pi-worktrees/.pi/extensions/pi-worktree.ts

/**
 * pi-worktree Extension
 *
 * Manages git worktrees through tool commands and an interactive `/worktree` command.
 *
 * Tools:
 * - git_worktree_create — Create a linked worktree for a branch
 * - git_worktree_list — List all linked worktrees
 * - git_worktree_switch — Switch working directory to a worktree
 * - git_worktree_remove — Remove a linked worktree
 *
 * Command:
 * - /worktree — Interactive picker to switch between worktrees
 */

import type { ExtensionAPI, ExtensionContext } from "@earendil-works/pi-coding-agent";
import { stat } from "node:fs/promises";
import { defineTool } from "@earendil-works/pi-coding-agent";
import { Type } from "@earendil-works/pi-ai";
import { parseWorktreeList, type WorktreeEntry } from "./pi-worktree-parser";
import {
	validateCreateWorktreeInput,
	buildWorktreeAddCommand,
	validatePathDoesNotExist,
	isCurrentBranch,
	type WorktreeError,
} from "./pi-worktree-create";

// ─── Type Definitions ──────────────────────────────────────────────

/** Result of listing all worktrees. */
interface WorktreeListResult {
	/** All worktrees in the repository. */
	worktrees: WorktreeEntry[];
	/** Number of worktrees found. */
	count: number;
	/** Current working directory used for comparison. */
	currentPath: string;
}

// ─── Tool Parameter Schemas ────────────────────────────────────────

const createWorktreeParams = Type.Object({
	path: Type.String({ description: "Path for the new worktree (relative or absolute)" }),
	branch: Type.Optional(Type.String({ description: "Branch name to check out. Defaults to 'main'." })),
	create_branch: Type.Optional(
		Type.Boolean({
			description: "If true and branch doesn't exist, create it. Defaults to true.",
		}),
	),
});

const listWorktreeParams = Type.Object({});

const switchWorktreeParams = Type.Object({
	target: Type.String({ description: "Path or branch name of the target worktree to switch to." }),
});

const removeWorktreeParams = Type.Object({
	path: Type.String({ description: "Path of the worktree to remove." }),
});

// ─── Helper Functions ──────────────────────────────────────────────

/**
 * Check if the target path exists using Bun's fs module.
 * @param checkPath - Path to check (resolved against cwd)
 * @param ctx - Extension context for working directory
 * @returns True if the path exists
 */
async function pathExists(checkPath: string, ctx: ExtensionContext): Promise<boolean> {
	const resolvedPath = checkPath.startsWith("/") ? checkPath : `${ctx.cwd}/${checkPath}`;

	try {
		await stat(resolvedPath);
		return true;
	} catch {
		return false;
	}
}

/**
 * Get the current branch name from git.
 * @param pi - Extension API for executing commands
 * @param ctx - Extension context for working directory
 * @returns Current branch name, or "unknown" if detection fails
 */
async function getCurrentBranch(pi: ExtensionAPI, ctx: ExtensionContext): Promise<string> {
	const result = await pi.exec("git", ["rev-parse", "--abbrev-ref", "HEAD"], { cwd: ctx.cwd });

	if (result.exitCode !== 0) {
		return "unknown";
	}

	return result.stdout.trim();
}

/**
 * Resolve a worktree target (path or branch name) to its full path.
 *
 * Used by git_worktree_switch and git_worktree_remove — dead code until those tools ship.
 *
 * @param target - Path or branch name to resolve
 * @param worktrees - List of all worktrees
 * @returns The resolved path, or undefined if not found
 */
function resolveWorktreeTarget(target: string, worktrees: WorktreeEntry[]): string | undefined {
	const exactMatch = worktrees.find((w) => w.path === target);
	if (exactMatch) return exactMatch.path;

	const branchMatch = worktrees.find((w) => w.branch === target);
	return branchMatch?.path;
}

/**
 * Format a WorktreeError into the tool response text.
 * @param error - The validation error
 * @returns Formatted error string with suggestion if available
 */
function formatValidationError(error: { message: string; suggestion?: string }): string {
	const base = `Error: ${error.message}`;
	return error.suggestion ? `${base} Suggestion: ${error.suggestion}` : base;
}

/**
 * Format a success response for worktree operations.
 * @param action - The action performed (e.g., "Created")
 * @param details - Key-value pairs to include in the message
 * @returns Formatted success string
 */
function formatSuccessResponse(action: string, details: Record<string, string>): string {
	const parts = Object.entries(details).map(([key, value]) => `${key} '${value}'`);
	return `${action} worktree ${parts.join(" on ")}.`;
}

// ─── Tool Factories ────────────────────────────────────────────────

/**
 * Create the git_worktree_create tool definition.
 * @param pi - Extension API for registering and executing tools
 * @returns The configured tool definition
 */
function createListWorktreeTool(pi: ExtensionAPI) {
	return defineTool({
		name: "git_worktree_list",
		label: "Git Worktree List",
		description: "List all linked worktrees in the current repo.",
		parameters: listWorktreeParams,
		async execute(_toolCallId, _params, _signal, _onUpdate, ctx) {
			const result = await pi.exec("git", ["worktree", "list"], { cwd: ctx.cwd });

			if (result.exitCode !== 0) {
				return {
					content: [{ type: "text", text: `Error listing worktrees: ${result.stderr}. Suggestion: Ensure you are inside a git repository.` }],
					isError: true,
				};
			}

			const worktreeEntries = parseWorktreeList(result.stdout, ctx.cwd);

			if (worktreeEntries.length === 0) {
				return {
					content: [{ type: "text", text: "No worktrees found." }],
					details: <WorktreeListResult>{
						worktrees: [],
						count: 0,
						currentPath: ctx.cwd,
						warning: "No worktrees exist. Use git_worktree_create to add one.",
					},
				};
			}

			const displayLines = worktreeEntries.map(
				(entry) => `${entry.branch} - ${entry.path}${entry.isCurrent ? " (current)" : ""}`,
			);

			return {
				content: [{ type: "text", text: displayLines.join("\n") }],
				details: <WorktreeListResult>{
					worktrees: worktreeEntries,
					count: worktreeEntries.length,
					currentPath: ctx.cwd,
				},
			};
		},
	});
}

/**
 * Create the git_worktree_create tool definition.
 * @param pi - Extension API for registering and executing tools
 * @returns The configured tool definition
 */
function createCreateWorktreeTool(pi: ExtensionAPI) {
	return defineTool({
		name: "git_worktree_create",
		label: "Git Worktree Create",
		description: "Create a linked worktree for a branch in the current repo.",
		parameters: createWorktreeParams,
		async execute(_toolCallId, params, _signal, _onUpdate, ctx) {
			const worktreePath = params.path;
			const branchName = params.branch || "main";
			const createBranch = params.create_branch ?? true;

			// 1. Validate input parameters
			const inputError = validateCreateWorktreeInput(worktreePath, branchName);
			if (inputError) {
				return {
					content: [{ type: "text", text: formatValidationError(inputError) }],
					isError: true,
				};
			}

			// 2. Check if path already exists — refuse if so
			const pathExistsResult = await pathExists(worktreePath, ctx);
			const pathError = validatePathDoesNotExist(worktreePath, () => pathExistsResult);
			if (pathError) {
				return {
					content: [{ type: "text", text: formatValidationError(pathError) }],
					isError: true,
				};
			}

			// 3. Check if creating on current branch — refuse if so
			const currentBranch = await getCurrentBranch(pi, ctx);
			if (isCurrentBranch(branchName, currentBranch)) {
				const currentBranchError: WorktreeError = {
					message: "Can't create worktree on the current branch — switch first.",
					suggestion: "Choose a different branch name or switch branches with 'git switch'.",
				};
				return {
					content: [{ type: "text", text: formatValidationError(currentBranchError) }],
					isError: true,
				};
			}

			// 4. Build and run git worktree add command
			const commandArgs = buildWorktreeAddCommand({
				path: worktreePath,
				branch: branchName,
				createBranch,
			});

			const result = await pi.exec("git", commandArgs, { cwd: ctx.cwd });

			if (result.exitCode !== 0) {
				return {
					content: [{
						type: "text",
						text: `Error creating worktree: ${result.stderr}. Suggestion: Check that the branch exists (or use create_branch=true) and that the parent directory is writable.`,
					}],
					isError: true,
				};
			}

			return {
				content: [{
					type: "text",
					text: formatSuccessResponse("Created", { at: worktreePath, branch: branchName }),
				}],
			};
		},
	});
}

/**
 * Create the git_worktree_switch tool definition.
 * @param _pi - Extension API (unused in stub)
 * @returns The configured tool definition
 */
function createSwitchWorktreeTool(_pi: ExtensionAPI) {
	return defineTool({
		name: "git_worktree_switch",
		label: "Git Worktree Switch",
		description: "Switch pi's working directory to a linked worktree.",
		parameters: switchWorktreeParams,
		async execute(_toolCallId, _params, _signal, _onUpdate, _ctx) {
			return {
				content: [{ type: "text", text: "Error: git_worktree_switch is not yet implemented. Suggestion: Use the `/worktree` command or `git worktree` manually until this tool is complete." }],
				isError: true,
			};
		},
	});
}

/**
 * Create the git_worktree_remove tool definition.
 * @param _pi - Extension API (unused in stub)
 * @returns The configured tool definition
 */
function createRemoveWorktreeTool(_pi: ExtensionAPI) {
	return defineTool({
		name: "git_worktree_remove",
		label: "Git Worktree Remove",
		description: "Remove a linked worktree.",
		parameters: removeWorktreeParams,
		async execute(_toolCallId, _params, _signal, _onUpdate, _ctx) {
			return {
				content: [{ type: "text", text: "Error: git_worktree_remove is not yet implemented. Suggestion: Use `git worktree remove` manually until this tool is complete." }],
				isError: true,
			};
		},
	});
}

// ─── Extension Entry Point ────────────────────────────────────────

export default function (pi: ExtensionAPI) {
	// Register tools via factory functions
	pi.registerTool(createCreateWorktreeTool(pi));
	pi.registerTool(createListWorktreeTool(pi));
	pi.registerTool(createSwitchWorktreeTool(pi));
	pi.registerTool(createRemoveWorktreeTool(pi));

	// ─── Command Registration ──────────────────────────────────────
	pi.registerCommand("worktree", {
		description: "Interactive picker to switch between linked worktrees.",
		handler: async (_args, _ctx) => {
			return {
				content: [{ type: "text", text: "Error: /worktree command is not yet implemented. Suggestion: Use `git worktree list` and navigate manually until this command is complete." }],
				isError: true,
			};
		},
	});
}