move gotd fork into repo. (#111)

- update to latest telegram layer
- remove some references to fields in tg.Entities that don't exist in
the schema
- originally added here:
https://github.com/beeper/td/commit/820929062a2ba0104397bc01235ab58a9cff780e
  - referenced here
-
https://github.com/mautrix/telegramgo/commit/124f0967ed195b5a380c9bd02e170ada9710dde3
-
https://github.com/mautrix/telegramgo/commit/4205047aab2e0639217148b5d125bfaab668bd8e

pkg/gotd/telegram/downloader/builder.go

@@ -0,0 +1,87 @@
+package downloader
+
+import (
+	"context"
+	"io"
+	"os"
+	"path/filepath"
+
+	"github.com/go-faster/errors"
+	"go.uber.org/multierr"
+
+	"go.mau.fi/mautrix-telegram/pkg/gotd/tg"
+)
+
+// Builder is a download builder.
+type Builder struct {
+	downloader *Downloader
+
+	schema  schema
+	hashes  []tg.FileHash
+	verify  bool
+	threads int
+}
+
+func newBuilder(downloader *Downloader, schema schema) *Builder {
+	return &Builder{
+		schema:     schema,
+		threads:    1,
+		downloader: downloader,
+	}
+}
+
+// WithThreads sets downloading goroutines limit.
+func (b *Builder) WithThreads(threads int) *Builder {
+	if threads > 0 {
+		b.threads = threads
+	}
+	return b
+}
+
+// WithVerify sets verify parameter.
+// If verify is true, file hashes will be checked
+// Verify is true by default for CDN downloads.
+func (b *Builder) WithVerify(verify bool) *Builder {
+	b.verify = verify
+	return b
+}
+
+func (b *Builder) reader() *reader {
+	if b.verify {
+		return verifiedReader(b.schema, newVerifier(b.schema, b.hashes...))
+	}
+
+	return plainReader(b.schema, b.downloader.partSize)
+}
+
+// Stream downloads file to given io.Writer.
+// NB: in this mode download can't be parallel.
+func (b *Builder) Stream(ctx context.Context, output io.Writer) (tg.StorageFileTypeClass, error) {
+	return b.downloader.stream(ctx, b.reader(), output)
+}
+
+// StreamToReader streams a file to the returned [io.Reader].
+// NB: in this mode download can't be parallel.
+func (b *Builder) StreamToReader(ctx context.Context) (tg.StorageFileTypeClass, io.Reader, error) {
+	var tgDC int
+	ctx = context.WithValue(ctx, "tg_dc", &tgDC)
+	return b.downloader.streamToReader(ctx, b.reader())
+}
+
+// Parallel downloads file to given io.WriterAt.
+func (b *Builder) Parallel(ctx context.Context, output io.WriterAt) (tg.StorageFileTypeClass, error) {
+	return b.downloader.parallel(ctx, b.reader(), b.threads, output)
+}
+
+// ToPath downloads file to given path.
+func (b *Builder) ToPath(ctx context.Context, path string) (_ tg.StorageFileTypeClass, err error) {
+	f, err := os.Create(filepath.Clean(path))
+	if err != nil {
+		return nil, errors.Wrap(err, "create output file")
+	}
+	defer func() {
+		multierr.AppendInto(&err, f.Close())
+	}()
+
+	return b.Parallel(ctx, f)
+}