from fastapi import FastAPI, Request
from fastapi.responses import StreamingResponse, JSONResponse
from pydantic import BaseModel
from typing import List, Optional, Union
import requests
import json

app = FastAPI()

API_URL = "https://api.typegpt.net/v1/chat/completions"
API_KEY = "sk-XzS5hhsa3vpIcRLz3prQirBQXOx2hPydPzSpzdRcE1YddnNm"
BACKEND_MODEL = "pixtral-large-latest"

# Load virtual model -> system prompt mappings
with open("model_map.json", "r") as f:
    MODEL_PROMPTS = json.load(f)

class Message(BaseModel):
    role: str
    content: str

class ChatRequest(BaseModel):
    model: str
    messages: List[Message]
    stream: Optional[bool] = False
    temperature: Optional[float] = 1.0
    top_p: Optional[float] = 1.0
    n: Optional[int] = 1
    stop: Optional[Union[str, List[str]]] = None
    presence_penalty: Optional[float] = 0.0
    frequency_penalty: Optional[float] = 0.0

def build_payload(chat: ChatRequest):
    system_prompt = MODEL_PROMPTS.get(chat.model, "You are a helpful assistant.")

    messages = [{"role": "system", "content": system_prompt}] + [
        {"role": msg.role, "content": msg.content} for msg in chat.messages
    ]

    return {
        "model": BACKEND_MODEL,
        "messages": messages,
        "stream": chat.stream,
        "temperature": chat.temperature,
        "top_p": chat.top_p,
        "n": chat.n,
        "stop": chat.stop,
        "presence_penalty": chat.presence_penalty,
        "frequency_penalty": chat.frequency_penalty
    }

def stream_generator(requested_model: str, payload: dict, headers: dict):
    with requests.post(API_URL, headers=headers, json=payload, stream=True) as r:
        for line in r.iter_lines(decode_unicode=True):
            if line and line.startswith("data:"):
                # Remove "data: " prefix
                content = line[6:].strip()
                try:
                    # Try to parse and replace model field
                    json_obj = json.loads(content)
                    if "model" in json_obj and json_obj["model"] == BACKEND_MODEL:
                        json_obj["model"] = requested_model
                    fixed_line = f"data: {json.dumps(json_obj)}\n\n"
                except json.JSONDecodeError:
                    fixed_line = f"data: {content}\n\n"
                yield fixed_line
            elif line:
                yield f"data: {line}\n\n"
        yield "data: [DONE]\n\n"

@app.post("/v1/chat/completions")
async def proxy_chat(request: Request):
    body = await request.json()
    chat_request = ChatRequest(**body)
    payload = build_payload(chat_request)
    headers = {
        "Authorization": f"Bearer {API_KEY}",
        "Content-Type": "application/json"
    }

    if chat_request.stream:
        return StreamingResponse(
            stream_generator(chat_request.model, payload, headers),
            media_type="text/event-stream"
        )
    else:
        response = requests.post(API_URL, headers=headers, json=payload)
        data = response.json()
        if "model" in data and data["model"] == BACKEND_MODEL:
            data["model"] = chat_request.model
        return JSONResponse(content=data)