feat(core): persist tasks and recover them after restart

pkg/tfile/payload.go

@@ -0,0 +1,86 @@
+package tfile
+
+import (
+	"github.com/gotd/td/telegram/downloader"
+	"github.com/gotd/td/tg"
+)
+
+// Payloadable is implemented by TGFile implementations that can serialize
+// themselves for task recovery.
+type Payloadable interface {
+	Payload() FilePayload
+}
+
+// FilePayloadOf returns the serializable form of f.
+func FilePayloadOf(f TGFile) (FilePayload, bool) {
+	p, ok := f.(Payloadable)
+	if !ok {
+		return FilePayload{}, false
+	}
+	return p.Payload(), true
+}
+
+// FilePayload is the minimal serializable representation of a TGFile,
+// used to rebuild tasks after a process restart.
+type FilePayload struct {
+	Kind          string `json:"kind"` // "document" | "photo"
+	ID            int64  `json:"id"`
+	AccessHash    int64  `json:"access_hash"`
+	FileReference []byte `json:"file_reference"`
+	ThumbSize     string `json:"thumb_size"`
+	Size          int64  `json:"size"`
+	Name          string `json:"name"`
+}
+
+// Payload returns the serializable representation of the file.
+func (f *tgFile) Payload() FilePayload {
+	p := FilePayload{
+		Size: f.size,
+		Name: f.name,
+	}
+	switch loc := f.location.(type) {
+	case *tg.InputDocumentFileLocation:
+		p.Kind = "document"
+		p.ID = loc.ID
+		p.AccessHash = loc.AccessHash
+		p.FileReference = loc.FileReference
+		p.ThumbSize = loc.ThumbSize
+	case *tg.InputPhotoFileLocation:
+		p.Kind = "photo"
+		p.ID = loc.ID
+		p.AccessHash = loc.AccessHash
+		p.FileReference = loc.FileReference
+		p.ThumbSize = loc.ThumbSize
+	}
+	return p
+}
+
+// Location rebuilds the Telegram file location from the payload.
+func (p FilePayload) Location() tg.InputFileLocationClass {
+	switch p.Kind {
+	case "photo":
+		return &tg.InputPhotoFileLocation{
+			ID:            p.ID,
+			AccessHash:    p.AccessHash,
+			FileReference: p.FileReference,
+			ThumbSize:     p.ThumbSize,
+		}
+	default:
+		return &tg.InputDocumentFileLocation{
+			ID:            p.ID,
+			AccessHash:    p.AccessHash,
+			FileReference: p.FileReference,
+			ThumbSize:     p.ThumbSize,
+		}
+	}
+}
+
+// FileFromPayload rebuilds a TGFile from its serialized payload.
+func FileFromPayload(p FilePayload, dler downloader.Client) TGFile {
+	return &tgFile{
+		location: p.Location(),
+		dler:     dler,
+		size:     p.Size,
+		name:     p.Name,
+	}
+}

pkg/tfile/payload_test.go

@@ -0,0 +1,61 @@
+package tfile
+
+import (
+	"reflect"
+	"testing"
+
+	"github.com/gotd/td/tg"
+)
+
+func TestFilePayloadDocumentRoundTrip(t *testing.T) {
+	file := NewTGFile(
+		&tg.InputDocumentFileLocation{
+			ID:            6287403840090150101,
+			AccessHash:    -8452541528324991878,
+			FileReference: []byte{0x02, 0x0e, 0x80, 0xd6},
+			ThumbSize:     "",
+		},
+		nil,
+		4194304000,
+		"常轨脱离Creative凸.7z.001",
+	)
+	p, ok := FilePayloadOf(file)
+	if !ok {
+		t.Fatalf("FilePayloadOf failed")
+	}
+	rebuilt := FileFromPayload(p, nil)
+	if !reflect.DeepEqual(rebuilt.Location(), file.Location()) {
+		t.Fatalf("location mismatch:\n got %#v\nwant %#v", rebuilt.Location(), file.Location())
+	}
+	if rebuilt.Size() != file.Size() || rebuilt.Name() != file.Name() {
+		t.Fatalf("size/name mismatch: got %d %q, want %d %q", rebuilt.Size(), rebuilt.Name(), file.Size(), file.Name())
+	}
+	if p.Kind != "document" {
+		t.Fatalf("kind = %q, want document", p.Kind)
+	}
+}
+
+func TestFilePayloadPhotoRoundTrip(t *testing.T) {
+	file := NewTGFile(
+		&tg.InputPhotoFileLocation{
+			ID:            123,
+			AccessHash:    456,
+			FileReference: []byte{0xaa, 0xbb},
+			ThumbSize:     "y",
+		},
+		nil,
+		0,
+		"photo_123.png",
+	)
+	p, ok := FilePayloadOf(file)
+	if !ok {
+		t.Fatalf("FilePayloadOf failed")
+	}
+	if p.Kind != "photo" {
+		t.Fatalf("kind = %q, want photo", p.Kind)
+	}
+	rebuilt := FileFromPayload(p, nil)
+	if !reflect.DeepEqual(rebuilt.Location(), file.Location()) {
+		t.Fatalf("location mismatch:\n got %#v\nwant %#v", rebuilt.Location(), file.Location())
+	}
+}