// Copyright 2024 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 expression

import (
	"github.com/cockroachdb/errors"
	"github.com/dolthub/go-mysql-server/sql"

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

// AssignmentCast handles assignment casts.
type AssignmentCast struct {
	expr       sql.Expression
	sourceType *pgtypes.DoltgresType
	targetType *pgtypes.DoltgresType
}

var _ sql.Expression = (*AssignmentCast)(nil)

// NewAssignmentCast returns a new *AssignmentCast expression.
func NewAssignmentCast(expr sql.Expression, sourceType *pgtypes.DoltgresType, targetType *pgtypes.DoltgresType) *AssignmentCast {
	targetType = checkForDomainType(targetType)
	sourceType = checkForDomainType(sourceType)
	return &AssignmentCast{
		expr:       expr,
		sourceType: sourceType,
		targetType: targetType,
	}
}

// Children implements the sql.Expression interface.
func (ac *AssignmentCast) Children() []sql.Expression {
	return []sql.Expression{ac.expr}
}

// Eval implements the sql.Expression interface.
func (ac *AssignmentCast) Eval(ctx *sql.Context, row sql.Row) (any, error) {
	val, err := ac.expr.Eval(ctx, row)
	if err != nil || val == nil {
		return val, err
	}
	castsColl, err := core.GetCastsCollectionFromContext(ctx, "")
	if err != nil {
		return nil, err
	}
	cast, err := castsColl.GetAssignmentCast(ctx, ac.sourceType, ac.targetType)
	if err != nil {
		return nil, err
	}
	if !cast.ID.IsValid() {
		return nil, errors.Errorf("ASSIGNMENT_CAST: target is of type %s but expression is of type %s: %s",
			ac.targetType.String(), ac.sourceType.String(), ac.expr.String())
	}
	return cast.Eval(ctx, val, ac.sourceType, ac.targetType)
}

// IsNullable implements the sql.Expression interface.
func (ac *AssignmentCast) IsNullable(ctx *sql.Context) bool {
	return true
}

// Resolved implements the sql.Expression interface.
func (ac *AssignmentCast) Resolved() bool {
	return ac.expr.Resolved()
}

// String implements the sql.Expression interface.
func (ac *AssignmentCast) String() string {
	return ac.expr.String()
}

// Type implements the sql.Expression interface.
func (ac *AssignmentCast) Type(ctx *sql.Context) sql.Type {
	return ac.targetType
}

// WithChildren implements the sql.Expression interface.
func (ac *AssignmentCast) WithChildren(ctx *sql.Context, children ...sql.Expression) (sql.Expression, error) {
	if len(children) != 1 {
		return nil, sql.ErrInvalidChildrenNumber.New(ac, len(children), 1)
	}
	return NewAssignmentCast(children[0], ac.sourceType, ac.targetType), nil
}

// checkForDomainType returns the underlying type if the given type is a domain type. Casting always applies to the base
// type.
func checkForDomainType(t *pgtypes.DoltgresType) *pgtypes.DoltgresType {
	if t.TypType == pgtypes.TypeType_Domain {
		t = t.DomainUnderlyingBaseType()
	}
	return t
}