/*
Copyright © 2020 Marvin

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 dbutil

import (
	"context"
	"database/sql"
	"fmt"
	"strings"

	"github.com/pingcap/parser"
	"github.com/pingcap/parser/ast"
	"github.com/pingcap/tidb/ddl"

	"github.com/pingcap/errors"
	"github.com/pingcap/parser/model"
	_ "github.com/pingcap/tidb/planner/core"        // to setup expression.EvalAstExpr. See: https://github.com/pingcap/tidb/blob/a94cff903cd1e7f3b050db782da84273ef5592f4/planner/core/optimizer.go#L202
	_ "github.com/pingcap/tidb/types/parser_driver" // for parser driver
)

// GetTableInfo returns table information.
func GetTableInfo(ctx context.Context, db *sql.DB, schemaName string, tableName string) (*model.TableInfo, error) {
	createTableSQL, err := GetCreateTableSQL(ctx, db, schemaName, tableName)
	if err != nil {
		return nil, errors.Trace(err)
	}

	parser2, err := GetParserForDB(db)
	if err != nil {
		return nil, errors.Trace(err)
	}
	return GetTableInfoBySQL(createTableSQL, parser2)
}

// GetTableInfoBySQL returns table information by given create table sql.
func GetTableInfoBySQL(createTableSQL string, parser2 *parser.Parser) (table *model.TableInfo, err error) {
	stmt, err := parser2.ParseOneStmt(createTableSQL, "", "")
	if err != nil {
		return nil, errors.Trace(err)
	}

	s, ok := stmt.(*ast.CreateTableStmt)
	if ok {
		table, err := ddl.BuildTableInfoFromAST(s)
		if err != nil {
			return nil, errors.Trace(err)
		}

		// put primary key in indices
		if table.PKIsHandle {
			pkIndex := &model.IndexInfo{
				Name:    model.NewCIStr("PRIMARY"),
				Primary: true,
				State:   model.StatePublic,
				Unique:  true,
				Columns: []*model.IndexColumn{
					{
						Name: table.GetPkName(),
					},
				},
			}

			table.Indices = append(table.Indices, pkIndex)
		}

		return table, nil
	}

	return nil, errors.Errorf("get table info from sql %s failed!", createTableSQL)
}

// EqualTableInfo returns true if this two table info have same columns and indices
func EqualTableInfo(tableInfo1, tableInfo2 *model.TableInfo) (bool, string) {
	// check columns
	if len(tableInfo1.Columns) != len(tableInfo2.Columns) {
		return false, fmt.Sprintf("column num not equal, one is %d another is %d", len(tableInfo1.Columns), len(tableInfo2.Columns))
	}

	for j, col := range tableInfo1.Columns {
		if col.Name.O != tableInfo2.Columns[j].Name.O {
			return false, fmt.Sprintf("column name not equal, one is %s another is %s", col.Name.O, tableInfo2.Columns[j].Name.O)
		}
		if col.Tp != tableInfo2.Columns[j].Tp {
			return false, fmt.Sprintf("column %s's type not equal, one is %v another is %v", col.Name.O, col.Tp, tableInfo2.Columns[j].Tp)
		}
	}

	// check index
	if len(tableInfo1.Indices) != len(tableInfo2.Indices) {
		return false, fmt.Sprintf("index num not equal, one is %d another is %d", len(tableInfo1.Indices), len(tableInfo2.Indices))
	}

	index2Map := make(map[string]*model.IndexInfo)
	for _, index := range tableInfo2.Indices {
		index2Map[index.Name.O] = index
	}

	for _, index1 := range tableInfo1.Indices {
		index2, ok := index2Map[index1.Name.O]
		if !ok {
			return false, fmt.Sprintf("index %s not exists", index1.Name.O)
		}

		if len(index1.Columns) != len(index2.Columns) {
			return false, fmt.Sprintf("index %s's columns num not equal, one is %d another is %d", index1.Name.O, len(index1.Columns), len(index2.Columns))
		}
		for j, col := range index1.Columns {
			if col.Name.O != index2.Columns[j].Name.O {
				return false, fmt.Sprintf("index %s's column not equal, one has %s another has %s", index1.Name.O, col.Name.O, index2.Columns[j].Name.O)
			}
		}
	}

	return true, ""
}

// FindColumnByName finds column by name.
func FindColumnByName(cols []*model.ColumnInfo, name string) *model.ColumnInfo {
	// column name don't distinguish capital and small letter
	name = strings.ToLower(name)
	for _, col := range cols {
		if col.Name.L == name {
			return col
		}
	}

	return nil
}