import asyncio
import json
import jwt
from fastapi import APIRouter, HTTPException, Query, Request
from fastapi.responses import StreamingResponse
from pydantic import BaseModel
from context_loader import load_context
from llm_client import complete
from session_logger import log_turn
from session_store import load as load_session, save as save_session, list_all, generate_session_id, delete as delete_session, rename as rename_session
from config import settings
from persona import set_context, validate as validate_persona
from auth_utils import COOKIE_NAME, decode_token
import user_settings
import event_bus


router = APIRouter()


class ChatRequest(BaseModel):
    message: str
    session_id: str | None = None
    tier: int | None = None
    model: str | None = None  # "claude" or "gemini" to override; None = use primary_backend
    include_long: bool = True
    include_mid: bool = True
    include_short: bool = True
    off_record: bool = False  # skip session log (in-memory context preserved)
    user: str = "scott"
    persona: str = "inara"


class BackendRequest(BaseModel):
    primary: str  # "claude", "gemini", or "local"


class NoteRequest(BaseModel):
    session_id: str
    note: str


class HistoryUpdate(BaseModel):
    messages: list[dict]


async def _stream_chat(req: ChatRequest):
    """
    SSE generator: sends keepalive events every 3s while the LLM works,
    then sends the final response. Keeps the browser connection alive
    regardless of how long the backend takes.

    Event types:
      data: {"type": "keepalive"}
      data: {"type": "response", "response": "...", "session_id": "...",
              "backend": "...", "fallback_used": bool}
      data: {"type": "error", "message": "..."}
    """
    try:
        user, persona = validate_persona(req.user, req.persona)
        set_context(user, persona)
    except ValueError as e:
        yield f"data: {json.dumps({'type': 'error', 'message': str(e)})}\n\n"
        return

    session_id = req.session_id or generate_session_id()
    tier = req.tier or settings.default_tier

    system_prompt = load_context(
        tier,
        include_long=req.include_long,
        include_mid=req.include_mid,
        include_short=req.include_short,
    )
    history = load_session(session_id)
    history.append({"role": "user", "content": req.message})

    task = asyncio.create_task(complete(
        system_prompt=system_prompt,
        messages=history,
        model=req.model,
    ))

    try:
        # Ping the browser every 3s so it doesn't drop the connection
        while not task.done():
            yield 'data: {"type":"keepalive"}\n\n'
            try:
                await asyncio.wait_for(asyncio.shield(task), timeout=3)
            except asyncio.TimeoutError:
                pass
            except Exception:
                break

        try:
            response_text, actual_backend = task.result()
            history.append({"role": "assistant", "content": response_text})
            save_session(session_id, history)
            if not req.off_record:
                log_turn(session_id, req.message, response_text)

            requested = req.model or settings.primary_backend
            payload = {
                "type": "response",
                "response": response_text,
                "session_id": session_id,
                "backend": actual_backend,
                "fallback_used": actual_backend != requested,
            }
            yield f"data: {json.dumps(payload)}\n\n"

        except Exception as e:
            yield f"data: {json.dumps({'type': 'error', 'message': str(e)})}\n\n"

    finally:
        # Ensure the LLM task is cancelled if the generator is torn down
        # (e.g. client disconnect or server shutdown). This propagates
        # CancelledError into _gemini() which kills the process group.
        if not task.done():
            task.cancel()
            try:
                await task
            except (asyncio.CancelledError, Exception):
                pass


@router.post("/chat")
async def chat(req: ChatRequest) -> StreamingResponse:
    return StreamingResponse(
        _stream_chat(req),
        media_type="text/event-stream",
        headers={"Cache-Control": "no-cache", "X-Accel-Buffering": "no"},
    )


_BACKEND_CYCLE = ("claude", "gemini", "local")
_BACKEND_FALLBACK = {"claude": "gemini", "gemini": "claude", "local": "claude"}


def _local_model_info(request: Request) -> dict | None:
    """Return active local model {label, model_name} for the session user, or None."""
    try:
        token    = request.cookies.get(COOKIE_NAME)
        username = decode_token(token) if token else None
        if not username:
            return None
        cfg = user_settings.get_active_local_model(username)
        if cfg:
            return {"label": cfg["label"], "model_name": cfg["model_name"]}
    except (jwt.InvalidTokenError, Exception):
        pass
    return None


@router.get("/backend")
async def get_backend(request: Request) -> dict:
    p = settings.primary_backend
    return {
        "primary":      p,
        "fallback":     _BACKEND_FALLBACK.get(p, "claude"),
        "local_model":  _local_model_info(request),
    }


@router.post("/backend")
async def set_backend(req: BackendRequest, request: Request) -> dict:
    if req.primary not in _BACKEND_CYCLE:
        raise HTTPException(status_code=400, detail="primary must be 'claude', 'gemini', or 'local'")
    settings.primary_backend = req.primary
    return {
        "primary":     req.primary,
        "fallback":    _BACKEND_FALLBACK[req.primary],
        "local_model": _local_model_info(request),
    }


def _set_ctx(user: str, persona: str) -> None:
    """Validate and set persona context from query params. Raises HTTPException on bad input."""
    try:
        u, p = validate_persona(user, persona)
        set_context(u, p)
    except ValueError as e:
        raise HTTPException(status_code=404, detail=str(e))


@router.get("/history/{session_id}")
async def get_history(
    session_id: str,
    user: str = Query("scott"),
    persona: str = Query("inara"),
) -> dict:
    _set_ctx(user, persona)
    return {"session_id": session_id, "messages": load_session(session_id)}


@router.get("/sessions")
async def list_sessions(
    user: str = Query("scott"),
    persona: str = Query("inara"),
) -> dict:
    _set_ctx(user, persona)
    return {"sessions": list_all()}


class SessionRename(BaseModel):
    name: str


@router.patch("/sessions/{session_id}")
async def rename_session_endpoint(
    session_id: str,
    req: SessionRename,
    user: str = Query("scott"),
    persona: str = Query("inara"),
) -> dict:
    _set_ctx(user, persona)
    found = rename_session(session_id, req.name.strip())
    if not found:
        raise HTTPException(status_code=404, detail=f"Session {session_id} not found")
    return {"ok": True, "session_id": session_id, "name": req.name.strip()}


@router.delete("/sessions/{session_id}")
async def delete_session_endpoint(
    session_id: str,
    user: str = Query("scott"),
    persona: str = Query("inara"),
) -> dict:
    _set_ctx(user, persona)
    found = delete_session(session_id)
    if not found:
        raise HTTPException(status_code=404, detail=f"Session {session_id} not found")
    return {"ok": True, "session_id": session_id}


@router.put("/history/{session_id}")
async def replace_history(
    session_id: str,
    req: HistoryUpdate,
    user: str = Query("scott"),
    persona: str = Query("inara"),
) -> dict:
    """Replace the full message list for a session (used by edit/delete UI)."""
    _set_ctx(user, persona)
    save_session(session_id, req.messages)
    return {"ok": True, "session_id": session_id}


@router.get("/events")
async def sse_events() -> StreamingResponse:
    """Server-sent events stream — pushes real-time Talk activity to the browser."""
    async def stream():
        q = event_bus.subscribe()
        try:
            while True:
                try:
                    event = await asyncio.wait_for(q.get(), timeout=20)
                    yield f"data: {json.dumps(event)}\n\n"
                except asyncio.TimeoutError:
                    yield 'data: {"type":"keepalive"}\n\n'
        except (GeneratorExit, asyncio.CancelledError):
            pass
        finally:
            event_bus.unsubscribe(q)

    return StreamingResponse(
        stream(),
        media_type="text/event-stream",
        headers={"Cache-Control": "no-cache", "X-Accel-Buffering": "no"},
    )


@router.post("/note")
async def add_note(
    req: NoteRequest,
    user: str = Query("scott"),
    persona: str = Query("inara"),
) -> dict:
    """Inject a public note into session history so the LLM sees it next turn."""
    _set_ctx(user, persona)
    history = load_session(req.session_id)
    history.append({"role": "user", "content": f"[NOTE] {req.note}"})
    save_session(req.session_id, history)
    return {"ok": True, "session_id": req.session_id}