From 2e79d9c834f7f98a58ac72c39b376082d71a3d63 Mon Sep 17 00:00:00 2001
From: Sasha Koshka <sashakoshka@tebibyte.media>
Date: Mon, 5 Sep 2022 13:31:38 -0400
Subject: [PATCH] Parse -> Fetch, now tries to hit cache

---
 parser/cache.go  |  2 +-
 parser/parser.go | 30 +++++++++++++++++++++++++-----
 2 files changed, 26 insertions(+), 6 deletions(-)

diff --git a/parser/cache.go b/parser/cache.go
index a2881c3..a07dbd6 100644
--- a/parser/cache.go
+++ b/parser/cache.go
@@ -2,7 +2,7 @@ package parser
 
 // cacheItem stores an item of the parser cache.
 type cacheItem struct {
-	section Section
+	tree    SyntaxTree
 	skimmed bool
 }
 
diff --git a/parser/parser.go b/parser/parser.go
index 215a679..9e4a994 100644
--- a/parser/parser.go
+++ b/parser/parser.go
@@ -18,15 +18,28 @@ type ParsingOperation struct {
 }
 
 // TODO:
-// - implement parser cache
-// - have this try to hit the cache, and actually parse on miss
+// * implement parser cache
+// * have this try to hit the cache, and actually parse on miss
 // - rename this to Fetch
 // - add `skim bool` argument. when this is true, don't parse any code or data
 //   section initialization values, just definitions and their default values.
 
-// Parse reads the files located in the module specified by modulePath, and
-// converts them into an abstract syntax tree.
-func Parse (modulePath string) (tree SyntaxTree, err error) {
+// Fetch returns the parsed module located at the specified path, and returns an
+// abstract syntax tree. If the module has not yet been parsed, it parses it
+// first.
+func Fetch (modulePath string) (tree SyntaxTree, err error) {
+	if modulePath[0] != '/' {
+		panic("module path did not begin at filesystem root")
+	}
+
+	// try to hit cache
+	cached, exists := cache[modulePath]
+	if exists {
+		tree = cached.tree
+		return
+	}
+
+	// miss, so parse the module.
 	parser := ParsingOperation {
 		modulePath: modulePath,
 		tree: SyntaxTree {
@@ -56,6 +69,13 @@ func Parse (modulePath string) (tree SyntaxTree, err error) {
 	}
 	
 	tree = parser.tree
+
+	// cache tree
+	cache[modulePath] = cacheItem {
+		tree:    tree,
+		skimmed: false,
+	}
+	
 	return
 }