package main

import (
	"fmt"
	"os"
	"path/filepath"

	"gorm.io/gorm"
)

// migrateDatabase applies schema changes and repairs legacy indexes. It is
// intentionally separate from startup so migration behavior can be tested on
// a disposable SQLite database before touching production data.
func migrateDatabase(db *gorm.DB) error {
	if err := db.AutoMigrate(&Task{}, &MediaAsset{}, &Setting{}, &User{}, &UserPermission{}, &CreditAccount{}, &CreditTransaction{}, &CreditReservation{}, &RedeemBatch{}, &RedeemCode{}, &RedeemRecord{}, &WebDAVConfig{}, &Session{}, &AuditLog{}); err != nil {
		return err
	}
	if err := db.Exec("DROP INDEX IF EXISTS idx_tasks_source_rid_quality").Error; err != nil {
		return err
	}
	if err := db.Exec("CREATE UNIQUE INDEX IF NOT EXISTS idx_tasks_user_source_rid_quality ON tasks(user_id, source, r_id, quality)").Error; err != nil {
		return err
	}
	if err := db.Exec("DROP INDEX IF EXISTS idx_credit_reservations_task_id").Error; err != nil {
		return err
	}
	return db.Exec("CREATE INDEX IF NOT EXISTS idx_credit_reservations_task_id ON credit_reservations(task_id)").Error
}

// backfillMediaAssets turns legacy completed tasks into shared media assets.
// Existing physical files are reused; no media is moved or deleted.
func backfillMediaAssets(db *gorm.DB, downloadDir string) error {
	var tasks []Task
	if err := db.Where("(asset_id = 0 OR asset_id IS NULL) AND status = ?", "done").Find(&tasks).Error; err != nil {
		return err
	}
	for i := range tasks {
		t := &tasks[i]
		key := assetKey(t.Source, t.RID, t.Quality)
		var asset MediaAsset
		result := db.Where("asset_key = ?", key).Limit(1).Find(&asset)
		if result.Error != nil {
			return result.Error
		}
		if result.RowsAffected == 0 {
			asset = MediaAsset{
				AssetKey:      key,
				Source:        t.Source,
				RID:           t.RID,
				Quality:       t.Quality,
				LocalPath:     t.LocalPath,
				Format:        t.Format,
				ActualQuality: t.ActualQuality,
				Size:          t.DownloadedBytes,
				Status:        "done",
			}
			if asset.LocalPath != "" {
				if fi, statErr := os.Stat(asset.LocalPath); statErr == nil && fi.Size() > 0 {
					asset.Size = fi.Size()
				}
			} else if downloadDir != "" {
				candidate := filepath.Join(downloadDir, safe(t.Artist)+" - "+safe(t.Title)+"."+t.Format)
				if fi, statErr := os.Stat(candidate); statErr == nil && fi.Size() > 0 {
					asset.LocalPath, asset.Size = candidate, fi.Size()
				}
			}
			if err := db.Create(&asset).Error; err != nil {
				return fmt.Errorf("create media asset for task %d: %w", t.ID, err)
			}
		}
		if t.AssetID != asset.ID {
			if err := db.Model(t).Update("asset_id", asset.ID).Error; err != nil {
				return fmt.Errorf("link media asset for task %d: %w", t.ID, err)
			}
		}
	}
	return nil
}