// Copyright 2024 PingCAP, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//	http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package metautil

import (
	"context"

	"github.com/pingcap/errors"
	"github.com/pingcap/tidb/pkg/meta/model"
)

// Database wraps the schema and tables of a database.
type Database struct {
	Info   *model.DBInfo
	Tables []*Table
}

// GetTable returns a table of the database by name.
func (db *Database) GetTable(name string) *Table {
	for _, table := range db.Tables {
		if table.Info.Name.String() == name {
			return table
		}
	}
	return nil
}

// LoadBackupTables loads schemas from BackupMeta.
func LoadBackupTables(ctx context.Context, reader *MetaReader, loadStats bool) (map[string]*Database, error) {
	ch := make(chan *Table)
	errCh := make(chan error)
	go func() {
		var opts []ReadSchemaOption
		if !loadStats {
			opts = []ReadSchemaOption{SkipStats}
		}
		if err := reader.ReadSchemasFiles(ctx, ch, opts...); err != nil {
			errCh <- errors.Trace(err)
		}
		close(ch)
	}()

	databases := make(map[string]*Database)
	for {
		select {
		case <-ctx.Done():
			return nil, ctx.Err()
		case err := <-errCh:
			return nil, errors.Trace(err)
		case table, ok := <-ch:
			if !ok {
				close(errCh)
				return databases, nil
			}
			dbName := table.DB.Name.String()
			db, ok := databases[dbName]
			if !ok {
				db = &Database{
					Info:   table.DB,
					Tables: make([]*Table, 0),
				}
				databases[dbName] = db
			}
			db.Tables = append(db.Tables, table)
		}
	}
}