// 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 types

import (
	"github.com/dolthub/go-mysql-server/sql"
	"gopkg.in/src-d/go-errors.v1"

	"github.com/dolthub/doltgresql/utils"

	"github.com/dolthub/doltgresql/core/id"
)

const (
	// StringMaxLength is the maximum number of characters (not bytes) that a Char, VarChar, or BpChar may contain.
	StringMaxLength = 10485760
	// StringUnbounded is used to represent that a type does not define a limit on the strings that it accepts. Values
	// are still limited by the field size limit, but it won't be enforced by the type.
	StringUnbounded = 0
)

// ErrLengthMustBeAtLeast1 is returned when given character length is less than 1.
var ErrLengthMustBeAtLeast1 = errors.NewKind(`length for type %s must be at least 1`)

// ErrLengthCannotExceed is returned when given character length exceeds the upper bound, 10485760.
var ErrLengthCannotExceed = errors.NewKind(`length for type %s cannot exceed 10485760`)

// VarChar is a varchar that has an unbounded length.
var VarChar = &DoltgresType{
	ID:                  toInternal("varchar"),
	TypLength:           int16(-1),
	PassedByVal:         false,
	TypType:             TypeType_Base,
	TypCategory:         TypeCategory_StringTypes,
	IsPreferred:         false,
	IsDefined:           true,
	Delimiter:           ",",
	RelID:               id.Null,
	SubscriptFunc:       toFuncID("-"),
	Elem:                internalNullType,
	Array:               internalNullType,
	InputFunc:           toFuncID("varcharin", toInternal("cstring"), toInternal("oid"), toInternal("int4")),
	OutputFunc:          toFuncID("varcharout", toInternal("varchar")),
	ReceiveFunc:         toFuncID("varcharrecv", toInternal("internal"), toInternal("oid"), toInternal("int4")),
	SendFunc:            toFuncID("varcharsend", toInternal("varchar")),
	ModInFunc:           toFuncID("varchartypmodin", toInternal("_cstring")),
	ModOutFunc:          toFuncID("varchartypmodout", toInternal("int4")),
	AnalyzeFunc:         toFuncID("-"),
	Align:               TypeAlignment_Int,
	Storage:             TypeStorage_Extended,
	NotNull:             false,
	BaseTypeType:        internalNullType,
	TypMod:              -1,
	NDims:               0,
	TypCollation:        id.NewCollation("pg_catalog", "default"),
	DefaulBin:           "",
	Default:             "",
	Acl:                 nil,
	Checks:              nil,
	attTypMod:           -1,
	CompareFunc:         toFuncID("bttextcmp", toInternal("text"), toInternal("text")), // TODO: temporarily added
	SerializationFunc:   serializeTypeVarChar,
	DeserializationFunc: deserializeTypeVarChar,
}

// NewVarCharType returns VarChar type with type modifier set
// representing the maximum number of characters that the type may hold.
func NewVarCharType(maxChars int32) (*DoltgresType, error) {
	typmod, err := GetTypModFromCharLength("varchar", maxChars)
	if err != nil {
		return nil, err
	}
	newType := *VarChar.WithAttTypMod(typmod)
	return &newType, nil
}

// MustCreateNewVarCharType panics if used with out-of-bound value.
func MustCreateNewVarCharType(maxChars int32) *DoltgresType {
	newType, err := NewVarCharType(maxChars)
	if err != nil {
		panic(err)
	}
	return newType
}

// GetTypModFromCharLength takes character type and its length and returns the type modifier value.
func GetTypModFromCharLength(typName string, l int32) (int32, error) {
	if l < 1 {
		return 0, ErrLengthMustBeAtLeast1.New(typName)
	} else if l > StringMaxLength {
		return 0, ErrLengthCannotExceed.New(typName)
	}
	return l + 4, nil
}

// GetCharLengthFromTypmod takes character type modifier and returns length value.
func GetCharLengthFromTypmod(typmod int32) int32 {
	return typmod - 4
}

// serializeTypeVarChar handles serialization from the standard representation to our serialized representation that is
// written in Dolt.
func serializeTypeVarChar(ctx *sql.Context, t *DoltgresType, val any) ([]byte, error) {
	str := val.(string)
	writer := utils.NewWriter(uint64(len(str) + 4))
	writer.String(str)
	return writer.Data(), nil
}

// deserializeTypeVarChar handles deserialization from the Dolt serialized format to our standard representation used by
// expressions and nodes.
func deserializeTypeVarChar(ctx *sql.Context, t *DoltgresType, data []byte) (any, error) {
	if len(data) == 0 {
		return nil, nil
	}
	reader := utils.NewReader(data)
	return reader.String(), nil
}