1 package lemmy
2 
3 import (
4 	"fmt"
5 	"net/http"
6 	"strconv"
7 	"strings"
8 	"sync"
9 	"time"
10 )
11 
12 type cache struct {
13 	post      map[int]entry
14 	community map[string]entry
15 	mu        *sync.Mutex
16 }
17 
18 type entry struct {
19 	post      Post
20 	community Community
21 	expiry    time.Time
22 }
23 
24 func (c *cache) store(p Post, com Community, dur time.Duration) {
25 	c.mu.Lock()
26 	defer c.mu.Unlock()
27 	t := time.Now().Add(dur)
28 	entry := entry{expiry: t}
29 	if p.Name() != "" {
30 		entry.post = p
31 		c.post[p.ID] = entry
32 	}
33 	if com.Name() != "" {
34 		entry.community = com
35 		c.community[com.Name()] = entry
36 	}
37 }
38 
39 func (c *cache) delete(p Post, com Community) {
40 	c.mu.Lock()
41 	defer c.mu.Unlock()
42 	delete(c.post, p.ID)
43 	delete(c.community, com.Name())
44 }
45 
46 // max-age=50
47 func parseMaxAge(s string) (time.Duration, error) {
48 	var want string
49 	elems := strings.Split(s, ",")
50 	for i := range elems {
51 		elems[i] = strings.TrimSpace(elems[i])
52 		if strings.HasPrefix(elems[i], "max-age") {
53 			want = elems[i]
54 		}
55 	}
56 	_, num, found := strings.Cut(want, "=")
57 	if !found {
58 		return 0, fmt.Errorf("missing = separator")
59 	}
60 	n, err := strconv.Atoi(num)
61 	if err != nil {
62 		return 0, fmt.Errorf("parse seconds: %w", err)
63 	}
64 	return time.Duration(n) * time.Second, nil
65 }
66 
67 // Cache-Control: public, max-age=50
68 func extractMaxAge(header http.Header) string {
69 	cc := header.Get("Cache-Control")
70 	if !strings.Contains(cc, "max-age=") {
71 		return ""
72 	}
73 	return cc
74 }