/**
* Todo Extension - Demonstrates state management via session entries
*
* This extension:
* - Registers a `todo` tool for the LLM to manage todos
* - Registers a `/todos` command for users to view the list
*
* State is stored in tool result details (not external files), which allows
* proper branching - when you branch, the todo state is automatically
* correct for that point in history.
*/
import { StringEnum } from "@earendil-works/pi-ai";
import type { ExtensionAPI, ExtensionContext, Theme } from "@earendil-works/pi-coding-agent";
import { matchesKey, Text, truncateToWidth } from "@earendil-works/pi-tui";
import { Type } from "typebox";
interface Todo {
id: number;
text: string;
done: boolean;
}
interface TodoDetails {
action: "list" | "add" | "toggle" | "clear";
todos: Todo[];
nextId: number;
error?: string;
}
const TodoParams = Type.Object({
action: StringEnum(["list", "add", "toggle", "clear"] as const),
text: Type.Optional(Type.String({ description: "Todo text (for add)" })),
id: Type.Optional(Type.Number({ description: "Todo ID (for toggle)" })),
});
/**
* UI component for the /todos command
*/
class TodoListComponent {
private todos: Todo[];
private theme: Theme;
private onClose: () => void;
private cachedWidth?: number;
private cachedLines?: string[];
constructor(todos: Todo[], theme: Theme, onClose: () => void) {
this.todos = todos;
this.theme = theme;
this.onClose = onClose;
}
handleInput(data: string): void {
if (matchesKey(data, "escape") || matchesKey(data, "ctrl+c")) {
this.onClose();
}
}
render(width: number): string[] {
if (this.cachedLines && this.cachedWidth === width) {
return this.cachedLines;
}
const lines: string[] = [];
const th = this.theme;
lines.push("");
const title = th.fg("accent", " Todos ");
const headerLine =
th.fg("borderMuted", "─".repeat(3)) + title + th.fg("borderMuted", "─".repeat(Math.max(0, width - 10)));
lines.push(truncateToWidth(headerLine, width));
lines.push("");
if (this.todos.length === 0) {
lines.push(truncateToWidth(` ${th.fg("dim", "No todos yet. Ask the agent to add some!")}`, width));
} else {
const done = this.todos.filter((t) => t.done).length;
const total = this.todos.length;
lines.push(truncateToWidth(` ${th.fg("muted", `${done}/${total} completed`)}`, width));
lines.push("");
for (const todo of this.todos) {
const check = todo.done ? th.fg("success", "✓") : th.fg("dim", "○");
const id = th.fg("accent", `#${todo.id}`);
const text = todo.done ? th.fg("dim", todo.text) : th.fg("text", todo.text);
lines.push(truncateToWidth(` ${check} ${id} ${text}`, width));
}
}
lines.push("");
lines.push(truncateToWidth(` ${th.fg("dim", "Press Escape to close")}`, width));
lines.push("");
this.cachedWidth = width;
this.cachedLines = lines;
return lines;
}
invalidate(): void {
this.cachedWidth = undefined;
this.cachedLines = undefined;
}
}
export default function (pi: ExtensionAPI) {
// In-memory state (reconstructed from session on load)
let todos: Todo[] = [];
let nextId = 1;
/**
* Reconstruct state from session entries.
* Scans tool results for this tool and applies them in order.
*/
const reconstructState = (ctx: ExtensionContext) => {
todos = [];
nextId = 1;
for (const entry of ctx.sessionManager.getBranch()) {
if (entry.type !== "message") continue;
const msg = entry.message;
if (msg.role !== "toolResult" || msg.toolName !== "todo") continue;
const details = msg.details as TodoDetails | undefined;
if (details) {
todos = details.todos;
nextId = details.nextId;
}
}
};
// Reconstruct state on session events
pi.on("session_start", async (_event, ctx) => reconstructState(ctx));
pi.on("session_tree", async (_event, ctx) => reconstructState(ctx));
// Register the todo tool for the LLM
pi.registerTool({
name: "todo",
label: "Todo",
description: "Manage a todo list. Actions: list, add (text), toggle (id), clear",
parameters: TodoParams,
async execute(_toolCallId, params, _signal, _onUpdate, _ctx) {
switch (params.action) {
case "list":
return {
content: [
{
type: "text",
text: todos.length
? todos.map((t) => `[${t.done ? "x" : " "}] #${t.id}: ${t.text}`).join("\n")
: "No todos",
},
],
details: { action: "list", todos: [...todos], nextId } as TodoDetails,
};
case "add": {
if (!params.text) {
return {
content: [{ type: "text", text: "Error: text required for add" }],
details: { action: "add", todos: [...todos], nextId, error: "text required" } as TodoDetails,
};
}
const newTodo: Todo = { id: nextId++, text: params.text, done: false };
todos.push(newTodo);
return {
content: [{ type: "text", text: `Added todo #${newTodo.id}: ${newTodo.text}` }],
details: { action: "add", todos: [...todos], nextId } as TodoDetails,
};
}
case "toggle": {
if (params.id === undefined) {
return {
content: [{ type: "text", text: "Error: id required for toggle" }],
details: { action: "toggle", todos: [...todos], nextId, error: "id required" } as TodoDetails,
};
}
const todo = todos.find((t) => t.id === params.id);
if (!todo) {
return {
content: [{ type: "text", text: `Todo #${params.id} not found` }],
details: {
action: "toggle",
todos: [...todos],
nextId,
error: `#${params.id} not found`,
} as TodoDetails,
};
}
todo.done = !todo.done;
return {
content: [{ type: "text", text: `Todo #${todo.id} ${todo.done ? "completed" : "uncompleted"}` }],
details: { action: "toggle", todos: [...todos], nextId } as TodoDetails,
};
}
case "clear": {
const count = todos.length;
todos = [];
nextId = 1;
return {
content: [{ type: "text", text: `Cleared ${count} todos` }],
details: { action: "clear", todos: [], nextId: 1 } as TodoDetails,
};
}
default:
return {
content: [{ type: "text", text: `Unknown action: ${params.action}` }],
details: {
action: "list",
todos: [...todos],
nextId,
error: `unknown action: ${params.action}`,
} as TodoDetails,
};
}
},
renderCall(args, theme, _context) {
let text = theme.fg("toolTitle", theme.bold("todo ")) + theme.fg("muted", args.action);
if (args.text) text += ` ${theme.fg("dim", `"${args.text}"`)}`;
if (args.id !== undefined) text += ` ${theme.fg("accent", `#${args.id}`)}`;
return new Text(text, 0, 0);
},
renderResult(result, { expanded }, theme, _context) {
const details = result.details as TodoDetails | undefined;
if (!details) {
const text = result.content[0];
return new Text(text?.type === "text" ? text.text : "", 0, 0);
}
if (details.error) {
return new Text(theme.fg("error", `Error: ${details.error}`), 0, 0);
}
const todoList = details.todos;
switch (details.action) {
case "list": {
if (todoList.length === 0) {
return new Text(theme.fg("dim", "No todos"), 0, 0);
}
let listText = theme.fg("muted", `${todoList.length} todo(s):`);
const display = expanded ? todoList : todoList.slice(0, 5);
for (const t of display) {
const check = t.done ? theme.fg("success", "✓") : theme.fg("dim", "○");
const itemText = t.done ? theme.fg("dim", t.text) : theme.fg("muted", t.text);
listText += `\n${check} ${theme.fg("accent", `#${t.id}`)} ${itemText}`;
}
if (!expanded && todoList.length > 5) {
listText += `\n${theme.fg("dim", `... ${todoList.length - 5} more`)}`;
}
return new Text(listText, 0, 0);
}
case "add": {
const added = todoList[todoList.length - 1];
return new Text(
theme.fg("success", "✓ Added ") +
theme.fg("accent", `#${added.id}`) +
" " +
theme.fg("muted", added.text),
0,
0,
);
}
case "toggle": {
const text = result.content[0];
const msg = text?.type === "text" ? text.text : "";
return new Text(theme.fg("success", "✓ ") + theme.fg("muted", msg), 0, 0);
}
case "clear":
return new Text(theme.fg("success", "✓ ") + theme.fg("muted", "Cleared all todos"), 0, 0);
}
},
});
// Register the /todos command for users
pi.registerCommand("todos", {
description: "Show all todos on the current branch",
handler: async (_args, ctx) => {
if (!ctx.hasUI) {
ctx.ui.notify("/todos requires interactive mode", "error");
return;
}
await ctx.ui.custom<void>((_tui, theme, _kb, done) => {
return new TodoListComponent(todos, theme, () => done());
});
},
});
}