context}
--- END CONTEXT ---
Answer:"""
        self.prompt_template = PromptTemplate(
            input_variables=["query", "context", "state", "statutes"],
            template=self.prompt_template_str
        )
        logging.info("RAGSystem initialized.")

    def extract_statutes(self, text: str) -> str:
        statute_pattern = r'\b(?:[A-Z]{2,}\.?\s+(?:Rev\.\s+)?Stat\.?|Code(?:\s+Ann\.?)?|Ann\.?\s+Laws|Statutes|CCP|USC|ILCS|Civ\.\s+Code|Penal\s+Code|Gen\.\s+Oblig\.\s+Law|R\.?S\.?|P\.?L\.?)\s+§\s*[\d\-]+(?:\.\d+)?(?:[\(\w\.\)]+)?|Title\s+\d+\s+USC\s+§\s*\d+(?:-\d+)?\b'
        statutes = re.findall(statute_pattern, text, re.IGNORECASE)
        valid_statutes = []
        for statute in statutes:
            statute = statute.strip()
            if '§' in statute and any(char.isdigit() for char in statute):
                 if not re.match(r'^\([\w\.]+\)$', statute) and 'http' not in statute:
                    if len(statute) > 5:
                        valid_statutes.append(statute)

        if valid_statutes:
            seen = set()
            unique_statutes = [s for s in valid_statutes if not (s.rstrip('.,;') in seen or seen.add(s.rstrip('.,;')))]
            logging.info(f"Extracted {len(unique_statutes)} unique statutes.")
            return "\n".join(f"- {s}" for s in unique_statutes)

        logging.info("No statutes found matching the pattern in the context.")
        return "No specific statutes found in the provided context."

    @lru_cache(maxsize=50)
    def process_query_cached(self, query: str, state: str, openai_api_key: str, n_results: int = 5) -> Dict[str, any]:
        logging.info(f"Processing query (cache key: '{query}'|'{state}'|key_hidden) with n_results={n_results}")

        if not state or state == "Select a state..." or "Error" in state:
            logging.warning("No valid state provided for query.")
            return {"answer": "<div class='error-message'>Error: Please select a valid state.</div>", "context_used": "N/A - Invalid Input"}
        if not query or not query.strip():
            logging.warning("No query provided.")
            return {"answer": "<div class='error-message'>Error: Please enter your question.</div>", "context_used": "N/A - Invalid Input"}
        if not openai_api_key or not openai_api_key.strip() or not openai_api_key.startswith("sk-"):
            logging.warning("No valid OpenAI API key provided.")
            return {"answer": "<div class='error-message'>Error: Please provide a valid OpenAI API key (starting with 'sk-'). Get one from <a href='https://platform.openai.com/api-keys' target='_blank'>OpenAI</a>.</div>", "context_used": "N/A - Invalid Input"}

        try:
            logging.info("Initializing temporary LLM and Chain for this query...")
            temp_llm = ChatOpenAI(
                temperature=0.2, openai_api_key=openai_api_key, model_name="gpt-3.5-turbo",
                max_tokens=1500, request_timeout=45
            )
            temp_chain = LLMChain(llm=temp_llm, prompt=self.prompt_template)
            logging.info("Temporary LLM and Chain initialized successfully.")
        except Exception as e:
            logging.error(f"LLM Initialization failed: {str(e)}", exc_info=True)
            error_msg = "Error: Failed to initialize AI model. Please check your network connection and API key validity."
            if "authentication" in str(e).lower():
                error_msg = "Error: OpenAI API Key is invalid or expired. Please check your key."
            return {"answer": f"<div class='error-message'>{error_msg}</div><div class='error-details'>Details: {str(e)}</div>", "context_used": "N/A - LLM Init Failed"}

        context = "No relevant context found."
        statutes_from_context = "Statute retrieval skipped due to context issues."
        try:
            logging.info(f"Querying Vector DB for query: '{query[:50]}...' in state '{state}'...")
            results = self.vector_db.query(query, state=state, n_results=n_results)
            logging.info(f"Vector DB query successful for state '{state}'. Processing results...")

            context_parts = []
            doc_results = results.get("document_results", {})
            docs = doc_results.get("documents", [[]])[0]
            metadatas = doc_results.get("metadatas", [[]])[0]
            if docs and metadatas and len(docs) == len(metadatas):
                logging.info(f"Found {len(docs)} document chunks.")
                for i, doc_content in enumerate(docs):
                    metadata = metadatas[i]
                    state_label = metadata.get('state', 'Unknown State')
                    chunk_id = metadata.get('chunk_id', 'N/A')
                    context_parts.append(f"**Source: Document Chunk {chunk_id} (State: {state_label})**\n{doc_content}")

            state_results_data = results.get("state_results", {})
            state_docs = state_results_data.get("documents", [[]])[0]
            state_metadatas = state_results_data.get("metadatas", [[]])[0]
            if state_docs and state_metadatas and len(state_docs) == len(state_metadatas):
                logging.info(f"Found {len(state_docs)} state summary documents.")
                for i, state_doc_content in enumerate(state_docs):
                    metadata = state_metadatas[i]
                    state_label = metadata.get('state', state)
                    context_parts.append(f"**Source: State Summary (State: {state_label})**\n{state_doc_content}")

            if context_parts:
                context = "\n\n---\n\n".join(context_parts)
                logging.info(f"Constructed context with {len(context_parts)} parts. Length: {len(context)} chars.")
                try:
                    statutes_from_context = self.extract_statutes(context)
                except Exception as e:
                    logging.error(f"Error extracting statutes: {e}", exc_info=True)
                    statutes_from_context = "Error extracting statutes from context."
            else:
                logging.warning("No relevant context parts found from vector DB query.")
                context = "No relevant context could be retrieved from the knowledge base for this query and state. The AI will answer from its general knowledge."
                statutes_from_context = "No specific statutes found as no context was retrieved."

        except Exception as e:
            logging.error(f"Vector DB query/context processing failed: {str(e)}", exc_info=True)
            context = f"Warning: Error retrieving documents from the knowledge base ({str(e)}). The AI will attempt to answer from its general knowledge, which may be less specific or accurate."
            statutes_from_context = "Statute retrieval skipped due to error retrieving context."

        try:
            logging.info("Invoking LLMChain with constructed input...")
            llm_input = {"query": query, "context": context, "state": state, "statutes": statutes_from_context}
            answer_dict = temp_chain.invoke(llm_input)
            answer_text = answer_dict.get('text', '').strip()

            if not answer_text:
                logging.warning("LLM returned an empty answer.")
                answer_text = "<div class='error-message'>The AI model returned an empty response. This might be due to the query, context limitations, or temporary issues. Please try rephrasing your question or try again later.</div>"
            else:
                logging.info("LLM generated answer successfully.")

            return {"answer": answer_text, "context_used": context}

        except Exception as e:
            logging.error(f"LLM processing failed: {str(e)}", exc_info=True)
            error_message = "Error: AI answer generation failed."
            details = f"Details: {str(e)}"
            if "authentication" in str(e).lower():
                error_message = "Error: Authentication failed. Please double-check your OpenAI API key."
                details = ""
            elif "rate limit" in str(e).lower():
                error_message = "Error: You've exceeded your OpenAI API rate limit or quota. Please check your usage and plan limits, or wait and try again."
                details = ""
            elif "context length" in str(e).lower():
                error_message = "Error: The request was too long for the AI model. This can happen with very complex questions or extensive retrieved context."
                details = "Try simplifying your question or asking about a more specific aspect."
            elif "timeout" in str(e).lower():
                 error_message = "Error: The request to the AI model timed out. The service might be busy."
                 details = "Please try again in a few moments."

            formatted_error = f"<div class='error-message'>{error_message}</div>"
            if details:
                formatted_error += f"<div class='error-details'>{details}</div>"

            return {"answer": formatted_error, "context_used": context}

    def process_query(self, query: str, state: str, openai_api_key: str, n_results: int = 5) -> Dict[str, any]:
        return self.process_query_cached(query.strip(), state, openai_api_key.strip(), n_results)

    def get_states(self) -> List[str]:
        try:
            states = self.vector_db.get_states()
            if not states:
                logging.warning("No states retrieved from vector_db. Returning empty list.")
                return []
            valid_states = sorted(list(set(s for s in states if s and isinstance(s, str) and s != "Select a state...")))
            logging.info(f"Retrieved {len(valid_states)} unique, valid states from VectorDatabase.")
            return valid_states
        except Exception as e:
            logging.error(f"Failed to get states from VectorDatabase: {str(e)}", exc_info=True)
            return ["Error: Could not load states"]

    def load_pdf(self, pdf_path: str) -> int:
        if not os.path.exists(pdf_path):
            logging.error(f"PDF file not found at path: {pdf_path}")
            raise FileNotFoundError(f"PDF file not found: {pdf_path}")
        try:
            logging.info(f"Attempting to load/verify data from PDF: {pdf_path}")
            num_states_processed = self.vector_db.process_and_load_pdf(pdf_path)
            doc_count = self.vector_db.document_collection.count()
            state_count = self.vector_db.state_collection.count()
            total_items = doc_count + state_count

            if total_items > 0:
                logging.info(f"Vector DB contains {total_items} items ({doc_count} docs, {state_count} states). PDF processed or data already existed.")
                current_states = self.get_states()
                return len(current_states) if current_states and "Error" not in current_states[0] else 0
            else:
                logging.warning(f"PDF processing completed, but the vector database appears empty. Check PDF content and processing logs.")
                return 0

        except Exception as e:
            logging.error(f"Failed to load or process PDF '{pdf_path}': {str(e)}", exc_info=True)
            raise RuntimeError(f"Failed to process PDF '{pdf_path}': {e}") from e

    # --- GRADIO INTERFACE (Completely Redesigned UI) ---
    def gradio_interface(self):
        def query_interface_wrapper(api_key: str, query: str, state: str) -> str:
            # Basic client-side validation for immediate feedback
            if not api_key or not api_key.strip() or not api_key.startswith("sk-"):
                 return "<div class='error-message'><span class='error-icon'>⚠️</span>Please provide a valid OpenAI API key (starting with 'sk-'). <a href='https://platform.openai.com/api-keys' target='_blank'>Get one here</a>.</div>"
            if not state or state == "Select a state..." or "Error" in state:
                return "<div class='error-message'><span class='error-icon'>⚠️</span>Please select a valid state from the dropdown.</div>"
            if not query or not query.strip():
                return "<div class='error-message'><span class='error-icon'>⚠️</span>Please enter your question in the text box.</div>"

            # Call the core processing logic
            result = self.process_query(query=query, state=state, openai_api_key=api_key)
            answer = result.get("answer", "<div class='error-message'><span class='error-icon'>⚠️</span>An unexpected error occurred.</div>")

            # Check if the answer already contains an error message (from deeper within process_query)
            if "<div class='error-message'>" in answer:
                 return answer # Return the pre-formatted error message directly
            else:
                 # Format the successful response with the new UI structure
                 formatted_response = f"<div class='response-header'><span class='response-icon'>📜</span>Response for {state}</div><hr class='divider'>{answer}"
                 return formatted_response

        try:
            available_states_list = self.get_states()
            dropdown_choices = ["Select a state..."] + (available_states_list if available_states_list and "Error" not in available_states_list[0] else ["Error: States unavailable"])
            initial_value = dropdown_choices[0]
        except Exception: # Catch-all for safety
            dropdown_choices = ["Error: Critical failure loading states"]
            initial_value = dropdown_choices[0]

        # Define example queries, filtering based on available states
        example_queries_base = [
            ["What are the rules for security deposit returns?", "California"],
            ["Can a landlord enter my apartment without notice?", "New York"],
            ["My landlord hasn't made necessary repairs. What can I do?", "Texas"],
        ]
        example_queries = []
        if available_states_list and "Error" not in available_states_list[0] and len(available_states_list) > 0:
            loaded_states_set = set(available_states_list)
            example_queries = [ex for ex in example_queries_base if ex[1] in loaded_states_set]
            # Add a generic example if no specific state examples match or if list is empty
            if not example_queries:
                 example_queries.append(["What basic rights do tenants have?", available_states_list[0] if available_states_list else "California"])
        else: # Fallback if states list is problematic
            example_queries.append(["What basic rights do tenants have?", "California"])


        # --- Custom CSS for "Legal Lumen" Theme ---
        custom_css = """
        /* New Theme: Legal Lumen */
        @import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700&family=Montserrat:wght@600;700;800&display=swap');

        :root {
            /* Light Theme Colors */
            --app-bg-light: #F8F9FA; /* Very light gray */
            --surface-bg-light: #FFFFFF; /* Pure white for cards */
            --text-primary-light: #212529; /* Dark charcoal */
            --text-secondary-light: #6C757D; /* Muted gray */
            --accent-main-light: #007bff; /* Vibrant professional blue */
            --accent-hover-light: #0056b3; /* Darker blue on hover */
            --accent-secondary-light: #6C757D; /* For secondary buttons, similar to text secondary */
            --accent-secondary-hover-light: #5A6268; /* Darker secondary hover */
            --border-light: #DEE2E6; /* Light border */
            --shadow-light: 0 0.5rem 1rem rgba(0,0,0,0.08); /* Subtle shadow */
            --focus-ring-light: rgba(0, 123, 255, 0.25); /* Blue focus ring */
            --error-bg-light: #F8D7DA; /* Light red for error backgrounds */
            --error-text-light: #721C24; /* Dark red for error text */
            --error-border-light: #F5C6CB; /* Red border for errors */

            /* Dark Theme Colors */
            --app-bg-dark: #212529; /* Deep dark gray */
            --surface-bg-dark: #343A40; /* Slightly lighter dark gray for cards */
            --text-primary-dark: #F8F9FA; /* Off-white */
            --text-secondary-dark: #ADB5BD; /* Muted light gray */
            --accent-main-dark: #8AB4F8; /* Lighter blue for dark mode */
            --accent-hover-dark: #669DF6; /* Darker blue on hover for dark mode */
            --accent-secondary-dark: #ADB5BD; /* For secondary buttons in dark mode */
            --accent-secondary-hover-dark: #97A0A8; /* Darker secondary hover in dark mode */
            --border-dark: #495057; /* Dark border */
            --shadow-dark: 0 0.5rem 1rem rgba(0,0,0,0.3); /* Darker shadow */
            --focus-ring-dark: rgba(138, 180, 248, 0.35); /* Muted blue focus ring for dark mode */
            --error-bg-dark: #721C24; /* Dark red for error backgrounds */
            --error-text-dark: #F8D7DA; /* Light red for error text */
            --error-border-dark: #F5C6CB; /* Red border for errors */

            /* General Styling Variables */
            --font-family-main: 'Inter', sans-serif;
            --font-family-header: 'Montserrat', sans-serif;
            --radius-sm: 4px; /* Small border radius */
            --radius-md: 8px; /* Medium border radius */
            --radius-lg: 12px; /* Large border radius */
            --transition-speed: 0.25s; /* Standard transition duration */
        }

        /* Base styles for the entire app */
        body, .gradio-container {
            font-family: var(--font-family-main) !important;
            background: var(--app-bg-light) !important;
            color: var(--text-primary-light) !important;
            margin: 0;
            padding: 0;
            min-height: 100vh;
            font-size: 16px;
            line-height: 1.6; /* Improved readability */
            -webkit-font-smoothing: antialiased; /* Smoother fonts */
            -moz-osx-font-smoothing: grayscale;
        }
        * { box-sizing: border-box; } /* Ensure consistent box model */

        /* Dark mode preference (applies styles when user's system is in dark mode) */
        @media (prefers-color-scheme: dark) {
            body, .gradio-container {
                background: var(--app-bg-dark) !important;
                color: var(--text-primary-dark) !important;
            }
        }

        /* Global container styling: max-width for content, centering, and padding */
        .gradio-container > .flex.flex-col {
            max-width: 900px; /* Slightly wider for better content flow */
            margin: 0 auto !important; /* Center the container */
            padding: 2rem 1.5rem 4rem 1.5rem !important; /* Generous top, side, and bottom padding */
            gap: 0 !important; /* Remove Gradio's default gap, manage spacing with element margins */
        }

        /* Header section styling: prominent, rounded banner */
        .app-header-wrapper {
            background: linear-gradient(135deg, var(--accent-main-light) 0%, var(--accent-hover-light) 100%); /* Gradient background for depth */
            color: #FFFFFF !important; /* White text for light theme header */
            padding: 3rem 2rem 4rem 2rem !important; /* More vertical padding for impact */
            text-align: center !important;
            border-radius: var(--radius-lg); /* Rounded corners for the header card */
            box-shadow: var(--shadow-light);
            margin-bottom: 3.5rem; /* Spacing between header and first content card */
            position: relative; /* For animation context */
            overflow: hidden; /* Ensure content stays within rounded corners */
        }
        .app-header {
            display: flex;
            flex-direction: column;
            align-items: center;
            position: relative;
            z-index: 1; /* Keep content above any potential background effects */
        }
        .app-header-logo {
            font-size: 4rem; /* Larger icon */
            margin-bottom: 1rem;
            display: block;
            line-height: 1; /* Prevent extra space below emoji */
            animation: bounceIn 0.8s ease-out; /* Simple entry animation for logo */
        }
        .app-header-title {
            font-family: var(--font-family-header) !important;
            font-size: 2.8rem; /* Much larger and bolder */
            font-weight: 800; /* Extra bold */
            margin: 0 0 0.75rem 0;
            letter-spacing: -0.04em; /* Tighter letter spacing for a modern look */
            text-shadow: 0 2px 4px rgba(0,0,0,0.2); /* Subtle text shadow for depth */
            animation: fadeInDown 1s ease-out; /* Entry animation for title */
        }
        .app-header-tagline {
            font-family: var(--font-family-main) !important;
            font-size: 1.25rem; /* Slightly larger tagline */
            font-weight: 300;
            opacity: 0.9;
            max-width: 600px;
            animation: fadeInUp 1s ease-out; /* Entry animation for tagline */
        }

        /* Dark mode header adjustments */
        @media (prefers-color-scheme: dark) {
            .app-header-wrapper {
                background: linear-gradient(135deg, var(--accent-main-dark) 0%, var(--accent-hover-dark) 100%);
                box-shadow: var(--shadow-dark);
            }
            .app-header-title { color: var(--text-primary-dark) !important; } /* Ensure title color adjusts for dark theme */
        }

        /* Keyframe animations for header elements */
        @keyframes bounceIn {
            0%, 20%, 40%, 60%, 80%, 100% {
                -webkit-transition-timing-function: cubic-bezier(0.215, 0.610, 0.355, 1.000);
                transition-timing-function: cubic-bezier(0.215, 0.610, 0.355, 1.000);
            }
            0% { opacity: 0; -webkit-transform: scale3d(0.3, 0.3, 0.3); transform: scale3d(0.3, 0.3, 0.3); }
            20% { -webkit-transform: scale3d(1.1, 1.1, 1.1); transform: scale3d(1.1, 1.1, 1.1); }
            40% { -webkit-transform: scale3d(0.9, 0.9, 0.9); transform: scale3d(0.9, 0.9, 0.9); }
            60% { opacity: 1; -webkit-transform: scale3d(1.03, 1.03, 1.03); transform: scale3d(1.03, 1.03, 1.03); }
            80% { -webkit-transform: scale3d(0.97, 0.97, 0.97); transform: scale3d(0.97, 0.97, 0.97); }
            100% { opacity: 1; -webkit-transform: scale3d(1, 1, 1); transform: scale3d(1, 1, 1); }
        }

        @keyframes fadeInDown {
            from { opacity: 0; transform: translate3d(0, -20px, 0); }
            to { opacity: 1; transform: translate3d(0, 0, 0); }
        }

        @keyframes fadeInUp {
            from { opacity: 0; transform: translate3d(0, 20px, 0); }
            to { opacity: 1; transform: translate3d(0, 0, 0); }
        }


        /* Styling for general content cards (surface elements) */
        .content-surface {
            background: var(--surface-bg-light) !important;
            border-radius: var(--radius-lg) !important;
            padding: 3rem !important; /* Consistent padding */
            box-shadow: var(--shadow-light) !important;
            border: 1px solid var(--border-light) !important;
            margin-bottom: 3rem; /* Spacing between cards */
            transition: background var(--transition-speed), border-color var(--transition-speed), box-shadow var(--transition-speed);
        }
        .content-surface:last-child { margin-bottom: 0; } /* No bottom margin for the last surface */
        @media (prefers-color-scheme: dark) {
            .content-surface {
                background: var(--surface-bg-dark) !important;
                box-shadow: var(--shadow-dark) !important;
                border: 1px solid var(--border-dark) !important;
            }
        }

        /* Section titles within content cards: centered, bold, with a clear separator */
        .section-title, .input-form-card h3, .examples-card .gr-examples-header {
            font-family: var(--font-family-header) !important;
            font-size: 1.65rem !important; /* Slightly larger than before */
            font-weight: 600 !important;
            color: var(--text-primary-light) !important;
            margin: 0 auto 2.2rem auto !important; /* Centered, with more space below title */
            padding-bottom: 1rem !important;
            border-bottom: 2px solid var(--border-light) !important; /* Thicker separator for emphasis */
            text-align: center !important;
            width: 100%;
        }
        @media (prefers-color-scheme: dark) {
            .section-title, .input-form-card h3, .examples-card .gr-examples-header {
                color: var(--text-primary-dark) !important;
                border-bottom-color: var(--border-dark) !important;
            }
        }

        /* General text styling within content surfaces */
        .content-surface p {
            font-size: 1.05rem; /* Slightly larger body text for readability */
            line-height: 1.7; /* Generous line height */
            color: var(--text-secondary-light);
            margin-bottom: 1rem;
        }
        .content-surface a {
            color: var(--accent-main-light);
            text-decoration: none;
            font-weight: 500;
            transition: color var(--transition-speed), text-decoration var(--transition-speed);
        }
        .content-surface a:hover {
            color: var(--accent-hover-light);
            text-decoration: underline;
        }
        .content-surface strong {
            font-weight: 600;
            color: var(--text-primary-light);
        }
        @media (prefers-color-scheme: dark) {
            .content-surface p { color: var(--text-secondary-dark); }
            .content-surface a { color: var(--accent-main-dark); }
            .content-surface a:hover { color: var(--accent-hover-dark); }
            .content-surface strong { color: var(--text-primary-dark); }
        }

        /* Input field group and layout: organized and symmetric */
        .input-field-group { margin-bottom: 2rem; }
        .input-row {
            display: flex;
            gap: 2rem; /* Increased gap for better spacing */
            flex-wrap: wrap; /* Allow wrapping on smaller screens */
            margin-bottom: 2.5rem; /* More space before buttons */
        }
        .input-field {
            flex: 1; /* Distribute space evenly */
            min-width: 280px; /* Adjusted minimum width before wrapping */
        }

        /* Input labels and info text */
        .gradio-input-label {
            font-size: 1rem !important; /* Slightly larger label */
            font-weight: 500 !important;
            color: var(--text-primary-light) !important;
            margin-bottom: 0.6rem !important;
            display: block !important;
        }
        .gradio-input-info {
            font-size: 0.85rem !important;
            color: var(--text-secondary-light) !important;
            margin-top: 0.4rem;
        }
        @media (prefers-color-scheme: dark) {
            .gradio-input-label { color: var(--text-primary-dark) !important; }
            .gradio-input-info { color: var(--text-secondary-dark) !important; }
        }

        /* Textbox, Dropdown, Password input styling: larger and more padded */
        .gradio-textbox textarea,
        .gradio-dropdown select,
        .gradio-textbox input[type=password] {
            border: 1px solid var(--border-light) !important;
            border-radius: var(--radius-md) !important;
            padding: 1rem 1.2rem !important; /* More padding */
            font-size: 1.05rem !important; /* Larger font size */
            background: var(--surface-bg-light) !important;
            color: var(--text-primary-light) !important;
            width: 100% !important;
            box-shadow: none !important;
            transition: border-color var(--transition-speed), box-shadow var(--transition-speed);
        }
        .gradio-textbox textarea { min-height: 140px; } /* Taller textarea for more input visibility */
        .gradio-textbox textarea::placeholder,
        .gradio-textbox input[type=password]::placeholder {
            color: #A0AEC0 !important; /* Consistent placeholder color */
        }
        .gradio-textbox textarea:focus,
        .gradio-dropdown select:focus,
        .gradio-textbox input[type=password]:focus {
            border-color: var(--accent-main-light) !important;
            box-shadow: 0 0 0 3px var(--focus-ring-light) !important; /* Accent color focus ring */
            outline: none !important;
        }
        @media (prefers-color-scheme: dark) {
            .gradio-textbox textarea,
            .gradio-dropdown select,
            .gradio-textbox input[type=password] {
                border: 1px solid var(--border-dark) !important;
                background: var(--surface-bg-dark) !important;
                color: var(--text-primary-dark) !important;
            }
            .gradio-textbox textarea::placeholder,
            .gradio-textbox input[type=password]::placeholder {
                color: #718096 !important;
            }
            .gradio-textbox textarea:focus,
            .gradio-dropdown select:focus,
            .gradio-textbox input[type=password]:focus {
                border-color: var(--accent-main-dark) !important;
                box-shadow: 0 0 0 3px var(--focus-ring-dark) !important;
            }
        }

        /* Custom dropdown arrow for consistent look (re-applied for new colors) */
        .gradio-dropdown select {
            appearance: none; /* Remove native arrow */
            -webkit-appearance: none;
            -moz-appearance: none;
            background-image: url('data:image/svg+xml;charset=US-ASCII,%3Csvg%20xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F2000%2Fsvg%22%20viewBox%3D%220%200%2020%2020%22%20fill%3D%22%236C757D%22%3E%3Cpath%20fill-rule%3D%22evenodd%22%20d%3D%22M5.293%207.293a1%201%200%20011.414%200L10%2010.586l3.293-3.293a1%201%200%20111.414%201.414l-4%204a1%201%200%2001-1.414%200l-4-4a1%201%200%20010-1.414z%22%20clip-rule%3D%22evenodd%22%2F%3E%3C%2Fsvg%3E');
            background-repeat: no-repeat;
            background-position: right 1.2rem center; /* Adjusted position */
            background-size: 1.1em; /* Slightly larger arrow */
            padding-right: 3.5rem !important; /* Make space for arrow */
        }
        @media (prefers-color-scheme: dark) {
            .gradio-dropdown select {
                background-image: url('data:image/svg+xml;charset=US-ASCII,%3Csvg%20xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F2000%2Fsvg%22%20viewBox%3D%220%200%2020%2020%22%20fill%3D%22%23ADB5BD%22%3E%3Cpath%20fill-rule%3D%22evenodd%22%20d%3D%22M5.293%207.293a1%201%200%20011.414%200L10%2010.586l3.293-3.293a1%201%200%20111.414%201.414l-4%204a1%201%200%2001-1.414%200l-4-4a1%201%200%20010-1.414z%22%20clip-rule%3D%22evenodd%22%2F%3E%3C%2Fsvg%3E');
            }
        }

        /* Button group and styling: dynamic and clear actions */
        .button-row {
            display: flex;
            gap: 1.5rem; /* More space between buttons */
            margin-top: 2rem;
            flex-wrap: wrap;
            justify-content: flex-end; /* Align buttons to the right */
        }
        .gradio-button {
            border-radius: var(--radius-md) !important;
            padding: 0.9rem 2rem !important; /* More padding */
            font-size: 1.05rem !important; /* Larger font */
            font-weight: 500 !important;
            border: 1px solid transparent !important;
            box-shadow: 0 2px 5px rgba(0,0,0,0.1); /* Subtle shadow for primary */
            transition: all var(--transition-speed) ease; /* Smooth transition for hover/active states */
        }
        .gradio-button:hover:not(:disabled) {
            transform: translateY(-3px); /* More pronounced lift on hover */
            box-shadow: 0 6px 12px rgba(0,0,0,0.15) !important;
        }
        .gradio-button:active:not(:disabled) { transform: translateY(-1px); } /* Slight press effect */
        .gradio-button:disabled {
            background: #E9ECEF !important;
            color: #ADB5BD !important;
            box-shadow: none !important;
            border-color: #DEE2E6 !important;
            cursor: not-allowed;
        }

        /* Primary button (Submit Query) */
        .gr-button-primary {
            background: var(--accent-main-light) !important;
            color: #FFFFFF !important;
            border-color: var(--accent-main-light) !important;
        }
        .gr-button-primary:hover:not(:disabled) {
            background: var(--accent-hover-light) !important;
            border-color: var(--accent-hover-light) !important;
        }

        /* Secondary button (Clear) */
        .gr-button-secondary {
            background: transparent !important; /* Transparent background */
            color: var(--accent-secondary-light) !important;
            border-color: var(--accent-secondary-light) !important; /* Border in accent color */
            box-shadow: none !important; /* No shadow for secondary button */
        }
        .gr-button-secondary:hover:not(:disabled) {
            background: rgba(0, 123, 255, 0.05) !important; /* Very light hover background */
            color: var(--accent-hover-light) !important;
            border-color: var(--accent-hover-light) !important;
            box-shadow: none !important;
        }

        @media (prefers-color-scheme: dark) {
            .gradio-button { box-shadow: 0 2px 5px rgba(0,0,0,0.2) !important; }
            .gradio-button:hover:not(:disabled) { box-shadow: 0 6px 12px rgba(0,0,0,0.3) !important; }
            .gradio-button:disabled {
                background: #495057 !important;
                color: #6C757D !important;
                border-color: #6C757D !important;
            }
            .gr-button-primary {
                background: var(--accent-main-dark) !important;
                color: var(--text-primary-dark) !important; /* Text color contrasts with dark accent */
                border-color: var(--accent-main-dark) !important;
            }
            .gr-button-primary:hover:not(:disabled) {
                background: var(--accent-hover-dark) !important;
                border-color: var(--accent-hover-dark) !important;
            }
            .gr-button-secondary {
                background: transparent !important;
                color: var(--accent-secondary-dark) !important;
                border-color: var(--accent-secondary-dark) !important;
            }
            .gr-button-secondary:hover:not(:disabled) {
                background: rgba(138, 180, 248, 0.1) !important; /* Light blue hover for dark secondary */
                color: var(--accent-hover-dark) !important;
                border-color: var(--accent-hover-dark) !important;
            }
        }

        /* Output Card Styling: clear structure for answers */
        .output-card .response-header {
            font-size: 1.4rem; /* Larger header */
            font-weight: 600;
            color: var(--text-primary-light);
            margin: 0 0 1.2rem 0;
            display: flex;
            align-items: center;
            gap: 0.8rem; /* Space between icon and text */
        }
        .output-card .response-icon {
            font-size: 1.6rem;
            color: var(--accent-main-light); /* Accent color for icon */
        }
        .output-card .divider {
            border: none;
            border-top: 1px solid var(--border-light);
            margin: 1.5rem 0 2rem 0; /* More spacing around divider */
        }
        .output-card .output-content-wrapper {
            font-size: 1.05rem;
            line-height: 1.7;
            color: var(--text-primary-light);
        }
        .output-card .output-content-wrapper p { margin-bottom: 1rem; }
        .output-card .output-content-wrapper ul,
        .output-card .output-content-wrapper ol {
            margin-left: 1.8rem; /* More indentation for lists */
            margin-bottom: 1rem;
            padding-left: 0;
            list-style-type: disc; /* Ensure consistent bullet style */
        }
        .output-card .output-content-wrapper ol { list-style-type: decimal; } /* Numbered lists */
        .output-card .output-content-wrapper li { margin-bottom: 0.6rem; }
        .output-card .output-content-wrapper strong { font-weight: 700; } /* Bolder strong text within output */
        .output-card .output-content-wrapper a {
            color: var(--accent-main-light);
            text-decoration: underline; /* Links in output should be underlined for clarity */
        }
        .output-card .output-content-wrapper a:hover {
            color: var(--accent-hover-light);
        }

        @media (prefers-color-scheme: dark) {
            .output-card .response-header { color: var(--text-primary-dark); }
            .output-card .response-icon { color: var(--accent-main-dark); }
            .output-card .divider { border-top: 1px solid var(--border-dark); }
            .output-card .output-content-wrapper { color: var(--text-primary-dark); }
            .output-card .output-content-wrapper a { color: var(--accent-main-dark); }
            .output-card .output-content-wrapper a:hover { color: var(--accent-hover-dark); }
        }

        /* Error and Success Messages: visually distinct and informative */
        .output-card .error-message {
            padding: 1rem 1.5rem;
            margin-top: 1.5rem;
            font-size: 1rem;
            border-radius: var(--radius-md);
            background: var(--error-bg-light);
            color: var(--error-text-light);
            border: 1px solid var(--error-border-light);
            display: flex; /* Use flexbox for icon and text alignment */
            align-items: flex-start; /* Align text to top if icon is taller */
            gap: 0.8em;
        }
        .output-card .error-message .error-icon {
            font-size: 1.4rem;
            line-height: 1; /* Ensure icon is vertically centered */
            padding-top: 0.1em; /* Fine tune vertical alignment */
        }
        .output-card .error-details {
            font-size: 0.9rem;
            margin-top: 0.6rem;
            opacity: 0.9;
            word-break: break-word; /* Prevent long URLs/messages from overflowing */
        }
        @media (prefers-color-scheme: dark) {
            .output-card .error-message {
                background: var(--error-bg-dark);
                color: var(--error-text-dark);
                border: 1px solid var(--error-border-dark);
            }
        }

        /* Placeholder styling for empty output area */
        .output-card .placeholder {
            padding: 3.5rem 1.5rem; /* More vertical padding */
            font-size: 1.15rem; /* Larger placeholder text */
            border-radius: var(--radius-lg);
            border: 2px dashed var(--border-light);
            color: var(--text-secondary-light);
            text-align: center;
            opacity: 0.8;
        }
        @media (prefers-color-scheme: dark) {
            .output-card .placeholder {
                border-color: var(--border-dark);
                color: var(--text-secondary-dark);
            }
        }

        /* Examples table styling: clean and interactive */
        .examples-card .gr-examples-table {
            border-radius: var(--radius-lg) !important;
            border: 1px solid var(--border-light) !important;
            overflow: hidden; /* Ensures border-radius is applied to table */
        }
        .examples-card .gr-examples-table th,
        .examples-card .gr-examples-table td {
            padding: 1rem 1.2rem !important; /* More padding */
            font-size: 0.98rem !important;
            border: none !important; /* Remove individual cell borders */
        }
        .examples-card .gr-examples-table th {
            background: var(--app-bg-light) !important; /* Match app background for table header for seamless look */
            color: var(--text-primary-light) !important;
            font-weight: 600 !important;
            text-align: left;
        }
        .examples-card .gr-examples-table td {
            background: var(--surface-bg-light) !important;
            color: var(--text-primary-light) !important;
            border-top: 1px solid var(--border-light) !important; /* Add horizontal rule between rows */
            cursor: pointer; /* Indicate clickable rows */
            transition: background var(--transition-speed);
        }
        .examples-card .gr-examples-table tr:hover td {
            background: rgba(0, 123, 255, 0.03) !important; /* Very light hover effect */
        }
        .examples-card .gr-examples-table tr:first-child td { border-top: none !important; } /* No top border for first row's cells */

        @media (prefers-color-scheme: dark) {
            .examples-card .gr-examples-table { border: 1px solid var(--border-dark) !important;}
            .examples-card .gr-examples-table th {
                background: var(--app-bg-dark) !important;
                color: var(--text-primary-dark) !important;
            }
            .examples-card .gr-examples-table td {
                background: var(--surface-bg-dark) !important;
                color: var(--text-primary-dark) !important;
                border-top: 1px solid var(--border-dark) !important;
            }
            .examples-card .gr-examples-table tr:hover td {
                background: rgba(138, 180, 248, 0.1) !important; /* Light blue hover for dark table */
            }
        }

        /* Footer styling: clean and informative */
        .app-footer-wrapper {
            border-top: 1px solid var(--border-light) !important;
            margin-top: 3.5rem; /* Spacing from last content card */
            padding-top: 3rem; /* Padding above footer content */
        }
        .app-footer {
            padding: 0 1.5rem !important;
            text-align: center !important;
            display: flex;
            flex-direction: column;
            align-items: center;
        }
        .app-footer p {
            font-size: 0.95rem !important;
            color: var(--text-secondary-light) !important;
            margin-bottom: 0.8rem;
            max-width: 650px; /* Constrain text width for readability */
        }
        .app-footer a {
            color: var(--accent-main-light) !important;
            font-weight: 500;
            transition: color var(--transition-speed), text-decoration var(--transition-speed);
        }
        .app-footer a:hover {
            color: var(--accent-hover-light) !important;
            text-decoration: underline;
        }
        @media (prefers-color-scheme: dark) {
            .app-footer-wrapper { border-top-color: var(--border-dark) !important; }
            .app-footer p { color: var(--text-secondary-dark) !important; }
            .app-footer a { color: var(--accent-main-dark) !important; }
            .app-footer a:hover { color: var(--accent-hover-dark) !important; }
        }

        /* Accessibility: Focus styles for keyboard navigation */
        :focus-visible {
            outline: 2px solid var(--accent-main-light) !important;
            outline-offset: 2px;
            box-shadow: 0 0 0 4px var(--focus-ring-light) !important; /* Thicker, more visible focus ring */
        }
        @media (prefers-color-scheme: dark) {
            :focus-visible {
                outline-color: var(--accent-main-dark) !important;
                box-shadow: 0 0 0 4px var(--focus-ring-dark) !important;
            }
        }
        /* Prevent double focus outline on Gradio buttons' internal span */
        .gradio-button span:focus { outline: none !important; }


        /* Essential overrides to ensure custom styles take precedence over Gradio defaults */
        .gradio-container > .flex { gap: 0 !important; } /* Remove main container gap */
        .gradio-markdown > *:first-child { margin-top: 0; } /* Remove top margin from first element in Markdown */
        .gradio-markdown > *:last-child { margin-bottom: 0; } /* Remove bottom margin from last element in Markdown */
        /* Remove default Gradio component borders/padding that interfere with custom styling */
        .gradio-dropdown, .gradio-textbox { border: none !important; padding: 0 !important; background: transparent !important; }

        /* Responsive adjustments for various screen sizes */
        @media (max-width: 992px) {
            .gradio-container > .flex.flex-col { max-width: 760px; padding: 1.5rem 1.25rem 3.5rem 1.25rem !important; }
            .content-surface { padding: 2.5rem !important; margin-bottom: 2.5rem; }
            .app-header-wrapper { padding: 2.5rem 1.5rem 3.5rem 1.5rem !important; margin-bottom: 3rem; }
            .app-header-title { font-size: 2.5rem; }
            .app-header-tagline { font-size: 1.15rem; }
            .section-title, .input-form-card h3, .examples-card .gr-examples-header { font-size: 1.5rem !important; margin-bottom: 2rem !important; }
            .input-row { gap: 1.5rem; }
            .gradio-textbox textarea { min-height: 120px; }
        }

        @media (max-width: 768px) {
            .gradio-container > .flex.flex-col { padding: 1rem 1rem 3rem 1rem !important; }
            .content-surface { padding: 2rem !important; margin-bottom: 2rem; }
            .app-header-wrapper { padding: 2rem 1.25rem 3rem 1.25rem !important; margin-bottom: 2.5rem; }
            .app-header-logo { font-size: 3.5rem; }
            .app-header-title { font-size: 2.2rem; letter-spacing: -0.03em; }
            .app-header-tagline { font-size: 1.05rem; }
            .section-title, .input-form-card h3, .examples-card .gr-examples-header { font-size: 1.4rem !important; margin-bottom: 1.8rem !important; }
            .input-row { flex-direction: column; gap: 1.25rem; } /* Stack inputs vertically */
            .input-field { min-width: 100%; }
            .button-row { justify-content: stretch; } /* Stretch buttons to full width */
            .gradio-button { width: 100%; }
            .output-card .response-header { font-size: 1.25rem; }
            .output-card .response-icon { font-size: 1.4rem; }
            .output-card .placeholder { padding: 3rem 1rem; font-size: 1.1rem; }
            .examples-card .gr-examples-table th, .examples-card .gr-examples-table td { padding: 0.8rem 1rem !important; font-size: 0.95rem !important; }
            .app-footer-wrapper { margin-top: 3rem; padding-top: 2.5rem; }
            .app-footer p { font-size: 0.9rem !important; }
        }

        @media (max-width: 480px) {
            .gradio-container > .flex.flex-col { padding: 0.75rem 0.75rem 2.5rem 0.75rem !important; }
            .content-surface { padding: 1.5rem !important; margin-bottom: 1.5rem; border-radius: var(--radius-md) !important; }
            .app-header-wrapper { padding: 1.5rem 1rem 2rem 1rem !important; margin-bottom: 2rem; border-radius: var(--radius-md); }
            .app-header-logo { font-size: 3rem; margin-bottom: 0.75rem; }
            .app-header-title { font-size: 2rem; letter-spacing: -0.02em; }
            .app-header-tagline { font-size: 0.95rem; }
            .section-title, .input-form-card h3, .examples-card .gr-examples-header { font-size: 1.25rem !important; margin-bottom: 1.5rem !important; padding-bottom: 0.75rem !important; }
            .gradio-textbox textarea, .gradio-dropdown select, .gradio-textbox input[type=password] { font-size: 0.95rem !important; padding: 0.8rem 1rem !important; }
            .gradio-textbox textarea { min-height: 100px; }
            .gradio-button { padding: 0.8rem 1.2rem !important; font-size: 0.95rem !important; }
            .output-card .response-header { font-size: 1.15rem; }
            .output-card .response-icon { font-size: 1.3rem; }
            .output-card .placeholder { padding: 2.5rem 0.8rem; font-size: 1rem; }
            .examples-card .gr-examples-table th, .examples-card .gr-examples-table td { padding: 0.6rem 0.8rem !important; font-size: 0.85rem !important; }
            .app-footer-wrapper { margin-top: 2.5rem; padding-top: 2rem; }
            .app-footer p { font-size: 0.85rem !important; }
        }
        """

        with gr.Blocks(theme=None, css=custom_css, title="Landlord-Tenant Rights Assistant") as demo:
            # --- Header Section: Prominent, dynamic banner ---
            with gr.Group(elem_classes="app-header-wrapper"):
                gr.Markdown(
                    """
                    <div class="app-header">
                        <span class="app-header-logo">⚖️</span>
                        <h1 class="app-header-title">Landlord-Tenant Rights Assistant</h1>
                        <p class="app-header-tagline">Empowering You with State-Specific Legal Insights</p>
                    </div>
                    """
                )

            # --- "Know Your Rights" Section: Informational card ---
            with gr.Group(elem_classes="content-surface"):
                gr.Markdown("<h3 class='section-title'>Know Your Rights</h3>")
                gr.Markdown(
                    """
                    <p>Navigate landlord-tenant laws with ease. Enter your <strong>OpenAI API key</strong>, select your state, and ask your question to get detailed, state-specific answers.</p>
                    <p>Don't have an API key? <a href='https://platform.openai.com/api-keys' target='_blank'>Get one free from OpenAI</a>.</p>
                    <p><strong>Disclaimer:</strong> This tool provides information only, not legal advice. For legal guidance, always consult a licensed attorney.</p>
                    """
                )

            # --- "Ask Your Question" Section (Input Form): Structured and clear inputs ---
            with gr.Group(elem_classes="content-surface input-form-card"):
                gr.Markdown("<h3>Ask Your Question</h3>")
                with gr.Column(elem_classes="input-field-group"):
                    api_key_input = gr.Textbox(
                        label="OpenAI API Key", type="password", placeholder="Enter your API key (e.g., sk-...)",
                        info="Required to process your query. Securely used per request, not stored.", lines=1
                    )
                with gr.Row(elem_classes="input-row"):
                    with gr.Column(elem_classes="input-field", min_width="58%"): # Allocate more width for the question
                        query_input = gr.Textbox(
                            label="Your Question", placeholder="E.g., What are the rules for security deposit returns in my state?",
                            lines=5, max_lines=10
                        )
                    with gr.Column(elem_classes="input-field", min_width="38%"): # Allocate less width for the dropdown
                        state_input = gr.Dropdown(
                            label="Select State", choices=dropdown_choices, value=initial_value,
                            allow_custom_value=False
                        )
                with gr.Row(elem_classes="button-row"):
                    clear_button = gr.Button("Clear", variant="secondary", elem_classes=["gr-button-secondary"])
                    submit_button = gr.Button("Submit Query", variant="primary", elem_classes=["gr-button-primary"])

            # --- Output Section: Clearly formatted answers or messages ---
            with gr.Group(elem_classes="content-surface output-card"):
                output = gr.Markdown(
                    value="<div class='placeholder'>Your answer will appear here after submitting your query.</div>",
                    elem_classes="output-content-wrapper" # This div will be replaced by the answer HTML
                )

            # --- "Explore Sample Questions" Section: Interactive examples ---
            if example_queries:
                with gr.Group(elem_classes="content-surface examples-card"):
                    gr.Examples(
                        examples=example_queries, inputs=[query_input, state_input],
                        label="Explore Sample Questions", examples_per_page=5
                    )
            else:
                with gr.Group(elem_classes="content-surface"):
                    gr.Markdown("<div class='placeholder'>Sample questions could not be loaded.</div>")

            # --- Footer Section: Disclaimer and author info ---
            with gr.Group(elem_classes="app-footer-wrapper"):
                gr.Markdown(
                    """
                    <div class="app-footer">
                        <p>This tool is for informational purposes only and does not constitute legal advice. For legal guidance, always consult with a licensed attorney in your jurisdiction.</p>
                        <p>Developed by <strong>Nischal Subedi</strong>.
                        Connect on <a href="https://www.linkedin.com/in/nischal1/" target='_blank'>LinkedIn</a>
                        or explore insights at <a href="https://datascientistinsights.substack.com/" target='_blank'>Substack</a>.</p>
                    </div>
                    """
                )

            # --- Event Listeners ---
            submit_button.click(
                fn=query_interface_wrapper, inputs=[api_key_input, query_input, state_input], outputs=output, api_name="submit_query"
            )
            clear_button.click(
                fn=lambda: (
                    "", # Clear API key input
                    "", # Clear query input
                    initial_value, # Reset state dropdown to initial value
                    "<div class='placeholder'>Inputs cleared. Ready for your next question.</div>" # Reset output to placeholder
                ),
                inputs=[], outputs=[api_key_input, query_input, state_input, output]
            )
        logging.info("Advanced UI (Legal Lumen theme) Gradio interface created.")
        return demo

# --- Main Execution Block (remains untouched from original logic) ---
if __name__ == "__main__":
    logging.info("Starting Landlord-Tenant Rights Bot application...")
    try:
        SCRIPT_DIR = os.path.dirname(os.path.abspath(__file__))
        DEFAULT_PDF_PATH = os.path.join(SCRIPT_DIR, "tenant-landlord.pdf")
        DEFAULT_DB_PATH = os.path.join(SCRIPT_DIR, "chroma_db")

        # Use environment variables if set, otherwise default paths
        PDF_PATH = os.getenv("PDF_PATH", DEFAULT_PDF_PATH)
        VECTOR_DB_PATH = os.getenv("VECTOR_DB_PATH", DEFAULT_DB_PATH)

        # Ensure directories exist
        os.makedirs(os.path.dirname(VECTOR_DB_PATH), exist_ok=True)
        # If PDF_PATH could point to a file in a non-existent subdirectory, uncomment:
        # if os.path.dirname(PDF_PATH):
        #     os.makedirs(os.path.dirname(PDF_PATH), exist_ok=True)


        # Validate PDF file existence before proceeding
        if not os.path.exists(PDF_PATH):
            logging.error(f"FATAL: PDF file not found at the specified path: {PDF_PATH}")
            print(f"\n--- CONFIGURATION ERROR ---\nPDF file ('{os.path.basename(PDF_PATH)}') not found at: {PDF_PATH}\nPlease ensure it exists or set 'PDF_PATH' environment variable.\n---------------------------\n")
            exit(1)

        # Initialize Vector Database and RAG System
        vector_db_instance = VectorDatabase(persist_directory=VECTOR_DB_PATH)
        rag = RAGSystem(vector_db=vector_db_instance)
        rag.load_pdf(PDF_PATH) # Load/process PDF data into the vector DB

        # Create and launch the Gradio interface
        app_interface = rag.gradio_interface()
        SERVER_PORT = 7860
        logging.info(f"Launching Gradio app on http://0.0.0.0:{SERVER_PORT}")
        print(f"\n--- Gradio App Running ---\nAccess at: http://localhost:{SERVER_PORT}\n(Share link will be available if you use share=True)\n--------------------------\n")
        app_interface.launch(server_name="0.0.0.0", server_port=SERVER_PORT, share=True)

    except Exception as e:
        logging.error(f"Application startup failed: {str(e)}", exc_info=True)
        print(f"\n--- FATAL STARTUP ERROR ---\n{str(e)}\nCheck logs for more details.\n---------------------------\n")
        exit(1)