From 2e73eae391a43caeb6f4390b0c39184522f1470c Mon Sep 17 00:00:00 2001
From: Andy Gayton <andy@thecablelounge.com>
Date: Fri, 24 Jan 2025 17:07:12 -0500
Subject: [PATCH] examples: add a todo app (#43)

---
 examples/todo-app/README.md  | 41 ++++++++++++++++
 examples/todo-app/handler.nu | 56 ++++++++++++++++++++++
 examples/todo-app/index.html | 92 ++++++++++++++++++++++++++++++++++++
 3 files changed, 189 insertions(+)
 create mode 100644 examples/todo-app/README.md
 create mode 100644 examples/todo-app/handler.nu
 create mode 100644 examples/todo-app/index.html

diff --git a/examples/todo-app/README.md b/examples/todo-app/README.md
new file mode 100644
index 0000000..1d89dbf
--- /dev/null
+++ b/examples/todo-app/README.md
@@ -0,0 +1,41 @@
+# Todo App Example
+
+A simple todo list application demonstrating how to build a web application using cross-stream's [built-in HTTP server](https://cablehead.github.io/xs/reference/http-server/).
+
+<img width="726" alt="image" src="https://github.com/user-attachments/assets/ccfcaa62-436e-4a85-95df-29a142a426cd" />
+
+## Features
+
+- Add new todos
+- Toggle todo completion status 
+- Persistent storage using cross-stream's event store
+
+## Structure
+
+- `handler.nu` - Event handler for processing HTTP requests and managing todos
+- `index.html` - Frontend interface with styling and JavaScript
+
+## Running the App
+
+1. Start cross-stream with HTTP server enabled:
+```bash
+xs serve ./store --http :5007
+```
+
+2. Load the handler and template:
+```nushell
+# Install minijinja-cli first: https://github.com/mitsuhiko/minijinja
+cat handler.nu | .append todo.handler.register
+cat index.html | .append index.html
+```
+
+3. Visit: http://localhost:5007 in your browser
+
+## Event Structure
+
+The todo state is rebuilt from two event types:
+
+- `todo` - Contains the text content of new todos
+- `todo.toggle` - Records completion status changes
+
+The handler aggregates these events to maintain the current state of all todos, with each todo having a unique ID, text content, and completion status.
diff --git a/examples/todo-app/handler.nu b/examples/todo-app/handler.nu
new file mode 100644
index 0000000..91011a3
--- /dev/null
+++ b/examples/todo-app/handler.nu
@@ -0,0 +1,56 @@
+{
+  process: {|frame|
+    if $frame.topic != "http.request" { return }
+
+    match $frame.meta {
+      {uri: "/" method: "GET"} => {
+        # Get todos
+        let todos = .cat | where topic =~ "todo" | reduce --fold {} {|f acc|
+          match $f.topic {
+            "todo" => ($acc | insert $f.id {text: (.cas $f.hash) done: false})
+            todo.toggle => ($acc | update ($f.meta.id) { $in | update done { not ($in) } })
+            _ => $acc
+          }
+        }
+
+        # Render template
+        {todos: $todos} | to json -r | minijinja-cli -f json -t (.head index.html | .cas $in.hash) '' - | .append http.response --meta {
+          request_id: $frame.id
+          status: 200
+          headers: {
+            Content-Type: "text/html"
+          }
+        }
+      }
+
+      {uri: "/" method: "POST"} => {
+        # Get the todo content and store it
+        .cas $frame.hash | url split-query | transpose -rdl | get todo | .append todo
+
+        # Redirect to GET /
+        .append http.response --meta {
+          request_id: $frame.id
+          status: 303
+          headers: {
+            Location: "/"
+          }
+        }
+      }
+
+      {uri: "/toggle" method: "POST"} => {
+        .cas $frame.hash | from json | .append todo.toggle --meta $in
+        "OK" | .append http.response --meta {request_id: $frame.id status: 200 headers: {Content-Type: "text/plain"}}
+      }
+
+      _ => {
+        "not found :/" | .append http.response --meta {
+          request_id: $frame.id
+          status: 404
+          headers: {
+            Content-Type: "text/html"
+          }
+        }
+      }
+    }
+  }
+}
diff --git a/examples/todo-app/index.html b/examples/todo-app/index.html
new file mode 100644
index 0000000..2e2ec4a
--- /dev/null
+++ b/examples/todo-app/index.html
@@ -0,0 +1,92 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <title>Todo List</title>
+    <style>
+      body {
+        max-width: 600px;
+        margin: 0 auto;
+        padding: 20px;
+        font-family: system-ui, sans-serif;
+      }
+      .todo-item {
+        padding: 10px;
+        margin: 5px 0;
+        background: #f5f5f5;
+        border-radius: 4px;
+        display: flex;
+        align-items: center;
+        gap: 10px;
+      }
+      .todo-item.done span {
+        text-decoration: line-through;
+        color: #666;
+      }
+      .todo-form {
+        margin-top: 20px;
+      }
+      textarea {
+        width: 100%;
+        padding: 10px;
+        margin-bottom: 10px;
+        border: 1px solid #ddd;
+        border-radius: 4px;
+      }
+      button {
+        padding: 8px 16px;
+        background: #0066cc;
+        color: white;
+        border: none;
+        border-radius: 4px;
+        cursor: pointer;
+      }
+      button:hover {
+        background: #0052a3;
+      }
+      input[type="checkbox"] {
+        width: 20px;
+        height: 20px;
+      }
+    </style>
+  </head>
+  <body>
+    <h1>Todos</h1>
+
+    <div class="todo-list">
+      {% for id, todo in todos | items %}
+      <div class="todo-item {% if todo.done %}done{% endif %}">
+        <input
+          type="checkbox"
+          {%
+          if
+          todo.done
+          %}checked{%
+          endif
+          %}
+          onchange="toggleTodo('{{ id }}', this.checked)"
+        />
+        <span>{{ todo.text }}</span>
+      </div>
+      {% else %}
+      <p>No todos yet. Add one below!</p>
+      {% endfor %}
+    </div>
+
+    <form class="todo-form" method="POST">
+      <textarea name="todo" rows="3" placeholder="Enter a new todo..."></textarea>
+      <button type="submit">Add Todo</button>
+    </form>
+
+    <script>
+      function toggleTodo(id, done) {
+        fetch(`/toggle`, {
+          method: "POST",
+          headers: {
+            "Content-Type": "application/json",
+          },
+          body: JSON.stringify({ id: id }),
+        }).then(() => window.location.reload());
+      }
+    </script>
+  </body>
+</html>