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// Copyright 2013 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package japanese
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import (
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	"unicode/utf8"
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	"golang.org/x/text/encoding"
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	"golang.org/x/text/encoding/internal"
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	"golang.org/x/text/encoding/internal/identifier"
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	"golang.org/x/text/transform"
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)
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// ISO2022JP is the ISO-2022-JP encoding.
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var ISO2022JP encoding.Encoding = &iso2022JP
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var iso2022JP = internal.Encoding{
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	internal.FuncEncoding{iso2022JPNewDecoder, iso2022JPNewEncoder},
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	"ISO-2022-JP",
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	identifier.ISO2022JP,
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}
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func iso2022JPNewDecoder() transform.Transformer {
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	return new(iso2022JPDecoder)
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}
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func iso2022JPNewEncoder() transform.Transformer {
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	return new(iso2022JPEncoder)
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}
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const (
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	asciiState = iota
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	katakanaState
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	jis0208State
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	jis0212State
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)
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const asciiEsc = 0x1b
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type iso2022JPDecoder int
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func (d *iso2022JPDecoder) Reset() {
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	*d = asciiState
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}
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func (d *iso2022JPDecoder) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
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	r, size := rune(0), 0
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	for ; nSrc < len(src); nSrc += size {
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		c0 := src[nSrc]
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		if c0 >= utf8.RuneSelf {
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			r, size = '\ufffd', 1
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			goto write
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		}
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		if c0 == asciiEsc {
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			if nSrc+2 >= len(src) {
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				if !atEOF {
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					return nDst, nSrc, transform.ErrShortSrc
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				}
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				// TODO: is it correct to only skip 1??
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				r, size = '\ufffd', 1
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				goto write
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			}
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			size = 3
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			c1 := src[nSrc+1]
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			c2 := src[nSrc+2]
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			switch {
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			case c1 == '$' && (c2 == '@' || c2 == 'B'): // 0x24 {0x40, 0x42}
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				*d = jis0208State
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				continue
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			case c1 == '$' && c2 == '(': // 0x24 0x28
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				if nSrc+3 >= len(src) {
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					if !atEOF {
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						return nDst, nSrc, transform.ErrShortSrc
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					}
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					r, size = '\ufffd', 1
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					goto write
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				}
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				size = 4
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				if src[nSrc+3] == 'D' {
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					*d = jis0212State
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					continue
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				}
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			case c1 == '(' && (c2 == 'B' || c2 == 'J'): // 0x28 {0x42, 0x4A}
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				*d = asciiState
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				continue
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			case c1 == '(' && c2 == 'I': // 0x28 0x49
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				*d = katakanaState
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				continue
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			}
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			r, size = '\ufffd', 1
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			goto write
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		}
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		switch *d {
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		case asciiState:
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			r, size = rune(c0), 1
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		case katakanaState:
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			if c0 < 0x21 || 0x60 <= c0 {
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				r, size = '\ufffd', 1
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				goto write
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			}
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			r, size = rune(c0)+(0xff61-0x21), 1
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		default:
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			if c0 == 0x0a {
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				*d = asciiState
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				r, size = rune(c0), 1
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				goto write
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			}
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			if nSrc+1 >= len(src) {
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				if !atEOF {
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					return nDst, nSrc, transform.ErrShortSrc
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				}
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				r, size = '\ufffd', 1
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				goto write
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			}
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			size = 2
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			c1 := src[nSrc+1]
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			i := int(c0-0x21)*94 + int(c1-0x21)
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			if *d == jis0208State && i < len(jis0208Decode) {
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				r = rune(jis0208Decode[i])
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			} else if *d == jis0212State && i < len(jis0212Decode) {
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				r = rune(jis0212Decode[i])
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			} else {
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				r = '\ufffd'
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				goto write
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			}
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			if r == 0 {
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				r = '\ufffd'
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			}
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		}
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	write:
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		if nDst+utf8.RuneLen(r) > len(dst) {
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			return nDst, nSrc, transform.ErrShortDst
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		}
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		nDst += utf8.EncodeRune(dst[nDst:], r)
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	}
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	return nDst, nSrc, err
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}
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type iso2022JPEncoder int
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func (e *iso2022JPEncoder) Reset() {
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	*e = asciiState
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}
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func (e *iso2022JPEncoder) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
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	r, size := rune(0), 0
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	for ; nSrc < len(src); nSrc += size {
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		r = rune(src[nSrc])
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		// Decode a 1-byte rune.
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		if r < utf8.RuneSelf {
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			size = 1
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		} else {
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			// Decode a multi-byte rune.
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			r, size = utf8.DecodeRune(src[nSrc:])
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			if size == 1 {
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				// All valid runes of size 1 (those below utf8.RuneSelf) were
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				// handled above. We have invalid UTF-8 or we haven't seen the
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				// full character yet.
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				if !atEOF && !utf8.FullRune(src[nSrc:]) {
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					err = transform.ErrShortSrc
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					break
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				}
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			}
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			// func init checks that the switch covers all tables.
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			//
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			// http://encoding.spec.whatwg.org/#iso-2022-jp says that "the index jis0212
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			// is not used by the iso-2022-jp encoder due to lack of widespread support".
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			//
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			// TODO: do we have to special-case U+00A5 and U+203E, as per
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			// http://encoding.spec.whatwg.org/#iso-2022-jp
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			// Doing so would mean that "\u00a5" would not be preserved
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			// after an encode-decode round trip.
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			switch {
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			case encode0Low <= r && r < encode0High:
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				if r = rune(encode0[r-encode0Low]); r>>tableShift == jis0208 {
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					goto writeJIS
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				}
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			case encode1Low <= r && r < encode1High:
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				if r = rune(encode1[r-encode1Low]); r>>tableShift == jis0208 {
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					goto writeJIS
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				}
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			case encode2Low <= r && r < encode2High:
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				if r = rune(encode2[r-encode2Low]); r>>tableShift == jis0208 {
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					goto writeJIS
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				}
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			case encode3Low <= r && r < encode3High:
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				if r = rune(encode3[r-encode3Low]); r>>tableShift == jis0208 {
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					goto writeJIS
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				}
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			case encode4Low <= r && r < encode4High:
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				if r = rune(encode4[r-encode4Low]); r>>tableShift == jis0208 {
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					goto writeJIS
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				}
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			case encode5Low <= r && r < encode5High:
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				if 0xff61 <= r && r < 0xffa0 {
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					goto writeKatakana
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				}
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				if r = rune(encode5[r-encode5Low]); r>>tableShift == jis0208 {
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					goto writeJIS
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				}
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			}
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			// Switch back to ASCII state in case of error so that an ASCII
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			// replacement character can be written in the correct state.
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			if *e != asciiState {
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				if nDst+3 > len(dst) {
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					err = transform.ErrShortDst
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					break
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				}
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				*e = asciiState
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				dst[nDst+0] = asciiEsc
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				dst[nDst+1] = '('
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				dst[nDst+2] = 'B'
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				nDst += 3
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			}
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			err = internal.ErrASCIIReplacement
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			break
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		}
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		if *e != asciiState {
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			if nDst+4 > len(dst) {
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				err = transform.ErrShortDst
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				break
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			}
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			*e = asciiState
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			dst[nDst+0] = asciiEsc
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			dst[nDst+1] = '('
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			dst[nDst+2] = 'B'
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			nDst += 3
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		} else if nDst >= len(dst) {
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			err = transform.ErrShortDst
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			break
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		}
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		dst[nDst] = uint8(r)
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		nDst++
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		continue
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	writeJIS:
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		if *e != jis0208State {
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			if nDst+5 > len(dst) {
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				err = transform.ErrShortDst
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				break
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			}
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			*e = jis0208State
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			dst[nDst+0] = asciiEsc
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			dst[nDst+1] = '$'
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			dst[nDst+2] = 'B'
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			nDst += 3
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		} else if nDst+2 > len(dst) {
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			err = transform.ErrShortDst
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			break
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		}
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		dst[nDst+0] = 0x21 + uint8(r>>codeShift)&codeMask
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		dst[nDst+1] = 0x21 + uint8(r)&codeMask
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		nDst += 2
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		continue
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	writeKatakana:
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		if *e != katakanaState {
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			if nDst+4 > len(dst) {
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				err = transform.ErrShortDst
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				break
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			}
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			*e = katakanaState
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			dst[nDst+0] = asciiEsc
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			dst[nDst+1] = '('
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			dst[nDst+2] = 'I'
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			nDst += 3
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		} else if nDst >= len(dst) {
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			err = transform.ErrShortDst
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			break
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		}
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		dst[nDst] = uint8(r - (0xff61 - 0x21))
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		nDst++
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		continue
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	}
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	if atEOF && err == nil && *e != asciiState {
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		if nDst+3 > len(dst) {
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			err = transform.ErrShortDst
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		} else {
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			*e = asciiState
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			dst[nDst+0] = asciiEsc
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			dst[nDst+1] = '('
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			dst[nDst+2] = 'B'
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			nDst += 3
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		}
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	}
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	return nDst, nSrc, err
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}
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