import asyncio
import json
import platform
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, get_name as get_session_name
from config import settings
from persona import set_context, validate as validate_persona
from auth_utils import COOKIE_NAME, decode_token
import model_registry
import event_bus
from model_registry import get_role_config


router = APIRouter()


def _backend_label(backend: str, username: str, role: str = "chat") -> str:
    """Human-readable label for the model that handled a request (legacy path)."""
    if backend == "claude":
        return "Claude"
    if backend == "gemini":
        return "Gemini"
    if backend == "local":
        cfg = model_registry.get_best_local_model(username, role)
        if cfg:
            return cfg.get("label") or cfg.get("model_name") or "Local"
        return "Local"
    return backend.title()


def _role_model_label(username: str, role: str, actual_backend: str) -> str:
    """Return the model label for a role, falling back to the generic backend label."""
    cfg = model_registry.get_model_for_role(username, role)
    if cfg:
        return cfg.get("label") or cfg.get("model_name") or _backend_label(actual_backend, username, role)
    return _backend_label(actual_backend, username, role)


class ChatRequest(BaseModel):
    message: str
    session_id: str | None = None
    tier: int | None = None
    model: str | None = None        # legacy backend override ("claude"|"gemini"|"local")
    slot: str | None = None         # Phase 3: explicit slot ("primary"|"backup_1"|"backup_2")
    chat_role: str = "chat"         # active role: "chat"|"coder"|"research"|"distill" etc.
    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

    role_cfg = get_role_config(user, req.chat_role)
    system_prompt = load_context(
        tier,
        include_long=req.include_long,
        include_mid=req.include_mid,
        include_short=req.include_short,
        inject_datetime=role_cfg.get("inject_datetime", True),
        inject_mode=role_cfg.get("inject_mode", True),
        mode="otr" if req.off_record else "chat",
    )
    history = load_session(session_id)
    history.append({"role": "user", "content": req.message, "off_record": req.off_record})

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

    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()
            if req.slot:
                slot_cfg = model_registry.get_model_for_slot(user, req.chat_role, req.slot)
                backend_label = (slot_cfg or {}).get("label") or _role_model_label(user, req.chat_role, actual_backend)
            else:
                backend_label = _role_model_label(user, req.chat_role, actual_backend)
            host = platform.node()
            history.append({
                "role": "assistant",
                "content": response_text,
                "backend": actual_backend,
                "backend_label": backend_label,
                "host": host,
                "off_record": req.off_record,
            })
            save_session(session_id, history)
            if not req.off_record:
                log_turn(session_id, req.message, response_text, backend_label, host)

            # fallback_used only makes sense for explicit backend selections.
            # In auto mode (req.model is None), just report what responded.
            fallback_used = bool(req.model and actual_backend != req.model)
            payload = {
                "type": "response",
                "response": response_text,
                "session_id": session_id,
                "backend": actual_backend,
                "backend_label": backend_label,
                "host": host,
                "fallback_used": fallback_used,
            }
            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 _request_user(request: Request) -> str | None:
    """Extract username from JWT cookie, or None."""
    try:
        token = request.cookies.get(COOKIE_NAME)
        return decode_token(token) if token else None
    except (jwt.InvalidTokenError, Exception):
        return None


def _local_model_info(request: Request) -> dict | None:
    """Return the best local model {label, model_name} for the session user, or None."""
    username = _request_user(request)
    if not username:
        return None
    try:
        cfg = model_registry.get_best_local_model(username, "chat")
        if cfg:
            return {"label": cfg.get("label", ""), "model_name": cfg.get("model_name", "")}
    except Exception:
        pass
    return None


def _chat_slot_models(username: str) -> list[dict]:
    """Return [{slot, label, type}] for each configured slot in the chat role, primary first."""
    registry = model_registry.get_registry(username)
    role_slots = registry.get("roles", {}).get("chat", {})
    result = []
    for slot_key in model_registry.PRIORITY_KEYS:
        model_id = role_slots.get(slot_key)
        if not model_id:
            continue
        resolved = model_registry._resolve_model(registry, model_id)
        if resolved:
            result.append({
                "slot":  slot_key,
                "label": resolved.get("label") or resolved.get("model_name") or "",
                "type":  resolved.get("type", ""),
            })
    return result


def _available_roles_for_toggle(username: str) -> list[dict]:
    """Return roles with a primary model assigned (excluding orchestrator) for the UI toggle.

    Returns [{role, label, model_label, type}] ordered by settings.defined_roles.
    """
    registry = model_registry.get_registry(username)
    roles_cfg = registry.get("roles", {})
    result = []
    for role_name in settings.get_defined_roles():
        if role_name == "orchestrator":
            continue
        primary_id = roles_cfg.get(role_name, {}).get("primary")
        if not primary_id:
            continue
        resolved = model_registry._resolve_model(registry, primary_id)
        if resolved:
            result.append({
                "role":        role_name,
                "label":       role_name.title(),
                "model_label": resolved.get("label") or resolved.get("model_name") or "",
                "type":        resolved.get("type", ""),
            })
    return result


@router.get("/backend")
async def get_backend(request: Request) -> dict:
    username        = _request_user(request)
    chat_models     = _chat_slot_models(username) if username else []
    available_roles = _available_roles_for_toggle(username) if username else []
    p = settings.primary_backend

    orch_label = None
    if username:
        orch_cfg = model_registry.get_model_for_role(username, "orchestrator")
        if orch_cfg:
            orch_label = orch_cfg.get("label") or orch_cfg.get("model_name") or None

    return {
        "chat_models":        chat_models,       # Phase 3: [{slot, label, type}] for chat-role slots
        "available_roles":    available_roles,    # kept for banner + backward compat
        "orchestrator_model": orch_label,
        # Legacy fields kept for backward compat
        "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)
    name = get_session_name(session_id)
    return {"session_id": session_id, "name": name, "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.post("/api/sessions/backfill-names")
async def backfill_session_names(
    request: Request,
    user: str = Query(""),
    persona: str = Query(""),
) -> dict:
    """Name every unnamed session using its first user message (truncated to 60 chars).
    Idempotent — only touches sessions that have no name set.
    user/persona default to the JWT session user + last-used persona cookie."""
    # Resolve user from JWT if not provided
    if not user:
        token = request.cookies.get(COOKIE_NAME)
        if not token:
            raise HTTPException(status_code=401, detail="Not authenticated")
        try:
            user = decode_token(token)
        except jwt.InvalidTokenError:
            raise HTTPException(status_code=401, detail="Invalid session")

    # Resolve persona from cookie if not provided
    if not persona:
        from persona import list_user_personas
        persona_cookie = request.cookies.get("cx_last_persona", "")
        available = list_user_personas(user)
        persona = persona_cookie if persona_cookie in available else (available[0] if available else "")
    if not persona:
        raise HTTPException(status_code=400, detail="No persona found for user")

    _set_ctx(user, persona)
    sessions = list_all()
    named = 0
    for s in sessions:
        if s.get("name"):
            continue
        messages = load_session(s["session_id"])
        first_user = next((m for m in messages if m.get("role") == "user"), None)
        if not first_user:
            continue
        text = (first_user.get("content") or "").strip()
        if not text:
            continue
        auto_name = text[:60].rstrip() + ("…" if len(text) > 60 else "")
        rename_session(s["session_id"], auto_name)
        named += 1
    return {"ok": True, "named": named, "total": len(sessions)}


@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}