"""Meetings router — code-first CRUD with participant/attend support."""
import math
from datetime import datetime
from typing import Optional
from fastapi import APIRouter, Depends, HTTPException, status, Query
from sqlalchemy.orm import Session
from pydantic import BaseModel

from app.core.config import get_db
from app.models import models
from app.models.meeting import Meeting, MeetingStatus, MeetingPriority, MeetingParticipant
from app.models.milestone import Milestone
from app.api.deps import get_current_user_or_apikey
from app.api.rbac import check_project_role

router = APIRouter(tags=["Meetings"])


# ---- helpers ----

def _find_meeting_by_code(db: Session, meeting_code: str) -> Meeting | None:
    return db.query(Meeting).filter(Meeting.meeting_code == str(meeting_code)).first()


def _resolve_project_id(db: Session, project_code: str | None) -> int | None:
    if not project_code:
        return None
    project = db.query(models.Project).filter(models.Project.project_code == project_code).first()
    if not project:
        raise HTTPException(status_code=404, detail="Project not found")
    return project.id


def _resolve_milestone(db: Session, milestone_code: str | None, project_id: int | None) -> Milestone | None:
    if not milestone_code:
        return None
    query = db.query(Milestone).filter(Milestone.milestone_code == milestone_code)
    if project_id:
        query = query.filter(Milestone.project_id == project_id)
    ms = query.first()
    if not ms:
        raise HTTPException(status_code=404, detail="Milestone not found")
    return ms


def _get_participant_usernames(db: Session, meeting: Meeting) -> list[str]:
    parts = db.query(MeetingParticipant).filter(MeetingParticipant.meeting_id == meeting.id).all()
    usernames = []
    for p in parts:
        user = db.query(models.User).filter(models.User.id == p.user_id).first()
        if user:
            usernames.append(user.username)
    return usernames


def _serialize_meeting(db: Session, meeting: Meeting) -> dict:
    project = db.query(models.Project).filter(models.Project.id == meeting.project_id).first()
    milestone = db.query(Milestone).filter(Milestone.id == meeting.milestone_id).first()
    return {
        "code": meeting.meeting_code,
        "meeting_code": meeting.meeting_code,
        "title": meeting.title,
        "description": meeting.description,
        "status": meeting.status.value if hasattr(meeting.status, "value") else meeting.status,
        "priority": meeting.priority.value if hasattr(meeting.priority, "value") else meeting.priority,
        "project_code": project.project_code if project else None,
        "milestone_code": milestone.milestone_code if milestone else None,
        "reporter_id": meeting.reporter_id,
        "meeting_time": meeting.scheduled_at.isoformat() if meeting.scheduled_at else None,
        "scheduled_at": meeting.scheduled_at.isoformat() if meeting.scheduled_at else None,
        "duration_minutes": meeting.duration_minutes,
        "participants": _get_participant_usernames(db, meeting),
        "created_at": meeting.created_at.isoformat() if meeting.created_at else None,
        "updated_at": meeting.updated_at.isoformat() if meeting.updated_at else None,
    }


# ---- CRUD ----

class MeetingCreateBody(BaseModel):
    project_code: str
    title: str
    milestone_code: Optional[str] = None
    description: Optional[str] = None
    meeting_time: Optional[str] = None
    duration_minutes: Optional[int] = None


@router.post("/meetings", status_code=status.HTTP_201_CREATED)
def create_meeting(
    body: MeetingCreateBody,
    db: Session = Depends(get_db),
    current_user: models.User = Depends(get_current_user_or_apikey),
):
    project_id = _resolve_project_id(db, body.project_code)
    if not project_id:
        raise HTTPException(status_code=400, detail="project_code is required")
    check_project_role(db, current_user.id, project_id, min_role="dev")

    milestone = _resolve_milestone(db, body.milestone_code, project_id)
    if not milestone:
        # If no milestone_code, try to use the first active milestone
        milestone = db.query(Milestone).filter(
            Milestone.project_id == project_id,
        ).order_by(Milestone.id.desc()).first()
    if not milestone:
        raise HTTPException(status_code=400, detail="No milestone available for project")

    milestone_code = milestone.milestone_code or f"m{milestone.id}"
    max_meeting = db.query(Meeting).filter(Meeting.milestone_id == milestone.id).order_by(Meeting.id.desc()).first()
    next_num = (max_meeting.id + 1) if max_meeting else 1
    meeting_code = f"{milestone_code}:M{next_num:05x}"

    scheduled_at = None
    if body.meeting_time:
        try:
            scheduled_at = datetime.fromisoformat(body.meeting_time.replace("Z", "+00:00"))
        except Exception:
            raise HTTPException(status_code=400, detail="Invalid meeting_time format")

    meeting = Meeting(
        title=body.title,
        description=body.description,
        status=MeetingStatus.SCHEDULED,
        priority=MeetingPriority.MEDIUM,
        project_id=project_id,
        milestone_id=milestone.id,
        reporter_id=current_user.id,
        meeting_code=meeting_code,
        scheduled_at=scheduled_at,
        duration_minutes=body.duration_minutes,
    )
    db.add(meeting)
    db.commit()
    db.refresh(meeting)

    # Auto-add creator as participant
    participant = MeetingParticipant(meeting_id=meeting.id, user_id=current_user.id)
    db.add(participant)
    db.commit()

    return _serialize_meeting(db, meeting)


@router.get("/meetings")
def list_meetings(
    project: str = None,
    project_code: str = None,
    status_value: str = Query(None, alias="status"),
    order_by: str = None,
    page: int = 1,
    page_size: int = 50,
    db: Session = Depends(get_db),
):
    query = db.query(Meeting)

    effective_project = project_code or project
    if effective_project:
        project_id = _resolve_project_id(db, effective_project)
        if project_id:
            query = query.filter(Meeting.project_id == project_id)

    if status_value:
        query = query.filter(Meeting.status == status_value)

    sort_fields = {
        "created": Meeting.created_at,
        "created_at": Meeting.created_at,
        "due-date": Meeting.scheduled_at,
        "scheduled_at": Meeting.scheduled_at,
        "name": Meeting.title,
        "title": Meeting.title,
    }
    sort_col = sort_fields.get(order_by, Meeting.created_at)
    query = query.order_by(sort_col.desc())

    total = query.count()
    page = max(1, page)
    page_size = min(max(1, page_size), 200)
    total_pages = math.ceil(total / page_size) if total else 1
    items = query.offset((page - 1) * page_size).limit(page_size).all()

    return {
        "items": [_serialize_meeting(db, m) for m in items],
        "total": total,
        "page": page,
        "page_size": page_size,
        "total_pages": total_pages,
    }


@router.get("/meetings/{meeting_code}")
def get_meeting(meeting_code: str, db: Session = Depends(get_db)):
    meeting = _find_meeting_by_code(db, meeting_code)
    if not meeting:
        raise HTTPException(status_code=404, detail="Meeting not found")
    return _serialize_meeting(db, meeting)


class MeetingUpdateBody(BaseModel):
    title: Optional[str] = None
    description: Optional[str] = None
    status: Optional[str] = None
    meeting_time: Optional[str] = None
    duration_minutes: Optional[int] = None


@router.patch("/meetings/{meeting_code}")
def update_meeting(
    meeting_code: str,
    body: MeetingUpdateBody,
    db: Session = Depends(get_db),
    current_user: models.User = Depends(get_current_user_or_apikey),
):
    meeting = _find_meeting_by_code(db, meeting_code)
    if not meeting:
        raise HTTPException(status_code=404, detail="Meeting not found")
    check_project_role(db, current_user.id, meeting.project_id, min_role="dev")

    update_data = body.model_dump(exclude_unset=True)
    if not update_data:
        raise HTTPException(status_code=400, detail="No supported fields to update")

    if "title" in update_data and update_data["title"] is not None:
        meeting.title = update_data["title"]
    if "description" in update_data:
        meeting.description = update_data["description"]
    if "status" in update_data and update_data["status"] is not None:
        meeting.status = MeetingStatus(update_data["status"])
    if "meeting_time" in update_data and update_data["meeting_time"] is not None:
        try:
            meeting.scheduled_at = datetime.fromisoformat(update_data["meeting_time"].replace("Z", "+00:00"))
        except Exception:
            raise HTTPException(status_code=400, detail="Invalid meeting_time format")
    if "duration_minutes" in update_data:
        meeting.duration_minutes = update_data["duration_minutes"]

    db.commit()
    db.refresh(meeting)
    return _serialize_meeting(db, meeting)


@router.delete("/meetings/{meeting_code}", status_code=status.HTTP_204_NO_CONTENT)
def delete_meeting(
    meeting_code: str,
    db: Session = Depends(get_db),
    current_user: models.User = Depends(get_current_user_or_apikey),
):
    meeting = _find_meeting_by_code(db, meeting_code)
    if not meeting:
        raise HTTPException(status_code=404, detail="Meeting not found")
    check_project_role(db, current_user.id, meeting.project_id, min_role="dev")
    db.delete(meeting)
    db.commit()
    return None


# ---- Attend ----

@router.post("/meetings/{meeting_code}/attend")
def attend_meeting(
    meeting_code: str,
    db: Session = Depends(get_db),
    current_user: models.User = Depends(get_current_user_or_apikey),
):
    meeting = _find_meeting_by_code(db, meeting_code)
    if not meeting:
        raise HTTPException(status_code=404, detail="Meeting not found")
    check_project_role(db, current_user.id, meeting.project_id, min_role="viewer")

    existing = db.query(MeetingParticipant).filter(
        MeetingParticipant.meeting_id == meeting.id,
        MeetingParticipant.user_id == current_user.id,
    ).first()
    if existing:
        return _serialize_meeting(db, meeting)

    participant = MeetingParticipant(meeting_id=meeting.id, user_id=current_user.id)
    db.add(participant)
    db.commit()
    return _serialize_meeting(db, meeting)