from datetime import date, timedelta, datetime, time

import asyncpg
import pytz

from app.config import get_settings
from app.exceptions import NotFoundError, AppError
from app.models.bookings import WeeklyScheduleCreate, SlotCreate


def _fmt_time(t) -> str:
    if t is None:
        return ""
    s = str(t)
    return s[:5]


async def get_schedule(db: asyncpg.Connection) -> list[dict]:
    rows = await db.fetch("SELECT * FROM weekly_schedule WHERE is_active = true ORDER BY day_of_week, start_time")
    return [dict(r) for r in rows]


async def create_schedule_entry(db: asyncpg.Connection, data: WeeklyScheduleCreate) -> dict:
    row = await db.fetchrow(
        """
        INSERT INTO weekly_schedule (day_of_week, start_time, end_time, slot_duration_minutes)
        VALUES ($1, $2, $3, $4)
        RETURNING *
        """,
        data.day_of_week, data.start_time, data.end_time, data.slot_duration_minutes,
    )
    return dict(row)


async def delete_schedule_entry(db: asyncpg.Connection, schedule_id: str):
    result = await db.execute("DELETE FROM weekly_schedule WHERE id = $1", schedule_id)
    if result == "DELETE 0":
        raise NotFoundError("schedule entry")


async def generate_slots(db: asyncpg.Connection, from_date: date, to_date: date) -> int:
    if (to_date - from_date).days > 90:
        raise AppError("RANGE_TOO_LARGE", "Date range cannot exceed 90 days", 400)

    schedule = await db.fetch("SELECT * FROM weekly_schedule WHERE is_active = true")
    if not schedule:
        raise AppError("NO_SCHEDULE", "No active weekly schedule configured", 400)

    blocked = await db.fetch(
        "SELECT date FROM blocked_dates WHERE date BETWEEN $1 AND $2",
        from_date, to_date,
    )
    blocked_set = {r["date"] for r in blocked}

    tz = pytz.timezone(get_settings().BUSINESS_TIMEZONE)
    created = 0
    current = from_date

    async with db.transaction():
        while current <= to_date:
            if current in blocked_set:
                current += timedelta(days=1)
                continue

            day_schedules = [s for s in schedule if s["day_of_week"] == current.weekday()]

            for sched in day_schedules:
                cursor = datetime.combine(current, sched["start_time"])
                end_limit = datetime.combine(current, sched["end_time"])
                duration = timedelta(minutes=sched["slot_duration_minutes"])

                while cursor + duration <= end_limit:
                    slot_end = cursor + duration
                    exists = await db.fetchval(
                        "SELECT 1 FROM time_slots WHERE date = $1 AND start_time = $2",
                        current, cursor.time(),
                    )
                    if not exists:
                        await db.execute(
                            "INSERT INTO time_slots (date, start_time, end_time) VALUES ($1, $2, $3)",
                            current, cursor.time(), slot_end.time(),
                        )
                        created += 1
                    cursor += duration

            current += timedelta(days=1)

    return created


async def create_slot(db: asyncpg.Connection, data: SlotCreate) -> dict:
    if data.start_time >= data.end_time:
        raise AppError("INVALID_SLOT", "start_time must be before end_time", 400)
    row = await db.fetchrow(
        "INSERT INTO time_slots (date, start_time, end_time) VALUES ($1, $2, $3) RETURNING *",
        data.date, data.start_time, data.end_time,
    )
    return dict(row)


async def delete_slot(db: asyncpg.Connection, slot_id: str):
    booked = await db.fetchval(
        "SELECT 1 FROM bookings WHERE slot_id = $1 AND status IN ('pending', 'confirmed')",
        slot_id,
    )
    if booked:
        raise AppError("SLOT_BOOKED", "Cannot delete a slot with active bookings", 409)
    result = await db.execute("DELETE FROM time_slots WHERE id = $1", slot_id)
    if result == "DELETE 0":
        raise NotFoundError("slot")


async def update_slot(db: asyncpg.Connection, slot_id: str, is_blocked: bool, block_reason: str | None) -> dict:
    row = await db.fetchrow(
        "UPDATE time_slots SET is_blocked = $2, block_reason = $3 WHERE id = $1 RETURNING *",
        slot_id, is_blocked, block_reason,
    )
    if not row:
        raise NotFoundError("slot")
    return dict(row)


async def list_slots(
    db: asyncpg.Connection,
    from_date: date,
    to_date: date,
    available_only: bool = False,
) -> list[dict]:
    query = """
        SELECT
            ts.id, ts.date, ts.start_time, ts.end_time,
            ts.is_blocked, ts.block_reason,
            EXISTS(
                SELECT 1 FROM bookings b
                WHERE b.slot_id = ts.id AND b.status IN ('pending', 'confirmed')
            ) AS is_booked
        FROM time_slots ts
        WHERE ts.date BETWEEN $1 AND $2
    """
    params: list = [from_date, to_date]

    if available_only:
        query += " AND ts.is_blocked = false"
        query += """
            AND NOT EXISTS(
                SELECT 1 FROM blocked_dates bd WHERE bd.date = ts.date
            )
            AND NOT EXISTS(
                SELECT 1 FROM bookings b WHERE b.slot_id = ts.id AND b.status IN ('pending', 'confirmed')
            )
            AND ts.date >= CURRENT_DATE
        """

    query += " ORDER BY ts.date, ts.start_time"
    rows = await db.fetch(query, *params)
    return [dict(r) for r in rows]


async def get_blocked_dates(db: asyncpg.Connection) -> list[dict]:
    rows = await db.fetch("SELECT * FROM blocked_dates ORDER BY date")
    return [dict(r) for r in rows]


async def add_blocked_date(db: asyncpg.Connection, date: date, reason: str | None) -> dict:
    row = await db.fetchrow(
        "INSERT INTO blocked_dates (date, reason) VALUES ($1, $2) ON CONFLICT (date) DO UPDATE SET reason = $2 RETURNING *",
        date, reason,
    )
    return dict(row)


async def remove_blocked_date(db: asyncpg.Connection, blocked_date_id: str):
    result = await db.execute("DELETE FROM blocked_dates WHERE id = $1", blocked_date_id)
    if result == "DELETE 0":
        raise NotFoundError("blocked date")