package dehub

import (
	"bytes"
	"encoding/binary"
	"hash"
	"testing"

	"gopkg.in/src-d/go-git.v4/plumbing"
	"gopkg.in/src-d/go-git.v4/plumbing/filemode"
)

type testHash struct {
	bytes.Buffer
}

var _ hash.Hash = new(testHash)

func (th *testHash) Sum(b []byte) []byte {
	return append(b, th.Buffer.Bytes()...)
}

func (th *testHash) Size() int {
	return th.Buffer.Len()
}

func (th *testHash) BlockSize() int {
	return 1
}

func (th *testHash) assertContents(t *testing.T, parts [][]byte) {
	b := th.Buffer.Bytes()
	for _, part := range parts {
		if len(part) > len(b) || !bytes.Equal(part, b[:len(part)]) {
			t.Fatalf("expected %q but only found %q", part, b)
		}
		b = b[len(part):]
	}
	if len(b) != 0 {
		t.Fatalf("unexpected extra bytes written to testHash: %q", b)
	}
}

func uvarint(i uint64) []byte {
	buf := make([]byte, binary.MaxVarintLen64)
	n := binary.PutUvarint(buf, i)
	return buf[:n]
}

func TestGenCommentFingerprint(t *testing.T) {
	type test struct {
		descr   string
		comment string
		exp     [][]byte
	}

	tests := []test{
		{
			descr:   "empty comment",
			comment: "",
			exp:     [][]byte{uvarint(0)},
		},
		{
			descr:   "normal comment",
			comment: "this is a normal comment",
			exp:     [][]byte{uvarint(24), []byte("this is a normal comment")},
		},
		{
			descr:   "comment with unicode",
			comment: "sick comment ⚡",
			exp:     [][]byte{uvarint(16), []byte("sick comment ⚡")},
		},
	}

	for _, test := range tests {
		t.Run(test.descr, func(t *testing.T) {
			th := new(testHash)
			genCommentFingerprint(th, test.comment)
			th.assertContents(t, test.exp)
		})
	}
}

func TestGenChangeFingerprint(t *testing.T) {
	type test struct {
		descr        string
		msg          string
		changedFiles []ChangedFile
		exp          [][]byte
	}

	hash := func(i byte) plumbing.Hash {
		var h plumbing.Hash
		h[0] = i
		return h
	}
	hashB := func(i byte) []byte {
		h := hash(i)
		return h[:]
	}

	tests := []test{
		{
			descr:        "empty",
			msg:          "",
			changedFiles: nil,
			exp:          [][]byte{uvarint(0), uvarint(0)},
		},
		{
			descr:        "empty changes",
			msg:          "some msg",
			changedFiles: nil,
			exp:          [][]byte{uvarint(8), []byte("some msg"), uvarint(0)},
		},
		{
			descr: "empty msg",
			msg:   "",
			changedFiles: []ChangedFile{{
				Path:   "foo",
				ToMode: filemode.Regular, ToHash: hash(1),
			}},
			exp: [][]byte{uvarint(0), uvarint(1),
				uvarint(3), []byte("foo"),
				filemode.Empty.Bytes(), hashB(0),
				filemode.Regular.Bytes(), hashB(1)},
		},
		{
			descr: "files added",
			msg:   "a",
			changedFiles: []ChangedFile{
				{
					Path:   "foo",
					ToMode: filemode.Regular, ToHash: hash(1),
				},
				{
					Path:   "somedir/bar",
					ToMode: filemode.Executable, ToHash: hash(2),
				},
			},
			exp: [][]byte{uvarint(1), []byte("a"), uvarint(2),
				uvarint(3), []byte("foo"),
				filemode.Empty.Bytes(), hashB(0),
				filemode.Regular.Bytes(), hashB(1),
				uvarint(11), []byte("somedir/bar"),
				filemode.Empty.Bytes(), hashB(0),
				filemode.Executable.Bytes(), hashB(2),
			},
		},
		{
			descr: "files added (unordered)",
			msg:   "a",
			changedFiles: []ChangedFile{
				{
					Path:   "somedir/bar",
					ToMode: filemode.Executable, ToHash: hash(2),
				},
				{
					Path:   "foo",
					ToMode: filemode.Regular, ToHash: hash(1),
				},
			},
			exp: [][]byte{uvarint(1), []byte("a"), uvarint(2),
				uvarint(3), []byte("foo"),
				filemode.Empty.Bytes(), hashB(0),
				filemode.Regular.Bytes(), hashB(1),
				uvarint(11), []byte("somedir/bar"),
				filemode.Empty.Bytes(), hashB(0),
				filemode.Executable.Bytes(), hashB(2),
			},
		},
		{
			descr: "file modified",
			msg:   "a",
			changedFiles: []ChangedFile{{
				Path:     "foo",
				FromMode: filemode.Regular, FromHash: hash(1),
				ToMode: filemode.Executable, ToHash: hash(2),
			}},
			exp: [][]byte{uvarint(1), []byte("a"), uvarint(1),
				uvarint(3), []byte("foo"),
				filemode.Regular.Bytes(), hashB(1),
				filemode.Executable.Bytes(), hashB(2),
			},
		},
		{
			descr: "file removed",
			msg:   "a",
			changedFiles: []ChangedFile{{
				Path:     "foo",
				FromMode: filemode.Regular, FromHash: hash(1),
			}},
			exp: [][]byte{uvarint(1), []byte("a"), uvarint(1),
				uvarint(3), []byte("foo"),
				filemode.Regular.Bytes(), hashB(1),
				filemode.Empty.Bytes(), hashB(0),
			},
		},
		{
			descr: "files added, modified, and removed",
			msg:   "aaa",
			changedFiles: []ChangedFile{
				{
					Path:   "foo",
					ToMode: filemode.Regular, ToHash: hash(1),
				},
				{
					Path:     "bar",
					FromMode: filemode.Regular, FromHash: hash(2),
					ToMode: filemode.Regular, ToHash: hash(3),
				},
				{
					Path:     "baz",
					FromMode: filemode.Executable, FromHash: hash(4),
				},
			},
			exp: [][]byte{uvarint(3), []byte("aaa"), uvarint(3),
				uvarint(3), []byte("bar"),
				filemode.Regular.Bytes(), hashB(2),
				filemode.Regular.Bytes(), hashB(3),
				uvarint(3), []byte("baz"),
				filemode.Executable.Bytes(), hashB(4),
				filemode.Empty.Bytes(), hashB(0),
				uvarint(3), []byte("foo"),
				filemode.Empty.Bytes(), hashB(0),
				filemode.Regular.Bytes(), hashB(1),
			},
		},
	}

	for _, test := range tests {
		t.Run(test.descr, func(t *testing.T) {
			th := new(testHash)
			genChangeFingerprint(th, test.msg, test.changedFiles)
			th.assertContents(t, test.exp)
		})
	}
}