package service

import (
	"context"
	"database/sql"
	"encoding/json"
	"fmt"
	"log/slog"
	"strings"
	"time"

	"github.com/TopherMayor/unified-media-manager/internal/db"
)

type QueueItem struct {
	ID             int64           `json:"id"`
	MediaID        int64           `json:"media_id"`
	ReleaseTitle   string          `json:"release_title"`
	ReleaseURL     *string         `json:"release_url,omitempty"`
	Indexer        string          `json:"indexer"`
	DownloadClient string          `json:"download_client"`
	Quality        json.RawMessage `json:"quality"`
	Size           *int64          `json:"size,omitempty"`
	Protocol       string          `json:"protocol"`
	Status         string          `json:"status"`
	Progress       float64         `json:"progress"`
	ErrorMessage   *string         `json:"error_message,omitempty"`
	BatchID        *string         `json:"batch_id,omitempty"`
	Priority       int             `json:"priority"`
	RetryCount     int             `json:"retry_count"`
	MaxRetries     int             `json:"max_retries"`
	CreatedAt      time.Time       `json:"created_at"`
	StartedAt      *time.Time      `json:"started_at,omitempty"`
	CompletedAt    *time.Time      `json:"completed_at,omitempty"`
	UpdatedAt      time.Time       `json:"updated_at"`
}

type QueueFilters struct {
	Status   string
	Page     int
	PageSize int
}

type QueueBatchDeleteRequest struct {
	Status  *string `json:"status,omitempty"`
	BatchID *string `json:"batch_id,omitempty"`
	IDs     []int64 `json:"ids,omitempty"`
}

const queueColumns = `id, media_id, release_title, release_url, indexer, download_client,
	quality, size, protocol, status, progress, error_message, batch_id, priority,
	retry_count, max_retries, created_at, started_at, completed_at, updated_at`

type QueueService struct {
	db *db.DB
}

func NewQueueService(database *db.DB) *QueueService {
	return &QueueService{db: database}
}

func scanQueueItem(scanner interface{ Scan(...interface{}) error }) (*QueueItem, error) {
	var item QueueItem
	var releaseURL, errorMsg, batchID sql.NullString
	var size sql.NullInt64
	var startedAt, completedAt sql.NullTime

	err := scanner.Scan(&item.ID, &item.MediaID, &item.ReleaseTitle, &releaseURL, &item.Indexer,
		&item.DownloadClient, &item.Quality, &size, &item.Protocol, &item.Status,
		&item.Progress, &errorMsg, &batchID, &item.Priority, &item.RetryCount,
		&item.MaxRetries, &item.CreatedAt, &startedAt, &completedAt, &item.UpdatedAt)
	if err != nil {
		return nil, err
	}

	if releaseURL.Valid {
		item.ReleaseURL = &releaseURL.String
	}
	if errorMsg.Valid {
		item.ErrorMessage = &errorMsg.String
	}
	if batchID.Valid {
		item.BatchID = &batchID.String
	}
	if size.Valid {
		item.Size = &size.Int64
	}
	if startedAt.Valid {
		item.StartedAt = &startedAt.Time
	}
	if completedAt.Valid {
		item.CompletedAt = &completedAt.Time
	}
	return &item, nil
}

func (s *QueueService) List(ctx context.Context, filters QueueFilters) ([]QueueItem, int, error) {
	qb := NewQueryBuilder(1)

	if filters.Status != "" {
		qb.Add("status = $%d", filters.Status)
	}

	var total int
	if err := s.db.Pool.QueryRow(ctx, "SELECT COUNT(*) FROM download_queue"+qb.Where(), qb.Args()...).Scan(&total); err != nil {
		return nil, 0, fmt.Errorf("count queue: %w", err)
	}

	query := fmt.Sprintf("SELECT %s FROM download_queue%s ORDER BY priority DESC, created_at ASC LIMIT $%d OFFSET $%d",
		queueColumns, qb.Where(), qb.Idx(), qb.Idx()+1)
	args := append(qb.Args(), filters.PageSize, (filters.Page-1)*filters.PageSize)

	rows, err := s.db.Pool.Query(ctx, query, args...)
	if err != nil {
		return nil, 0, fmt.Errorf("list queue: %w", err)
	}
	defer rows.Close()

	var items []QueueItem
	for rows.Next() {
		item, err := scanQueueItem(rows)
		if err != nil {
			slog.Error("failed to scan queue item", "error", err)
			continue
		}
		items = append(items, *item)
	}

	return items, total, nil
}

func (s *QueueService) Delete(ctx context.Context, id int64) error {
	tag, err := s.db.Pool.Exec(ctx,
		"UPDATE download_queue SET status = 'cancelled', updated_at = NOW() WHERE id = $1", id)
	if err != nil {
		return fmt.Errorf("cancel queue item: %w", err)
	}
	if tag.RowsAffected() == 0 {
		return fmt.Errorf("queue item not found")
	}
	return nil
}

func (s *QueueService) BatchDelete(ctx context.Context, req QueueBatchDeleteRequest) (int64, error) {
	qb := NewQueryBuilder(1)

	if req.Status != nil {
		qb.Add("status = $%d", *req.Status)
	}
	if req.BatchID != nil {
		qb.Add("batch_id = $%d", *req.BatchID)
	}
	if len(req.IDs) > 0 {
		qb.Add("id = ANY($%d)", req.IDs)
	}

	if len(qb.conditions) == 0 {
		return 0, fmt.Errorf("must provide status, batch_id, or ids")
	}

	query := fmt.Sprintf("UPDATE download_queue SET status = 'cancelled', updated_at = NOW() WHERE %s",
		strings.Join(qb.conditions, " AND "))
	tag, err := s.db.Pool.Exec(ctx, query, qb.Args()...)
	if err != nil {
		return 0, fmt.Errorf("batch cancel queue: %w", err)
	}

	return tag.RowsAffected(), nil
}

func (s *QueueService) Clear(ctx context.Context) (int64, error) {
	tag, err := s.db.Pool.Exec(ctx,
		"DELETE FROM download_queue WHERE status IN ('imported', 'failed', 'cancelled')")
	if err != nil {
		return 0, fmt.Errorf("clear queue: %w", err)
	}
	return tag.RowsAffected(), nil
}

func (s *QueueService) Retry(ctx context.Context, id int64) error {
	tag, err := s.db.Pool.Exec(ctx,
		`UPDATE download_queue SET status = 'pending', progress = 0, error_message = NULL,
		 retry_count = retry_count + 1, updated_at = NOW() WHERE id = $1 AND status = 'failed'`, id)
	if err != nil {
		return fmt.Errorf("retry queue item: %w", err)
	}
	if tag.RowsAffected() == 0 {
		return fmt.Errorf("queue item not found or not failed")
	}
	return nil
}

func (s *QueueService) RetryFailed(ctx context.Context) (int64, error) {
	tag, err := s.db.Pool.Exec(ctx,
		`UPDATE download_queue SET status = 'pending', progress = 0, error_message = NULL,
		 retry_count = retry_count + 1, updated_at = NOW()
		 WHERE status = 'failed' AND retry_count < max_retries`)
	if err != nil {
		return 0, fmt.Errorf("retry all failed: %w", err)
	}
	return tag.RowsAffected(), nil
}

type CreateQueueEntryRequest struct {
	MediaID        int64           `json:"media_id"`
	MediaType      string          `json:"media_type"`
	ReleaseTitle   string          `json:"release_title"`
	Indexer        string          `json:"indexer"`
	DownloadClient string          `json:"download_client"`
	Quality        json.RawMessage `json:"quality"`
	Protocol       string          `json:"protocol"`
	DownloadID     string          `json:"download_id"`
}

func (s *QueueService) CreateQueueEntry(ctx context.Context, req CreateQueueEntryRequest) (int64, error) {
	var id int64
	err := s.db.Pool.QueryRow(ctx,
		`INSERT INTO download_queue (media_id, media_type, release_title, indexer, download_client, quality, protocol, status, progress, download_id)
		 VALUES ($1, $2, $3, $4, $5, $6, $7, 'downloading', 0, $8) RETURNING id`,
		req.MediaID, req.MediaType, req.ReleaseTitle, req.Indexer, req.DownloadClient,
		req.Quality, req.Protocol, req.DownloadID).Scan(&id)
	if err != nil {
		return 0, fmt.Errorf("create queue entry: %w", err)
	}
	return id, nil
}