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Use short-lived in-memory cache to cache previewed feeds (#31)
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,109 @@ | ||
| package cache | ||
|
|
||
| import ( | ||
| "encoding/json" | ||
| "fmt" | ||
| "os" | ||
| "path/filepath" | ||
| "time" | ||
|
|
||
| "github.com/guyfedwards/nom/internal/rss" | ||
| ) | ||
|
|
||
| var DefaultPath = filepath.Join(os.TempDir(), "nom") | ||
|
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| type FileCache struct { | ||
| expiry time.Duration | ||
| path string | ||
| content CacheContent | ||
| } | ||
|
|
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| // Write writes content to a file at the location specified in the cache | ||
| func (c *FileCache) Write(key string, content rss.RSS) error { | ||
| err := createCacheIfNotExists(c.path) | ||
| if err != nil { | ||
| return fmt.Errorf("createcache: %w", err) | ||
| } | ||
|
|
||
| data, err := os.ReadFile(filepath.Join(c.path, "cache.json")) | ||
| if err != nil { | ||
| return fmt.Errorf("cache Write: %w", err) | ||
| } | ||
|
|
||
| var cc CacheContent | ||
|
|
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| err = json.Unmarshal(data, &cc) | ||
| if err != nil { | ||
| return fmt.Errorf("cache Write json unmarshal: %w", err) | ||
| } | ||
|
|
||
| cc[key] = content | ||
|
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| str, err := json.Marshal(cc) | ||
| if err != nil { | ||
| return fmt.Errorf("cache write marshal json: %w", err) | ||
| } | ||
|
|
||
| err = os.WriteFile(filepath.Join(c.path, "cache.json"), str, 0655) | ||
| if err != nil { | ||
| return fmt.Errorf("cache Write: %w", err) | ||
| } | ||
|
|
||
| return nil | ||
| } | ||
|
|
||
| // Read reads from the cache, returning a ErrFileCacheMiss if nothing found or | ||
| // if the cache is older than the expiry | ||
| func (c *FileCache) Read(key string) (rss.RSS, error) { | ||
| err := createCacheIfNotExists(c.path) | ||
| if err != nil { | ||
| return rss.RSS{}, fmt.Errorf("cache read: %w", err) | ||
| } | ||
|
|
||
| data, err := os.ReadFile(filepath.Join(c.path, "cache.json")) | ||
| if err != nil { | ||
| return rss.RSS{}, fmt.Errorf("cache read file: %w", err) | ||
| } | ||
|
|
||
| var cc CacheContent | ||
|
|
||
| err = json.Unmarshal(data, &cc) | ||
| if err != nil { | ||
| return rss.RSS{}, fmt.Errorf("cache read unmarshal: %w", err) | ||
| } | ||
|
|
||
| if _, ok := cc[key]; !ok { | ||
| return rss.RSS{}, ErrCacheMiss | ||
| } | ||
|
|
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| return cc[key], nil | ||
| } | ||
|
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| func createCacheIfNotExists(path string) error { | ||
| cachePath := filepath.Join(path, "cache.json") | ||
| info, _ := os.Stat(cachePath) | ||
| if info != nil { | ||
| return nil | ||
| } | ||
|
|
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| fmt.Println("No existing cache found, creating") | ||
|
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| err := os.MkdirAll(path, 0755) | ||
| if err != nil { | ||
| return fmt.Errorf("createDirIfNotExists: %w", err) | ||
| } | ||
|
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| var cc = make(CacheContent) | ||
|
|
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| str, err := json.Marshal(cc) | ||
| if err != nil { | ||
| return fmt.Errorf("createDirIfNotExists: %w", err) | ||
| } | ||
|
|
||
| err = os.WriteFile(cachePath, []byte(str), 0655) | ||
| if err != nil { | ||
| return fmt.Errorf("createDirIfNotExists: %w", err) | ||
| } | ||
|
|
||
| return nil | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,23 @@ | ||
| package cache | ||
|
|
||
| import "github.com/guyfedwards/nom/internal/rss" | ||
|
|
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| type MemoryCache struct { | ||
| content CacheContent | ||
| } | ||
|
|
||
| func (c *MemoryCache) Write(key string, content rss.RSS) error { | ||
| if c.content == nil { | ||
| c.content = make(CacheContent) | ||
| } | ||
| c.content[key] = content | ||
| return nil | ||
| } | ||
|
|
||
| func (c *MemoryCache) Read(key string) (rss.RSS, error) { | ||
| if _, ok := c.content[key]; !ok { | ||
| return rss.RSS{}, ErrCacheMiss | ||
| } | ||
|
|
||
| return c.content[key], nil | ||
| } |
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