From 95f6cf3e166d80922378807ac931517ae2fe557e Mon Sep 17 00:00:00 2001
From: Peter Sanchez <peter@netlandish.com>
Date: Thu, 25 Jan 2024 18:57:25 -0600
Subject: [PATCH] Adding base Cache interface. Very simple. Will think a bit
 more about any additional options to add.

References: https://todo.code.netlandish.com/~netlandish/gobwebs/7
---
 cache/cache.go      | 48 +++++++++++++++++++++++++++++++++++++++++++++
 cache/middleware.go | 39 ++++++++++++++++++++++++++++++++++++
 2 files changed, 87 insertions(+)
 create mode 100644 cache/cache.go
 create mode 100644 cache/middleware.go

diff --git a/cache/cache.go b/cache/cache.go
new file mode 100644
index 0000000..a5e2162
--- /dev/null
+++ b/cache/cache.go
@@ -0,0 +1,48 @@
+package cache
+
+type Cache interface {
+	Get(key string) (any, error)
+	Set(key string, value any) (bool, error)
+	Delete(key string) (bool, error)
+}
+
+type DummyCache struct {
+	cache map[string]any
+	limit int
+}
+
+func (d *DummyCache) Get(key string) (any, error) {
+	val := d.cache[key]
+	return val, nil
+}
+
+func (d *DummyCache) Set(key string, value any) (bool, error) {
+	var evicted bool
+	if len(d.cache) >= d.limit {
+		for k := range d.cache {
+			d.Delete(k)
+			if len(d.cache) < d.limit {
+				break
+			}
+		}
+		evicted = true
+	}
+	d.cache[key] = value
+	return evicted, nil
+}
+
+func (d *DummyCache) Delete(key string) (bool, error) {
+	var present bool
+	if _, ok := d.cache[key]; ok {
+		present = true
+	}
+	delete(d.cache, key)
+	return present, nil
+}
+
+func NewDummyCache(limit int) *DummyCache {
+	return &DummyCache{
+		cache: make(map[string]any),
+		limit: limit,
+	}
+}
diff --git a/cache/middleware.go b/cache/middleware.go
new file mode 100644
index 0000000..f784ce0
--- /dev/null
+++ b/cache/middleware.go
@@ -0,0 +1,39 @@
+package cache
+
+import (
+	"context"
+	"errors"
+
+	"github.com/labstack/echo/v4"
+)
+
+var cacheCtxKey = &contextKey{"cache"}
+
+type contextKey struct {
+	name string
+}
+
+// Context adds cache manager to context for immediate use
+func Context(ctx context.Context, cache Cache) context.Context {
+	return context.WithValue(ctx, cacheCtxKey, cache)
+}
+
+// ForContext pulls cache manager value for context
+func ForContext(ctx context.Context) Cache {
+	cache, ok := ctx.Value(cacheCtxKey).(Cache)
+	if !ok {
+		panic(errors.New("invalid cache context"))
+	}
+	return cache
+}
+
+// Middleware will add the provided Cache instance to the context
+func Middleware(cache Cache) echo.MiddlewareFunc {
+	return func(next echo.HandlerFunc) echo.HandlerFunc {
+		return func(c echo.Context) error {
+			ctx := Context(c.Request().Context(), cache)
+			c.SetRequest(c.Request().WithContext(ctx))
+			return next(c)
+		}
+	}
+}
-- 
2.45.2