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iter.go
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iter.go
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// Package participants contains channel participants iteration helper.
package participants
import (
"context"
"golang.org/x/xerrors"
"github.com/gotd/td/telegram/message/peer"
"github.com/gotd/td/tg"
)
// Elem is a channel participants iterator element.
type Elem struct {
Participant tg.ChannelParticipantClass
Entities peer.Entities
}
// Iterator is a channel participants 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.ChannelsChannelParticipantsClass) error {
if m.lastBatch {
return nil
}
var (
participants tg.ChannelParticipantClassArray
entities peer.Entities
)
switch prts := r.(type) {
case *tg.ChannelsChannelParticipants: // channels.channelParticipants#f56ee2a8
participants = prts.Participants
entities = peer.NewEntities(prts.MapUsers().UserToMap(), map[int]*tg.Chat{}, map[int]*tg.Channel{})
m.count = prts.Count
m.lastBatch = len(participants) < m.limit
default: // channels.channelParticipantsNotModified#f0173fe9
return xerrors.Errorf("unexpected type %T", r)
}
m.totalGot = true
m.offset += len(participants)
m.bufCur = -1
m.buf = m.buf[:0]
for i := range participants {
m.buf = append(m.buf, Elem{Participant: participants[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, xerrors.Errorf("fetch total: %w", err)
}
switch prts := r.(type) {
case *tg.ChannelsChannelParticipants: // channels.channelParticipants#f56ee2a8
m.count = prts.Count
default: // channels.channelParticipantsNotModified#f0173fe9
return 0, xerrors.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
}