1package filecache
 2
 3import (
 4	"encoding/hex"
 5	"errors"
 6	"io"
 7	"os"
 8	"path"
 9	"path/filepath"
10)
11
12// New returns a new Cache implemented by fileCache.
13func New(dir string) Cache {
14	return newFileCache(dir)
15}
16
17func newFileCache(dir string) *fileCache {
18	return &fileCache{dirPath: dir}
19}
20
21// fileCache persists compiled functions into dirPath.
22//
23// Note: this can be expanded to do binary signing/verification, set TTL on each entry, etc.
24type fileCache struct {
25	dirPath string
26}
27
28func (fc *fileCache) path(key Key) string {
29	return path.Join(fc.dirPath, hex.EncodeToString(key[:]))
30}
31
32func (fc *fileCache) Get(key Key) (content io.ReadCloser, ok bool, err error) {
33	f, err := os.Open(fc.path(key))
34	if errors.Is(err, os.ErrNotExist) {
35		return nil, false, nil
36	} else if err != nil {
37		return nil, false, err
38	} else {
39		return f, true, nil
40	}
41}
42
43func (fc *fileCache) Add(key Key, content io.Reader) (err error) {
44	path := fc.path(key)
45	dirPath, fileName := filepath.Split(path)
46
47	file, err := os.CreateTemp(dirPath, fileName+".*.tmp")
48	if err != nil {
49		return
50	}
51	defer func() {
52		file.Close()
53		if err != nil {
54			_ = os.Remove(file.Name())
55		}
56	}()
57	if _, err = io.Copy(file, content); err != nil {
58		return
59	}
60	if err = file.Sync(); err != nil {
61		return
62	}
63	if err = file.Close(); err != nil {
64		return
65	}
66	err = os.Rename(file.Name(), path)
67	return
68}
69
70func (fc *fileCache) Delete(key Key) (err error) {
71	err = os.Remove(fc.path(key))
72	if errors.Is(err, os.ErrNotExist) {
73		err = nil
74	}
75	return
76}