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

from app.core.database import get_db
from app.core.security import get_current_user
from app.models.user import User, NamedRoute, RouteSegment, Activity

router = APIRouter()


class SegmentCreate(BaseModel):
    name: str
    start_distance_m: float
    end_distance_m: float
    description: Optional[str] = None


class RouteCreate(BaseModel):
    name: str
    description: Optional[str] = None
    sport_type: Optional[str] = None
    activity_id: int


class RouteOut(BaseModel):
    id: int
    name: str
    description: Optional[str]
    sport_type: Optional[str]
    reference_polyline: Optional[str]
    bounding_box: Optional[dict]
    distance_m: Optional[float]
    auto_detected: Optional[bool]
    created_at: datetime
    activity_count: int = 0

    class Config:
        from_attributes = True


class SegmentOut(BaseModel):
    id: int
    name: str
    start_distance_m: float
    end_distance_m: float
    description: Optional[str]
    auto_generated: Optional[bool] = False
    auto_generated_type: Optional[str] = None

    class Config:
        from_attributes = True


class AutoGenerateRequest(BaseModel):
    type: str  # "1km" | "turns" | "hills"
    gradient_pct: float = 5.0
    turn_angle_deg: float = 45.0


class SegmentTimeEntry(BaseModel):
    activity_id: int
    date: datetime
    name: str
    duration_s: float


@router.get("/", response_model=List[RouteOut])
async def list_routes(
    db: AsyncSession = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    # Fetch routes with activity counts in one query
    count_subq = (
        select(Activity.named_route_id, func.count(Activity.id).label("cnt"))
        .where(Activity.user_id == current_user.id, Activity.named_route_id.isnot(None))
        .group_by(Activity.named_route_id)
        .subquery()
    )
    result = await db.execute(
        select(NamedRoute, func.coalesce(count_subq.c.cnt, 0).label("activity_count"))
        .outerjoin(count_subq, NamedRoute.id == count_subq.c.named_route_id)
        .where(NamedRoute.user_id == current_user.id)
        .order_by(desc(NamedRoute.created_at))
    )
    rows = result.all()
    out = []
    for route, cnt in rows:
        d = {c.name: getattr(route, c.name) for c in route.__table__.columns}
        d["activity_count"] = cnt
        out.append(RouteOut(**d))
    return out


@router.get("/recent-activities")
async def recent_activities_for_route(
    days: int = Query(14, ge=1, le=90),
    sport_type: Optional[str] = None,
    db: AsyncSession = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    """Return recent activities for the route creation dropdown."""
    cutoff = datetime.now(timezone.utc) - timedelta(days=days)
    q = select(Activity).where(
        Activity.user_id == current_user.id,
        Activity.start_time >= cutoff,
        Activity.sport_type != "swimming",
    )
    if sport_type:
        q = q.where(Activity.sport_type == sport_type)
    q = q.order_by(desc(Activity.start_time)).limit(50)
    result = await db.execute(q)
    activities = result.scalars().all()
    return [
        {
            "id": a.id,
            "name": a.name,
            "sport_type": a.sport_type,
            "start_time": a.start_time,
            "distance_m": a.distance_m,
            "duration_s": a.duration_s,
        }
        for a in activities
    ]


@router.post("/", response_model=RouteOut)
async def create_route(
    body: RouteCreate,
    db: AsyncSession = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    act_result = await db.execute(
        select(Activity).where(
            Activity.id == body.activity_id,
            Activity.user_id == current_user.id,
        )
    )
    activity = act_result.scalar_one_or_none()
    if not activity:
        raise HTTPException(status_code=404, detail="Activity not found")

    route = NamedRoute(
        user_id=current_user.id,
        name=body.name,
        description=body.description,
        sport_type=body.sport_type or activity.sport_type,
        reference_polyline=activity.polyline,
        bounding_box=activity.bounding_box,
        distance_m=activity.distance_m,
        auto_detected=False,
    )
    db.add(route)
    await db.flush()
    activity.named_route_id = route.id
    await db.commit()
    await db.refresh(route)
    return route


@router.get("/{route_id}", response_model=RouteOut)
async def get_route(
    route_id: int,
    db: AsyncSession = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    result = await db.execute(
        select(NamedRoute).where(
            NamedRoute.id == route_id,
            NamedRoute.user_id == current_user.id,
        )
    )
    route = result.scalar_one_or_none()
    if not route:
        raise HTTPException(status_code=404, detail="Route not found")
    return route


@router.get("/{route_id}/activities")
async def route_activities(
    route_id: int,
    db: AsyncSession = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    result = await db.execute(
        select(Activity).where(
            Activity.named_route_id == route_id,
            Activity.user_id == current_user.id,
        ).order_by(Activity.duration_s)
    )
    activities = result.scalars().all()
    return [
        {
            "id": a.id,
            "name": a.name,
            "start_time": a.start_time,
            "duration_s": a.duration_s,
            "distance_m": a.distance_m,
            "avg_heart_rate": a.avg_heart_rate,
            "avg_speed_ms": a.avg_speed_ms,
        }
        for a in activities
    ]


@router.post("/{route_id}/merge/{source_id}", response_model=RouteOut)
async def merge_routes(
    route_id: int,
    source_id: int,
    db: AsyncSession = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    """Move all activities from source route into route_id, then delete source route."""
    from sqlalchemy import update

    target = (await db.execute(
        select(NamedRoute).where(NamedRoute.id == route_id, NamedRoute.user_id == current_user.id)
    )).scalar_one_or_none()
    source = (await db.execute(
        select(NamedRoute).where(NamedRoute.id == source_id, NamedRoute.user_id == current_user.id)
    )).scalar_one_or_none()
    if not target or not source:
        raise HTTPException(status_code=404, detail="Route not found")
    if route_id == source_id:
        raise HTTPException(status_code=400, detail="Cannot merge a route with itself")

    await db.execute(
        update(Activity)
        .where(Activity.named_route_id == source_id, Activity.user_id == current_user.id)
        .values(named_route_id=route_id)
    )
    await db.delete(source)
    await db.commit()
    await db.refresh(target)
    return target


@router.delete("/{route_id}")
async def delete_route(
    route_id: int,
    db: AsyncSession = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    from sqlalchemy import update as sa_update
    route = (await db.execute(
        select(NamedRoute).where(NamedRoute.id == route_id, NamedRoute.user_id == current_user.id)
    )).scalar_one_or_none()
    if not route:
        raise HTTPException(status_code=404, detail="Route not found")
    # Unlink activities before deleting
    await db.execute(
        sa_update(Activity)
        .where(Activity.named_route_id == route_id, Activity.user_id == current_user.id)
        .values(named_route_id=None)
    )
    await db.delete(route)
    await db.commit()
    return {"status": "ok"}


@router.post("/{route_id}/assign-activity")
async def assign_activity_to_route(
    route_id: int,
    body: dict,
    db: AsyncSession = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    activity_id = body.get("activity_id")
    act_result = await db.execute(
        select(Activity).where(
            Activity.id == activity_id,
            Activity.user_id == current_user.id,
        )
    )
    activity = act_result.scalar_one_or_none()
    if not activity:
        raise HTTPException(status_code=404, detail="Activity not found")
    activity.named_route_id = route_id
    await db.commit()
    return {"status": "ok"}


async def _get_owned_route(route_id: int, user_id: int, db: AsyncSession) -> NamedRoute:
    result = await db.execute(
        select(NamedRoute).where(NamedRoute.id == route_id, NamedRoute.user_id == user_id)
    )
    route = result.scalar_one_or_none()
    if not route:
        raise HTTPException(status_code=404, detail="Route not found")
    return route


@router.get("/{route_id}/segments", response_model=List[SegmentOut])
async def list_segments(
    route_id: int,
    db: AsyncSession = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    await _get_owned_route(route_id, current_user.id, db)
    result = await db.execute(
        select(RouteSegment)
        .where(RouteSegment.route_id == route_id)
        .order_by(RouteSegment.start_distance_m)
    )
    return result.scalars().all()


@router.post("/{route_id}/segments", response_model=SegmentOut)
async def create_segment(
    route_id: int,
    body: SegmentCreate,
    db: AsyncSession = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    await _get_owned_route(route_id, current_user.id, db)
    segment = RouteSegment(
        route_id=route_id,
        name=body.name,
        start_distance_m=body.start_distance_m,
        end_distance_m=body.end_distance_m,
        description=body.description,
        auto_generated=False,
    )
    db.add(segment)
    await db.commit()
    await db.refresh(segment)
    return segment


@router.delete("/{route_id}/segments/{segment_id}", status_code=204)
async def delete_segment(
    route_id: int,
    segment_id: int,
    db: AsyncSession = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    await _get_owned_route(route_id, current_user.id, db)
    result = await db.execute(
        select(RouteSegment).where(
            RouteSegment.id == segment_id, RouteSegment.route_id == route_id
        )
    )
    seg = result.scalar_one_or_none()
    if not seg:
        raise HTTPException(status_code=404, detail="Segment not found")
    await db.delete(seg)
    await db.commit()


@router.post("/{route_id}/segments/auto", response_model=List[SegmentOut])
async def auto_generate_segments(
    route_id: int,
    body: AutoGenerateRequest,
    db: AsyncSession = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    """Auto-generate segments: 1km splits, turns, or hills."""
    from app.services.route_matcher import (
        generate_1km_segments, generate_turn_segments, generate_hill_segments,
    )
    from sqlalchemy import delete as sql_delete

    route = await _get_owned_route(route_id, current_user.id, db)

    if body.type not in ("1km", "turns", "hills"):
        raise HTTPException(status_code=400, detail="type must be '1km', 'turns', or 'hills'")

    # Clear only auto-generated segments of the same type so other auto types are preserved
    await db.execute(
        sql_delete(RouteSegment).where(
            RouteSegment.route_id == route_id,
            RouteSegment.auto_generated == True,
            RouteSegment.auto_generated_type == body.type,
        )
    )

    raw_segments: list[tuple[str, float, float]] = []

    if body.type == "1km":
        if not route.distance_m:
            raise HTTPException(status_code=400, detail="Route has no distance recorded")
        raw_segments = generate_1km_segments(route.reference_polyline or "", route.distance_m)

    elif body.type == "turns":
        if not route.reference_polyline:
            raise HTTPException(status_code=400, detail="Route has no polyline")
        raw_segments = generate_turn_segments(route.reference_polyline, body.turn_angle_deg)

    elif body.type == "hills":
        if not route.reference_polyline:
            raise HTTPException(status_code=400, detail="Route has no polyline")
        # Find most recent matched activity for elevation data
        act_result = await db.execute(
            select(Activity)
            .where(Activity.named_route_id == route_id, Activity.user_id == current_user.id)
            .order_by(desc(Activity.start_time))
            .limit(1)
        )
        act = act_result.scalar_one_or_none()
        if not act:
            raise HTTPException(status_code=400, detail="No matched activities found for elevation data")
        from app.models.user import ActivityDataPoint
        dp_result = await db.execute(
            select(ActivityDataPoint)
            .where(ActivityDataPoint.activity_id == act.id)
            .order_by(ActivityDataPoint.timestamp)
        )
        dps = dp_result.scalars().all()
        dp_list = [{"distance_m": p.distance_m, "altitude_m": p.altitude_m} for p in dps]
        raw_segments = generate_hill_segments(dp_list, body.gradient_pct)

    new_segments = []
    for name, start_m, end_m in raw_segments:
        seg = RouteSegment(
            route_id=route_id,
            name=name,
            start_distance_m=start_m,
            end_distance_m=end_m,
            auto_generated=True,
            auto_generated_type=body.type,
        )
        db.add(seg)
        new_segments.append(seg)

    await db.commit()
    for seg in new_segments:
        await db.refresh(seg)
    return new_segments


class SegmentBestOut(BaseModel):
    segment_id: int
    name: str
    start_distance_m: float
    end_distance_m: float
    auto_generated: bool
    best_s: Optional[float]
    best_activity_id: Optional[int]
    count: int


@router.get("/{route_id}/segment-bests", response_model=List[SegmentBestOut])
async def get_segment_bests(
    route_id: int,
    db: AsyncSession = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    """Return best time per segment across all matched activities for a route."""
    from app.services.route_matcher import find_segment_times
    from app.models.user import ActivityDataPoint
    from collections import defaultdict

    await _get_owned_route(route_id, current_user.id, db)

    segs_result = await db.execute(
        select(RouteSegment)
        .where(RouteSegment.route_id == route_id)
        .order_by(RouteSegment.start_distance_m)
    )
    segments = segs_result.scalars().all()
    if not segments:
        return []

    acts_result = await db.execute(
        select(Activity)
        .where(Activity.named_route_id == route_id, Activity.user_id == current_user.id)
        .order_by(desc(Activity.start_time))
        .limit(20)
    )
    activities = acts_result.scalars().all()
    if not activities:
        return [
            SegmentBestOut(
                segment_id=s.id, name=s.name,
                start_distance_m=s.start_distance_m, end_distance_m=s.end_distance_m,
                auto_generated=bool(s.auto_generated), best_s=None, best_activity_id=None, count=0,
            )
            for s in segments
        ]

    act_ids = [a.id for a in activities]

    dp_result = await db.execute(
        select(ActivityDataPoint)
        .where(ActivityDataPoint.activity_id.in_(act_ids))
        .order_by(ActivityDataPoint.activity_id, ActivityDataPoint.timestamp)
    )
    all_dps = dp_result.scalars().all()

    # Group data points by activity_id
    dp_by_act = defaultdict(list)
    for dp in all_dps:
        if dp.distance_m is not None:
            dp_by_act[dp.activity_id].append({"distance_m": dp.distance_m, "timestamp": dp.timestamp})

    bests = []
    for seg in segments:
        best_s = None
        best_act_id = None
        count = 0
        for act_id in act_ids:
            dp_list = dp_by_act.get(act_id, [])
            duration = find_segment_times(dp_list, seg.start_distance_m, seg.end_distance_m)
            if duration is not None:
                count += 1
                if best_s is None or duration < best_s:
                    best_s = duration
                    best_act_id = act_id
        bests.append(SegmentBestOut(
            segment_id=seg.id, name=seg.name,
            start_distance_m=seg.start_distance_m, end_distance_m=seg.end_distance_m,
            auto_generated=bool(seg.auto_generated),
            best_s=best_s, best_activity_id=best_act_id, count=count,
        ))
    return bests


@router.get("/{route_id}/segments/{segment_id}/times", response_model=List[SegmentTimeEntry])
async def get_segment_times(
    route_id: int,
    segment_id: int,
    db: AsyncSession = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    """Return the last 10 times this segment was traversed across matched activities."""
    from app.services.route_matcher import find_segment_times
    from app.models.user import ActivityDataPoint

    await _get_owned_route(route_id, current_user.id, db)

    seg_result = await db.execute(
        select(RouteSegment).where(
            RouteSegment.id == segment_id, RouteSegment.route_id == route_id
        )
    )
    seg = seg_result.scalar_one_or_none()
    if not seg:
        raise HTTPException(status_code=404, detail="Segment not found")

    acts_result = await db.execute(
        select(Activity)
        .where(Activity.named_route_id == route_id, Activity.user_id == current_user.id)
        .order_by(desc(Activity.start_time))
        .limit(10)
    )
    activities = acts_result.scalars().all()

    times = []
    for act in activities:
        dp_result = await db.execute(
            select(ActivityDataPoint)
            .where(ActivityDataPoint.activity_id == act.id)
            .order_by(ActivityDataPoint.timestamp)
        )
        dps = dp_result.scalars().all()
        dp_list = [
            {"distance_m": p.distance_m, "timestamp": p.timestamp}
            for p in dps
            if p.distance_m is not None
        ]
        duration = find_segment_times(dp_list, seg.start_distance_m, seg.end_distance_m)
        if duration:
            times.append(SegmentTimeEntry(
                activity_id=act.id,
                date=act.start_time,
                name=act.name,
                duration_s=duration,
            ))
    return times