package git

/*
#include <git2.h>
#include <git2/errors.h>

extern int _go_git_odb_foreach(git_odb *db, void *payload);
*/
import "C"
import (
	"unsafe"
	"reflect"
	"runtime"
)

type Odb struct {
	ptr *C.git_odb
}

// OdbBackends need public Ptrs: client apps init the backend
type OdbBackend struct {
  Ptr *C.git_odb_backend
}

func NewOdb() (odb *Odb, err error) {
  odb = new(Odb)

  ret := C.git_odb_new(&odb.ptr)
  if ret < 0 {
    return nil, LastError()
  }

  runtime.SetFinalizer(odb, (*Odb).Free)
  return
}

func (v *Odb) AddBackend(backend *OdbBackend, priority int) (err error) {
  ret := C.git_odb_add_backend(v.ptr, backend.Ptr, C.int(priority))
  if ret < 0 {
    err = LastError()
  }
  return nil
}

func (v *Odb) Exists(oid *Oid) bool {
	ret := C.git_odb_exists(v.ptr, oid.toC())
	return ret != 0
}

func (v *Odb) Write(data []byte, otype ObjectType) (oid *Oid, err error) {
	oid = new(Oid)
	hdr := (*reflect.SliceHeader)(unsafe.Pointer(&data))
	ret := C.git_odb_write(oid.toC(), v.ptr, unsafe.Pointer(hdr.Data), C.size_t(hdr.Len), C.git_otype(otype))

	if ret < 0 {
		err = LastError()
	}

	return
}

func (v *Odb) Read(oid *Oid) (obj *OdbObject, err error) {
	obj = new(OdbObject)
	ret := C.git_odb_read(&obj.ptr, v.ptr, oid.toC())
	if ret < 0 {
		return nil, LastError()
	}

	runtime.SetFinalizer(obj, (*OdbObject).Free)
	return
}

//export odbForEachCb
func odbForEachCb(id *C.git_oid, payload unsafe.Pointer) int {
	ch := *(*chan *Oid)(payload)
	oid := newOidFromC(id)
	// Because the channel is unbuffered, we never read our own data. If ch is
	// readable, the user has sent something on it, which means we should
	// abort.
	select {
	case ch <- oid:
	case <-ch:
			return -1
	}
	return 0;
}

func (v *Odb) forEachWrap(ch chan *Oid) {
	C._go_git_odb_foreach(v.ptr, unsafe.Pointer(&ch))
	close(ch)
}

func (v *Odb) ForEach() chan *Oid {
	ch := make(chan *Oid, 0)
	go v.forEachWrap(ch)
	return ch
}

// NewReadStream opens a read stream from the ODB. Reading from it will give you the
// contents of the object.
func (v *Odb) NewReadStream(id *Oid) (*OdbReadStream, error) {
	stream := new(OdbReadStream)
	ret := C.git_odb_open_rstream(&stream.ptr, v.ptr, id.toC())
	if ret < 0 {
		return nil, LastError()
	}

	runtime.SetFinalizer(stream, (*OdbReadStream).Free)
	return stream, nil
}

// NewWriteStream opens a write stream to the ODB, which allows you to
// create a new object in the database. The size and type must be
// known in advance
func (v *Odb) NewWriteStream(size int, otype ObjectType) (*OdbWriteStream, error) {
	stream := new(OdbWriteStream)
	ret := C.git_odb_open_wstream(&stream.ptr, v.ptr, C.size_t(size), C.git_otype(otype))
	if ret < 0 {
		return nil, LastError()
	}

	runtime.SetFinalizer(stream, (*OdbWriteStream).Free)
	return stream, nil
}

type OdbObject struct {
	ptr *C.git_odb_object
}

func (v *OdbObject) Free() {
	runtime.SetFinalizer(v, nil)
	C.git_odb_object_free(v.ptr)
}

func (object *OdbObject) Id() (oid *Oid) {
	return newOidFromC(C.git_odb_object_id(object.ptr))
}

func (object *OdbObject) Len() (len uint64) {
	return uint64(C.git_odb_object_size(object.ptr))
}

func (object *OdbObject) Data() (data []byte) {
	var c_blob unsafe.Pointer = C.git_odb_object_data(object.ptr)
	var blob []byte

	len := int(C.git_odb_object_size(object.ptr))

	sliceHeader := (*reflect.SliceHeader)((unsafe.Pointer(&blob)))
	sliceHeader.Cap = len
	sliceHeader.Len = len
	sliceHeader.Data = uintptr(c_blob)

	return blob
}

type OdbReadStream struct {
	ptr *C.git_odb_stream
}

// Read reads from the stream
func (stream *OdbReadStream) Read(data []byte) (int, error) {
	header := (*reflect.SliceHeader)(unsafe.Pointer(&data))
	ptr := (*C.char)(unsafe.Pointer(header.Data))
	size := C.size_t(header.Cap)
	ret := C.git_odb_stream_read(stream.ptr, ptr, size)
	if ret < 0 {
		return 0, LastError()
	}

	header.Len = int(ret)

	return len(data), nil
}

// Close is a dummy function in order to implement the Closer and
// ReadCloser interfaces
func (stream *OdbReadStream) Close() error {
	return nil
}

func (stream *OdbReadStream) Free() {
	runtime.SetFinalizer(stream, nil)
	C.git_odb_stream_free(stream.ptr)
}

type OdbWriteStream struct {
	ptr *C.git_odb_stream
	Id Oid
}

// Write writes to the stream
func (stream *OdbWriteStream) Write(data []byte) (int, error) {
	header := (*reflect.SliceHeader)(unsafe.Pointer(&data))
	ptr := (*C.char)(unsafe.Pointer(header.Data))
	size := C.size_t(header.Len)

	ret := C.git_odb_stream_write(stream.ptr, ptr, size)
	if ret < 0 {
		return 0, LastError()
	}

	return len(data), nil
}

// Close signals that all the data has been written and stores the
// resulting object id in the stream's Id field.
func (stream *OdbWriteStream) Close() error {
	ret := C.git_odb_stream_finalize_write(stream.Id.toC(), stream.ptr)
	if ret < 0 {
		return LastError()
	}

	return nil
}

func (stream *OdbWriteStream) Free() {
	runtime.SetFinalizer(stream, nil)
	C.git_odb_stream_free(stream.ptr)
}