1 files changed, 98 insertions, 0 deletions
diff --git a/src/compiler/transform/index.ts b/src/compiler/transform/index.ts
new file mode 100644
index 000000000..6a81b92b0
--- /dev/null
+++ b/src/compiler/transform/index.ts
@@ -0,0 +1,98 @@
+import type { Ast, TemplateNode } from '../../parser/interfaces';
+import type { NodeVisitor, TransformOptions, Transformer, VisitorFn } from '../../@types/transformer';
+
+import { walk } from 'estree-walker';
+
+// Transformers
+import transformStyles from './styles.js';
+import transformDoctype from './doctype.js';
+import transformModuleScripts from './module-scripts.js';
+import transformCodeBlocks from './prism.js';
+
+interface VisitorCollection {
+  enter: Map<string, VisitorFn[]>;
+  leave: Map<string, VisitorFn[]>;
+}
+
+/** Add visitors to given collection */
+function addVisitor(visitor: NodeVisitor, collection: VisitorCollection, nodeName: string, event: 'enter' | 'leave') {
+  if (typeof visitor[event] !== 'function') return;
+  if (!collection[event]) collection[event] = new Map<string, VisitorFn[]>();
+
+  const visitors = collection[event].get(nodeName) || [];
+  visitors.push(visitor[event] as any);
+  collection[event].set(nodeName, visitors);
+}
+
+/** Compile visitor actions from transformer */
+function collectVisitors(transformer: Transformer, htmlVisitors: VisitorCollection, cssVisitors: VisitorCollection, finalizers: Array<() => Promise<void>>) {
+  if (transformer.visitors) {
+    if (transformer.visitors.html) {
+      for (const [nodeName, visitor] of Object.entries(transformer.visitors.html)) {
+        addVisitor(visitor, htmlVisitors, nodeName, 'enter');
+        addVisitor(visitor, htmlVisitors, nodeName, 'leave');
+      }
+    }
+    if (transformer.visitors.css) {
+      for (const [nodeName, visitor] of Object.entries(transformer.visitors.css)) {
+        addVisitor(visitor, cssVisitors, nodeName, 'enter');
+        addVisitor(visitor, cssVisitors, nodeName, 'leave');
+      }
+    }
+  }
+  finalizers.push(transformer.finalize);
+}
+
+/** Utility for formatting visitors */
+function createVisitorCollection() {
+  return {
+    enter: new Map<string, VisitorFn[]>(),
+    leave: new Map<string, VisitorFn[]>(),
+  };
+}
+
+/** Walk AST with collected visitors */
+function walkAstWithVisitors(tmpl: TemplateNode, collection: VisitorCollection) {
+  walk(tmpl, {
+    enter(node, parent, key, index) {
+      if (collection.enter.has(node.type)) {
+        const fns = collection.enter.get(node.type)!;
+        for (let fn of fns) {
+          fn.call(this, node, parent, key, index);
+        }
+      }
+    },
+    leave(node, parent, key, index) {
+      if (collection.leave.has(node.type)) {
+        const fns = collection.leave.get(node.type)!;
+        for (let fn of fns) {
+          fn.call(this, node, parent, key, index);
+        }
+      }
+    },
+  });
+}
+
+/**
+ * Transform
+ * Step 2/3 in Astro SSR.
+ * Transform is the point at which we mutate the AST before sending off to
+ * Codegen, and then to Snowpack. In some ways, it‘s a preprocessor.
+ */
+export async function transform(ast: Ast, opts: TransformOptions) {
+  const htmlVisitors = createVisitorCollection();
+  const cssVisitors = createVisitorCollection();
+  const finalizers: Array<() => Promise<void>> = [];
+
+  const optimizers = [transformStyles(opts), transformDoctype(opts), transformModuleScripts(opts), transformCodeBlocks(ast.module)];
+
+  for (const optimizer of optimizers) {
+    collectVisitors(optimizer, htmlVisitors, cssVisitors, finalizers);
+  }
+
+  walkAstWithVisitors(ast.css, cssVisitors);
+  walkAstWithVisitors(ast.html, htmlVisitors);
+
+  // Run all of the finalizer functions in parallel because why not.
+  await Promise.all(finalizers.map((fn) => fn()));
+}