import logging
import re
import time
from typing import List, Dict, Any, Optional
from langgraph.graph import StateGraph, END
from langgraph.checkpoint.memory import MemorySaver # Or SqliteSaver etc.

from pydantic import BaseModel, Field

from langchain_core.messages import HumanMessage, AIMessage, SystemMessage
from langchain_core.output_parsers import StrOutputParser, JsonOutputParser

from .config import settings
from .schemas import PlannerState, KeyIssue, GraphConfig # Import schemas
from .prompts import get_initial_planner_prompt, KEY_ISSUE_STRUCTURING_PROMPT
from .llm_interface import get_llm, invoke_llm
from .graph_operations import (
    generate_cypher_auto, generate_cypher_guided,
    retrieve_documents, evaluate_documents
)
from .processing import process_documents

logger = logging.getLogger(__name__)

# --- Graph Nodes ---

def start_planning(state: PlannerState) -> Dict[str, Any]:
    """Generates the initial plan based on the user query."""
    logger.info("Node: start_planning")
    user_query = state['user_query']
    if not user_query:
        return {"error": "User query is empty."}

    initial_prompt = get_initial_planner_prompt(settings.plan_method, user_query)
    llm = get_llm(settings.main_llm_model)
    chain = initial_prompt | llm | StrOutputParser()

    try:
        plan_text = invoke_llm(chain,{}) # Prompt already includes query
        logger.debug(f"Raw plan text: {plan_text}")

        # Extract plan steps (simple regex, might need refinement)
        plan_match = re.search(r"Plan:(.*?)<END_OF_PLAN>", plan_text, re.DOTALL | re.IGNORECASE)
        if plan_match:
            plan_steps = [step.strip() for step in re.split(r"\n\s*\d+\.\s*", plan_match.group(1)) if step.strip()]
            logger.info(f"Extracted plan: {plan_steps}")
            return {
                "plan": plan_steps,
                "current_plan_step_index": 0,
                "messages": [AIMessage(content=plan_text)],
                 "step_outputs": {} # Initialize step outputs
            }
        else:
            logger.error("Could not parse plan from LLM response.")
            return {"error": "Failed to parse plan from LLM response.", "messages": [AIMessage(content=plan_text)]}
    except Exception as e:
        logger.error(f"Error during plan generation: {e}", exc_info=True)
        return {"error": f"LLM error during plan generation: {e}"}


def execute_plan_step(state: PlannerState) -> Dict[str, Any]:
    """Executes the current step of the plan (retrieval, processing)."""
    current_index = state['current_plan_step_index']
    plan = state['plan']
    user_query = state['user_query'] # Use original query for context

    if current_index >= len(plan):
        logger.warning("Plan step index out of bounds, attempting to finalize.")
        # This should ideally be handled by the conditional edge, but as a fallback
        return {"error": "Plan execution finished unexpectedly."}

    step_description = plan[current_index]
    logger.info(f"Node: execute_plan_step - Step {current_index + 1}/{len(plan)}: {step_description}")

    # --- Determine Query for Retrieval ---
    # Simple approach: Use step description or original query?
    # Let's use the step description combined with the original query for context.
    query_for_retrieval = f"Regarding the query '{user_query}', focus on: {step_description}"
    logger.info(f"Query for retrieval: {query_for_retrieval}")

    # --- Generate Cypher ---
    cypher_query = ""
    if settings.cypher_gen_method == 'auto':
        cypher_query = generate_cypher_auto(query_for_retrieval)
    elif settings.cypher_gen_method == 'guided':
        cypher_query = generate_cypher_guided(query_for_retrieval, current_index)
    # TODO: Add cypher validation if settings.validate_cypher is True

    # --- Retrieve Documents ---
    retrieved_docs = retrieve_documents(cypher_query)

    # --- Evaluate Documents ---
    evaluated_docs = evaluate_documents(retrieved_docs, query_for_retrieval)

    # --- Process Documents ---
    # Using configured processing steps
    processed_docs_content = process_documents(evaluated_docs, settings.process_steps)

    # --- Store Step Output ---
    # Store the processed content relevant to this step
    step_output = "\n\n".join(processed_docs_content) if processed_docs_content else "No relevant information found for this step."
    current_step_outputs = state.get('step_outputs', {})
    current_step_outputs[current_index] = step_output

    logger.info(f"Finished executing plan step {current_index + 1}. Stored output.")

    return {
        "current_plan_step_index": current_index + 1,
        "messages": [SystemMessage(content=f"Completed plan step {current_index + 1}. Context gathered:\n{step_output[:500]}...")], # Add summary message
        "step_outputs": current_step_outputs
    }

class KeyIssue(BaseModel):
    # define your fields here
    id: int
    description: str

class KeyIssueList(BaseModel):
    key_issues: List[KeyIssue] = Field(description="List of key issues")

class KeyIssueInvoke(BaseModel):
    id: int
    title: str
    description: str
    challenges: List[str]
    potential_impact: Optional[str] = None

def generate_structured_issues(state: PlannerState) -> Dict[str, Any]:
    """Generates the final structured Key Issues based on all gathered context."""
    logger.info("Node: generate_structured_issues")

    user_query = state['user_query']
    step_outputs = state.get('step_outputs', {})

    # --- Combine Context from All Steps ---
    full_context = f"Original User Query: {user_query}\n\n"
    full_context += "Context gathered during planning:\n"
    for i, output in sorted(step_outputs.items()):
        full_context += f"--- Context from Step {i+1} ---\n{output}\n\n"

    if not step_outputs:
        full_context += "No context was gathered during the planning steps.\n"

    logger.info(f"Generating key issues using combined context (length: {len(full_context)} chars).")
    # logger.debug(f"Full Context for Key Issue Generation:\n{full_context}") # Optional: log full context

    # --- Call LLM for Structured Output ---
    issue_llm = get_llm(settings.main_llm_model)
    # Use PydanticOutputParser for robust parsing
    output_parser = JsonOutputParser(pydantic_object=KeyIssueList)

    
    prompt = KEY_ISSUE_STRUCTURING_PROMPT.partial(
        schema=output_parser.get_format_instructions(), # Inject schema instructions if needed by prompt
    )

    chain = prompt | issue_llm | output_parser

    try:
        structured_issues_obj = invoke_llm(chain, {
            "user_query": user_query,
            "context": full_context
        })
        print(f"structured_issues_obj => type : {type(structured_issues_obj)}, value : {structured_issues_obj}")
    
        # If the output is a dict with a key 'key_issues', extract it
        if isinstance(structured_issues_obj, dict) and 'key_issues' in structured_issues_obj:
            issues_data = structured_issues_obj['key_issues']
        else:
            issues_data = structured_issues_obj  # Assume it's already a list of dicts
    
        # Always convert to KeyIssueInvoke objects
        key_issues_list = [KeyIssueInvoke(**issue_dict) for issue_dict in issues_data]
    
        # Ensure IDs are sequential if the LLM didn't assign them correctly
        for i, issue in enumerate(key_issues_list):
            issue.id = i + 1
    
        logger.info(f"Successfully generated {len(key_issues_list)} structured key issues.")
        final_message = f"Generated {len(key_issues_list)} Key Issues based on the query '{user_query}'."
        return {
            "key_issues": key_issues_list,
            "messages": [AIMessage(content=final_message)],
            "error": None
        }
    except Exception as e:
        logger.error(f"Failed to generate or parse structured key issues: {e}", exc_info=True)
        # Attempt to get raw output for debugging if possible
        raw_output = "Could not retrieve raw output."
        try:
             raw_chain = prompt | issue_llm | StrOutputParser()
             raw_output = invoke_llm(raw_chain, {"user_query": user_query, "context": full_context})
             logger.debug(f"Raw output from failed JSON parsing:\n{raw_output}")
        except Exception as raw_e:
             logger.error(f"Could not even get raw output: {raw_e}")
    
        return {"error": f"Failed to generate structured key issues: {e}. Raw output hint: {raw_output[:500]}..."}


# --- Conditional Edges ---

def should_continue_planning(state: PlannerState) -> str:
    """Determines if there are more plan steps to execute."""
    logger.debug("Edge: should_continue_planning")
    if state.get("error"):
        logger.error(f"Error state detected: {state['error']}. Ending execution.")
        return "error_state" # Go to a potential error handling end node

    current_index = state['current_plan_step_index']
    plan_length = len(state.get('plan', []))

    if current_index < plan_length:
        logger.debug(f"Continuing plan execution. Next step index: {current_index}")
        return "continue_execution"
    else:
        logger.debug("Plan finished. Proceeding to final generation.")
        return "finalize"


# --- Build Graph ---
def build_graph():
    """Builds the LangGraph workflow."""
    workflow = StateGraph(PlannerState)

    # Add nodes
    workflow.add_node("start_planning", start_planning)
    workflow.add_node("execute_plan_step", execute_plan_step)
    workflow.add_node("generate_issues", generate_structured_issues)
    # Optional: Add an error handling node
    workflow.add_node("error_node", lambda state: {"messages": [SystemMessage(content=f"Execution failed: {state.get('error', 'Unknown error')}") ]})


    # Define edges
    workflow.set_entry_point("start_planning")
    workflow.add_edge("start_planning", "execute_plan_step") # Assume plan is always generated

    workflow.add_conditional_edges(
        "execute_plan_step",
        should_continue_planning,
        {
            "continue_execution": "execute_plan_step", # Loop back to execute next step
            "finalize": "generate_issues",          # Move to final generation
            "error_state": "error_node"             # Go to error node
        }
    )

    workflow.add_edge("generate_issues", END)
    workflow.add_edge("error_node", END) # End after error

    # Compile the graph with memory (optional)
    # memory = MemorySaver() # Use if state needs persistence between runs
    # app_graph = workflow.compile(checkpointer=memory)
    app_graph = workflow.compile()
    return app_graph