cache_file.go

// Copyright 2017-2026 Allow2 Pty Ltd. All rights reserved.
// Use of this source code is governed by the Allow2 API and SDK Licence.

package allow2service

import (
	"encoding/json"
	"os"
	"path/filepath"
	"regexp"
	"time"
)

// FileCache is a file-based permission cache.
// Each cache entry is stored as a separate JSON file in the cache directory.
type FileCache struct {
	cacheDir string
}

// fileCacheEntry represents a cached value with expiry.
type fileCacheEntry struct {
	Value     string `json:"value"`
	ExpiresAt int64  `json:"expiresAt"`
}

// NewFileCache creates a new FileCache with the given directory.
// The directory is created if it does not exist.
func NewFileCache(cacheDir string) *FileCache {
	_ = os.MkdirAll(cacheDir, 0700)
	return &FileCache{cacheDir: cacheDir}
}

// Get retrieves a cached value by key.
func (c *FileCache) Get(key string) (string, bool) {
	path := c.keyToPath(key)

	contents, err := os.ReadFile(path)
	if err != nil {
		return "", false
	}

	var entry fileCacheEntry
	if err := json.Unmarshal(contents, &entry); err != nil {
		_ = os.Remove(path)
		return "", false
	}

	if time.Now().Unix() >= entry.ExpiresAt {
		_ = os.Remove(path)
		return "", false
	}

	return entry.Value, true
}

// Set stores a value in cache with the given TTL in seconds.
func (c *FileCache) Set(key, value string, ttlSeconds int) {
	path := c.keyToPath(key)

	entry := fileCacheEntry{
		Value:     value,
		ExpiresAt: time.Now().Unix() + int64(ttlSeconds),
	}

	data, err := json.Marshal(entry)
	if err != nil {
		return
	}

	_ = os.WriteFile(path, data, 0600)
}

// Delete removes a cached value.
func (c *FileCache) Delete(key string) {
	path := c.keyToPath(key)
	_ = os.Remove(path)
}

// safeKeyRegex matches characters that are NOT safe for filenames.
var safeKeyRegex = regexp.MustCompile(`[^a-zA-Z0-9_\-]`)

// keyToPath converts a cache key to a safe filesystem path.
func (c *FileCache) keyToPath(key string) string {
	safeKey := safeKeyRegex.ReplaceAllString(key, "_")
	return filepath.Join(c.cacheDir, safeKey+".json")
}