feat(cache): implement dynamic interface caching abstraction

[Pyr33x]

Summary by CodeRabbit

• New Features

  • Cache backend configurable via PROXY_CACHE (memory or redis); default is in-memory.
  • Cache TTL configurable via PROXY_TTL (seconds); applied at cache creation.

• Enhancements

  • Introduced interchangeable cache implementations (in-memory and Redis) with unified API and TTL support.
  • Runtime falls back to in-memory cache when Redis is unavailable.

• Documentation

  • README updated with PROXY_CACHE/PROXY_TTL usage, Docker/Compose guidance, and Redis notes.

_{✏️ Tip: You can customize this high-level summary in your review settings.}

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📥 Commits

Reviewing files that changed from the base of the PR and between 4336d80 and f9baf65.

📒 Files selected for processing (1)

• internal/proxy/proxy.go (2 hunks)

Walkthrough

Adds a Store abstraction for caching, implements memory and Redis Store backends, updates Cache to use Store, and surfaces cache type and TTL via configuration and proxy initialization; README and proxy code updated to select and pass TTL to the new cache constructor.

Changes

Cohort / File(s)	Summary
Cache core / Store abstraction internal/cache/cache.go	Replaced direct Redis dependency with a Store interface (Get/Set/Clear). Cache now stores store Store and expiration time.Duration. Constructor changed to NewCacheRepository(store Store, logger *zap.Logger, ttl time.Duration). Get/Put/Clear delegate to Store.
In-memory store internal/cache/memory.go	Added memoryStore using sync.Map and memoryEntry (value + expiration). Implements Get(ctx, key) ([]byte, error), Set(ctx, key, value []byte, ttl time.Duration) error, and Clear(ctx) error. Enforces TTL on access and removes expired entries.
Redis store internal/cache/redis.go	Added redisStore wrapper around *redis.Client with NewRedisStore. Implements Get/Set/Clear operating on raw bytes and honoring TTL via Redis commands.
Proxy initialization internal/proxy/proxy.go	Updated to select cache backend based on config (PROXY_CACHE) and to pass a cache.Store and explicit TTL to NewCacheRepository. Introduces fallback to memory store when Redis not configured or unavailable.
Configuration pkg/config/config.go	Proxy struct extended with exported Cache string and TTL int64. New() reads PROXY_CACHE (default "memory") and PROXY_TTL (default 60) from environment.
Documentation / Examples README.md	Docs updated to document PROXY_CACHE (redis

Estimated code review effort

🎯 4 (Complex) | ⏱️ ~45 minutes

• Check proxy logic for any unconditional overwrite of a created Redis store by MemoryStore and intended fallback behavior.
• Verify TTL unit conversion/propagation: int64 config → time.Duration used by stores and Cache.
• Inspect memoryStore concurrency (sync.Map usage) and expiration race conditions.
• Confirm consistent error semantics between memoryStore (nil on miss) and redisStore (propagates client errors).
• Review marshalling/unmarshalling and nil-byte handling in cache.go Get/Put.

Poem

I nibble bytes from field to den,
A store in burrows built for men.
Memory hops, Redis hums,
TTL drums, the timeout drums.
Hop—cache set! —the rabbit grins 🐇✨

Pre-merge checks and finishing touches

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	You can run @coderabbitai generate docstrings to improve docstring coverage.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes the main change: introducing a dynamic Store interface abstraction for caching, replacing direct Redis dependency with pluggable in-memory and Redis implementations.

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[coderabbitai]

Actionable comments posted: 4

🧹 Nitpick comments (4)

pkg/config/config.go (1)

49-51: Consider adding validation or documentation for valid cache types.

The Cache field accepts any string but only "redis" and "memory" are valid values. Consider documenting valid values in a comment or adding validation to fail fast on invalid configuration.

 			Proxy: Proxy{
 				Port:  envy.GetString("PROXY_PORT", "1337"),
-				Cache: envy.GetString("PROXY_CACHE", "memory"),
+				Cache: envy.GetString("PROXY_CACHE", "memory"), // valid: "memory", "redis"
 				TTL:   envy.GetInt64("PROXY_TTL", 60), // in seconds
 			},

internal/cache/memory.go (1)

22-36: Lazy expiration means expired entries accumulate in memory.

Entries are only evicted when accessed. With many keys that are never re-accessed, memory usage will grow unbounded. This is acceptable for low-traffic caches but consider documenting this limitation or adding periodic cleanup for production use.

internal/cache/cache.go (2)

46-53: Error case logged as "cache miss" may obscure actual failures.

When store.Get returns an error (e.g., Redis connection failure), it's logged as a "MISS" which could mask infrastructure issues. Consider distinguishing between a store error and a cache miss.

 	raw, err := c.store.Get(ctx, key)
 	if err != nil {
-		c.logger.Info("cache miss",
+		c.logger.Warn("cache get error",
 			zap.String("key", key),
-			zap.String("state", "MISS"),
+			zap.Error(err),
 		)
 		return nil, false
 	}

---

61-64: Unmarshal errors are silently swallowed.

If cached data is corrupted or in an unexpected format, the error is not logged, making debugging difficult. Add logging for unmarshal failures.

 	var val CacheValue
 	if err := json.Unmarshal(raw, &val); err != nil {
+		c.logger.Error("failed to unmarshal cached value",
+			zap.String("key", key),
+			zap.Error(err),
+		)
 		return nil, false
 	}

📜 Review details

Configuration used: CodeRabbit UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 243dc35 and 0894285.

📒 Files selected for processing (5)

• internal/cache/cache.go (6 hunks)
• internal/cache/memory.go (1 hunks)
• internal/cache/redis.go (1 hunks)
• internal/proxy/proxy.go (2 hunks)
• pkg/config/config.go (2 hunks)

🧰 Additional context used

🧬 Code graph analysis (3)

pkg/config/config.go (1)

internal/cache/cache.go (1)

• Cache (20-24)

internal/proxy/proxy.go (5)

internal/cache/cache.go (3)

• Store (14-18)
• Cache (20-24)
• NewCacheRepository (32-38)

pkg/config/config.go (4)

• Server (11-14)
• Proxy (20-24)
• New (42-67)
• Redis (30-33)

internal/adapter/redis/redis.go (1)

• New (16-31)

internal/cache/redis.go (1)

• NewRedisStore (14-16)

internal/cache/memory.go (1)

• NewMemoryStore (18-20)

internal/cache/memory.go (1)

internal/cache/cache.go (1)

• Store (14-18)

🪛 GitHub Actions: 🔨 Lint

internal/proxy/proxy.go

[error] 34-34: GolangCI-Lint: ineffectual assignment to cacheStorage (ineffassign)

🪛 GitHub Check: lint (stable, ubuntu-latest)

internal/proxy/proxy.go

[failure] 34-34:
ineffectual assignment to cacheStorage (ineffassign)

🔇 Additional comments (6)

internal/cache/redis.go (1)

10-24: LGTM!

The Redis store implementation correctly delegates to the Redis client and properly implements the Store interface. The Get and Set methods handle byte conversion and TTL appropriately.

pkg/config/config.go (1)

20-24: LGTM!

The new Cache and TTL fields extend the proxy configuration cleanly. The defaults (memory cache with 60-second TTL) are sensible.

internal/proxy/proxy.go (1)

45-45: LGTM!

The TTL conversion from int64 seconds to time.Duration is correctly applied when creating the cache repository.

internal/cache/memory.go (1)

38-50: LGTM!

The Set method correctly computes expiration time and stores entries atomically using sync.Map.Store.

internal/cache/cache.go (2)

14-18: LGTM!

The Store interface is well-designed with a minimal, focused API that cleanly abstracts the underlying storage mechanism.

---

32-38: LGTM!

The NewCacheRepository constructor and the Put/Clear methods are well-implemented with appropriate error handling and logging.

Also applies to: 69-94, 96-98