"""
Scan Processor - Background worker for flight scans

This module processes pending flight scans by:
1. Querying flights using searcher_v3.py (with SOCS cookie integration)
2. Updating scan status and progress in real-time
3. Saving discovered routes to the database

Runs as async background tasks within the FastAPI application.
"""

import asyncio
import logging
from datetime import datetime, date, timedelta
import json

from database import get_connection
from airports import get_airports_for_country, lookup_airport
from searcher_v3 import search_multiple_routes


logger = logging.getLogger(__name__)

# ─────────────────────────────────────────────────────────────────────────────
# Task registry — tracks running asyncio tasks so they can be cancelled.
# ─────────────────────────────────────────────────────────────────────────────

_running_tasks: dict[int, asyncio.Task] = {}
_cancel_reasons: dict[int, str] = {}


def cancel_scan_task(scan_id: int) -> bool:
    """Cancel the background task for a scan. Returns True if a task was found and cancelled."""
    task = _running_tasks.get(scan_id)
    if task and not task.done():
        task.cancel()
        return True
    return False


def pause_scan_task(scan_id: int) -> bool:
    """Signal the running task to stop with status='paused'. Returns True if task was found."""
    _cancel_reasons[scan_id] = 'paused'
    return cancel_scan_task(scan_id)


def stop_scan_task(scan_id: int) -> bool:
    """Signal the running task to stop with status='cancelled'. Returns True if task was found."""
    _cancel_reasons[scan_id] = 'cancelled'
    return cancel_scan_task(scan_id)


def _write_route_incremental(scan_id: int, destination: str,
                              dest_name: str, dest_city: str,
                              new_flights: list):
    """
    Write or update a route row and its individual flight rows immediately.

    Called from progress_callback each time a (scan_id, destination, date)
    query returns results. Merges into the existing route row if one already
    exists, using a running weighted average for avg_price.

    Opens its own DB connection — safe to call from the event loop thread.
    """
    prices = [f.get('price') for f in new_flights if f.get('price')]
    if not prices:
        return

    new_airlines = list({f.get('airline') for f in new_flights if f.get('airline')})
    new_count = len(prices)
    new_min = min(prices)
    new_max = max(prices)
    new_avg = sum(prices) / new_count

    try:
        conn = get_connection()
        cursor = conn.cursor()

        cursor.execute("""
            SELECT id, flight_count, min_price, max_price, avg_price, airlines
            FROM routes
            WHERE scan_id = ? AND destination = ?
        """, (scan_id, destination))
        existing = cursor.fetchone()

        if existing is None:
            cursor.execute("""
                INSERT INTO routes (
                    scan_id, destination, destination_name, destination_city,
                    flight_count, airlines, min_price, max_price, avg_price
                ) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?)
            """, (
                scan_id, destination, dest_name, dest_city,
                new_count, json.dumps(new_airlines),
                new_min, new_max, new_avg,
            ))
        else:
            old_count = existing['flight_count'] or 0
            old_min = existing['min_price']
            old_max = existing['max_price']
            old_avg = existing['avg_price'] or 0.0
            old_airlines = json.loads(existing['airlines']) if existing['airlines'] else []

            merged_count = old_count + new_count
            merged_min = min(old_min, new_min) if old_min is not None else new_min
            merged_max = max(old_max, new_max) if old_max is not None else new_max
            merged_avg = (old_avg * old_count + new_avg * new_count) / merged_count
            merged_airlines = json.dumps(list(set(old_airlines) | set(new_airlines)))

            cursor.execute("""
                UPDATE routes
                SET flight_count = ?,
                    min_price    = ?,
                    max_price    = ?,
                    avg_price    = ?,
                    airlines     = ?
                WHERE scan_id = ? AND destination = ?
            """, (
                merged_count, merged_min, merged_max, merged_avg, merged_airlines,
                scan_id, destination,
            ))

        for flight in new_flights:
            if not flight.get('price'):
                continue
            cursor.execute("""
                INSERT INTO flights (
                    scan_id, destination, date, airline,
                    departure_time, arrival_time, price, stops
                ) VALUES (?, ?, ?, ?, ?, ?, ?, ?)
            """, (
                scan_id,
                destination,
                flight.get('date', ''),
                flight.get('airline'),
                flight.get('departure_time'),
                flight.get('arrival_time'),
                flight.get('price'),
                flight.get('stops', 0),
            ))

        conn.commit()
        conn.close()

    except Exception as e:
        logger.error(f"[Scan {scan_id}] Failed to write incremental route {destination}: {e}")


async def process_scan(scan_id: int):
    """
    Process a pending scan by querying flights and saving routes.

    Args:
        scan_id: The ID of the scan to process

    This function:
    1. Updates scan status to 'running'
    2. Resolves destination airports from country
    3. Queries flights for each destination
    4. Saves routes to database
    5. Updates progress counters in real-time
    6. Sets final status to 'completed' or 'failed'
    """
    conn = None
    try:
        logger.info(f"[Scan {scan_id}] Starting scan processing")

        # Get scan details
        conn = get_connection()
        cursor = conn.cursor()

        cursor.execute("""
            SELECT origin, country, start_date, end_date, seat_class, adults
            FROM scans
            WHERE id = ?
        """, (scan_id,))

        row = cursor.fetchone()
        if not row:
            logger.error(f"[Scan {scan_id}] Scan not found in database")
            return

        origin, country_or_airports, start_date_str, end_date_str, seat_class, adults = row

        logger.info(f"[Scan {scan_id}] Scan details: {origin} -> {country_or_airports}, {start_date_str} to {end_date_str}")

        # Update status to 'running' and record when processing started
        cursor.execute("""
            UPDATE scans
            SET status = 'running', started_at = CURRENT_TIMESTAMP, updated_at = CURRENT_TIMESTAMP
            WHERE id = ?
        """, (scan_id,))
        conn.commit()

        # Determine mode: country (2 letters) or specific airports (comma-separated)
        try:
            if len(country_or_airports) == 2 and country_or_airports.isalpha():
                # Country mode: resolve airports from country code
                logger.info(f"[Scan {scan_id}] Mode: Country search ({country_or_airports})")
                destinations = get_airports_for_country(country_or_airports)
                if not destinations:
                    raise ValueError(f"No airports found for country: {country_or_airports}")

                destination_codes = [d['iata'] for d in destinations]

                logger.info(f"[Scan {scan_id}] Found {len(destination_codes)} destination airports: {destination_codes}")

            else:
                # Specific airports mode: parse comma-separated list
                destination_codes = [code.strip() for code in country_or_airports.split(',')]
                destinations = [
                    lookup_airport(code) or {'iata': code, 'name': code, 'city': ''}
                    for code in destination_codes
                ]
                logger.info(f"[Scan {scan_id}] Mode: Specific airports ({len(destination_codes)} destinations: {destination_codes})")

        except Exception as e:
            logger.error(f"[Scan {scan_id}] Failed to resolve airports: {str(e)}")
            cursor.execute("""
                UPDATE scans
                SET status = 'failed',
                    error_message = ?,
                    completed_at = CURRENT_TIMESTAMP,
                    updated_at = CURRENT_TIMESTAMP
                WHERE id = ?
            """, (f"Failed to resolve airports: {str(e)}", scan_id))
            conn.commit()
            return

        # Note: Don't update total_routes yet - we'll set it after we know the actual number of route queries

        # Generate dates to scan — every day in the window
        start_date = datetime.strptime(start_date_str, '%Y-%m-%d').date()
        end_date = datetime.strptime(end_date_str, '%Y-%m-%d').date()

        dates = []
        current = start_date
        while current <= end_date:
            dates.append(current.strftime('%Y-%m-%d'))
            current += timedelta(days=1)

        logger.info(f"[Scan {scan_id}] Will scan {len(dates)} dates: {dates}")

        # Build routes list: [(origin, destination, date), ...]
        routes_to_scan = []
        for dest in destination_codes:
            for scan_date in dates:
                routes_to_scan.append((origin, dest, scan_date))

        logger.info(f"[Scan {scan_id}] Total route queries: {len(routes_to_scan)}")

        # Update total_routes with actual number of queries
        cursor.execute("""
            UPDATE scans
            SET total_routes = ?,
                updated_at = CURRENT_TIMESTAMP
            WHERE id = ?
        """, (len(routes_to_scan), scan_id))
        conn.commit()

        # Progress callback — updates DB progress counter and writes routes live
        # Signature: callback(origin, destination, date, status, count, error=None, flights=None)
        routes_scanned_count = 0

        def progress_callback(origin: str, destination: str, date: str,
                            status: str, count: int, error: str = None,
                            flights: list = None):
            nonlocal routes_scanned_count

            if status in ('cache_hit', 'api_success', 'error'):
                routes_scanned_count += 1

                # Write route + flights to DB immediately if results available
                if flights and status in ('cache_hit', 'api_success'):
                    for f in flights:
                        f['date'] = date
                    dest_info = next((d for d in destinations if d['iata'] == destination), None)
                    dest_name = dest_info.get('name', destination) if dest_info else destination
                    dest_city = dest_info.get('city', '') if dest_info else ''
                    _write_route_incremental(scan_id, destination, dest_name, dest_city, flights)

                # Update progress counter
                try:
                    progress_conn = get_connection()
                    progress_cursor = progress_conn.cursor()

                    progress_cursor.execute("""
                        UPDATE scans
                        SET routes_scanned = routes_scanned + 1,
                            updated_at = CURRENT_TIMESTAMP
                        WHERE id = ?
                    """, (scan_id,))

                    progress_conn.commit()
                    progress_conn.close()

                    if routes_scanned_count % 10 == 0:
                        logger.info(f"[Scan {scan_id}] Progress: {routes_scanned_count}/{len(routes_to_scan)} routes ({status}: {origin}→{destination})")

                except Exception as e:
                    logger.error(f"[Scan {scan_id}] Failed to update progress: {str(e)}")

        # Query flights using searcher_v3
        logger.info(f"[Scan {scan_id}] Starting flight queries...")

        results = await search_multiple_routes(
            routes=routes_to_scan,
            seat_class=seat_class or 'economy',
            adults=adults or 1,
            use_cache=True,
            cache_threshold_hours=24,
            max_workers=3,  # Limit concurrency to avoid rate limiting
            progress_callback=progress_callback
        )

        logger.info(f"[Scan {scan_id}] Flight queries complete.")

        # Routes and flights were written incrementally by progress_callback.
        routes_saved = cursor.execute(
            "SELECT COUNT(*) FROM routes WHERE scan_id = ?", (scan_id,)
        ).fetchone()[0]
        total_flights_saved = cursor.execute(
            "SELECT COALESCE(SUM(flight_count), 0) FROM routes WHERE scan_id = ?", (scan_id,)
        ).fetchone()[0]

        # Update scan to completed and record finish time
        cursor.execute("""
            UPDATE scans
            SET status = 'completed',
                total_flights = ?,
                completed_at = CURRENT_TIMESTAMP,
                updated_at = CURRENT_TIMESTAMP
            WHERE id = ?
        """, (total_flights_saved, scan_id))
        conn.commit()

        logger.info(f"[Scan {scan_id}] ✅ Scan completed successfully! {routes_saved} routes saved with {total_flights_saved} flights")

    except asyncio.CancelledError:
        reason = _cancel_reasons.pop(scan_id, 'cancelled')
        logger.info(f"[Scan {scan_id}] Scan {reason} by user request")
        try:
            if conn:
                cursor = conn.cursor()
                cursor.execute("""
                    UPDATE scans
                    SET status = ?,
                        completed_at = CURRENT_TIMESTAMP,
                        updated_at = CURRENT_TIMESTAMP
                    WHERE id = ?
                """, (reason, scan_id))
                conn.commit()
        except Exception as update_error:
            logger.error(f"[Scan {scan_id}] Failed to update {reason} status: {str(update_error)}")
        raise  # must re-raise so asyncio marks the task as cancelled

    except Exception as e:
        logger.error(f"[Scan {scan_id}] ❌ Scan failed with error: {str(e)}", exc_info=True)

        # Update scan to failed
        try:
            if conn:
                cursor = conn.cursor()
                cursor.execute("""
                    UPDATE scans
                    SET status = 'failed',
                        error_message = ?,
                        completed_at = CURRENT_TIMESTAMP,
                        updated_at = CURRENT_TIMESTAMP
                    WHERE id = ?
                """, (str(e), scan_id))
                conn.commit()
        except Exception as update_error:
            logger.error(f"[Scan {scan_id}] Failed to update error status: {str(update_error)}")

    finally:
        if conn:
            conn.close()


def start_scan_processor(scan_id: int):
    """
    Start processing a scan as a background task.

    Args:
        scan_id: The ID of the scan to process

    Returns:
        asyncio.Task: The background task
    """
    task = asyncio.create_task(process_scan(scan_id))
    _running_tasks[scan_id] = task
    task.add_done_callback(lambda _: _running_tasks.pop(scan_id, None))
    logger.info(f"[Scan {scan_id}] Background task created")
    return task


def start_resume_processor(scan_id: int):
    """
    Resume processing a paused scan as a background task.

    The API endpoint has already reset status to 'pending' and cleared counters.
    process_scan() will transition the status to 'running' and re-run all routes,
    getting instant cache hits for already-queried routes.

    Args:
        scan_id: The ID of the paused scan to resume

    Returns:
        asyncio.Task: The background task
    """
    task = asyncio.create_task(process_scan(scan_id))
    _running_tasks[scan_id] = task
    task.add_done_callback(lambda _: _running_tasks.pop(scan_id, None))
    logger.info(f"[Scan {scan_id}] Resume task created")
    return task