// Copyright 2011 The Go Authors. All rights reserved.

// Use of this source code is governed by a BSD-style

// license that can be found in the LICENSE file.

// Note: the file data_test.go that is generated should not be checked in.

//go:generate go run maketables.go triegen.go

//go:generate go test -tags test

// Package norm contains types and functions for normalizing Unicode strings.

package norm // import "golang.org/x/text/unicode/norm"

import (

	"unicode/utf8"

	"golang.org/x/text/transform"

)

// A Form denotes a canonical representation of Unicode code points.

// The Unicode-defined normalization and equivalence forms are:

//

//

// For a Form f, this documentation uses the notation f(x) to mean

// the bytes or string x converted to the given form.

// A position n in x is called a boundary if conversion to the form can

// proceed independently on both sides:

//

// References: https://unicode.org/reports/tr15/ and

// https://unicode.org/notes/tn5/.

type Form int

const (

	NFC Form = iota

	NFD

	NFKC

	NFKD

)

// Bytes returns f(b). May return b if f(b) = b.

func (f Form) Bytes(b []byte) []byte {

	src := inputBytes(b)

	ft := formTable[f]

	n, ok := ft.quickSpan(src, 0, len(b), true)

	if ok {

		return b

	}

	out := make([]byte, n, len(b))

	copy(out, b[0:n])

	rb := reorderBuffer{f: *ft, src: src, nsrc: len(b), out: out, flushF: appendFlush}

	return doAppendInner(&rb, n)

}

// String returns f(s).

func (f Form) String(s string) string {

	src := inputString(s)

	ft := formTable[f]

	n, ok := ft.quickSpan(src, 0, len(s), true)

	if ok {

		return s

	}

	out := make([]byte, n, len(s))

	copy(out, s[0:n])

	rb := reorderBuffer{f: *ft, src: src, nsrc: len(s), out: out, flushF: appendFlush}

	return string(doAppendInner(&rb, n))

}

// IsNormal returns true if b == f(b).

func (f Form) IsNormal(b []byte) bool {

	src := inputBytes(b)

	ft := formTable[f]

	bp, ok := ft.quickSpan(src, 0, len(b), true)

	if ok {

		return true

	}

	rb := reorderBuffer{f: *ft, src: src, nsrc: len(b)}

	rb.setFlusher(nil, cmpNormalBytes)

	for bp < len(b) {

		rb.out = b[bp:]

		if bp = decomposeSegment(&rb, bp, true); bp < 0 {

			return false

		}

		bp, _ = rb.f.quickSpan(rb.src, bp, len(b), true)

	}

	return true

}

func cmpNormalBytes(rb *reorderBuffer) bool {

	b := rb.out

	for i := 0; i < rb.nrune; i++ {

		info := rb.rune[i]

		if int(info.size) > len(b) {

			return false

		}

		p := info.pos

		pe := p + info.size

		for ; p < pe; p++ {

			if b[0] != rb.byte[p] {

				return false

			}

			b = b[1:]

		}

	}

	return true

}

// IsNormalString returns true if s == f(s).

func (f Form) IsNormalString(s string) bool {

	src := inputString(s)

	ft := formTable[f]

	bp, ok := ft.quickSpan(src, 0, len(s), true)

	if ok {

		return true

	}

	rb := reorderBuffer{f: *ft, src: src, nsrc: len(s)}

	rb.setFlusher(nil, func(rb *reorderBuffer) bool {

		for i := 0; i < rb.nrune; i++ {

			info := rb.rune[i]

			if bp+int(info.size) > len(s) {

				return false

			}

			p := info.pos

			pe := p + info.size

			for ; p < pe; p++ {

				if s[bp] != rb.byte[p] {

					return false

				}

				bp++

			}

		}

		return true

	})

	for bp < len(s) {

		if bp = decomposeSegment(&rb, bp, true); bp < 0 {

			return false

		}

		bp, _ = rb.f.quickSpan(rb.src, bp, len(s), true)

	}

	return true

}

// patchTail fixes a case where a rune may be incorrectly normalized

// if it is followed by illegal continuation bytes. It returns the

// patched buffer and whether the decomposition is still in progress.

func patchTail(rb *reorderBuffer) bool {

	info, p := lastRuneStart(&rb.f, rb.out)

	if p == -1 || info.size == 0 {

		return true

	}

	end := p + int(info.size)

	extra := len(rb.out) - end

	if extra > 0 {

		// Potentially allocating memory. However, this only

		// happens with ill-formed UTF-8.

		x := make([]byte, 0)

		x = append(x, rb.out[len(rb.out)-extra:]...)

		rb.out = rb.out[:end]

		decomposeToLastBoundary(rb)

		rb.doFlush()

		rb.out = append(rb.out, x...)

		return false

	}

	buf := rb.out[p:]

	rb.out = rb.out[:p]

	decomposeToLastBoundary(rb)

	if s := rb.ss.next(info); s == ssStarter {

		rb.doFlush()

		rb.ss.first(info)

	} else if s == ssOverflow {

		rb.doFlush()

		rb.insertCGJ()

		rb.ss = 0

	}

	rb.insertUnsafe(inputBytes(buf), 0, info)

	return true

}

func appendQuick(rb *reorderBuffer, i int) int {

	if rb.nsrc == i {

		return i

	}

	end, _ := rb.f.quickSpan(rb.src, i, rb.nsrc, true)

	rb.out = rb.src.appendSlice(rb.out, i, end)

	return end

}

// Append returns f(append(out, b...)).

// The buffer out must be nil, empty, or equal to f(out).

func (f Form) Append(out []byte, src ...byte) []byte {

	return f.doAppend(out, inputBytes(src), len(src))

}

func (f Form) doAppend(out []byte, src input, n int) []byte {

	if n == 0 {

		return out

	}

	ft := formTable[f]

	// Attempt to do a quickSpan first so we can avoid initializing the reorderBuffer.

	if len(out) == 0 {

		p, _ := ft.quickSpan(src, 0, n, true)

		out = src.appendSlice(out, 0, p)

		if p == n {

			return out

		}

		rb := reorderBuffer{f: *ft, src: src, nsrc: n, out: out, flushF: appendFlush}

		return doAppendInner(&rb, p)

	}

	rb := reorderBuffer{f: *ft, src: src, nsrc: n}

	return doAppend(&rb, out, 0)

}

func doAppend(rb *reorderBuffer, out []byte, p int) []byte {

	rb.setFlusher(out, appendFlush)

	src, n := rb.src, rb.nsrc

	doMerge := len(out) > 0

	if q := src.skipContinuationBytes(p); q > p {

		// Move leading non-starters to destination.

		rb.out = src.appendSlice(rb.out, p, q)

		p = q

		doMerge = patchTail(rb)

	}

	fd := &rb.f

	if doMerge {

		var info Properties

		if p < n {

			info = fd.info(src, p)

			if !info.BoundaryBefore() || info.nLeadingNonStarters() > 0 {

				if p == 0 {

					decomposeToLastBoundary(rb)

				}

				p = decomposeSegment(rb, p, true)

			}

		}

		if info.size == 0 {

			rb.doFlush()

			// Append incomplete UTF-8 encoding.

			return src.appendSlice(rb.out, p, n)

		}

		if rb.nrune > 0 {

			return doAppendInner(rb, p)

		}

	}

	p = appendQuick(rb, p)

	return doAppendInner(rb, p)

}

func doAppendInner(rb *reorderBuffer, p int) []byte {

	for n := rb.nsrc; p < n; {

		p = decomposeSegment(rb, p, true)

		p = appendQuick(rb, p)

	}

	return rb.out

}

// AppendString returns f(append(out, []byte(s))).

// The buffer out must be nil, empty, or equal to f(out).

func (f Form) AppendString(out []byte, src string) []byte {

	return f.doAppend(out, inputString(src), len(src))

}

// QuickSpan returns a boundary n such that b[0:n] == f(b[0:n]).

// It is not guaranteed to return the largest such n.

func (f Form) QuickSpan(b []byte) int {

	n, _ := formTable[f].quickSpan(inputBytes(b), 0, len(b), true)

	return n

}

// Span implements transform.SpanningTransformer. It returns a boundary n such

// that b[0:n] == f(b[0:n]). It is not guaranteed to return the largest such n.

func (f Form) Span(b []byte, atEOF bool) (n int, err error) {

	n, ok := formTable[f].quickSpan(inputBytes(b), 0, len(b), atEOF)

	if n < len(b) {

		if !ok {

			err = transform.ErrEndOfSpan

		} else {

			err = transform.ErrShortSrc

		}

	}

	return n, err

}

// SpanString returns a boundary n such that s[0:n] == f(s[0:n]).

// It is not guaranteed to return the largest such n.

func (f Form) SpanString(s string, atEOF bool) (n int, err error) {

	n, ok := formTable[f].quickSpan(inputString(s), 0, len(s), atEOF)

	if n < len(s) {

		if !ok {

			err = transform.ErrEndOfSpan

		} else {

			err = transform.ErrShortSrc

		}

	}

	return n, err

}

// quickSpan returns a boundary n such that src[0:n] == f(src[0:n]) and

// whether any non-normalized parts were found. If atEOF is false, n will

// not point past the last segment if this segment might be become

// non-normalized by appending other runes.

func (f *formInfo) quickSpan(src input, i, end int, atEOF bool) (n int, ok bool) {

	var lastCC uint8

	ss := streamSafe(0)

	lastSegStart := i

	for n = end; i < n; {

		if j := src.skipASCII(i, n); i != j {

			i = j

			lastSegStart = i - 1

			lastCC = 0

			ss = 0

			continue

		}

		info := f.info(src, i)

		if info.size == 0 {

			if atEOF {

				// include incomplete runes

				return n, true

			}

			return lastSegStart, true

		}

		// This block needs to be before the next, because it is possible to

		// have an overflow for runes that are starters (e.g. with U+FF9E).

		switch ss.next(info) {

		case ssStarter:

			lastSegStart = i

		case ssOverflow:

			return lastSegStart, false

		case ssSuccess:

			if lastCC > info.ccc {

				return lastSegStart, false

			}

		}

		if f.composing {

			if !info.isYesC() {

				break

			}

		} else {

			if !info.isYesD() {

				break

			}

		}

		lastCC = info.ccc

		i += int(info.size)

	}

	if i == n {

		if !atEOF {

			n = lastSegStart

		}

		return n, true

	}

	return lastSegStart, false

}

// QuickSpanString returns a boundary n such that s[0:n] == f(s[0:n]).

// It is not guaranteed to return the largest such n.

func (f Form) QuickSpanString(s string) int {

	n, _ := formTable[f].quickSpan(inputString(s), 0, len(s), true)

	return n

}

// FirstBoundary returns the position i of the first boundary in b

// or -1 if b contains no boundary.

func (f Form) FirstBoundary(b []byte) int {

	return f.firstBoundary(inputBytes(b), len(b))

}

func (f Form) firstBoundary(src input, nsrc int) int {

	i := src.skipContinuationBytes(0)

	if i >= nsrc {

		return -1

	}

	fd := formTable[f]

	ss := streamSafe(0)

	// We should call ss.first here, but we can't as the first rune is

	// skipped already. This means FirstBoundary can't really determine

	// CGJ insertion points correctly. Luckily it doesn't have to.

	for {

		info := fd.info(src, i)

		if info.size == 0 {

			return -1

		}

		if s := ss.next(info); s != ssSuccess {

			return i

		}

		i += int(info.size)

		if i >= nsrc {

			if !info.BoundaryAfter() && !ss.isMax() {