// 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 (
	"bytes"
	"fmt"
	"strconv"
	"strings"

	"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"
	"github.com/dolthub/doltgresql/utils"
)

// initBpChar registers the functions to the catalog.
func initBpChar() {
	framework.RegisterFunction(bpcharin)
	framework.RegisterFunction(bpcharout)
	framework.RegisterFunction(bpcharrecv)
	framework.RegisterFunction(bpcharsend)
	framework.RegisterFunction(bpchartypmodin)
	framework.RegisterFunction(bpchartypmodout)
	framework.RegisterFunction(bpcharcmp)
}

// bpcharin represents the PostgreSQL function of bpchar type IO input.
var bpcharin = framework.Function3{
	Name:       "bpcharin",
	Return:     pgtypes.BpChar,
	Parameters: [3]*pgtypes.DoltgresType{pgtypes.Cstring, pgtypes.Oid, pgtypes.Int32},
	Strict:     true,
	Callable: func(ctx *sql.Context, _ [4]*pgtypes.DoltgresType, val1, val2, val3 any) (any, error) {
		input := val1.(string)
		typmod := val3.(int32)
		maxChars := int32(pgtypes.StringMaxLength)
		if typmod != -1 {
			maxChars = pgtypes.GetCharLengthFromTypmod(typmod)
			if maxChars < pgtypes.StringUnbounded {
				maxChars = pgtypes.StringMaxLength
			}
		}
		str, runeLength := truncateString(input, maxChars)
		if runeLength > maxChars {
			return input, errors.Wrap(pgtypes.ErrCastOutOfRange, fmt.Sprintf("value too long for type varying(%v)", maxChars))
		} else {
			return str, nil
		}
	},
}

// bpcharout represents the PostgreSQL function of bpchar type IO output.
var bpcharout = framework.Function1{
	Name:       "bpcharout",
	Return:     pgtypes.Cstring,
	Parameters: [1]*pgtypes.DoltgresType{pgtypes.BpChar},
	Strict:     true,
	Callable: func(ctx *sql.Context, t [2]*pgtypes.DoltgresType, val any) (any, error) {
		typ := t[0]
		tm := typ.GetAttTypMod()
		if tm == -1 {
			return val.(string), nil
		}
		maxChars := pgtypes.GetCharLengthFromTypmod(tm)
		if maxChars < 1 {
			return val.(string), nil
		} else {
			str, runeCount := truncateString(val.(string), maxChars)
			if runeCount < maxChars {
				return str + strings.Repeat(" ", int(maxChars-runeCount)), nil
			}
			return str, nil
		}
	},
}

// bpcharrecv represents the PostgreSQL function of bpchar type IO receive.
var bpcharrecv = framework.Function3{
	Name:       "bpcharrecv",
	Return:     pgtypes.BpChar,
	Parameters: [3]*pgtypes.DoltgresType{pgtypes.Internal, pgtypes.Oid, pgtypes.Int32},
	Strict:     true,
	Callable: func(ctx *sql.Context, t [4]*pgtypes.DoltgresType, val1, val2, val3 any) (any, error) {
		data := val1.([]byte)
		if data == nil {
			return nil, nil
		}
		return t[3].IoInput(ctx, string(data))
	},
}

// bpcharsend represents the PostgreSQL function of bpchar type IO send.
var bpcharsend = framework.Function1{
	Name:       "bpcharsend",
	Return:     pgtypes.Bytea,
	Parameters: [1]*pgtypes.DoltgresType{pgtypes.BpChar},
	Strict:     true,
	Callable: func(ctx *sql.Context, t [2]*pgtypes.DoltgresType, val any) (any, error) {
		if wrapper, ok := val.(sql.AnyWrapper); ok {
			var err error
			val, err = wrapper.UnwrapAny(ctx)
			if err != nil {
				return nil, err
			}
			if val == nil {
				return nil, nil
			}
		}
		str, err := t[0].IoOutput(ctx, val)
		if err != nil {
			return nil, err
		}
		writer := utils.NewWireWriter()
		writer.WriteString(str)
		return writer.BufferData(), nil
	},
}

// bpchartypmodin represents the PostgreSQL function of bpchar type IO typmod input.
var bpchartypmodin = framework.Function1{
	Name:       "bpchartypmodin",
	Return:     pgtypes.Int32,
	Parameters: [1]*pgtypes.DoltgresType{pgtypes.CstringArray},
	Strict:     true,
	Callable: func(ctx *sql.Context, _ [2]*pgtypes.DoltgresType, val any) (any, error) {
		return getTypModFromStringArr("char", val.([]any))
	},
}

// bpchartypmodout represents the PostgreSQL function of bpchar type IO typmod output.
var bpchartypmodout = framework.Function1{
	Name:       "bpchartypmodout",
	Return:     pgtypes.Cstring,
	Parameters: [1]*pgtypes.DoltgresType{pgtypes.Int32},
	Strict:     true,
	Callable: func(ctx *sql.Context, _ [2]*pgtypes.DoltgresType, val any) (any, error) {
		typmod := val.(int32)
		if typmod < 5 {
			return "", nil
		}
		maxChars := pgtypes.GetCharLengthFromTypmod(typmod)
		return fmt.Sprintf("(%v)", maxChars), nil
	},
}

// bpcharcmp represents the PostgreSQL function of bpchar type compare.
var bpcharcmp = framework.Function2{
	Name:       "bpcharcmp",
	Return:     pgtypes.Int32,
	Parameters: [2]*pgtypes.DoltgresType{pgtypes.BpChar, pgtypes.BpChar},
	Strict:     true,
	Callable: func(ctx *sql.Context, _ [3]*pgtypes.DoltgresType, val1, val2 any) (any, error) {
		return int32(bytes.Compare([]byte(val1.(string)), []byte(val2.(string)))), nil
	},
}

// truncateString returns a string that has been truncated to the given length. Uses the rune count rather than the
// byte count. Returns the input string if it's smaller than the length. Also returns the rune count of the string.
func truncateString(val string, runeLimit int32) (string, int32) {
	var n int32
	for pos := range val {
		if n >= runeLimit {
			return val[:pos], n
		}
		n++
	}
	return val, n
}

func getTypModFromStringArr(typName string, inputArr []any) (int32, error) {
	if len(inputArr) == 0 {
		return 0, pgtypes.ErrTypmodArrayMustBe1D.New()
	} else if len(inputArr) > 1 {
		return 0, errors.Errorf("invalid type modifier")
	}

	l, err := strconv.ParseInt(inputArr[0].(string), 10, 32)
	if err != nil {
		return 0, err
	}
	return pgtypes.GetTypModFromCharLength(typName, int32(l))
}