// 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 cast

import (
	"github.com/cockroachdb/apd/v3"
	"github.com/cockroachdb/errors"
	"github.com/dolthub/go-mysql-server/sql"
	"github.com/dolthub/go-mysql-server/sql/types"

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

// initNumeric handles all casts that are built-in. This comprises only the source types.
func initNumeric(builtInCasts map[id.Cast]casts.Cast) {
	numericAssignment(builtInCasts)
	numericImplicit(builtInCasts)
}

// numericAssignment registers all assignment casts. This comprises only the source types.
func numericAssignment(builtInCasts map[id.Cast]casts.Cast) {
	framework.MustAddAssignmentTypeCast(builtInCasts, framework.TypeCast{
		FromType: pgtypes.Numeric,
		ToType:   pgtypes.Int16,
		Function: func(ctx *sql.Context, val any, _, targetType *pgtypes.DoltgresType) (any, error) {
			d := val.(*apd.Decimal)
			if d.Cmp(pgtypes.NumericValueMinInt16) < 0 || d.Cmp(pgtypes.NumericValueMaxInt16) > 0 {
				return nil, errors.Wrap(pgtypes.ErrCastOutOfRange, "smallint out of range")
			}
			i := types.DecimalRoundedIntPart(d)
			return int16(i), nil
		},
	})
	framework.MustAddAssignmentTypeCast(builtInCasts, framework.TypeCast{
		FromType: pgtypes.Numeric,
		ToType:   pgtypes.Int32,
		Function: func(ctx *sql.Context, val any, _, targetType *pgtypes.DoltgresType) (any, error) {
			d := val.(*apd.Decimal)
			if d.Cmp(pgtypes.NumericValueMinInt32) < 0 || d.Cmp(pgtypes.NumericValueMaxInt32) > 0 {
				return nil, errors.Wrap(pgtypes.ErrCastOutOfRange, "integer out of range")
			}
			i := types.DecimalRoundedIntPart(d)
			return int32(i), nil
		},
	})
	framework.MustAddAssignmentTypeCast(builtInCasts, framework.TypeCast{
		FromType: pgtypes.Numeric,
		ToType:   pgtypes.Int64,
		Function: func(ctx *sql.Context, val any, _, targetType *pgtypes.DoltgresType) (any, error) {
			d := val.(*apd.Decimal)
			if d.Cmp(pgtypes.NumericValueMinInt64) < 0 || d.Cmp(pgtypes.NumericValueMaxInt64) > 0 {
				return nil, errors.Wrap(pgtypes.ErrCastOutOfRange, "bigint out of range")
			}
			return types.DecimalRoundedIntPart(d), nil
		},
	})
}

// numericImplicit registers all implicit casts. This comprises only the source types.
func numericImplicit(builtInCasts map[id.Cast]casts.Cast) {
	framework.MustAddImplicitTypeCast(builtInCasts, framework.TypeCast{
		FromType: pgtypes.Numeric,
		ToType:   pgtypes.Float32,
		Function: func(ctx *sql.Context, val any, _, targetType *pgtypes.DoltgresType) (any, error) {
			d := val.(*apd.Decimal)
			f, _ := d.Float64()
			return float32(f), nil
		},
	})
	framework.MustAddImplicitTypeCast(builtInCasts, framework.TypeCast{
		FromType: pgtypes.Numeric,
		ToType:   pgtypes.Float64,
		Function: func(ctx *sql.Context, val any, _, targetType *pgtypes.DoltgresType) (any, error) {
			d := val.(*apd.Decimal)
			f, _ := d.Float64()
			return f, nil
		},
	})
	framework.MustAddImplicitTypeCast(builtInCasts, framework.TypeCast{
		FromType: pgtypes.Numeric,
		ToType:   pgtypes.Numeric,
		Function: func(ctx *sql.Context, val any, _, targetType *pgtypes.DoltgresType) (any, error) {
			return pgtypes.GetNumericValueWithTypmod(val.(*apd.Decimal), targetType.GetAttTypMod())
		},
	})
}