From 6e123054e2ded82f04890a64eb896406f0b3d51c Mon Sep 17 00:00:00 2001
From: Simon Martens <simon.martens@mailbox.org>
Date: Sat, 28 Dec 2024 12:34:28 +0100
Subject: [PATCH] Cache for file embedding + unsafe mebedding

---
 functions/embedding.go | 51 +++++++++++++++++++++++++++++++++---------
 1 file changed, 41 insertions(+), 10 deletions(-)

diff --git a/functions/embedding.go b/functions/embedding.go
index dd0a192..c7eb90b 100644
--- a/functions/embedding.go
+++ b/functions/embedding.go
@@ -4,22 +4,53 @@ import (
 	"html/template"
 	"io"
 	"io/fs"
+	"sync"
 )
 
-// TODO: this needs to be cached, FS reads are expensive
+var embed_cache sync.Map
+
+// INFO: We initialize the cache in both functions, which is only valid if both of these get
+// called in the same context, eg. when creating a template engine.
 func EmbedSafe(fs fs.FS) func(string) template.HTML {
+	embed_cache.Clear()
 	return func(path string) template.HTML {
-		f, err := fs.Open(path)
+		val, err := getFileData(fs, path)
 		if err != nil {
-			return ""
+			return template.HTML("")
 		}
 
-		defer f.Close()
-		data, err := io.ReadAll(f)
-		if err != nil {
-			return ""
-		}
-
-		return template.HTML(data)
+		return template.HTML(val)
 	}
 }
+
+func EmbedUnsafe(fs fs.FS) func(string) string {
+	embed_cache.Clear()
+	return func(path string) string {
+		val, err := getFileData(fs, path)
+		if err != nil {
+			return ""
+		}
+
+		return string(val)
+	}
+}
+
+func getFileData(fs fs.FS, path string) ([]byte, error) {
+	if val, ok := embed_cache.Load(path); ok {
+		return val.([]byte), nil
+	}
+
+	f, err := fs.Open(path)
+	if err != nil {
+		return nil, err
+	}
+	defer f.Close()
+
+	data, err := io.ReadAll(f)
+	if err != nil {
+		return nil, err
+	}
+
+	embed_cache.Store(path, data)
+	return data, nil
+}