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/query/photos/iter.go

@@ -0,0 +1,174 @@
+// Package photos contains photos iteration helper.
+package photos
+
+import (
+	"context"
+
+	"github.com/go-faster/errors"
+
+	"go.mau.fi/mautrix-telegram/pkg/gotd/telegram/message/peer"
+	"go.mau.fi/mautrix-telegram/pkg/gotd/tg"
+)
+
+// Elem is a photo iterator element.
+type Elem struct {
+	Photo    tg.PhotoClass
+	Entities peer.Entities
+}
+
+// Iterator is a photo stream iterator.
+type Iterator struct {
+	// Current state.
+	lastErr error
+	// Buffer state.
+	buf    []Elem
+	bufCur int
+	// Request state.
+	limit     int
+	lastBatch bool
+	// Offset parameters state.
+	offset int
+	// Remote state.
+	count    int
+	totalGot bool
+
+	// Query builder.
+	query Query
+}
+
+// NewIterator creates new iterator.
+func NewIterator(query Query, limit int) *Iterator {
+	return &Iterator{
+		buf:    make([]Elem, 0, limit),
+		bufCur: -1,
+		limit:  limit,
+		query:  query,
+	}
+}
+
+// Offset sets Offset request parameter.
+func (m *Iterator) Offset(offset int) *Iterator {
+	m.offset = offset
+	return m
+}
+
+func (m *Iterator) apply(r tg.PhotosPhotosClass) error {
+	if m.lastBatch {
+		return nil
+	}
+
+	var (
+		photos   []tg.PhotoClass
+		entities peer.Entities
+	)
+	switch phts := r.(type) {
+	case *tg.PhotosPhotos: // photos.photos#8dca6aa5
+		photos = phts.Photos
+		entities = peer.NewEntities(phts.MapUsers().UserToMap(), map[int64]*tg.Chat{}, map[int64]*tg.Channel{})
+
+		m.count = len(phts.Photos)
+		m.lastBatch = true
+	case *tg.PhotosPhotosSlice: // photos.photosSlice#15051f54
+		photos = phts.Photos
+		entities = peer.NewEntities(phts.MapUsers().UserToMap(), map[int64]*tg.Chat{}, map[int64]*tg.Channel{})
+
+		m.count = phts.Count
+		m.lastBatch = len(phts.Photos) < m.limit
+	default:
+		return errors.Errorf("unexpected type %T", r)
+	}
+	m.totalGot = true
+	m.offset += len(photos)
+
+	m.bufCur = -1
+	m.buf = m.buf[:0]
+	for i := range photos {
+		m.buf = append(m.buf, Elem{Photo: photos[i], Entities: entities})
+	}
+
+	return nil
+}
+
+func (m *Iterator) requestNext(ctx context.Context) error {
+	r, err := m.query.Query(ctx, Request{
+		Offset: m.offset,
+		Limit:  m.limit,
+	})
+	if err != nil {
+		return err
+	}
+
+	return m.apply(r)
+}
+
+func (m *Iterator) bufNext() bool {
+	if len(m.buf)-1 <= m.bufCur {
+		return false
+	}
+
+	m.bufCur++
+	return true
+}
+
+// Total returns last fetched count of elements.
+// If count was not fetched before, it requests server using FetchTotal.
+func (m *Iterator) Total(ctx context.Context) (int, error) {
+	if m.totalGot {
+		return m.count, nil
+	}
+
+	return m.FetchTotal(ctx)
+}
+
+// FetchTotal fetches and returns count of elements.
+func (m *Iterator) FetchTotal(ctx context.Context) (int, error) {
+	r, err := m.query.Query(ctx, Request{
+		Limit: 1,
+	})
+	if err != nil {
+		return 0, errors.Wrap(err, "fetch total")
+	}
+
+	switch phts := r.(type) {
+	case *tg.PhotosPhotos: // photos.photos#8dca6aa5
+		m.count = len(phts.Photos)
+	case *tg.PhotosPhotosSlice: // photos.photosSlice#15051f54
+		m.count = phts.Count
+	default:
+		return 0, errors.Errorf("unexpected type %T", r)
+	}
+
+	m.totalGot = true
+	return m.count, nil
+}
+
+// Next prepares the next message for reading with the Value method.
+// It returns true on success, or false if there is no next message or an error happened while preparing it.
+// Err should be consulted to distinguish between the two cases.
+func (m *Iterator) Next(ctx context.Context) bool {
+	if m.lastErr != nil {
+		return false
+	}
+
+	if !m.bufNext() {
+		// If buffer is empty, we should fetch next batch.
+		if err := m.requestNext(ctx); err != nil {
+			m.lastErr = err
+			return false
+		}
+		// Try again with new buffer.
+		return m.bufNext()
+	}
+
+	return true
+}
+
+// Value returns current message.
+func (m *Iterator) Value() Elem {
+	return m.buf[m.bufCur]
+}
+
+// Err returns the error, if any, that was encountered during iteration.
+func (m *Iterator) Err() error {
+	return m.lastErr
+}