// 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 functions

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

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

// initDiv registers the functions to the catalog.
func initDiv() {
	framework.RegisterFunction(div_numeric)
}

// div_numeric represents the PostgreSQL function of the same name, taking the same parameters.
var div_numeric = framework.Function2{
	Name:       "div",
	Return:     pgtypes.Numeric,
	Parameters: [2]*pgtypes.DoltgresType{pgtypes.Numeric, pgtypes.Numeric},
	Strict:     true,
	Callable: func(ctx *sql.Context, _ [3]*pgtypes.DoltgresType, val1 any, val2 any) (any, error) {
		num1 := val1.(*apd.Decimal)
		num2 := val2.(*apd.Decimal)
		if num1.Form == apd.NaN || num2.Form == apd.NaN ||
			(num1.Form == apd.Infinite && num2.Form == apd.Infinite) {
			return pgtypes.NumericNaN, nil
		}
		if num2.IsZero() {
			return nil, errors.Errorf("division by zero")
		}
		if num1.Form == apd.Infinite {
			return num1, nil
		}
		if num2.Form == apd.Infinite {
			return apd.New(0, 0), nil
		}

		p := num1.NumDigits()
		if num1.Exponent > 0 {
			p += int64(num1.Exponent)
		}
		if num2.Exponent < 0 {
			p += int64(-num2.Exponent)
		}

		res := new(apd.Decimal)
		_, err := sql.DecimalCtx.WithPrecision(uint32(p)).QuoInteger(res, num1, num2)
		if err != nil {
			return nil, err
		}
		return res, nil
	},
}