package dbsync

import (
	"context"
	"fmt"
	"strings"
)

// DropTableResult 控制台删表结果。
type DropTableResult struct {
	OK           bool   `json:"ok"`
	Side         string `json:"side"`
	Table        string `json:"table"`
	Dropped      bool   `json:"dropped"`
	MetaCleared  int64  `json:"meta_cleared,omitempty"`
	Message      string `json:"message,omitempty"`
}

// DropTableOnEndpoint 删除业务表（禁止 _ajz_*）；并清理 _ajz_sync_meta 中该表残留。
// 注意：仅作用于当前 endpoint（线上 A 或本机 B），不向另一侧同步 DDL。
func DropTableOnEndpoint(ctx context.Context, ep Endpoint, side, table string) (*DropTableResult, error) {
	table = strings.TrimSpace(table)
	side = strings.TrimSpace(side)
	if side == "" {
		side = "remote"
	}
	if table == "" {
		return nil, fmt.Errorf("table required")
	}
	if strings.HasPrefix(table, "_ajz_") {
		return nil, fmt.Errorf("同步系统表不可删: %s", table)
	}
	if strings.EqualFold(table, "sqlite_master") || strings.HasPrefix(strings.ToLower(table), "sqlite_") {
		return nil, fmt.Errorf("系统表不可删: %s", table)
	}

	db, owned, err := openInspectDB(ep)
	if err != nil {
		return &DropTableResult{OK: false, Side: side, Table: table, Message: err.Error()}, err
	}
	if owned {
		defer db.Close()
	}

	exists, err := tableExists(ctx, db, ep.Driver, table)
	if err != nil {
		return nil, err
	}
	if !exists {
		return &DropTableResult{
			OK:      true,
			Side:    side,
			Table:   table,
			Dropped: false,
			Message: "表不存在（可能已删）",
		}, nil
	}

	ddl := fmt.Sprintf(`DROP TABLE IF EXISTS %s`, quoteIdent(ep.Driver, table))
	if _, err := db.ExecContext(ctx, ddl); err != nil {
		return nil, fmt.Errorf("drop table: %w", err)
	}

	var metaCleared int64
	if metaExists, _ := tableExists(ctx, db, ep.Driver, MetaTable); metaExists {
		q := fmt.Sprintf(`DELETE FROM %s WHERE table_name = ?`, quoteIdent(ep.Driver, MetaTable))
		if ep.Driver == DriverPostgres {
			q = fmt.Sprintf(`DELETE FROM %s WHERE table_name = $1`, quoteIdent(ep.Driver, MetaTable))
		}
		res, err := db.ExecContext(ctx, q, table)
		if err == nil && res != nil {
			metaCleared, _ = res.RowsAffected()
		}
	}

	// 若该 DSN 在 remote 池里，丢掉缓存连接，避免旧 schema 缓存感。
	InvalidateRemote(ep.Driver, ep.DSN)

	return &DropTableResult{
		OK:          true,
		Side:        side,
		Table:       table,
		Dropped:     true,
		MetaCleared: metaCleared,
		Message:     "已删除；若另一侧仍有同名表，不会自动同步删除，需分别处理或避免再次 push/ensure",
	}, nil
}