// Copyright 2026 Dolthub, 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 hook

import (
	"github.com/cockroachdb/errors"
	"github.com/dolthub/dolt/go/libraries/doltcore/doltdb"
	"github.com/dolthub/go-mysql-server/sql"
	"github.com/dolthub/go-mysql-server/sql/plan"

	"github.com/dolthub/doltgresql/core"
	"github.com/dolthub/doltgresql/core/id"
	pgtypes "github.com/dolthub/doltgresql/server/types"
)

// beforeTableModifyColumnChange represents what properties of a column changed when a call is made to BeforeTableModifyColumn.
type beforeTableModifyColumnChange uint8

const (
	beforeTableModifyColumnChange_None beforeTableModifyColumnChange = iota
	beforeTableModifyColumnChange_Type
)

// BeforeTableModifyColumn handles validation that's unique to Doltgres.
func BeforeTableModifyColumn(ctx *sql.Context, runner sql.StatementRunner, nodeInterface sql.Node) (sql.Node, error) {
	n, ok := nodeInterface.(*plan.ModifyColumn)
	if !ok {
		return nil, errors.Errorf("MODIFY COLUMN pre-hook expected `*plan.ModifyColumn` but received `%T`", nodeInterface)
	}

	// Figure out what was changed. We know it's not the name because we have a dedicated *RenameColumn node.
	changed := beforeTableModifyColumnChange_None
	newColumn := n.NewColumn()
	for _, col := range n.TargetSchema() {
		if col.Name == newColumn.Name {
			if !col.Type.Equals(newColumn.Type) {
				changed = beforeTableModifyColumnChange_Type
			}
		}
	}
	if changed == beforeTableModifyColumnChange_None {
		return n, nil
	}

	// Grab the table being altered (so we know the schema)
	doltTable := core.SQLNodeToDoltTable(n.Table)
	if doltTable == nil {
		// If this table isn't a Dolt table then we don't have anything to do
		return n, nil
	}
	_, root, err := core.GetRootFromContext(ctx)
	if err != nil {
		return n, nil
	}
	tableName := doltTable.TableName()
	tableAsType := id.NewType(tableName.Schema, tableName.Name)
	allTableNames, err := root.GetAllTableNames(ctx, false)
	if err != nil {
		return nil, err
	}

	for _, otherTableName := range allTableNames {
		if doltdb.IsSystemTable(otherTableName) {
			// System tables don't use any table types
			continue
		}
		otherTable, ok, err := root.GetTable(ctx, otherTableName)
		if err != nil {
			return nil, err
		}
		if !ok {
			return nil, errors.Errorf("root returned table name `%s` but it could not be found?", otherTableName.String())
		}
		otherTableSch, err := otherTable.GetSchema(ctx)
		if err != nil {
			return nil, err
		}
		for _, otherCol := range otherTableSch.GetAllCols().GetColumns() {
			colType := otherCol.TypeInfo.ToSqlType()
			dgtype, ok := colType.(*pgtypes.DoltgresType)
			if !ok {
				// If this isn't a Doltgres type, then it can't be a table type so we can ignore it
				continue
			}
			if dgtype.ID != tableAsType {
				// This column isn't our table type, so we can ignore it
				continue
			}
			return nil, errors.Errorf(`cannot alter table "%s" because column "%s.%s" uses its row type`,
				tableName.Name, otherTableName.Name, otherCol.Name)
		}
	}
	return n, nil
}