// 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.

package norm

import (
	"fmt"
	"testing"

	"golang.org/x/text/transform"
)

func TestTransform(t *testing.T) {
	tests := []struct {
		f       Form
		in, out string
		eof     bool
		dstSize int
		err     error
	}{
		{NFC, "ab", "ab", true, 2, nil},
		{NFC, "qx", "qx", true, 2, nil},
		{NFD, "qx", "qx", true, 2, nil},
		{NFC, "", "", true, 1, nil},
		{NFD, "", "", true, 1, nil},
		{NFC, "", "", false, 1, nil},
		{NFD, "", "", false, 1, nil},

		// Normalized segment does not fit in destination.
		{NFD, "ö", "", true, 1, transform.ErrShortDst},
		{NFD, "ö", "", true, 2, transform.ErrShortDst},

		// As an artifact of the algorithm, only full segments are written.
		// This is not strictly required, and some bytes could be written.
		// In practice, for Transform to not block, the destination buffer
		// should be at least MaxSegmentSize to work anyway and these edge
		// conditions will be relatively rare.
		{NFC, "ab", "", true, 1, transform.ErrShortDst},
		// This is even true for inert runes.
		{NFC, "qx", "", true, 1, transform.ErrShortDst},
		{NFC, "a\u0300abc", "\u00e0a", true, 4, transform.ErrShortDst},

		// We cannot write a segment if successive runes could still change the result.
		{NFD, "ö", "", false, 3, transform.ErrShortSrc},
		{NFC, "a\u0300", "", false, 4, transform.ErrShortSrc},
		{NFD, "a\u0300", "", false, 4, transform.ErrShortSrc},
		{NFC, "ö", "", false, 3, transform.ErrShortSrc},

		{NFD, "abc", "", false, 1, transform.ErrShortDst},
		{NFC, "abc", "", false, 1, transform.ErrShortDst},
		{NFC, "abc", "a", false, 2, transform.ErrShortDst},
		{NFD, "éfff", "", false, 2, transform.ErrShortDst},
		{NFC, "e\u0301fffff", "\u00e9fff", false, 6, transform.ErrShortDst},
		{NFD, "ééééé", "e\u0301e\u0301e\u0301", false, 15, transform.ErrShortDst},

		{NFC, "a\u0300", "", true, 1, transform.ErrShortDst},
		// Theoretically could fit, but won't due to simplified checks.
		{NFC, "a\u0300", "", true, 2, transform.ErrShortDst},
		{NFC, "a\u0300", "", true, 3, transform.ErrShortDst},
		{NFC, "a\u0300", "\u00e0", true, 4, nil},

		{NFD, "öa\u0300", "o\u0308", false, 8, transform.ErrShortSrc},
		{NFD, "öa\u0300ö", "o\u0308a\u0300", true, 8, transform.ErrShortDst},
		{NFD, "öa\u0300ö", "o\u0308a\u0300", false, 12, transform.ErrShortSrc},

		// Illegal input is copied verbatim.
		{NFD, "\xbd\xb2=\xbc ", "\xbd\xb2=\xbc ", true, 8, nil},
	}
	b := make([]byte, 100)
	for i, tt := range tests {
		t.Run(fmt.Sprintf("%d:%s", i, tt.in), func(t *testing.T) {
			nDst, _, err := tt.f.Transform(b[:tt.dstSize], []byte(tt.in), tt.eof)
			out := string(b[:nDst])
			if out != tt.out || err != tt.err {
				t.Errorf("was %+q (%v); want %+q (%v)", out, err, tt.out, tt.err)
			}
			if want := tt.f.String(tt.in)[:nDst]; want != out {
				t.Errorf("incorrect normalization: was %+q; want %+q", out, want)
			}
		})
	}
}

var transBufSizes = []int{
	MaxTransformChunkSize,
	3 * MaxTransformChunkSize / 2,
	2 * MaxTransformChunkSize,
	3 * MaxTransformChunkSize,
	100 * MaxTransformChunkSize,
}

func doTransNorm(f Form, buf []byte, b []byte) []byte {
	acc := []byte{}
	for p := 0; p < len(b); {
		nd, ns, _ := f.Transform(buf[:], b[p:], true)
		p += ns
		acc = append(acc, buf[:nd]...)
	}
	return acc
}

func TestTransformNorm(t *testing.T) {
	for _, sz := range transBufSizes {
		buf := make([]byte, sz)
		runNormTests(t, fmt.Sprintf("Transform:%d", sz), func(f Form, out []byte, s string) []byte {
			return doTransNorm(f, buf, append(out, s...))
		})
	}
}