package git

/*
#include <git2.h>

extern int _go_git_diff_foreach(git_diff *diff, int eachFile, int eachHunk, int eachLine, void *payload);
extern void _go_git_setup_diff_notify_callbacks(git_diff_options* opts);
extern int _go_git_diff_blobs(git_blob *old, const char *old_path, git_blob *new, const char *new_path, git_diff_options *opts, int eachFile, int eachHunk, int eachLine, void *payload);
*/
import "C"
import (
	"errors"
	"runtime"
	"unsafe"
)

type DiffFlag int

const (
	DiffFlagBinary    DiffFlag = C.GIT_DIFF_FLAG_BINARY
	DiffFlagNotBinary DiffFlag = C.GIT_DIFF_FLAG_NOT_BINARY
	DiffFlagValidOid  DiffFlag = C.GIT_DIFF_FLAG_VALID_ID
)

type Delta int

const (
	DeltaUnmodified Delta = C.GIT_DELTA_UNMODIFIED
	DeltaAdded      Delta = C.GIT_DELTA_ADDED
	DeltaDeleted    Delta = C.GIT_DELTA_DELETED
	DeltaModified   Delta = C.GIT_DELTA_MODIFIED
	DeltaRenamed    Delta = C.GIT_DELTA_RENAMED
	DeltaCopied     Delta = C.GIT_DELTA_COPIED
	DeltaIgnored    Delta = C.GIT_DELTA_IGNORED
	DeltaUntracked  Delta = C.GIT_DELTA_UNTRACKED
	DeltaTypeChange Delta = C.GIT_DELTA_TYPECHANGE
)

type DiffLineType int

const (
	DiffLineContext      DiffLineType = C.GIT_DIFF_LINE_CONTEXT
	DiffLineAddition     DiffLineType = C.GIT_DIFF_LINE_ADDITION
	DiffLineDeletion     DiffLineType = C.GIT_DIFF_LINE_DELETION
	DiffLineContextEOFNL DiffLineType = C.GIT_DIFF_LINE_CONTEXT_EOFNL
	DiffLineAddEOFNL     DiffLineType = C.GIT_DIFF_LINE_ADD_EOFNL
	DiffLineDelEOFNL     DiffLineType = C.GIT_DIFF_LINE_DEL_EOFNL

	DiffLineFileHdr DiffLineType = C.GIT_DIFF_LINE_FILE_HDR
	DiffLineHunkHdr DiffLineType = C.GIT_DIFF_LINE_HUNK_HDR
	DiffLineBinary  DiffLineType = C.GIT_DIFF_LINE_BINARY
)

type DiffFile struct {
	Path  string
	Oid   *Oid
	Size  int
	Flags DiffFlag
	Mode  uint16
}

func diffFileFromC(file *C.git_diff_file) DiffFile {
	return DiffFile{
		Path:  C.GoString(file.path),
		Oid:   newOidFromC(&file.id),
		Size:  int(file.size),
		Flags: DiffFlag(file.flags),
		Mode:  uint16(file.mode),
	}
}

type DiffDelta struct {
	Status     Delta
	Flags      DiffFlag
	Similarity uint16
	OldFile    DiffFile
	NewFile    DiffFile
}

func diffDeltaFromC(delta *C.git_diff_delta) DiffDelta {
	return DiffDelta{
		Status:     Delta(delta.status),
		Flags:      DiffFlag(delta.flags),
		Similarity: uint16(delta.similarity),
		OldFile:    diffFileFromC(&delta.old_file),
		NewFile:    diffFileFromC(&delta.new_file),
	}
}

type DiffHunk struct {
	OldStart int
	OldLines int
	NewStart int
	NewLines int
	Header   string
}

func diffHunkFromC(hunk *C.git_diff_hunk) DiffHunk {
	return DiffHunk{
		OldStart: int(hunk.old_start),
		OldLines: int(hunk.old_lines),
		NewStart: int(hunk.new_start),
		NewLines: int(hunk.new_lines),
		Header:   C.GoStringN(&hunk.header[0], C.int(hunk.header_len)),
	}
}

type DiffLine struct {
	Origin    DiffLineType
	OldLineno int
	NewLineno int
	NumLines  int
	Content   string
}

func diffLineFromC(line *C.git_diff_line) DiffLine {
	return DiffLine{
		Origin:    DiffLineType(line.origin),
		OldLineno: int(line.old_lineno),
		NewLineno: int(line.new_lineno),
		NumLines:  int(line.num_lines),
		Content:   C.GoStringN(line.content, C.int(line.content_len)),
	}
}

type Diff struct {
	ptr *C.git_diff
}

func (diff *Diff) NumDeltas() (int, error) {
	if diff.ptr == nil {
		return -1, ErrInvalid
	}
	return int(C.git_diff_num_deltas(diff.ptr)), nil
}

func (diff *Diff) GetDelta(index int) (DiffDelta, error) {
	if diff.ptr == nil {
		return DiffDelta{}, ErrInvalid
	}
	ptr := C.git_diff_get_delta(diff.ptr, C.size_t(index))
	return diffDeltaFromC(ptr), nil
}

func newDiffFromC(ptr *C.git_diff) *Diff {
	if ptr == nil {
		return nil
	}

	diff := &Diff{
		ptr: ptr,
	}

	runtime.SetFinalizer(diff, (*Diff).Free)
	return diff
}

func (diff *Diff) Free() error {
	if diff.ptr == nil {
		return ErrInvalid
	}
	runtime.SetFinalizer(diff, nil)
	C.git_diff_free(diff.ptr)
	diff.ptr = nil
	return nil
}

func (diff *Diff) FindSimilar(opts *DiffFindOptions) error {

	var copts *C.git_diff_find_options
	if opts != nil {
		copts = &C.git_diff_find_options{
			version:                       C.GIT_DIFF_FIND_OPTIONS_VERSION,
			flags:                         C.uint32_t(opts.Flags),
			rename_threshold:              C.uint16_t(opts.RenameThreshold),
			copy_threshold:                C.uint16_t(opts.CopyThreshold),
			rename_from_rewrite_threshold: C.uint16_t(opts.RenameFromRewriteThreshold),
			break_rewrite_threshold:       C.uint16_t(opts.BreakRewriteThreshold),
			rename_limit:                  C.size_t(opts.RenameLimit),
		}
	}

	runtime.LockOSThread()
	defer runtime.UnlockOSThread()

	ecode := C.git_diff_find_similar(diff.ptr, copts)
	if ecode < 0 {
		return MakeGitError(ecode)
	}

	return nil
}

type DiffStats struct {
	ptr *C.git_diff_stats
}

func (stats *DiffStats) Free() error {
	if stats.ptr == nil {
		return ErrInvalid
	}
	runtime.SetFinalizer(stats, nil)
	C.git_diff_stats_free(stats.ptr)
	stats.ptr = nil
	return nil
}

func (stats *DiffStats) Insertions() int {
	return int(C.git_diff_stats_insertions(stats.ptr))
}

func (stats *DiffStats) Deletions() int {
	return int(C.git_diff_stats_deletions(stats.ptr))
}

func (stats *DiffStats) FilesChanged() int {
	return int(C.git_diff_stats_files_changed(stats.ptr))
}

type DiffStatsFormat int

const (
	DiffStatsNone           DiffStatsFormat = C.GIT_DIFF_STATS_NONE
	DiffStatsFull           DiffStatsFormat = C.GIT_DIFF_STATS_FULL
	DiffStatsShort          DiffStatsFormat = C.GIT_DIFF_STATS_SHORT
	DiffStatsNumber         DiffStatsFormat = C.GIT_DIFF_STATS_NUMBER
	DiffStatsIncludeSummary DiffStatsFormat = C.GIT_DIFF_STATS_INCLUDE_SUMMARY
)

func (stats *DiffStats) String(format DiffStatsFormat,
	width uint) (string, error) {
	buf := C.git_buf{}
	defer C.git_buf_free(&buf)

	runtime.LockOSThread()
	defer runtime.UnlockOSThread()

	ret := C.git_diff_stats_to_buf(&buf,
		stats.ptr, C.git_diff_stats_format_t(format), C.size_t(width))
	if ret < 0 {
		return "", MakeGitError(ret)
	}

	return C.GoString(buf.ptr), nil
}

func (diff *Diff) Stats() (*DiffStats, error) {
	stats := new(DiffStats)

	runtime.LockOSThread()
	defer runtime.UnlockOSThread()

	if ecode := C.git_diff_get_stats(&stats.ptr, diff.ptr); ecode < 0 {
		return nil, MakeGitError(ecode)
	}
	runtime.SetFinalizer(stats, (*DiffStats).Free)

	return stats, nil
}

type diffForEachData struct {
	FileCallback DiffForEachFileCallback
	HunkCallback DiffForEachHunkCallback
	LineCallback DiffForEachLineCallback
	Error        error
}

type DiffForEachFileCallback func(DiffDelta, float64) (DiffForEachHunkCallback, error)

type DiffDetail int

const (
	DiffDetailFiles DiffDetail = iota
	DiffDetailHunks
	DiffDetailLines
)

func (diff *Diff) ForEach(cbFile DiffForEachFileCallback, detail DiffDetail) error {
	if diff.ptr == nil {
		return ErrInvalid
	}

	intHunks := C.int(0)
	if detail >= DiffDetailHunks {
		intHunks = C.int(1)
	}

	intLines := C.int(0)
	if detail >= DiffDetailLines {
		intLines = C.int(1)
	}

	data := &diffForEachData{
		FileCallback: cbFile,
	}

	handle := pointerHandles.Track(data)
	defer pointerHandles.Untrack(handle)

	ecode := C._go_git_diff_foreach(diff.ptr, 1, intHunks, intLines, handle)
	if ecode < 0 {
		return data.Error
	}
	return nil
}

//export diffForEachFileCb
func diffForEachFileCb(delta *C.git_diff_delta, progress C.float, handle unsafe.Pointer) int {
	payload := pointerHandles.Get(handle)
	data, ok := payload.(*diffForEachData)
	if !ok {
		panic("could not retrieve data for handle")
	}

	data.HunkCallback = nil
	if data.FileCallback != nil {
		cb, err := data.FileCallback(diffDeltaFromC(delta), float64(progress))
		if err != nil {
			data.Error = err
			return -1
		}
		data.HunkCallback = cb
	}

	return 0
}

type DiffForEachHunkCallback func(DiffHunk) (DiffForEachLineCallback, error)

//export diffForEachHunkCb
func diffForEachHunkCb(delta *C.git_diff_delta, hunk *C.git_diff_hunk, handle unsafe.Pointer) int {
	payload := pointerHandles.Get(handle)
	data, ok := payload.(*diffForEachData)
	if !ok {
		panic("could not retrieve data for handle")
	}

	data.LineCallback = nil
	if data.HunkCallback != nil {
		cb, err := data.HunkCallback(diffHunkFromC(hunk))
		if err != nil {
			data.Error = err
			return -1
		}
		data.LineCallback = cb
	}

	return 0
}

type DiffForEachLineCallback func(DiffLine) error

//export diffForEachLineCb
func diffForEachLineCb(delta *C.git_diff_delta, hunk *C.git_diff_hunk, line *C.git_diff_line, handle unsafe.Pointer) int {
	payload := pointerHandles.Get(handle)
	data, ok := payload.(*diffForEachData)
	if !ok {
		panic("could not retrieve data for handle")
	}

	err := data.LineCallback(diffLineFromC(line))
	if err != nil {
		data.Error = err
		return -1
	}

	return 0
}

func (diff *Diff) Patch(deltaIndex int) (*Patch, error) {
	if diff.ptr == nil {
		return nil, ErrInvalid
	}
	var patchPtr *C.git_patch

	runtime.LockOSThread()
	defer runtime.UnlockOSThread()

	ecode := C.git_patch_from_diff(&patchPtr, diff.ptr, C.size_t(deltaIndex))
	if ecode < 0 {
		return nil, MakeGitError(ecode)
	}

	return newPatchFromC(patchPtr), nil
}

type DiffOptionsFlag int

const (
	DiffNormal                 DiffOptionsFlag = C.GIT_DIFF_NORMAL
	DiffReverse                DiffOptionsFlag = C.GIT_DIFF_REVERSE
	DiffIncludeIgnored         DiffOptionsFlag = C.GIT_DIFF_INCLUDE_IGNORED
	DiffRecurseIgnoredDirs     DiffOptionsFlag = C.GIT_DIFF_RECURSE_IGNORED_DIRS
	DiffIncludeUntracked       DiffOptionsFlag = C.GIT_DIFF_INCLUDE_UNTRACKED
	DiffRecurseUntracked       DiffOptionsFlag = C.GIT_DIFF_RECURSE_UNTRACKED_DIRS
	DiffIncludeUnmodified      DiffOptionsFlag = C.GIT_DIFF_INCLUDE_UNMODIFIED
	DiffIncludeTypeChange      DiffOptionsFlag = C.GIT_DIFF_INCLUDE_TYPECHANGE
	DiffIncludeTypeChangeTrees DiffOptionsFlag = C.GIT_DIFF_INCLUDE_TYPECHANGE_TREES
	DiffIgnoreFilemode         DiffOptionsFlag = C.GIT_DIFF_IGNORE_FILEMODE
	DiffIgnoreSubmodules       DiffOptionsFlag = C.GIT_DIFF_IGNORE_SUBMODULES
	DiffIgnoreCase             DiffOptionsFlag = C.GIT_DIFF_IGNORE_CASE

	DiffDisablePathspecMatch    DiffOptionsFlag = C.GIT_DIFF_DISABLE_PATHSPEC_MATCH
	DiffSkipBinaryCheck         DiffOptionsFlag = C.GIT_DIFF_SKIP_BINARY_CHECK
	DiffEnableFastUntrackedDirs DiffOptionsFlag = C.GIT_DIFF_ENABLE_FAST_UNTRACKED_DIRS

	DiffForceText   DiffOptionsFlag = C.GIT_DIFF_FORCE_TEXT
	DiffForceBinary DiffOptionsFlag = C.GIT_DIFF_FORCE_BINARY

	DiffIgnoreWhitespace       DiffOptionsFlag = C.GIT_DIFF_IGNORE_WHITESPACE
	DiffIgnoreWhitespaceChange DiffOptionsFlag = C.GIT_DIFF_IGNORE_WHITESPACE_CHANGE
	DiffIgnoreWitespaceEol     DiffOptionsFlag = C.GIT_DIFF_IGNORE_WHITESPACE_EOL

	DiffShowUntrackedContent DiffOptionsFlag = C.GIT_DIFF_SHOW_UNTRACKED_CONTENT
	DiffShowUnmodified       DiffOptionsFlag = C.GIT_DIFF_SHOW_UNMODIFIED
	DiffPatience             DiffOptionsFlag = C.GIT_DIFF_PATIENCE
	DiffMinimal              DiffOptionsFlag = C.GIT_DIFF_MINIMAL
)

type DiffNotifyCallback func(diffSoFar *Diff, deltaToAdd DiffDelta, matchedPathspec string) error

type DiffOptions struct {
	Flags            DiffOptionsFlag
	IgnoreSubmodules SubmoduleIgnore
	Pathspec         []string
	NotifyCallback   DiffNotifyCallback

	ContextLines   uint32
	InterhunkLines uint32
	IdAbbrev       uint16

	MaxSize int

	OldPrefix string
	NewPrefix string
}

func DefaultDiffOptions() (DiffOptions, error) {
	opts := C.git_diff_options{}

	runtime.LockOSThread()
	defer runtime.UnlockOSThread()

	ecode := C.git_diff_init_options(&opts, C.GIT_DIFF_OPTIONS_VERSION)
	if ecode < 0 {
		return DiffOptions{}, MakeGitError(ecode)
	}

	return DiffOptions{
		Flags:            DiffOptionsFlag(opts.flags),
		IgnoreSubmodules: SubmoduleIgnore(opts.ignore_submodules),
		Pathspec:         makeStringsFromCStrings(opts.pathspec.strings, int(opts.pathspec.count)),
		ContextLines:     uint32(opts.context_lines),
		InterhunkLines:   uint32(opts.interhunk_lines),
		IdAbbrev:         uint16(opts.id_abbrev),
		MaxSize:          int(opts.max_size),
		OldPrefix:        "a",
		NewPrefix:        "b",
	}, nil
}

type DiffFindOptionsFlag int

const (
	DiffFindByConfig                    DiffFindOptionsFlag = C.GIT_DIFF_FIND_BY_CONFIG
	DiffFindRenames                     DiffFindOptionsFlag = C.GIT_DIFF_FIND_RENAMES
	DiffFindRenamesFromRewrites         DiffFindOptionsFlag = C.GIT_DIFF_FIND_RENAMES_FROM_REWRITES
	DiffFindCopies                      DiffFindOptionsFlag = C.GIT_DIFF_FIND_COPIES
	DiffFindCopiesFromUnmodified        DiffFindOptionsFlag = C.GIT_DIFF_FIND_COPIES_FROM_UNMODIFIED
	DiffFindRewrites                    DiffFindOptionsFlag = C.GIT_DIFF_FIND_REWRITES
	DiffFindBreakRewrites               DiffFindOptionsFlag = C.GIT_DIFF_BREAK_REWRITES
	DiffFindAndBreakRewrites            DiffFindOptionsFlag = C.GIT_DIFF_FIND_AND_BREAK_REWRITES
	DiffFindForUntracked                DiffFindOptionsFlag = C.GIT_DIFF_FIND_FOR_UNTRACKED
	DiffFindAll                         DiffFindOptionsFlag = C.GIT_DIFF_FIND_ALL
	DiffFindIgnoreLeadingWhitespace     DiffFindOptionsFlag = C.GIT_DIFF_FIND_IGNORE_LEADING_WHITESPACE
	DiffFindIgnoreWhitespace            DiffFindOptionsFlag = C.GIT_DIFF_FIND_IGNORE_WHITESPACE
	DiffFindDontIgnoreWhitespace        DiffFindOptionsFlag = C.GIT_DIFF_FIND_DONT_IGNORE_WHITESPACE
	DiffFindExactMatchOnly              DiffFindOptionsFlag = C.GIT_DIFF_FIND_EXACT_MATCH_ONLY
	DiffFindBreakRewritesForRenamesOnly DiffFindOptionsFlag = C.GIT_DIFF_BREAK_REWRITES_FOR_RENAMES_ONLY
	DiffFindRemoveUnmodified            DiffFindOptionsFlag = C.GIT_DIFF_FIND_REMOVE_UNMODIFIED
)

//TODO implement git_diff_similarity_metric
type DiffFindOptions struct {
	Flags                      DiffFindOptionsFlag
	RenameThreshold            uint16
	CopyThreshold              uint16
	RenameFromRewriteThreshold uint16
	BreakRewriteThreshold      uint16
	RenameLimit                uint
}

func DefaultDiffFindOptions() (DiffFindOptions, error) {
	opts := C.git_diff_find_options{}

	runtime.LockOSThread()
	defer runtime.UnlockOSThread()

	ecode := C.git_diff_find_init_options(&opts, C.GIT_DIFF_FIND_OPTIONS_VERSION)
	if ecode < 0 {
		return DiffFindOptions{}, MakeGitError(ecode)
	}

	return DiffFindOptions{
		Flags:                      DiffFindOptionsFlag(opts.flags),
		RenameThreshold:            uint16(opts.rename_threshold),
		CopyThreshold:              uint16(opts.copy_threshold),
		RenameFromRewriteThreshold: uint16(opts.rename_from_rewrite_threshold),
		BreakRewriteThreshold:      uint16(opts.break_rewrite_threshold),
		RenameLimit:                uint(opts.rename_limit),
	}, nil
}

var (
	ErrDeltaSkip = errors.New("Skip delta")
)

type diffNotifyData struct {
	Callback DiffNotifyCallback
	Diff     *Diff
	Error    error
}

//export diffNotifyCb
func diffNotifyCb(_diff_so_far unsafe.Pointer, delta_to_add *C.git_diff_delta, matched_pathspec *C.char, handle unsafe.Pointer) int {
	diff_so_far := (*C.git_diff)(_diff_so_far)

	payload := pointerHandles.Get(handle)
	data, ok := payload.(*diffNotifyData)
	if !ok {
		panic("could not retrieve data for handle")
	}

	if data != nil {
		if data.Diff == nil {
			data.Diff = newDiffFromC(diff_so_far)
		}

		err := data.Callback(data.Diff, diffDeltaFromC(delta_to_add), C.GoString(matched_pathspec))

		if err == ErrDeltaSkip {
			return 1
		} else if err != nil {
			data.Error = err
			return -1
		} else {
			return 0
		}
	}
	return 0
}

func diffOptionsToC(opts *DiffOptions) (copts *C.git_diff_options, notifyData *diffNotifyData) {
	cpathspec := C.git_strarray{}
	if opts != nil {
		notifyData = &diffNotifyData{
			Callback: opts.NotifyCallback,
		}

		if opts.Pathspec != nil {
			cpathspec.count = C.size_t(len(opts.Pathspec))
			cpathspec.strings = makeCStringsFromStrings(opts.Pathspec)
		}

		copts = &C.git_diff_options{
			version:           C.GIT_DIFF_OPTIONS_VERSION,
			flags:             C.uint32_t(opts.Flags),
			ignore_submodules: C.git_submodule_ignore_t(opts.IgnoreSubmodules),
			pathspec:          cpathspec,
			context_lines:     C.uint32_t(opts.ContextLines),
			interhunk_lines:   C.uint32_t(opts.InterhunkLines),
			id_abbrev:         C.uint16_t(opts.IdAbbrev),
			max_size:          C.git_off_t(opts.MaxSize),
			old_prefix:        C.CString(opts.OldPrefix),
			new_prefix:        C.CString(opts.NewPrefix),
		}

		if opts.NotifyCallback != nil {
			C._go_git_setup_diff_notify_callbacks(copts)
			copts.payload = pointerHandles.Track(notifyData)
		}
	}
	return
}

func freeDiffOptions(copts *C.git_diff_options) {
	if copts != nil {
		cpathspec := copts.pathspec
		freeStrarray(&cpathspec)
		C.free(unsafe.Pointer(copts.old_prefix))
		C.free(unsafe.Pointer(copts.new_prefix))
		if copts.payload != nil {
			pointerHandles.Untrack(copts.payload)
		}
	}
}

func (v *Repository) DiffTreeToTree(oldTree, newTree *Tree, opts *DiffOptions) (*Diff, error) {
	var diffPtr *C.git_diff
	var oldPtr, newPtr *C.git_tree

	if oldTree != nil {
		oldPtr = oldTree.cast_ptr
	}

	if newTree != nil {
		newPtr = newTree.cast_ptr
	}

	copts, notifyData := diffOptionsToC(opts)
	defer freeDiffOptions(copts)

	runtime.LockOSThread()
	defer runtime.UnlockOSThread()

	ecode := C.git_diff_tree_to_tree(&diffPtr, v.ptr, oldPtr, newPtr, copts)
	if ecode < 0 {
		return nil, MakeGitError(ecode)
	}

	if notifyData != nil && notifyData.Diff != nil {
		return notifyData.Diff, nil
	}
	return newDiffFromC(diffPtr), nil
}

func (v *Repository) DiffTreeToWorkdir(oldTree *Tree, opts *DiffOptions) (*Diff, error) {
	var diffPtr *C.git_diff
	var oldPtr *C.git_tree

	if oldTree != nil {
		oldPtr = oldTree.cast_ptr
	}

	copts, notifyData := diffOptionsToC(opts)
	defer freeDiffOptions(copts)

	runtime.LockOSThread()
	defer runtime.UnlockOSThread()

	ecode := C.git_diff_tree_to_workdir(&diffPtr, v.ptr, oldPtr, copts)
	if ecode < 0 {
		return nil, MakeGitError(ecode)
	}

	if notifyData != nil && notifyData.Diff != nil {
		return notifyData.Diff, nil
	}
	return newDiffFromC(diffPtr), nil
}

func (v *Repository) DiffTreeToIndex(oldTree *Tree, index *Index, opts *DiffOptions) (*Diff, error) {
	var diffPtr *C.git_diff
	var oldPtr *C.git_tree
	var indexPtr *C.git_index

	if oldTree != nil {
		oldPtr = oldTree.cast_ptr
	}

	if index != nil {
		indexPtr = index.ptr
	}

	copts, notifyData := diffOptionsToC(opts)
	defer freeDiffOptions(copts)

	runtime.LockOSThread()
	defer runtime.UnlockOSThread()

	ecode := C.git_diff_tree_to_index(&diffPtr, v.ptr, oldPtr, indexPtr, copts)
	if ecode < 0 {
		return nil, MakeGitError(ecode)
	}

	if notifyData != nil && notifyData.Diff != nil {
		return notifyData.Diff, nil
	}
	return newDiffFromC(diffPtr), nil
}

func (v *Repository) DiffTreeToWorkdirWithIndex(oldTree *Tree, opts *DiffOptions) (*Diff, error) {
	var diffPtr *C.git_diff
	var oldPtr *C.git_tree

	if oldTree != nil {
		oldPtr = oldTree.cast_ptr
	}

	copts, notifyData := diffOptionsToC(opts)
	defer freeDiffOptions(copts)

	runtime.LockOSThread()
	defer runtime.UnlockOSThread()

	ecode := C.git_diff_tree_to_workdir_with_index(&diffPtr, v.ptr, oldPtr, copts)
	if ecode < 0 {
		return nil, MakeGitError(ecode)
	}

	if notifyData != nil && notifyData.Diff != nil {
		return notifyData.Diff, nil
	}
	return newDiffFromC(diffPtr), nil
}

func (v *Repository) DiffIndexToWorkdir(index *Index, opts *DiffOptions) (*Diff, error) {
	var diffPtr *C.git_diff
	var indexPtr *C.git_index

	if index != nil {
		indexPtr = index.ptr
	}

	copts, notifyData := diffOptionsToC(opts)
	defer freeDiffOptions(copts)

	runtime.LockOSThread()
	defer runtime.UnlockOSThread()

	ecode := C.git_diff_index_to_workdir(&diffPtr, v.ptr, indexPtr, copts)
	if ecode < 0 {
		return nil, MakeGitError(ecode)
	}

	if notifyData != nil && notifyData.Diff != nil {
		return notifyData.Diff, nil
	}
	return newDiffFromC(diffPtr), nil
}

// DiffBlobs performs a diff between two arbitrary blobs. You can pass
// whatever file names you'd like for them to appear as in the diff.
func DiffBlobs(oldBlob *Blob, oldAsPath string, newBlob *Blob, newAsPath string, opts *DiffOptions, fileCallback DiffForEachFileCallback, detail DiffDetail) error {
	data := &diffForEachData{
		FileCallback: fileCallback,
	}

	intHunks := C.int(0)
	if detail >= DiffDetailHunks {
		intHunks = C.int(1)
	}

	intLines := C.int(0)
	if detail >= DiffDetailLines {
		intLines = C.int(1)
	}

	handle := pointerHandles.Track(data)
	defer pointerHandles.Untrack(handle)

	var oldBlobPtr, newBlobPtr *C.git_blob
	if oldBlob != nil {
		oldBlobPtr = oldBlob.cast_ptr
	}
	if newBlob != nil {
		newBlobPtr = newBlob.cast_ptr
	}

	oldBlobPath := C.CString(oldAsPath)
	defer C.free(unsafe.Pointer(oldBlobPath))
	newBlobPath := C.CString(newAsPath)
	defer C.free(unsafe.Pointer(newBlobPath))

	copts, _ := diffOptionsToC(opts)
	defer freeDiffOptions(copts)

	runtime.LockOSThread()
	defer runtime.UnlockOSThread()

	ecode := C._go_git_diff_blobs(oldBlobPtr, oldBlobPath, newBlobPtr, newBlobPath, copts, 1, intHunks, intLines, handle)
	if ecode < 0 {
		return MakeGitError(ecode)
	}

	return nil
}