"""Calendar: unified read-only month view of appointments, meetings, and tasks."""

from fastapi import APIRouter, Request, Depends
from fastapi.templating import Jinja2Templates
from sqlalchemy.ext.asyncio import AsyncSession
from sqlalchemy import text
from datetime import date, timedelta
import calendar

from core.database import get_db
from core.sidebar import get_sidebar_data

router = APIRouter(prefix="/calendar", tags=["calendar"])
templates = Jinja2Templates(directory="templates")


@router.get("/")
async def calendar_view(
    request: Request,
    year: int = None,
    month: int = None,
    db: AsyncSession = Depends(get_db),
):
    today = date.today()
    year = year or today.year
    month = month or today.month

    # Clamp to valid range
    if month < 1 or month > 12:
        month = today.month
    if year < 2000 or year > 2100:
        year = today.year

    first_day = date(year, month, 1)
    last_day = date(year, month, calendar.monthrange(year, month)[1])

    # Prev/next month
    prev_month = first_day - timedelta(days=1)
    next_month = last_day + timedelta(days=1)

    sidebar = await get_sidebar_data(db)

    # Appointments in this month (by start_at)
    appt_result = await db.execute(text("""
        SELECT id, title, start_at, end_at, all_day, location
        FROM appointments
        WHERE is_deleted = false
          AND start_at::date >= :first AND start_at::date <= :last
        ORDER BY start_at
    """), {"first": first_day, "last": last_day})
    appointments = [dict(r._mapping) for r in appt_result]

    # Meetings in this month (by meeting_date)
    meet_result = await db.execute(text("""
        SELECT id, title, meeting_date, start_at, location, status
        FROM meetings
        WHERE is_deleted = false
          AND meeting_date >= :first AND meeting_date <= :last
        ORDER BY meeting_date, start_at
    """), {"first": first_day, "last": last_day})
    meetings = [dict(r._mapping) for r in meet_result]

    # Tasks with due dates in this month (open/in_progress only)
    task_result = await db.execute(text("""
        SELECT t.id, t.title, t.due_date, t.priority, t.status,
               p.name as project_name
        FROM tasks t
        LEFT JOIN projects p ON t.project_id = p.id
        WHERE t.is_deleted = false
          AND t.status IN ('open', 'in_progress')
          AND t.due_date >= :first AND t.due_date <= :last
        ORDER BY t.due_date, t.priority
    """), {"first": first_day, "last": last_day})
    tasks = [dict(r._mapping) for r in task_result]

    # Build day-indexed event map
    days_map = {}
    for a in appointments:
        day = a["start_at"].date().day if a["start_at"] else None
        if day:
            days_map.setdefault(day, []).append({
                "type": "appointment",
                "id": a["id"],
                "title": a["title"],
                "time": None if a["all_day"] else a["start_at"].strftime("%-I:%M %p"),
                "url": f"/appointments/{a['id']}",
                "all_day": a["all_day"],
            })

    for m in meetings:
        day = m["meeting_date"].day if m["meeting_date"] else None
        if day:
            time_str = m["start_at"].strftime("%-I:%M %p") if m["start_at"] else None
            days_map.setdefault(day, []).append({
                "type": "meeting",
                "id": m["id"],
                "title": m["title"],
                "time": time_str,
                "url": f"/meetings/{m['id']}",
                "all_day": False,
            })

    for t in tasks:
        day = t["due_date"].day if t["due_date"] else None
        if day:
            days_map.setdefault(day, []).append({
                "type": "task",
                "id": t["id"],
                "title": t["title"],
                "time": None,
                "url": f"/tasks/{t['id']}",
                "priority": t["priority"],
                "project_name": t.get("project_name"),
                "all_day": False,
            })

    # Build calendar grid (weeks of days)
    # Monday=0, Sunday=6
    cal = calendar.Calendar(firstweekday=6)  # Sunday start
    weeks = cal.monthdayscalendar(year, month)

    return templates.TemplateResponse("calendar.html", {
        "request": request,
        "sidebar": sidebar,
        "year": year,
        "month": month,
        "month_name": calendar.month_name[month],
        "weeks": weeks,
        "days_map": days_map,
        "today": today,
        "first_day": first_day,
        "prev_year": prev_month.year,
        "prev_month": prev_month.month,
        "next_year": next_month.year,
        "next_month": next_month.month,
        "page_title": f"Calendar - {calendar.month_name[month]} {year}",
        "active_nav": "calendar",
    })