package lz4_test

import (
	"bytes"
	"errors"
	"fmt"
	"io"
	"io/ioutil"
	"os"
	"reflect"
	"strings"
	"testing"

	"github.com/pierrec/lz4/v4"
)

func _o(s ...lz4.Option) []lz4.Option {
	return s
}

func TestReader(t *testing.T) {
	goldenFiles := []string{
		"testdata/e.txt.lz4",
		"testdata/gettysburg.txt.lz4",
		"testdata/Mark.Twain-Tom.Sawyer.txt.lz4",
		"testdata/Mark.Twain-Tom.Sawyer_long.txt.lz4",
		"testdata/pg1661.txt.lz4",
		"testdata/pi.txt.lz4",
		"testdata/random.data.lz4",
		"testdata/repeat.txt.lz4",
		"testdata/pg_control.tar.lz4",
	}

	for _, fname := range goldenFiles {
		for _, opts := range [][]lz4.Option{
			nil,
			_o(lz4.ConcurrencyOption(-1)),
		} {
			label := fmt.Sprintf("%s %v", fname, opts)
			t.Run(label, func(t *testing.T) {
				fname := fname
				t.Parallel()

				f, err := os.Open(fname)
				if err != nil {
					t.Fatal(err)
				}
				defer f.Close()

				rawfile := strings.TrimSuffix(fname, ".lz4")
				raw, err := ioutil.ReadFile(rawfile)
				if err != nil {
					t.Fatal(err)
				}

				out := new(bytes.Buffer)
				zr := lz4.NewReader(f)
				if err := zr.Apply(opts...); err != nil {
					t.Fatal(err)
				}
				n, err := io.Copy(out, zr)
				if err != nil {
					t.Error(err)
				}

				if got, want := int(n), len(raw); got != want {
					t.Errorf("invalid size: got %d; want %d", got, want)
				}

				if got, want := out.Bytes(), raw; !reflect.DeepEqual(got, want) {
					t.Fatal("uncompressed data does not match original")
				}

				if len(raw) < 20 {
					return
				}

				f2, err := os.Open(fname)
				if err != nil {
					t.Fatal(err)
				}
				defer f2.Close()

				out.Reset()
				zr = lz4.NewReader(f2)
				_, err = io.CopyN(out, zr, 10)
				if err != nil {
					t.Fatal(err)
				}
				if !reflect.DeepEqual(out.Bytes(), raw[:10]) {
					t.Fatal("partial read does not match original")
				}
			})
		}
	}
}

func TestReader_Reset(t *testing.T) {
	data := pg1661LZ4
	buf := new(bytes.Buffer)
	src := bytes.NewReader(data)
	zr := lz4.NewReader(src)

	// Partial read.
	_, _ = io.CopyN(buf, zr, int64(len(data))/2)

	buf.Reset()
	src.Reset(data)
	// Another time to maybe trigger some edge case.
	src.Reset(data)
	zr.Reset(src)
	if _, err := io.Copy(buf, zr); err != nil {
		t.Fatal(err)
	}
	if !reflect.DeepEqual(buf.Bytes(), pg1661) {
		t.Fatal("result does not match original")
	}
}

type brokenWriter int

func (w *brokenWriter) Write(p []byte) (n int, err error) {
	n = len(p)
	if n > int(*w) {
		n = int(*w)
		err = errors.New("broken")
	}
	*w -= brokenWriter(n)
	return
}

// WriteTo should report the number of bytes successfully written,
// not the number successfully decompressed.
func TestWriteToBrokenWriter(t *testing.T) {
	const capacity = 10
	w := brokenWriter(capacity)
	r := lz4.NewReader(bytes.NewReader(pg1661LZ4))

	n, err := r.WriteTo(&w)
	switch {
	case n > capacity:
		t.Errorf("reported number of bytes written %d too big", n)
	case err == nil:
		t.Error("no error from broken Writer")
	case err.Error() != "broken":
		t.Errorf("unexpected error %q", err.Error())
	}
}

func TestReaderLegacy(t *testing.T) {
	goldenFiles := []string{
		"testdata/vmlinux_LZ4_19377.lz4",
		"testdata/bzImage_lz4_isolated.lz4",
	}

	for _, fname := range goldenFiles {
		for _, opts := range [][]lz4.Option{
			nil,
			_o(lz4.ConcurrencyOption(-1)),
		} {
			label := fmt.Sprintf("%s %v", fname, opts)
			t.Run(label, func(t *testing.T) {
				fname := fname
				t.Parallel()

				var out bytes.Buffer
				rawfile := strings.TrimSuffix(fname, ".lz4")
				raw, err := ioutil.ReadFile(rawfile)
				if err != nil {
					t.Fatal(err)
				}

				f, err := os.Open(fname)
				if err != nil {
					t.Fatal(err)
				}
				defer f.Close()

				zr := lz4.NewReader(f)
				if err := zr.Apply(opts...); err != nil {
					t.Fatal(err)
				}
				n, err := io.Copy(&out, zr)
				if err != nil {
					t.Fatal(err, n)
				}

				if got, want := int(n), len(raw); got != want {
					t.Errorf("invalid sizes: got %d; want %d", got, want)
				}

				if got, want := out.Bytes(), raw; !bytes.Equal(got, want) {
					t.Fatal("uncompressed data does not match original")
				}

				if len(raw) < 20 {
					return
				}

				f2, err := os.Open(fname)
				if err != nil {
					t.Fatal(err)
				}
				defer f2.Close()

				out.Reset()
				zr = lz4.NewReader(f2)
				_, err = io.CopyN(&out, zr, 10)
				if err != nil {
					t.Fatal(err)
				}

				if !bytes.Equal(out.Bytes(), raw[:10]) {
					t.Fatal("partial read does not match original")
				}

				out.Reset()
				_, err = io.CopyN(&out, zr, 10)
				if err != nil {
					t.Fatal(err)
				}

				if !bytes.Equal(out.Bytes(), raw[10:20]) {
					t.Fatal("after seek, partial read does not match original")
				}
			})
		}
	}
}