feat: add progress reporting

Author: tharropoulos

src/progress.ts

@@ -0,0 +1,47 @@
+export class ProgressReporter {
+  readonly #jsonMode: boolean;
+
+  constructor(jsonMode: boolean) {
+    this.#jsonMode = jsonMode;
+  }
+
+  startStep(name: string): StepHandle {
+    if (this.#jsonMode) {
+      process.stdout.write(`${JSON.stringify({ event: "step:start", name })}\n`);
+    } else {
+      process.stdout.write(`* ${name}\n`);
+    }
+    return new StepHandle(name, this.#jsonMode);
+  }
+
+  info(message: string): void {
+    if (this.#jsonMode) {
+      process.stdout.write(`${JSON.stringify({ event: "info", message })}\n`);
+      return;
+    }
+    process.stdout.write(`  ${message}\n`);
+  }
+}
+
+class StepHandle {
+  readonly #name: string;
+  readonly #jsonMode: boolean;
+  readonly #startedAt: number;
+
+  constructor(name: string, jsonMode: boolean) {
+    this.#name = name;
+    this.#jsonMode = jsonMode;
+    this.#startedAt = Date.now();
+  }
+
+  done(details?: string): void {
+    const elapsedMs = Date.now() - this.#startedAt;
+    if (this.#jsonMode) {
+      process.stdout.write(`${JSON.stringify({ event: "step:done", name: this.#name, elapsedMs, details })}\n`);
+      return;
+    }
+
+    const suffix = details === undefined ? "" : ` ${details}`;
+    process.stdout.write(`  done ${this.#name} (${elapsedMs}ms)${suffix}\n`);
+  }
+}