initial project setup

src/write.ts

@@ -0,0 +1,88 @@
+// Copyright (c) Microsoft Corporation
+// Licensed under the MIT license.
+
+import { resolvePath } from "@typespec/compiler";
+import { JsContext, Module, isModule } from "./ctx.js";
+
+import { emitModuleBody } from "./common/namespace.js";
+import { OnceQueue, createOnceQueue } from "./util/once-queue.js";
+
+import * as prettier from "prettier";
+
+import { EOL } from "os";
+import path from "path";
+import { bifilter } from "./util/iter.js";
+
+/**
+ * Writes the tree of modules to the output directory.
+ *
+ * @param ctx - The emitter context.
+ * @param baseOutputPath - The base output directory to write the module tree to.
+ * @param rootModule - The root module to begin emitting from.
+ * @param format - Whether to format the output using Prettier.
+ */
+export async function writeModuleTree(
+  ctx: JsContext,
+  baseOutputPath: string,
+  rootModule: Module,
+  format: boolean,
+): Promise<void> {
+  const queue = createOnceQueue(rootModule);
+
+  while (!queue.isEmpty()) {
+    const module = queue.take()!;
+    await writeModuleFile(ctx, baseOutputPath, module, queue, format);
+  }
+}
+
+/**
+ * Write a single module file to the output directory.
+ *
+ * @param ctx - The emitter context.
+ * @param baseOutputPath - The base output directory to write the module tree to.
+ * @param module - The module to write.
+ * @param queue - The queue of modules to write.
+ * @param format - Whether to format the output using Prettier.
+ * @param spit - The function used to write the file to disk (default: `ctx.program.host.writeFile`).
+ */
+export async function writeModuleFile(
+  ctx: JsContext,
+  baseOutputPath: string,
+  module: Module,
+  queue: OnceQueue<Module>,
+  format: boolean,
+  spit: (path: string, contents: string) => Promise<void> = async (name, contents) => {
+    await ctx.program.host.mkdirp(path.dirname(name));
+    await ctx.program.host.writeFile(name, contents);
+  },
+): Promise<void> {
+  const moduleText = [
+    "// Generated by Microsoft TypeSpec",
+    "",
+    ...emitModuleBody(ctx, module, queue),
+  ];
+
+  const [declaredModules, declaredText] = bifilter(module.declarations, isModule);
+
+  if (declaredText.length === 0) {
+    // Early exit to avoid writing an empty module.
+    return;
+  }
+
+  const isIndex = module.cursor.path.length === 0 || declaredModules.length > 0;
+
+  const moduleRelativePath =
+    module.cursor.path.length > 0
+      ? module.cursor.path.join("/") + (isIndex ? "/index.ts" : ".ts")
+      : "index.ts";
+
+  const modulePath = resolvePath(baseOutputPath, moduleRelativePath);
+
+  const text = format
+    ? await prettier.format(moduleText.join(EOL), {
+        parser: "typescript",
+      })
+    : moduleText.join(EOL);
+
+  await spit(modulePath, text);
+}