1 files changed, 89 insertions, 0 deletions
diff --git a/src/js/builtins/codegen/builtin-parser.ts b/src/js/builtins/codegen/builtin-parser.ts
new file mode 100644
index 000000000..e96d79c63
--- /dev/null
+++ b/src/js/builtins/codegen/builtin-parser.ts
@@ -0,0 +1,89 @@
+import { applyReplacements } from "./replacements";
+
+/**
+ * Slices a string until it hits a }, but keeping in mind JS comments,
+ * regex, template literals, comments, and matching {
+ *
+ * Used to extract function bodies without parsing the code.
+ *
+ * If you pass replace=true, it will run replacements on the code
+ */
+export function sliceSourceCode(
+  contents: string,
+  replace: boolean,
+): { result: string; rest: string; usesThis: boolean } {
+  let bracketCount = 0;
+  let i = 0;
+  let result = "";
+  let usesThis = false;
+  while (contents.length) {
+    // TODO: template literal, regexp
+    // these are important because our replacement logic would replace intrinsics
+    // within these, when it should remain as the literal dollar.
+    // but this isn't used in the codebase
+    i = contents.match(/\/\*|\/\/|'|"|{|}|`/)?.index ?? contents.length;
+    const chunk = replace ? applyReplacements(contents.slice(0, i)) : contents.slice(0, i);
+    if (chunk.includes("this")) usesThis = true;
+    result += chunk;
+    contents = contents.slice(i);
+    if (!contents.length) break;
+    if (contents.startsWith("/*")) {
+      i = contents.slice(2).indexOf("*/") + 2;
+    } else if (contents.startsWith("//")) {
+      i = contents.slice(2).indexOf("\n") + 2;
+    } else if (contents.startsWith("'")) {
+      i = contents.slice(1).match(/(?<!\\)'/)!.index! + 2;
+    } else if (contents.startsWith('"')) {
+      i = contents.slice(1).match(/(?<!\\)"/)!.index! + 2;
+    } else if (contents.startsWith("`")) {
+      const { result: result2, rest } = sliceTemplateLiteralSourceCode(contents.slice(1), replace);
+      result += "`" + result2;
+      contents = rest;
+      continue;
+    } else if (contents.startsWith("{")) {
+      bracketCount++;
+      i = 1;
+    } else if (contents.startsWith("}")) {
+      bracketCount--;
+      if (bracketCount <= 0) {
+        result += "}";
+        contents = contents.slice(1);
+        break;
+      }
+      i = 1;
+    } else {
+      throw new Error("TODO");
+    }
+    result += contents.slice(0, i);
+    contents = contents.slice(i);
+  }
+
+  return { result, rest: contents, usesThis };
+}
+
+function sliceTemplateLiteralSourceCode(contents: string, replace: boolean) {
+  let i = 0;
+  let result = "";
+  let usesThis = false;
+  while (contents.length) {
+    i = contents.match(/`|\${/)!.index!;
+    result += contents.slice(0, i);
+    contents = contents.slice(i);
+    if (!contents.length) break;
+    if (contents.startsWith("`")) {
+      result += "`";
+      contents = contents.slice(1);
+      break;
+    } else if (contents.startsWith("$")) {
+      const { result: result2, rest, usesThis: usesThisVal } = sliceSourceCode(contents.slice(1), replace);
+      result += "$" + result2;
+      contents = rest;
+      usesThis ||= usesThisVal;
+      continue;
+    } else {
+      throw new Error("TODO");
+    }
+  }
+
+  return { result, rest: contents, usesThis };
+}