from fastapi import APIRouter, Depends, HTTPException, Query
from sqlalchemy.ext.asyncio import AsyncSession
from sqlalchemy import select, func, desc, delete
from pydantic import BaseModel
from typing import Optional, List
from datetime import datetime

from app.core.database import get_db
from app.core.security import get_current_user
from app.models.user import User, Activity, ActivityDataPoint, ActivityLap, PersonalRecord

router = APIRouter()


class ActivitySummary(BaseModel):
    id: int
    name: str
    sport_type: str
    start_time: datetime
    distance_m: Optional[float]
    duration_s: Optional[float]
    elevation_gain_m: Optional[float]
    avg_heart_rate: Optional[float]
    avg_cadence: Optional[float]
    avg_speed_ms: Optional[float]
    calories: Optional[float]
    polyline: Optional[str]
    bounding_box: Optional[dict]
    hr_zones: Optional[dict]
    named_route_id: Optional[int]

    class Config:
        from_attributes = True


class ActivityDetail(ActivitySummary):
    end_time: Optional[datetime]
    elevation_loss_m: Optional[float]
    max_heart_rate: Optional[float]
    avg_power: Optional[float]
    normalized_power: Optional[float]
    max_speed_ms: Optional[float]
    avg_temperature_c: Optional[float]
    training_stress_score: Optional[float]
    vo2max_estimate: Optional[float]


class DataPointOut(BaseModel):
    timestamp: Optional[datetime]
    latitude: Optional[float]
    longitude: Optional[float]
    altitude_m: Optional[float]
    heart_rate: Optional[float]
    cadence: Optional[float]
    speed_ms: Optional[float]
    power: Optional[float]
    temperature_c: Optional[float]
    distance_m: Optional[float]

    class Config:
        from_attributes = True


class LapOut(BaseModel):
    lap_number: int
    start_time: Optional[datetime]
    duration_s: Optional[float]
    distance_m: Optional[float]
    avg_heart_rate: Optional[float]
    avg_cadence: Optional[float]
    avg_speed_ms: Optional[float]
    avg_power: Optional[float]

    class Config:
        from_attributes = True


@router.get("/stats/ytd")
async def ytd_stats(
    db: AsyncSession = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    """Return year-to-date distance totals grouped by sport type."""
    from datetime import date, timezone
    year_start = datetime(date.today().year, 1, 1, tzinfo=timezone.utc)
    result = await db.execute(
        select(Activity.sport_type, func.sum(Activity.distance_m).label("total_m"))
        .where(Activity.user_id == current_user.id, Activity.start_time >= year_start)
        .group_by(Activity.sport_type)
    )
    rows = result.all()
    totals = {r.sport_type: (r.total_m or 0) / 1000 for r in rows}
    return {
        "running_km": round(totals.get("running", 0), 2),
        "cycling_km": round(totals.get("cycling", 0), 2),
        "hiking_km": round(totals.get("hiking", 0), 2),
        "walking_km": round(totals.get("walking", 0), 2),
        "total_km": round(sum(totals.values()), 2),
    }


@router.get("/", response_model=List[ActivitySummary])
async def list_activities(
    page: int = Query(1, ge=1),
    per_page: int = Query(20, ge=1, le=100),
    sport_type: Optional[str] = None,
    from_date: Optional[datetime] = None,
    to_date: Optional[datetime] = None,
    db: AsyncSession = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    q = select(Activity).where(Activity.user_id == current_user.id)

    if sport_type:
        q = q.where(Activity.sport_type == sport_type)
    if from_date:
        q = q.where(Activity.start_time >= from_date)
    if to_date:
        q = q.where(Activity.start_time <= to_date)

    q = q.order_by(desc(Activity.start_time))
    q = q.offset((page - 1) * per_page).limit(per_page)

    result = await db.execute(q)
    return result.scalars().all()


@router.get("/{activity_id}", response_model=ActivityDetail)
async def get_activity(
    activity_id: int,
    db: AsyncSession = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    result = await db.execute(
        select(Activity).where(
            Activity.id == activity_id,
            Activity.user_id == current_user.id,
        )
    )
    activity = result.scalar_one_or_none()
    if not activity:
        raise HTTPException(status_code=404, detail="Activity not found")
    return activity


@router.get("/{activity_id}/data-points", response_model=List[DataPointOut])
async def get_data_points(
    activity_id: int,
    downsample: int = Query(0, ge=0, description="Return every Nth point; 0 = all"),
    db: AsyncSession = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    act = await db.execute(
        select(Activity).where(
            Activity.id == activity_id,
            Activity.user_id == current_user.id,
        )
    )
    if not act.scalar_one_or_none():
        raise HTTPException(status_code=404, detail="Activity not found")

    q = select(ActivityDataPoint).where(
        ActivityDataPoint.activity_id == activity_id
    ).order_by(ActivityDataPoint.timestamp)

    result = await db.execute(q)
    points = result.scalars().all()

    if downsample > 1:
        points = points[::downsample]

    return points


@router.get("/{activity_id}/laps", response_model=List[LapOut])
async def get_laps(
    activity_id: int,
    db: AsyncSession = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    act = await db.execute(
        select(Activity).where(
            Activity.id == activity_id,
            Activity.user_id == current_user.id,
        )
    )
    if not act.scalar_one_or_none():
        raise HTTPException(status_code=404, detail="Activity not found")

    result = await db.execute(
        select(ActivityLap)
        .where(ActivityLap.activity_id == activity_id)
        .order_by(ActivityLap.lap_number)
    )
    return result.scalars().all()


@router.get("/{activity_id}/lap-bests")
async def get_lap_bests(
    activity_id: int,
    db: AsyncSession = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    """Best (fastest) time per lap number across all activities on the same route."""
    act = (await db.execute(
        select(Activity).where(
            Activity.id == activity_id,
            Activity.user_id == current_user.id,
        )
    )).scalar_one_or_none()
    if not act:
        raise HTTPException(status_code=404, detail="Activity not found")
    if not act.named_route_id:
        return {}

    # Best per lap number across OTHER activities on the same route, so the
    # comparison is meaningful (excluding this activity from its own benchmark).
    rows = (await db.execute(
        select(ActivityLap.lap_number, func.min(ActivityLap.duration_s))
        .join(Activity, Activity.id == ActivityLap.activity_id)
        .where(
            Activity.named_route_id == act.named_route_id,
            Activity.user_id == current_user.id,
            Activity.id != activity_id,
            ActivityLap.duration_s.isnot(None),
        )
        .group_by(ActivityLap.lap_number)
    )).all()
    return {str(lap_number): best for lap_number, best in rows}


@router.get("/{activity_id}/route-leaderboard")
async def get_route_leaderboard(
    activity_id: int,
    db: AsyncSession = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    """Fastest-time leaderboard across all of this user's activities on the same
    route. Returns this activity's rank/gap plus the top 10. Null if the activity
    has no associated route (or no timed efforts to rank)."""
    act = (await db.execute(
        select(Activity).where(
            Activity.id == activity_id,
            Activity.user_id == current_user.id,
        )
    )).scalar_one_or_none()
    if not act:
        raise HTTPException(status_code=404, detail="Activity not found")
    if not act.named_route_id:
        return None

    rows = (await db.execute(
        select(
            Activity.id, Activity.name, Activity.start_time,
            Activity.duration_s, Activity.distance_m, Activity.avg_heart_rate,
        )
        .where(
            Activity.named_route_id == act.named_route_id,
            Activity.user_id == current_user.id,
            Activity.duration_s.isnot(None),
        )
        .order_by(Activity.duration_s)
    )).all()
    if not rows:
        return None

    fastest_s = rows[0].duration_s
    entries = []
    current = None
    for i, r in enumerate(rows):
        entry = {
            "rank": i + 1,
            "activity_id": r.id,
            "name": r.name,
            "start_time": r.start_time,
            "duration_s": r.duration_s,
            "distance_m": r.distance_m,
            "avg_heart_rate": r.avg_heart_rate,
            "gap_s": r.duration_s - fastest_s,
            "is_current": r.id == activity_id,
        }
        if entry["is_current"]:
            current = entry
        entries.append(entry)

    return {
        "route_id": act.named_route_id,
        "total": len(entries),
        "fastest_s": fastest_s,
        "current": current,
        "top": entries[:10],
    }


@router.patch("/{activity_id}/name")
async def rename_activity(
    activity_id: int,
    body: dict,
    db: AsyncSession = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    result = await db.execute(
        select(Activity).where(
            Activity.id == activity_id,
            Activity.user_id == current_user.id,
        )
    )
    activity = result.scalar_one_or_none()
    if not activity:
        raise HTTPException(status_code=404, detail="Activity not found")

    activity.name = body.get("name", activity.name)
    await db.commit()
    return {"id": activity_id, "name": activity.name}


@router.delete("/{activity_id}", status_code=204)
async def delete_activity(
    activity_id: int,
    db: AsyncSession = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    result = await db.execute(
        select(Activity).where(
            Activity.id == activity_id,
            Activity.user_id == current_user.id,
        )
    )
    activity = result.scalar_one_or_none()
    if not activity:
        raise HTTPException(status_code=404, detail="Activity not found")
    # PersonalRecord.activity_id has no cascade, so remove the activity's PR rows
    # first or the delete fails the FK constraint. (segment_efforts cascade in DB;
    # data_points/laps cascade via the ORM relationship.)
    await db.execute(delete(PersonalRecord).where(PersonalRecord.activity_id == activity_id))
    await db.delete(activity)
    await db.commit()


@router.post("/{activity_id}/reprocess")
async def reprocess_activity(
    activity_id: int,
    db: AsyncSession = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    """Re-parse the source FIT file and update polyline, data points etc."""
    import os
    result = await db.execute(
        select(Activity).where(
            Activity.id == activity_id,
            Activity.user_id == current_user.id,
        )
    )
    activity = result.scalar_one_or_none()
    if not activity:
        raise HTTPException(status_code=404, detail="Activity not found")
    if not activity.source_file:
        raise HTTPException(status_code=400, detail="No source file stored for this activity")
    if not os.path.exists(activity.source_file):
        raise HTTPException(status_code=404, detail="Source file no longer exists on disk")

    source_file = activity.source_file
    source_type = activity.source_type or "fit"

    await db.execute(delete(ActivityDataPoint).where(ActivityDataPoint.activity_id == activity_id))
    await db.execute(delete(ActivityLap).where(ActivityLap.activity_id == activity_id))
    # Drop PR rows referencing this activity (no cascade); the re-parse re-computes them.
    await db.execute(delete(PersonalRecord).where(PersonalRecord.activity_id == activity_id))
    await db.delete(activity)
    await db.commit()

    from app.workers.tasks import process_activity_file
    task = process_activity_file.delay(source_file, current_user.id, source_type)
    return {"task_id": task.id, "status": "queued"}