import json
from datetime import datetime, timezone
from uuid import UUID

from fastapi import APIRouter, Depends, HTTPException

from app.middleware.auth import get_current_user_id
from app.models import (
    OpenSessionOut,
    ResumeCard,
    SessionCheckpointRequest,
    SessionEndRequest,
    SessionJoinRequest,
    SessionJoinResponse,
    SessionOut,
    SessionResumeResponse,
    SessionStartRequest,
    StepOut,
)
from app.services import llm, push
from app.services.db import get_pool

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

SESSION_COLUMNS = "id, user_id, task_id, platform, started_at, ended_at, status, checkpoint, created_at"


def _parse_session_row(row) -> SessionOut:
    result = dict(row)
    result["checkpoint"] = json.loads(result["checkpoint"]) if isinstance(result["checkpoint"], str) else result["checkpoint"]
    return SessionOut(**result)


@router.post("/start", response_model=SessionOut, status_code=201)
async def start_session(req: SessionStartRequest, user_id: str = Depends(get_current_user_id)):
    pool = await get_pool()

    # Check if an active session already exists for this account
    active = await pool.fetchrow(
        f"SELECT {SESSION_COLUMNS} FROM sessions WHERE user_id = $1::uuid AND status = 'active'",
        user_id,
    )
    if active:
        # Idempotently return the existing active session and don't create a new one
        return _parse_session_row(active)

    checkpoint = {}
    if req.task_id:
        task = await pool.fetchrow(
            "SELECT id, title, description FROM tasks WHERE id = $1 AND user_id = $2::uuid",
            req.task_id,
            user_id,
        )
        if not task:
            raise HTTPException(status_code=404, detail="Task not found")

        await pool.execute(
            "UPDATE tasks SET status = 'in_progress', updated_at = now() WHERE id = $1",
            req.task_id,
        )
        checkpoint["goal"] = task["title"]

    if req.work_app_bundle_ids:
        checkpoint["work_app_bundle_ids"] = req.work_app_bundle_ids

    checkpoint["devices"] = [req.platform]

    row = await pool.fetchrow(
        f"""INSERT INTO sessions (user_id, task_id, platform, checkpoint)
            VALUES ($1::uuid, $2, $3, $4)
            RETURNING {SESSION_COLUMNS}""",
        user_id,
        req.task_id,
        req.platform,
        json.dumps(checkpoint),
    )

    # Notify other devices about new session
    if req.task_id:
        task_row = await pool.fetchrow("SELECT title FROM tasks WHERE id = $1", req.task_id)
        task_title = task_row["title"] if task_row else "Focus Session"
        await push.send_push(user_id, "ipad" if req.platform == "mac" else "mac", {
            "type": "session_started",
            "session_id": str(row["id"]),
            "task_title": task_title,
            "platform": req.platform,
        })
        # Start Live Activity on all registered devices
        await push.send_activity_start(user_id, task_title, task_id=req.task_id)

    return _parse_session_row(row)


@router.get("/active", response_model=SessionOut)
async def get_active_session(user_id: str = Depends(get_current_user_id)):
    pool = await get_pool()
    row = await pool.fetchrow(
        f"SELECT {SESSION_COLUMNS} FROM sessions WHERE user_id = $1::uuid AND status = 'active'",
        user_id,
    )
    if not row:
        raise HTTPException(status_code=404, detail="No active session")
    return _parse_session_row(row)


@router.get("/open", response_model=list[OpenSessionOut])
async def get_open_sessions(user_id: str = Depends(get_current_user_id)):
    """All active + interrupted sessions. Used by VLM on startup for session-aware analysis."""
    pool = await get_pool()
    rows = await pool.fetch(
        f"SELECT {SESSION_COLUMNS} FROM sessions WHERE user_id = $1::uuid AND status IN ('active', 'interrupted') ORDER BY started_at DESC",
        user_id,
    )
    results = []
    for row in rows:
        checkpoint = json.loads(row["checkpoint"]) if isinstance(row["checkpoint"], str) else (row["checkpoint"] or {})
        task_info = None
        if row["task_id"]:
            task_row = await pool.fetchrow(
                "SELECT title, description FROM tasks WHERE id = $1", row["task_id"]
            )
            if task_row:
                task_info = {"title": task_row["title"], "goal": task_row["description"]}
        results.append(OpenSessionOut(
            id=row["id"],
            task_id=row["task_id"],
            task=task_info,
            status=row["status"],
            platform=row["platform"],
            started_at=row["started_at"],
            ended_at=row["ended_at"],
            checkpoint=checkpoint,
        ))
    return results


@router.post("/{session_id}/join", response_model=SessionJoinResponse)
async def join_session(
    session_id: UUID,
    req: SessionJoinRequest,
    user_id: str = Depends(get_current_user_id),
):
    pool = await get_pool()

    session = await pool.fetchrow(
        f"SELECT {SESSION_COLUMNS} FROM sessions WHERE id = $1 AND user_id = $2::uuid",
        session_id,
        user_id,
    )
    if not session:
        raise HTTPException(status_code=404, detail="Session not found")
    if session["status"] != "active":
        raise HTTPException(status_code=400, detail="Session is not active")

    # Update checkpoint with joining device
    checkpoint = json.loads(session["checkpoint"]) if isinstance(session["checkpoint"], str) else (session["checkpoint"] or {})
    devices = checkpoint.get("devices", [session["platform"]])
    if req.platform not in devices:
        devices.append(req.platform)
    checkpoint["devices"] = devices
    if req.work_app_bundle_ids:
        checkpoint["work_app_bundle_ids"] = req.work_app_bundle_ids

    await pool.execute(
        "UPDATE sessions SET checkpoint = $1 WHERE id = $2",
        json.dumps(checkpoint),
        session_id,
    )

    # Build response with full task + step context
    task_info = None
    current_step = None
    all_steps = []
    suggested_app_scheme = None
    suggested_app_name = None

    if session["task_id"]:
        task_row = await pool.fetchrow(
            "SELECT id, title, description FROM tasks WHERE id = $1",
            session["task_id"],
        )
        if task_row:
            task_info = {
                "id": str(task_row["id"]),
                "title": task_row["title"],
                "goal": task_row["description"],
            }
            # Suggest a work app based on task
            try:
                suggestion = await llm.suggest_work_apps(task_row["title"], task_row["description"])
                suggested_app_scheme = suggestion.get("suggested_app_scheme")
                suggested_app_name = suggestion.get("suggested_app_name")
            except Exception:
                pass

        step_rows = await pool.fetch(
            """SELECT id, task_id, sort_order, title, description, estimated_minutes,
                      status, checkpoint_note, last_checked_at, completed_at, created_at
               FROM steps WHERE task_id = $1 ORDER BY sort_order""",
            session["task_id"],
        )
        all_steps = [StepOut(**dict(r)) for r in step_rows]

        # Find current in-progress step
        for s in step_rows:
            if s["status"] == "in_progress":
                current_step = {
                    "id": str(s["id"]),
                    "title": s["title"],
                    "status": s["status"],
                    "checkpoint_note": s["checkpoint_note"],
                }
                break

    return SessionJoinResponse(
        session_id=session["id"],
        joined=True,
        task=task_info,
        current_step=current_step,
        all_steps=all_steps,
        suggested_app_scheme=suggested_app_scheme,
        suggested_app_name=suggested_app_name,
    )


@router.post("/{session_id}/checkpoint", response_model=SessionOut)
async def save_checkpoint(
    session_id: UUID,
    req: SessionCheckpointRequest,
    user_id: str = Depends(get_current_user_id),
):
    pool = await get_pool()

    session = await pool.fetchrow(
        "SELECT id, status FROM sessions WHERE id = $1 AND user_id = $2::uuid",
        session_id,
        user_id,
    )
    if not session:
        raise HTTPException(status_code=404, detail="Session not found")
    if session["status"] != "active":
        raise HTTPException(status_code=400, detail="Session is not active")

    checkpoint = req.model_dump(exclude_unset=True)
    if "current_step_id" in checkpoint and checkpoint["current_step_id"]:
        checkpoint["current_step_id"] = str(checkpoint["current_step_id"])

    row = await pool.fetchrow(
        f"""UPDATE sessions SET checkpoint = checkpoint || $1::jsonb
            WHERE id = $2
            RETURNING {SESSION_COLUMNS}""",
        json.dumps(checkpoint),
        session_id,
    )
    return _parse_session_row(row)


@router.post("/{session_id}/end", response_model=SessionOut)
async def end_session(
    session_id: UUID,
    req: SessionEndRequest,
    user_id: str = Depends(get_current_user_id),
):
    pool = await get_pool()

    row = await pool.fetchrow(
        f"""UPDATE sessions SET status = $1, ended_at = now()
            WHERE id = $2 AND user_id = $3::uuid AND status = 'active'
            RETURNING {SESSION_COLUMNS}""",
        req.status,
        session_id,
        user_id,
    )
    if not row:
        raise HTTPException(status_code=404, detail="Active session not found")

    # Notify other joined devices that session ended
    checkpoint = json.loads(row["checkpoint"]) if isinstance(row["checkpoint"], str) else (row["checkpoint"] or {})
    devices = checkpoint.get("devices", [])
    for device in devices:
        if device != row["platform"]:
            await push.send_push(user_id, device, {
                "type": "session_ended",
                "session_id": str(row["id"]),
                "ended_by": row["platform"],
            })

    # End Live Activity on all devices
    task_title = checkpoint.get("goal", "Session ended")
    await push.send_activity_end(user_id, task_title=task_title, task_id=row["task_id"])

    return _parse_session_row(row)


@router.get("/{session_id}/resume", response_model=SessionResumeResponse)
async def resume_session(session_id: UUID, user_id: str = Depends(get_current_user_id)):
    pool = await get_pool()

    session = await pool.fetchrow(
        f"SELECT {SESSION_COLUMNS} FROM sessions WHERE id = $1 AND user_id = $2::uuid",
        session_id,
        user_id,
    )
    if not session:
        raise HTTPException(status_code=404, detail="Session not found")

    checkpoint = json.loads(session["checkpoint"]) if isinstance(session["checkpoint"], str) else (session["checkpoint"] or {})

    task_info = None
    current_step = None
    completed_count = 0
    total_count = 0
    next_step_title = None

    if session["task_id"]:
        task_row = await pool.fetchrow(
            "SELECT id, title, description FROM tasks WHERE id = $1",
            session["task_id"],
        )
        if task_row:
            task_info = {"title": task_row["title"], "overall_goal": task_row["description"]}

        step_rows = await pool.fetch(
            "SELECT id, sort_order, title, status, checkpoint_note, last_checked_at FROM steps WHERE task_id = $1 ORDER BY sort_order",
            session["task_id"],
        )
        total_count = len(step_rows)

        found_current = False
        for s in step_rows:
            if s["status"] == "done":
                completed_count += 1
            elif s["status"] == "in_progress" and not found_current:
                current_step = {
                    "id": str(s["id"]),
                    "title": s["title"],
                    "checkpoint_note": s["checkpoint_note"],
                    "last_checked_at": s["last_checked_at"].isoformat() if s["last_checked_at"] else None,
                }
                found_current = True
            elif found_current and next_step_title is None:
                next_step_title = s["title"]

    now = datetime.now(timezone.utc)
    last_activity = session["ended_at"] or session["started_at"]
    minutes_away = int((now - last_activity).total_seconds() / 60)

    resume_card_data = await llm.generate_resume_card(
        task_title=task_info["title"] if task_info else "Unknown task",
        goal=task_info.get("overall_goal") if task_info else None,
        current_step_title=current_step["title"] if current_step else None,
        checkpoint_note=current_step["checkpoint_note"] if current_step else None,
        completed_count=completed_count,
        total_count=total_count,
        next_step_title=next_step_title,
        minutes_away=minutes_away,
        attention_score=checkpoint.get("attention_score"),
    )

    return SessionResumeResponse(
        session_id=session["id"],
        task=task_info,
        current_step=current_step,
        progress={
            "completed": completed_count,
            "total": total_count,
            "attention_score": checkpoint.get("attention_score"),
            "distraction_count": checkpoint.get("distraction_count", 0),
        },
        resume_card=ResumeCard(**resume_card_data),
    )