“use strict”;

// Description of supported double byte encodings and aliases. // Tables are not require()-d until they are needed to speed up library load. // require()-s are direct to support Browserify.

module.exports = {

// == Japanese/ShiftJIS ====================================================
// All japanese encodings are based on JIS X set of standards:
// JIS X 0201 - Single-byte encoding of ASCII + ¥ + Kana chars at 0xA1-0xDF.
// JIS X 0208 - Main set of 6879 characters, placed in 94x94 plane, to be encoded by 2 bytes. 
//              Has several variations in 1978, 1983, 1990 and 1997.
// JIS X 0212 - Supplementary plane of 6067 chars in 94x94 plane. 1990. Effectively dead.
// JIS X 0213 - Extension and modern replacement of 0208 and 0212. Total chars: 11233.
//              2 planes, first is superset of 0208, second - revised 0212.
//              Introduced in 2000, revised 2004. Some characters are in Unicode Plane 2 (0x2xxxx)

// Byte encodings are:
//  * Shift_JIS: Compatible with 0201, uses not defined chars in top half as lead bytes for double-byte
//               encoding of 0208. Lead byte ranges: 0x81-0x9F, 0xE0-0xEF; Trail byte ranges: 0x40-0x7E, 0x80-0x9E, 0x9F-0xFC.
//               Windows CP932 is a superset of Shift_JIS. Some companies added more chars, notably KDDI.
//  * EUC-JP:    Up to 3 bytes per character. Used mostly on *nixes.
//               0x00-0x7F       - lower part of 0201
//               0x8E, 0xA1-0xDF - upper part of 0201
//               (0xA1-0xFE)x2   - 0208 plane (94x94).
//               0x8F, (0xA1-0xFE)x2 - 0212 plane (94x94).
//  * JIS X 208: 7-bit, direct encoding of 0208. Byte ranges: 0x21-0x7E (94 values). Uncommon.
//               Used as-is in ISO2022 family.
//  * ISO2022-JP: Stateful encoding, with escape sequences to switch between ASCII, 
//                0201-1976 Roman, 0208-1978, 0208-1983.
//  * ISO2022-JP-1: Adds esc seq for 0212-1990.
//  * ISO2022-JP-2: Adds esc seq for GB2313-1980, KSX1001-1992, ISO8859-1, ISO8859-7.
//  * ISO2022-JP-3: Adds esc seq for 0201-1976 Kana set, 0213-2000 Planes 1, 2.
//  * ISO2022-JP-2004: Adds 0213-2004 Plane 1.
//
// After JIS X 0213 appeared, Shift_JIS-2004, EUC-JISX0213 and ISO2022-JP-2004 followed, with just changing the planes.
//
// Overall, it seems that it's a mess :( http://www8.plala.or.jp/tkubota1/unicode-symbols-map2.html

'shiftjis': {
    type: '_dbcs',
    table: function() { return require('./tables/shiftjis.json') },
    encodeAdd: {'\u00a5': 0x5C, '\u203E': 0x7E},
    encodeSkipVals: [{from: 0xED40, to: 0xF940}],
},
'csshiftjis': 'shiftjis',
'mskanji': 'shiftjis',
'sjis': 'shiftjis',
'windows31j': 'shiftjis',
'ms31j': 'shiftjis',
'xsjis': 'shiftjis',
'windows932': 'shiftjis',
'ms932': 'shiftjis',
'932': 'shiftjis',
'cp932': 'shiftjis',

'eucjp': {
    type: '_dbcs',
    table: function() { return require('./tables/eucjp.json') },
    encodeAdd: {'\u00a5': 0x5C, '\u203E': 0x7E},
},

// TODO: KDDI extension to Shift_JIS
// TODO: IBM CCSID 942 = CP932, but F0-F9 custom chars and other char changes.
// TODO: IBM CCSID 943 = Shift_JIS = CP932 with original Shift_JIS lower 128 chars.

// == Chinese/GBK ==========================================================
// http://en.wikipedia.org/wiki/GBK
// We mostly implement W3C recommendation: https://www.w3.org/TR/encoding/#gbk-encoder

// Oldest GB2312 (1981, ~7600 chars) is a subset of CP936
'gb2312': 'cp936',
'gb231280': 'cp936',
'gb23121980': 'cp936',
'csgb2312': 'cp936',
'csiso58gb231280': 'cp936',
'euccn': 'cp936',

// Microsoft's CP936 is a subset and approximation of GBK.
'windows936': 'cp936',
'ms936': 'cp936',
'936': 'cp936',
'cp936': {
    type: '_dbcs',
    table: function() { return require('./tables/cp936.json') },
},

// GBK (~22000 chars) is an extension of CP936 that added user-mapped chars and some other.
'gbk': {
    type: '_dbcs',
    table: function() { return require('./tables/cp936.json').concat(require('./tables/gbk-added.json')) },
},
'xgbk': 'gbk',
'isoir58': 'gbk',

// GB18030 is an algorithmic extension of GBK.
// Main source: https://www.w3.org/TR/encoding/#gbk-encoder
// http://icu-project.org/docs/papers/gb18030.html
// http://source.icu-project.org/repos/icu/data/trunk/charset/data/xml/gb-18030-2000.xml
// http://www.khngai.com/chinese/charmap/tblgbk.php?page=0
'gb18030': {
    type: '_dbcs',
    table: function() { return require('./tables/cp936.json').concat(require('./tables/gbk-added.json')) },
    gb18030: function() { return require('./tables/gb18030-ranges.json') },
    encodeSkipVals: [0x80],
    encodeAdd: {'€': 0xA2E3},
},

'chinese': 'gb18030',

// == Korean ===============================================================
// EUC-KR, KS_C_5601 and KS X 1001 are exactly the same.
'windows949': 'cp949',
'ms949': 'cp949',
'949': 'cp949',
'cp949': {
    type: '_dbcs',
    table: function() { return require('./tables/cp949.json') },
},

'cseuckr': 'cp949',
'csksc56011987': 'cp949',
'euckr': 'cp949',
'isoir149': 'cp949',
'korean': 'cp949',
'ksc56011987': 'cp949',
'ksc56011989': 'cp949',
'ksc5601': 'cp949',

// == Big5/Taiwan/Hong Kong ================================================
// There are lots of tables for Big5 and cp950. Please see the following links for history:
// http://moztw.org/docs/big5/  http://www.haible.de/bruno/charsets/conversion-tables/Big5.html
// Variations, in roughly number of defined chars:
//  * Windows CP 950: Microsoft variant of Big5. Canonical: http://www.unicode.org/Public/MAPPINGS/VENDORS/MICSFT/WINDOWS/CP950.TXT
//  * Windows CP 951: Microsoft variant of Big5-HKSCS-2001. Seems to be never public. http://me.abelcheung.org/articles/research/what-is-cp951/
//  * Big5-2003 (Taiwan standard) almost superset of cp950.
//  * Unicode-at-on (UAO) / Mozilla 1.8. Falling out of use on the Web. Not supported by other browsers.
//  * Big5-HKSCS (-2001, -2004, -2008). Hong Kong standard. 
//    many unicode code points moved from PUA to Supplementary plane (U+2XXXX) over the years.
//    Plus, it has 4 combining sequences.
//    Seems that Mozilla refused to support it for 10 yrs. https://bugzilla.mozilla.org/show_bug.cgi?id=162431 https://bugzilla.mozilla.org/show_bug.cgi?id=310299
//    because big5-hkscs is the only encoding to include astral characters in non-algorithmic way.
//    Implementations are not consistent within browsers; sometimes labeled as just big5.
//    MS Internet Explorer switches from big5 to big5-hkscs when a patch applied.
//    Great discussion & recap of what's going on https://bugzilla.mozilla.org/show_bug.cgi?id=912470#c31
//    In the encoder, it might make sense to support encoding old PUA mappings to Big5 bytes seq-s.
//    Official spec: http://www.ogcio.gov.hk/en/business/tech_promotion/ccli/terms/doc/2003cmp_2008.txt
//                   http://www.ogcio.gov.hk/tc/business/tech_promotion/ccli/terms/doc/hkscs-2008-big5-iso.txt
// 
// Current understanding of how to deal with Big5(-HKSCS) is in the Encoding Standard, http://encoding.spec.whatwg.org/#big5-encoder
// Unicode mapping (http://www.unicode.org/Public/MAPPINGS/OBSOLETE/EASTASIA/OTHER/BIG5.TXT) is said to be wrong.

'windows950': 'cp950',
'ms950': 'cp950',
'950': 'cp950',
'cp950': {
    type: '_dbcs',
    table: function() { return require('./tables/cp950.json') },
},

// Big5 has many variations and is an extension of cp950. We use Encoding Standard's as a consensus.
'big5': 'big5hkscs',
'big5hkscs': {
    type: '_dbcs',
    table: function() { return require('./tables/cp950.json').concat(require('./tables/big5-added.json')) },
    encodeSkipVals: [0xa2cc],
},

'cnbig5': 'big5hkscs',
'csbig5': 'big5hkscs',
'xxbig5': 'big5hkscs',

};