Initial commit: demo todo CLI with Claude Code setup

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.claude/agents/test-writer.md

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+---
+name: test-writer
+description: Writes node:test unit tests for functions in src/ that lack coverage. Use when asked to add or improve tests.
+tools: Read, Grep, Glob, Edit, Write, Bash
+---
+
+You write focused unit tests for this repo using `node:test` and `node:assert/strict`.
+
+- Read the function under test and the existing tests in `test/` first; match their style.
+- Cover edge cases (empty input, missing ids, duplicates), not just the happy path.
+- Run `npm test` before finishing. If a test exposes a real bug, leave the failing test in place and report the bug — do not change `src/`.

.claude/settings.json

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+{
+  "$schema": "https://json.schemastore.org/claude-code-settings.json",
+  "permissions": {
+    "allow": [
+      "Bash(npm test)",
+      "Bash(npm start:*)",
+      "Bash(node --test:*)",
+      "Bash(git status)",
+      "Bash(git diff:*)",
+      "Bash(git log:*)"
+    ],
+    "deny": [
+      "Bash(git push --force:*)",
+      "Read(./.env)"
+    ]
+  },
+  "hooks": {
+    "PostToolUse": [
+      {
+        "matcher": "Edit|Write",
+        "hooks": [
+          {
+            "type": "command",
+            "command": "f=$(jq -r '.tool_input.file_path // empty'); case \"$f\" in *.js) node --check \"$f\" || { echo \"Syntax error in $f\" >&2; exit 2; } ;; esac"
+          }
+        ]
+      }
+    ]
+  }
+}

.claude/skills/changelog/SKILL.md

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+---
+name: changelog
+description: Draft a changelog entry from the git commits since the last tag (or all commits if there is no tag). Use when the user asks for release notes or a changelog.
+---
+
+1. Find the range: `git describe --tags --abbrev=0` — if it fails, use the full history.
+2. Read the commits in that range with `git log --oneline <range>`.
+3. Group them under **Added**, **Changed**, **Fixed** (skip empty groups), one bullet per user-visible change, in plain language.
+4. Print the entry. Only write it to `CHANGELOG.md` if the user asks.

.gitignore

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+node_modules/
+todos.json
+.DS_Store
+
+# Personal Claude Code overrides (not shared)
+.claude/settings.local.json
+CLAUDE.local.md

CLAUDE.md

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+# claude-playground
+
+A tiny zero-dependency Node.js todo CLI, used as a sandbox for trying Claude Code features.
+
+## Commands
+- `npm test` — run the test suite (built-in `node:test`, no install needed)
+- `npm start -- add "something"` / `npm start -- ls` — run the CLI (data in `todos.json`, override with `TODO_FILE`)
+
+## Conventions
+- ES modules, Node >= 20, no third-party dependencies.
+- `src/todo.js` holds pure functions; keep I/O in `load`/`save` and `src/cli.js`.
+- Every behavior change gets a test in `test/`.
+- Commit messages: short imperative subject line.
+
+## Remote
+Gitea at code.westerkam.org — `origin` = `git@code.westerkam.org:christian/claude-playground.git`.

README.md

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+# claude-playground
+
+A tiny todo CLI that exists to try out [Claude Code](https://docs.claude.com/en/docs/claude-code) features.
+
+```sh
+npm test
+npm start -- add "try Claude Code"
+npm start -- done 1
+npm start -- ls
+```
+
+## What's set up
+
+| File | Claude Code feature |
+| --- | --- |
+| `CLAUDE.md` | Project memory, loaded into every session |
+| `.claude/settings.json` | Shared permissions + a hook that syntax-checks `.js` files after every edit |
+| `.claude/skills/changelog/` | A custom skill — run `/changelog` |
+| `.claude/agents/test-writer.md` | A custom subagent — "use the test-writer agent to…" |
+
+## Things to try
+
+- *"There's a bug in how ids are assigned after removing a todo — find it and fix it with a test."*
+- *"Use the test-writer agent to cover `src/todo.js`."*
+- *"Add a `--json` flag to `ls`."* then `/code-review`
+- `/changelog` after a few commits
+- Press `shift+tab` to cycle permission modes (e.g. plan mode before a bigger change)
+- `/memory` to edit CLAUDE.md, `/agents` and `/hooks` to inspect the setup

package.json

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+{
+  "name": "claude-playground",
+  "version": "0.1.0",
+  "description": "A tiny todo CLI used as a sandbox for trying Claude Code features",
+  "type": "module",
+  "bin": { "todo": "./src/cli.js" },
+  "scripts": {
+    "start": "node src/cli.js",
+    "test": "node --test"
+  },
+  "engines": { "node": ">=20" },
+  "license": "MIT"
+}

src/cli.js

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+#!/usr/bin/env node
+import { load, save, add, complete, remove, format } from "./todo.js";
+
+const FILE = process.env.TODO_FILE ?? "todos.json";
+const [cmd, ...args] = process.argv.slice(2);
+let todos = load(FILE);
+
+switch (cmd) {
+  case "add":
+    todos = add(todos, args.join(" "));
+    break;
+  case "done":
+    todos = complete(todos, Number(args[0]));
+    break;
+  case "rm":
+    todos = remove(todos, Number(args[0]));
+    break;
+  case "ls":
+  case undefined:
+    console.log(format(todos));
+    process.exit(0);
+  default:
+    console.error(`Unknown command: ${cmd}\nUsage: todo [ls | add <text> | done <id> | rm <id>]`);
+    process.exit(1);
+}
+
+save(FILE, todos);
+console.log(format(todos));

src/todo.js

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+import { readFileSync, writeFileSync, existsSync } from "node:fs";
+
+export function load(path) {
+  if (!existsSync(path)) return [];
+  return JSON.parse(readFileSync(path, "utf8"));
+}
+
+export function save(path, todos) {
+  writeFileSync(path, JSON.stringify(todos, null, 2) + "\n");
+}
+
+export function add(todos, text) {
+  const id = todos.length + 1;
+  return [...todos, { id, text, done: false }];
+}
+
+export function complete(todos, id) {
+  return todos.map((t) => (t.id === id ? { ...t, done: true } : t));
+}
+
+export function remove(todos, id) {
+  return todos.filter((t) => t.id !== id);
+}
+
+export function format(todos) {
+  if (todos.length === 0) return "Nothing to do.";
+  return todos.map((t) => `${t.done ? "[x]" : "[ ]"} ${t.id}. ${t.text}`).join("\n");
+}

test/todo.test.js

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+import { test } from "node:test";
+import assert from "node:assert/strict";
+import { add, complete, remove, format } from "../src/todo.js";
+
+test("add appends an open todo", () => {
+  const todos = add([], "buy milk");
+  assert.deepEqual(todos, [{ id: 1, text: "buy milk", done: false }]);
+});
+
+test("complete marks only the matching todo", () => {
+  const todos = complete(add(add([], "a"), "b"), 2);
+  assert.equal(todos[0].done, false);
+  assert.equal(todos[1].done, true);
+});
+
+test("remove drops the matching todo", () => {
+  const todos = remove(add(add([], "a"), "b"), 1);
+  assert.deepEqual(todos.map((t) => t.text), ["b"]);
+});
+
+test("format renders an empty list", () => {
+  assert.equal(format([]), "Nothing to do.");
+});