package database

import (
	"gorm.io/gorm"

	"github.com/truewhile/MeBox/internal/model"
)

// AutoMigrate creates tables for every model registered in the model package.
func AutoMigrate(db *gorm.DB) error {
	// 必须先于 AutoMigrate：旧库中可能已有重复的 (user_id, media_id) 历史行，
	// 不去重会导致唯一索引 uniq_user_history 创建失败。
	if err := dedupePlaybackHistories(db); err != nil {
		return err
	}
	if err := db.AutoMigrate(model.AllModels()...); err != nil {
		return err
	}
	if err := ensurePostgresColumnCompatibility(db); err != nil {
		return err
	}
	if err := ensurePerformanceIndexes(db); err != nil {
		return err
	}
	if err := ensureLibraryRootsCompatibility(db); err != nil {
		return err
	}
	if err := ensureEmbyMountsCompatibility(db); err != nil {
		return err
	}
	if isSQLite(db) {
		if err := ensureMediaSearchIndex(db); err != nil {
			return err
		}
		return ensureSQLiteQueryOptimizer(db)
	}
	return nil
}

func ensureSQLiteQueryOptimizer(db *gorm.DB) error {
	// Refresh planner statistics so indexes on large media tables are used.
	return db.Exec("ANALYZE").Error
}

// dedupePlaybackHistories removes duplicate (user_id, media_id) rows left by
// the former read-then-write upsert, so the uniq_user_history composite unique
// index can be created on existing databases. Keeps the most recent row per
// pair, preferring live rows over soft-deleted ones.
func dedupePlaybackHistories(db *gorm.DB) error {
	if !db.Migrator().HasTable("playback_histories") {
		return nil
	}
	return db.Exec(`
DELETE FROM playback_histories WHERE id IN (
	SELECT id FROM (
		SELECT id, ROW_NUMBER() OVER (
			PARTITION BY user_id, media_id
			ORDER BY deleted_at IS NULL DESC, watched_at DESC, id DESC
		) AS rn
		FROM playback_histories
	) ranked
	WHERE ranked.rn > 1
)`).Error
}

func ensurePostgresColumnCompatibility(db *gorm.DB) error {
	if !isPostgres(db) {
		return nil
	}
	statements := []string{
		`ALTER TABLE media ALTER COLUMN container TYPE varchar(128)`,
		`ALTER TABLE media ALTER COLUMN genres TYPE text`,
		`ALTER TABLE media ALTER COLUMN series_id TYPE varchar(128)`,
		`ALTER TABLE media ALTER COLUMN duplicate_of TYPE varchar(128)`,
		`ALTER TABLE playback_histories ALTER COLUMN media_id TYPE varchar(128)`,
		`ALTER TABLE favorites ALTER COLUMN media_id TYPE varchar(128)`,
		`ALTER TABLE playlist_items ALTER COLUMN media_id TYPE varchar(128)`,
	}
	for _, stmt := range statements {
		if err := db.Exec(stmt).Error; err != nil {
			return err
		}
	}
	return nil
}

func ensurePerformanceIndexes(db *gorm.DB) error {
	statements := []string{
		// 完整多级排序索引：媒体库分页与首页预览的 ORDER BY
		// (release_date, year, updated_at, created_at, id) DESC 与索引列完全一致，
		// LIMIT 分页沿索引顺序直取，免去对整库行做临时 B-tree 排序。
		`CREATE INDEX IF NOT EXISTS idx_media_library_recent_active ON media(library_id, release_date DESC, year DESC, updated_at DESC, created_at DESC, id DESC) WHERE deleted_at IS NULL`,
		// 计数覆盖索引：首页 CountByLibraries 的 GROUP BY library_id + nsfw 谓词
		// 全部落在索引键/部分索引条件上，纯索引扫描即可完成，不回表。
		`CREATE INDEX IF NOT EXISTS idx_media_library_nsfw_active ON media(library_id, nsfw) WHERE deleted_at IS NULL`,
		// 旧的两键前缀索引被上面的完整排序索引完全覆盖，删除以降低写放大。
		`DROP INDEX IF EXISTS idx_media_library_release_active`,
		`CREATE INDEX IF NOT EXISTS idx_media_library_created_active ON media(library_id, created_at DESC) WHERE deleted_at IS NULL`,
		`CREATE INDEX IF NOT EXISTS idx_media_library_episode_active ON media(library_id, season_num, episode_num, created_at DESC) WHERE deleted_at IS NULL`,
		`CREATE INDEX IF NOT EXISTS idx_media_library_root_active ON media(library_id, library_root_id) WHERE deleted_at IS NULL`,
		`CREATE INDEX IF NOT EXISTS idx_media_series_active ON media(series_id, season_num, episode_num) WHERE deleted_at IS NULL`,
		`CREATE INDEX IF NOT EXISTS idx_favorites_user_media_active ON favorites(user_id, media_id) WHERE deleted_at IS NULL`,
		`CREATE INDEX IF NOT EXISTS idx_playback_histories_user_media_active ON playback_histories(user_id, media_id, watched_at DESC) WHERE deleted_at IS NULL`,
		`CREATE INDEX IF NOT EXISTS idx_playback_histories_resume_active ON playback_histories(user_id, completed, watched_at DESC) WHERE deleted_at IS NULL`,
		`CREATE INDEX IF NOT EXISTS idx_play_profiles_user_created_active ON play_profiles(user_id, created_at DESC) WHERE deleted_at IS NULL`,
	}
	if isSQLite(db) {
		statements = append(statements,
			`CREATE INDEX IF NOT EXISTS idx_media_title_active ON media(title COLLATE NOCASE) WHERE deleted_at IS NULL`,
			`CREATE INDEX IF NOT EXISTS idx_media_original_name_active ON media(original_name COLLATE NOCASE) WHERE deleted_at IS NULL`,
		)
	} else {
		statements = append(statements,
			`CREATE INDEX IF NOT EXISTS idx_media_title_active ON media(title) WHERE deleted_at IS NULL`,
			`CREATE INDEX IF NOT EXISTS idx_media_original_name_active ON media(original_name) WHERE deleted_at IS NULL`,
		)
	}
	for _, stmt := range statements {
		if err := db.Exec(stmt).Error; err != nil {
			return err
		}
	}
	return nil
}

func ensureEmbyMountsCompatibility(db *gorm.DB) error {
	if !db.Migrator().HasTable(&model.EmbyMount{}) {
		return nil
	}
	if !db.Migrator().HasColumn(&model.EmbyMount{}, "sort_order") {
		if err := db.Migrator().AddColumn(&model.EmbyMount{}, "sort_order"); err != nil {
			return err
		}
	}
	// 针对已有数据：只给 sort_order=0/NULL 的行按创建时间补号（从现有
	// 最大值之后递增），不能整表重排——此前无条件按 created_at 从 0 重新
	// 编号，会把用户自定义的顺序覆盖掉。
	var zeroCount int64
	if err := db.Model(&model.EmbyMount{}).Where("sort_order = 0 OR sort_order IS NULL").Count(&zeroCount).Error; err == nil && zeroCount > 0 {
		// max 只统计非 0 行：sort_order=0 与 NULL 同样视为“未分配”，
		// 全部为 0 时从 0 开始编号（与迁移前的初始化语义一致）。
		var maxOrder int
		_ = db.Raw("SELECT COALESCE(MAX(sort_order), -1) FROM emby_mounts WHERE sort_order > 0").Scan(&maxOrder).Error
		var mounts []model.EmbyMount
		if err := db.Where("sort_order = 0 OR sort_order IS NULL").Order("created_at asc, id asc").Find(&mounts).Error; err == nil {
			for i, m := range mounts {
				_ = db.Exec("UPDATE emby_mounts SET sort_order = ? WHERE id = ?", maxOrder+1+i, m.ID).Error
			}
		}
	}
	return nil
}