// Copyright 2015 PingCAP, 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,
// See the License for the specific language governing permissions and
// limitations under the License.

package charset

import (
	"strings"

	"github.com/juju/errors"
	"github.com/pingcap/tidb/mysql"
)

// Charset is a charset.
// Now we only support MySQL.
type Charset struct {
	Name             string
	DefaultCollation string
	Collations       map[string]*Collation
	Desc             string
	Maxlen           int
}

// Collation is a collation.
// Now we only support MySQL.
type Collation struct {
	ID          int
	CharsetName string
	Name        string
	IsDefault   bool
}

var charsets = make(map[string]*Charset)

// All the supported charsets should be in the following table.
var charsetInfos = []*Charset{
	{CharsetUTF8, CollationUTF8, make(map[string]*Collation), "UTF-8 Unicode", 3},
	{CharsetUTF8MB4, CollationUTF8MB4, make(map[string]*Collation), "UTF-8 Unicode", 4},
	{CharsetASCII, CollationASCII, make(map[string]*Collation), "US ASCII", 1},
	{CharsetLatin1, CollationLatin1, make(map[string]*Collation), "Latin1", 1},
	{CharsetBin, CollationBin, make(map[string]*Collation), "binary", 1},
}

// Desc is a charset description.
type Desc struct {
	Name             string
	Desc             string
	DefaultCollation string
	Maxlen           int
}

// GetAllCharsets gets all charset descriptions in the local charsets.
func GetAllCharsets() []*Desc {
	descs := make([]*Desc, 0, len(charsets))
	// The charsetInfos is an array, so the iterate order will be stable.
	for _, ci := range charsetInfos {
		c, ok := charsets[ci.Name]
		if !ok {
			continue
		}
		desc := &Desc{
			Name:             c.Name,
			DefaultCollation: c.DefaultCollation,
			Desc:             c.Desc,
			Maxlen:           c.Maxlen,
		}
		descs = append(descs, desc)
	}
	return descs
}

// ValidCharsetAndCollation checks the charset and the collation validity
// and returns a boolean.
func ValidCharsetAndCollation(cs string, co string) bool {
	// We will use utf8 as a default charset.
	if cs == "" {
		cs = "utf8"
	}
	cs = strings.ToLower(cs)
	c, ok := charsets[cs]
	if !ok {
		return false
	}

	if co == "" {
		return true
	}
	_, ok = c.Collations[co]
	if !ok {
		return false
	}

	return true
}

// GetDefaultCollation returns the default collation for charset.
func GetDefaultCollation(charset string) (string, error) {
	charset = strings.ToLower(charset)
	if charset == CharsetBin {
		return CollationBin, nil
	}
	c, ok := charsets[charset]
	if !ok {
		return "", errors.Errorf("Unknown charset %s", charset)
	}
	return c.DefaultCollation, nil
}

// GetCharsetInfo returns charset and collation for cs as name.
func GetCharsetInfo(cs string) (string, string, error) {
	c, ok := charsets[strings.ToLower(cs)]
	if !ok {
		return "", "", errors.Errorf("Unknown charset %s", cs)
	}
	return c.Name, c.DefaultCollation, nil
}

// GetCharsetDesc gets charset descriptions in the local charsets.
func GetCharsetDesc(cs string) (*Desc, error) {
	c, ok := charsets[strings.ToLower(cs)]
	if !ok {
		return nil, errors.Errorf("Unknown charset %s", cs)
	}
	desc := &Desc{
		Name:             c.Name,
		DefaultCollation: c.DefaultCollation,
		Desc:             c.Desc,
		Maxlen:           c.Maxlen,
	}
	return desc, nil
}

// GetCharsetInfoByID returns charset and collation for id as cs_number.
func GetCharsetInfoByID(coID int) (string, string, error) {
	if coID == mysql.DefaultCollationID {
		return mysql.DefaultCharset, mysql.DefaultCollationName, nil
	}
	for _, collation := range collations {
		if coID == collation.ID {
			return collation.CharsetName, collation.Name, nil
		}
	}
	return "", "", errors.Errorf("Unknown charset id %d", coID)
}

// GetCollations returns a list for all collations.
func GetCollations() []*Collation {
	return collations
}

const (
	// CharsetBin is used for marking binary charset.
	CharsetBin = "binary"
	// CollationBin is the default collation for CharsetBin.
	CollationBin = "binary"
	// CharsetUTF8 is the default charset for string types.
	CharsetUTF8 = "utf8"
	// CollationUTF8 is the default collation for CharsetUTF8.
	CollationUTF8 = "utf8_bin"
	// CharsetUTF8MB4 represents 4 bytes utf8, which works the same way as utf8 in Go.
	CharsetUTF8MB4 = "utf8mb4"
	// CollationUTF8MB4 is the default collation for CharsetUTF8MB4.
	CollationUTF8MB4 = "utf8mb4_bin"
	// CharsetASCII is a subset of UTF8.
	CharsetASCII = "ascii"
	// CollationASCII is the default collation for CharsetACSII.
	CollationASCII = "ascii_bin"
	// CharsetLatin1 is a single byte charset.
	CharsetLatin1 = "latin1"
	// CollationLatin1 is the default collation for CharsetLatin1.
	CollationLatin1 = "latin1_bin"
)

var collations = []*Collation{
	{1, "big5", "big5_chinese_ci", true},
	{2, "latin2", "latin2_czech_cs", false},
	{3, "dec8", "dec8_swedish_ci", true},
	{4, "cp850", "cp850_general_ci", true},
	{5, "latin1", "latin1_german1_ci", false},
	{6, "hp8", "hp8_english_ci", true},
	{7, "koi8r", "koi8r_general_ci", true},
	{8, "latin1", "latin1_swedish_ci", true},
	{9, "latin2", "latin2_general_ci", true},
	{10, "swe7", "swe7_swedish_ci", true},
	{11, "ascii", "ascii_general_ci", true},
	{12, "ujis", "ujis_japanese_ci", true},
	{13, "sjis", "sjis_japanese_ci", true},
	{14, "cp1251", "cp1251_bulgarian_ci", false},
	{15, "latin1", "latin1_danish_ci", false},
	{16, "hebrew", "hebrew_general_ci", true},
	{18, "tis620", "tis620_thai_ci", true},
	{19, "euckr", "euckr_korean_ci", true},
	{20, "latin7", "latin7_estonian_cs", false},
	{21, "latin2", "latin2_hungarian_ci", false},
	{22, "koi8u", "koi8u_general_ci", true},
	{23, "cp1251", "cp1251_ukrainian_ci", false},
	{24, "gb2312", "gb2312_chinese_ci", true},
	{25, "greek", "greek_general_ci", true},
	{26, "cp1250", "cp1250_general_ci", true},
	{27, "latin2", "latin2_croatian_ci", false},
	{28, "gbk", "gbk_chinese_ci", true},
	{29, "cp1257", "cp1257_lithuanian_ci", false},
	{30, "latin5", "latin5_turkish_ci", true},
	{31, "latin1", "latin1_german2_ci", false},
	{32, "armscii8", "armscii8_general_ci", true},
	{33, "utf8", "utf8_general_ci", true},
	{34, "cp1250", "cp1250_czech_cs", false},
	{35, "ucs2", "ucs2_general_ci", true},
	{36, "cp866", "cp866_general_ci", true},
	{37, "keybcs2", "keybcs2_general_ci", true},
	{38, "macce", "macce_general_ci", true},
	{39, "macroman", "macroman_general_ci", true},
	{40, "cp852", "cp852_general_ci", true},
	{41, "latin7", "latin7_general_ci", true},
	{42, "latin7", "latin7_general_cs", false},
	{43, "macce", "macce_bin", false},
	{44, "cp1250", "cp1250_croatian_ci", false},
	{45, "utf8mb4", "utf8mb4_general_ci", true},
	{46, "utf8mb4", "utf8mb4_bin", false},
	{47, "latin1", "latin1_bin", false},
	{48, "latin1", "latin1_general_ci", false},
	{49, "latin1", "latin1_general_cs", false},
	{50, "cp1251", "cp1251_bin", false},
	{51, "cp1251", "cp1251_general_ci", true},
	{52, "cp1251", "cp1251_general_cs", false},
	{53, "macroman", "macroman_bin", false},
	{54, "utf16", "utf16_general_ci", true},
	{55, "utf16", "utf16_bin", false},
	{56, "utf16le", "utf16le_general_ci", true},
	{57, "cp1256", "cp1256_general_ci", true},
	{58, "cp1257", "cp1257_bin", false},
	{59, "cp1257", "cp1257_general_ci", true},
	{60, "utf32", "utf32_general_ci", true},
	{61, "utf32", "utf32_bin", false},
	{62, "utf16le", "utf16le_bin", false},
	{63, "binary", "binary", true},
	{64, "armscii8", "armscii8_bin", false},
	{65, "ascii", "ascii_bin", false},
	{66, "cp1250", "cp1250_bin", false},
	{67, "cp1256", "cp1256_bin", false},
	{68, "cp866", "cp866_bin", false},
	{69, "dec8", "dec8_bin", false},
	{70, "greek", "greek_bin", false},
	{71, "hebrew", "hebrew_bin", false},
	{72, "hp8", "hp8_bin", false},
	{73, "keybcs2", "keybcs2_bin", false},
	{74, "koi8r", "koi8r_bin", false},
	{75, "koi8u", "koi8u_bin", false},
	{77, "latin2", "latin2_bin", false},
	{78, "latin5", "latin5_bin", false},
	{79, "latin7", "latin7_bin", false},
	{80, "cp850", "cp850_bin", false},
	{81, "cp852", "cp852_bin", false},
	{82, "swe7", "swe7_bin", false},
	{83, "utf8", "utf8_bin", false},
	{84, "big5", "big5_bin", false},
	{85, "euckr", "euckr_bin", false},
	{86, "gb2312", "gb2312_bin", false},
	{87, "gbk", "gbk_bin", false},
	{88, "sjis", "sjis_bin", false},
	{89, "tis620", "tis620_bin", false},
	{90, "ucs2", "ucs2_bin", false},
	{91, "ujis", "ujis_bin", false},
	{92, "geostd8", "geostd8_general_ci", true},
	{93, "geostd8", "geostd8_bin", false},
	{94, "latin1", "latin1_spanish_ci", false},
	{95, "cp932", "cp932_japanese_ci", true},
	{96, "cp932", "cp932_bin", false},
	{97, "eucjpms", "eucjpms_japanese_ci", true},
	{98, "eucjpms", "eucjpms_bin", false},
	{99, "cp1250", "cp1250_polish_ci", false},
	{101, "utf16", "utf16_unicode_ci", false},
	{102, "utf16", "utf16_icelandic_ci", false},
	{103, "utf16", "utf16_latvian_ci", false},
	{104, "utf16", "utf16_romanian_ci", false},
	{105, "utf16", "utf16_slovenian_ci", false},
	{106, "utf16", "utf16_polish_ci", false},
	{107, "utf16", "utf16_estonian_ci", false},
	{108, "utf16", "utf16_spanish_ci", false},
	{109, "utf16", "utf16_swedish_ci", false},
	{110, "utf16", "utf16_turkish_ci", false},
	{111, "utf16", "utf16_czech_ci", false},
	{112, "utf16", "utf16_danish_ci", false},
	{113, "utf16", "utf16_lithuanian_ci", false},
	{114, "utf16", "utf16_slovak_ci", false},
	{115, "utf16", "utf16_spanish2_ci", false},
	{116, "utf16", "utf16_roman_ci", false},
	{117, "utf16", "utf16_persian_ci", false},
	{118, "utf16", "utf16_esperanto_ci", false},
	{119, "utf16", "utf16_hungarian_ci", false},
	{120, "utf16", "utf16_sinhala_ci", false},
	{121, "utf16", "utf16_german2_ci", false},
	{122, "utf16", "utf16_croatian_ci", false},
	{123, "utf16", "utf16_unicode_520_ci", false},
	{124, "utf16", "utf16_vietnamese_ci", false},
	{128, "ucs2", "ucs2_unicode_ci", false},
	{129, "ucs2", "ucs2_icelandic_ci", false},
	{130, "ucs2", "ucs2_latvian_ci", false},
	{131, "ucs2", "ucs2_romanian_ci", false},
	{132, "ucs2", "ucs2_slovenian_ci", false},
	{133, "ucs2", "ucs2_polish_ci", false},
	{134, "ucs2", "ucs2_estonian_ci", false},
	{135, "ucs2", "ucs2_spanish_ci", false},
	{136, "ucs2", "ucs2_swedish_ci", false},
	{137, "ucs2", "ucs2_turkish_ci", false},
	{138, "ucs2", "ucs2_czech_ci", false},
	{139, "ucs2", "ucs2_danish_ci", false},
	{140, "ucs2", "ucs2_lithuanian_ci", false},
	{141, "ucs2", "ucs2_slovak_ci", false},
	{142, "ucs2", "ucs2_spanish2_ci", false},
	{143, "ucs2", "ucs2_roman_ci", false},
	{144, "ucs2", "ucs2_persian_ci", false},
	{145, "ucs2", "ucs2_esperanto_ci", false},
	{146, "ucs2", "ucs2_hungarian_ci", false},
	{147, "ucs2", "ucs2_sinhala_ci", false},
	{148, "ucs2", "ucs2_german2_ci", false},
	{149, "ucs2", "ucs2_croatian_ci", false},
	{150, "ucs2", "ucs2_unicode_520_ci", false},
	{151, "ucs2", "ucs2_vietnamese_ci", false},
	{159, "ucs2", "ucs2_general_mysql500_ci", false},
	{160, "utf32", "utf32_unicode_ci", false},
	{161, "utf32", "utf32_icelandic_ci", false},
	{162, "utf32", "utf32_latvian_ci", false},
	{163, "utf32", "utf32_romanian_ci", false},
	{164, "utf32", "utf32_slovenian_ci", false},
	{165, "utf32", "utf32_polish_ci", false},
	{166, "utf32", "utf32_estonian_ci", false},
	{167, "utf32", "utf32_spanish_ci", false},
	{168, "utf32", "utf32_swedish_ci", false},
	{169, "utf32", "utf32_turkish_ci", false},
	{170, "utf32", "utf32_czech_ci", false},
	{171, "utf32", "utf32_danish_ci", false},
	{172, "utf32", "utf32_lithuanian_ci", false},
	{173, "utf32", "utf32_slovak_ci", false},
	{174, "utf32", "utf32_spanish2_ci", false},
	{175, "utf32", "utf32_roman_ci", false},
	{176, "utf32", "utf32_persian_ci", false},
	{177, "utf32", "utf32_esperanto_ci", false},
	{178, "utf32", "utf32_hungarian_ci", false},
	{179, "utf32", "utf32_sinhala_ci", false},
	{180, "utf32", "utf32_german2_ci", false},
	{181, "utf32", "utf32_croatian_ci", false},
	{182, "utf32", "utf32_unicode_520_ci", false},
	{183, "utf32", "utf32_vietnamese_ci", false},
	{192, "utf8", "utf8_unicode_ci", false},
	{193, "utf8", "utf8_icelandic_ci", false},
	{194, "utf8", "utf8_latvian_ci", false},
	{195, "utf8", "utf8_romanian_ci", false},
	{196, "utf8", "utf8_slovenian_ci", false},
	{197, "utf8", "utf8_polish_ci", false},
	{198, "utf8", "utf8_estonian_ci", false},
	{199, "utf8", "utf8_spanish_ci", false},
	{200, "utf8", "utf8_swedish_ci", false},
	{201, "utf8", "utf8_turkish_ci", false},
	{202, "utf8", "utf8_czech_ci", false},
	{203, "utf8", "utf8_danish_ci", false},
	{204, "utf8", "utf8_lithuanian_ci", false},
	{205, "utf8", "utf8_slovak_ci", false},
	{206, "utf8", "utf8_spanish2_ci", false},
	{207, "utf8", "utf8_roman_ci", false},
	{208, "utf8", "utf8_persian_ci", false},
	{209, "utf8", "utf8_esperanto_ci", false},
	{210, "utf8", "utf8_hungarian_ci", false},
	{211, "utf8", "utf8_sinhala_ci", false},
	{212, "utf8", "utf8_german2_ci", false},
	{213, "utf8", "utf8_croatian_ci", false},
	{214, "utf8", "utf8_unicode_520_ci", false},
	{215, "utf8", "utf8_vietnamese_ci", false},
	{223, "utf8", "utf8_general_mysql500_ci", false},
	{224, "utf8mb4", "utf8mb4_unicode_ci", false},
	{225, "utf8mb4", "utf8mb4_icelandic_ci", false},
	{226, "utf8mb4", "utf8mb4_latvian_ci", false},
	{227, "utf8mb4", "utf8mb4_romanian_ci", false},
	{228, "utf8mb4", "utf8mb4_slovenian_ci", false},
	{229, "utf8mb4", "utf8mb4_polish_ci", false},
	{230, "utf8mb4", "utf8mb4_estonian_ci", false},
	{231, "utf8mb4", "utf8mb4_spanish_ci", false},
	{232, "utf8mb4", "utf8mb4_swedish_ci", false},
	{233, "utf8mb4", "utf8mb4_turkish_ci", false},
	{234, "utf8mb4", "utf8mb4_czech_ci", false},
	{235, "utf8mb4", "utf8mb4_danish_ci", false},
	{236, "utf8mb4", "utf8mb4_lithuanian_ci", false},
	{237, "utf8mb4", "utf8mb4_slovak_ci", false},
	{238, "utf8mb4", "utf8mb4_spanish2_ci", false},
	{239, "utf8mb4", "utf8mb4_roman_ci", false},
	{240, "utf8mb4", "utf8mb4_persian_ci", false},
	{241, "utf8mb4", "utf8mb4_esperanto_ci", false},
	{242, "utf8mb4", "utf8mb4_hungarian_ci", false},
	{243, "utf8mb4", "utf8mb4_sinhala_ci", false},
	{244, "utf8mb4", "utf8mb4_german2_ci", false},
	{245, "utf8mb4", "utf8mb4_croatian_ci", false},
	{246, "utf8mb4", "utf8mb4_unicode_520_ci", false},
	{247, "utf8mb4", "utf8mb4_vietnamese_ci", false},
}

// init method always puts to the end of file.
func init() {
	for _, c := range charsetInfos {
		charsets[c.Name] = c
	}
	for _, c := range collations {
		charset, ok := charsets[c.CharsetName]
		if !ok {
			continue
		}
		charset.Collations[c.Name] = c
	}
}