94 lines
2.0 KiB
Go
94 lines
2.0 KiB
Go
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package reddit
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import (
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"context"
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"sync"
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"time"
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)
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// StreamService allows streaming new content from Reddit as it appears.
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type StreamService struct {
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client *Client
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}
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// Posts streams posts from the specified subreddit.
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// It returns 2 channels and a function:
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// - a channel into which new posts will be sent
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// - a channel into which any errors will be sent
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// - a function that the client can call once to stop the streaming and close the channels
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// Because of the 100 post limit imposed by Reddit when fetching posts, some high-traffic
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// streams might drop submissions between API requests, such as when streaming r/all.
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func (s *StreamService) Posts(subreddit string) (<-chan *Post, <-chan error, func()) {
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posts := make(chan *Post)
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errs := make(chan error)
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ticker := time.NewTicker(time.Second * 5)
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// originally used the "before" parameter, but if that post gets deleted, subsequent requests
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// would just return empty listings; easier to just keep track of all post ids encountered
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ids := set{}
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go func() {
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for ; ; <-ticker.C {
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result, err := s.getPosts(subreddit)
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if err != nil {
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errs <- err
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continue
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}
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for _, post := range result.Posts {
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id := post.FullID
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// if this post id is already part of the set, it means that it and the ones
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// after it in the list have already been streamed, so break out of the loop
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if ids.Exists(id) {
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break
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}
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ids.Add(id)
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posts <- post
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}
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}
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}()
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var once sync.Once
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return posts, errs, func() {
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once.Do(func() {
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ticker.Stop()
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close(posts)
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close(errs)
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})
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}
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}
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func (s *StreamService) getPosts(subreddit string) (*Posts, error) {
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opts := &ListOptions{
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Limit: 100,
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}
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result, _, err := s.client.Subreddit.NewPosts(context.Background(), subreddit, opts)
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if err != nil {
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return nil, err
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}
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return result, nil
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}
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type set map[string]struct{}
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func (s set) Add(v string) {
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s[v] = struct{}{}
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}
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func (s set) Delete(v string) {
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delete(s, v)
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}
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func (s set) Len() int {
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return len(s)
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}
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func (s set) Exists(v string) bool {
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_, ok := s[v]
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return ok
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}
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