package business

import (
	"fmt"
	"strings"

	"gorm.io/gorm"
)

type businessQueryIndex struct {
	table, name string
	columns     []string
}

var businessQueryIndexes = []businessQueryIndex{
	{"tab_promote", "idx_sw_promote_created", []string{"source_db", "create_time", "id"}},
	{"tab_spend", "idx_sw_spend_time_summary", []string{"pay_status", "pay_time", "source_db", "pay_amount"}},
	{"tab_spend", "idx_sw_spend_promote_summary", []string{"promote_id", "pay_status", "source_db", "pay_amount"}},
	{"tab_sw_report_day", "idx_sw_report_pay_scan", []string{"dedup_mode", "stat_date", "source_db", "promote_id", "game_id", "total_pay"}},
	{"tab_sw_report_day_key", "idx_sw_report_key_scan", []string{"dedup_mode", "stat_date", "source_db", "promote_id", "game_id", "metric", "identity_key"}},
	{"tab_sw_report_server_day", "idx_sw_server_pay_game_scan", []string{"game_name", "dedup_mode", "stat_date", "source_db", "game_id", "server_num", "total_pay"}},
	{"tab_sw_report_server_day_key", "idx_sw_server_key_game_scan", []string{"game_name", "dedup_mode", "stat_date", "source_db", "game_id", "server_num", "metric", "identity_key"}},
}

var reportBuildQueryIndexes = []businessQueryIndex{
	{"tab_user", "idx_sw_user_report_identity", []string{"id", "source_db", "puid", "promote_id", "idcard"}},
	{"tab_user_play_info", "idx_sw_play_report_active", []string{"play_time", "user_id", "source_db", "promote_id", "game_id", "server_id"}},
}

// 只为已经接入的业务表增加索引，不创建平台表、不改写记录。
// 按实际筛选前缀排列，并覆盖聚合读取列，避免大范围回表。
func migrateBusinessQueryIndexes(db *gorm.DB) error {
	return migrateQueryIndexes(db, businessQueryIndexes)
}

func migrateReportBuildQueryIndexes(db *gorm.DB) error {
	return migrateQueryIndexes(db, reportBuildQueryIndexes)
}

func migrateQueryIndexes(db *gorm.DB, indexes []businessQueryIndex) error {
	if db.Dialector.Name() != "mysql" {
		return nil
	}
	groups := make(map[string][]businessQueryIndex)
	tables := []string{}
	for _, index := range indexes {
		if _, exists := groups[index.table]; !exists {
			tables = append(tables, index.table)
		}
		groups[index.table] = append(groups[index.table], index)
	}
	for _, table := range tables {
		available, err := businessTableAvailable(db, table)
		if err != nil {
			return err
		}
		if !available {
			continue
		}
		additions := []string{}
		for _, index := range groups[table] {
			var existing []string
			if err := db.Raw("SELECT column_name FROM information_schema.statistics WHERE table_schema=DATABASE() AND table_name=? AND index_name=? ORDER BY seq_in_index", index.table, index.name).Scan(&existing).Error; err != nil {
				return err
			}
			if len(existing) > 0 {
				if strings.Join(existing, ",") != strings.Join(index.columns, ",") {
					return fmt.Errorf("%s.%s 的现有索引列不符", index.table, index.name)
				}
				continue
			}
			columns := "`" + strings.Join(index.columns, "`,`") + "`"
			additions = append(additions, "ADD INDEX `"+index.name+"` ("+columns+")")
		}
		// 同一大表的多个索引合并构建，减少重复扫描。
		if len(additions) > 0 {
			build := func(conn *gorm.DB) error {
				return conn.Exec("ALTER TABLE `" + table + "` " + strings.Join(additions, ",") + ", ALGORITHM=INPLACE, LOCK=NONE").Error
			}
			// Later indexes also evaluate the historical generated time column.
			// Apply the same connection-local compatibility rule as its first index.
			if table == "tab_user" && db.Migrator().HasColumn(table, "sw_register_time_unix") {
				err = withLegacyRegistrationCast(db, build)
			} else {
				err = build(db)
			}
			if err != nil {
				return fmt.Errorf("add query indexes on %s: %w", table, err)
			}
		}
	}
	return nil
}