"""In-session copilot endpoints.

Contextual AI assistant during flow navigation:
  POST /copilot/conversations        — Start conversation (requires tree_id)
  POST /copilot/conversations/{id}/messages — Send message, get response + suggestions
  GET  /copilot/conversations/{id}   — Get conversation history
"""
import logging
from typing import Annotated
from uuid import UUID

from fastapi import APIRouter, Depends, HTTPException, Request, status
from sqlalchemy.ext.asyncio import AsyncSession

from app.core.rate_limit import limiter
from app.api.deps import get_current_active_user, get_db, require_engineer_or_admin
from app.core.config import settings
from app.core.ai_quota_service import check_ai_quota, record_ai_usage, get_user_plan
from app.models.user import User
from app.schemas.copilot import (
    CopilotStartRequest,
    CopilotStartResponse,
    CopilotMessageRequest,
    CopilotMessageResponse,
    CopilotConversationResponse,
    SuggestedFlow,
)
from app.services import copilot_service

logger = logging.getLogger(__name__)

router = APIRouter(prefix="/copilot", tags=["copilot"])


def _require_ai_enabled() -> None:
    if not settings.ai_enabled:
        raise HTTPException(
            status_code=status.HTTP_503_SERVICE_UNAVAILABLE,
            detail="AI is not configured. Set GOOGLE_AI_API_KEY or ANTHROPIC_API_KEY.",
        )


@router.post("/conversations", response_model=CopilotStartResponse, status_code=201)
@limiter.limit("10/minute")
async def start_conversation(
    request: Request,
    data: CopilotStartRequest,
    current_user: Annotated[User, Depends(get_current_active_user)],
    db: Annotated[AsyncSession, Depends(get_db)],
    _: None = Depends(require_engineer_or_admin),
):
    """Start a new copilot conversation for a flow."""
    _require_ai_enabled()

    allowed, quota_status = await check_ai_quota(
        user_id=current_user.id,
        account_id=current_user.account_id,
        db=db,
        billing_anchor=current_user.ai_billing_cycle_anchor_at,
        is_super_admin=current_user.is_super_admin,
    )
    if not allowed:
        reset_key = "daily_reset_at" if quota_status.get("deny_reason") == "daily" else "monthly_reset_at"
        raise HTTPException(
            status_code=status.HTTP_429_TOO_MANY_REQUESTS,
            detail={
                "message": f"AI limit exceeded ({quota_status['deny_reason']})",
                "reset_at": quota_status.get(reset_key),
                "quota": quota_status,
            },
        )

    try:
        conversation, greeting = await copilot_service.start_conversation(
            user_id=current_user.id,
            account_id=current_user.account_id,
            tree_id=data.tree_id,
            session_id=data.session_id,
            current_node_id=data.current_node_id,
            db=db,
        )
    except ValueError as e:
        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail=str(e))
    except Exception as e:
        logger.exception("Copilot conversation start failed: %s", e)
        raise HTTPException(
            status_code=status.HTTP_502_BAD_GATEWAY,
            detail=f"AI provider error ({type(e).__name__}). Please try again.",
        )

    await db.commit()

    return CopilotStartResponse(
        conversation_id=conversation.id,
        greeting=greeting,
    )


@router.post("/conversations/{conversation_id}/messages", response_model=CopilotMessageResponse)
@limiter.limit("10/minute")
async def post_message(
    request: Request,
    conversation_id: UUID,
    data: CopilotMessageRequest,
    current_user: Annotated[User, Depends(get_current_active_user)],
    db: Annotated[AsyncSession, Depends(get_db)],
    _: None = Depends(require_engineer_or_admin),
):
    """Send a message and get AI response with flow suggestions."""
    _require_ai_enabled()

    plan = await get_user_plan(current_user.account_id, db)

    try:
        ai_content, suggested_flows = await copilot_service.send_message(
            conversation_id=conversation_id,
            user_id=current_user.id,
            message=data.message,
            current_node_id=data.current_node_id,
            db=db,
        )
    except ValueError as e:
        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail=str(e))
    except Exception as e:
        logger.exception("Copilot message failed: %s", e)
        await record_ai_usage(
            user_id=current_user.id,
            account_id=current_user.account_id,
            conversation_id=None,
            generation_type="copilot_message",
            tier=plan,
            input_tokens=0,
            output_tokens=0,
            estimated_cost=0,
            succeeded=False,
            counts_toward_quota=False,
            error_code=type(e).__name__,
            extra_data={"copilot_conversation_id": str(conversation_id)},
            db=db,
        )
        await db.commit()
        raise HTTPException(
            status_code=status.HTTP_502_BAD_GATEWAY,
            detail=f"AI provider error ({type(e).__name__}). Please try again.",
        )

    await record_ai_usage(
        user_id=current_user.id,
        account_id=current_user.account_id,
        conversation_id=None,
        generation_type="copilot_message",
        tier=plan,
        input_tokens=0,
        output_tokens=0,
        estimated_cost=0,
        succeeded=True,
        counts_toward_quota=False,
        error_code=None,
        extra_data={"copilot_conversation_id": str(conversation_id)},
        db=db,
    )
    await db.commit()

    return CopilotMessageResponse(
        content=ai_content,
        suggested_flows=[SuggestedFlow(**sf) for sf in suggested_flows],
    )


@router.get("/conversations/{conversation_id}", response_model=CopilotConversationResponse)
async def get_conversation(
    conversation_id: UUID,
    current_user: Annotated[User, Depends(get_current_active_user)],
    db: Annotated[AsyncSession, Depends(get_db)],
):
    """Get copilot conversation history."""
    from sqlalchemy import select
    from app.models.copilot_conversation import CopilotConversation

    result = await db.execute(
        select(CopilotConversation).where(
            CopilotConversation.id == conversation_id,
            CopilotConversation.user_id == current_user.id,
        )
    )
    conversation = result.scalar_one_or_none()
    if not conversation:
        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="Conversation not found")

    return CopilotConversationResponse.model_validate(conversation)