/**
 * `sl0ppi init` — opt a directory in as a project.
 *
 * Writes `.sl0ppi/layout.kdl`, the pane fragment sl0ppi wraps in a tab. The
 * template is mostly comments on purpose: the vocabulary and the
 * `start_suspended` habit are the two things a newcomer cannot guess, and both
 * are cheap to explain at the point of use.
 */

import { existsSync, mkdirSync, writeFileSync } from "node:fs";
import { basename, join, resolve } from "node:path";
import { LAYOUT_FILE, MARKER_DIR } from "../core/discover.ts";

export const TEMPLATE = `// sl0ppi project layout.
//
// PANE NODES ONLY. sl0ppi wraps these in the tab that carries the project's
// identity (its \`purpose\`) and cwd, so do not add \`layout {}\` or \`tab {}\` here.
// \`sl0ppi print\` shows the composed result.
//
// Purposes are how tooling finds a pane. sl0ppi owns the vocabulary; the
// terminal stores the string and never interprets it:
//
//   agent:<name>    an agent pane      (\`sl0ppi agent\` looks for agent:main)
//   service:<name>  a long-running process
//   logs:<name>     a log tail
//   human:<name>    a pane meant for a person
//
// start_suspended stages a command without running it: the pane and the layout
// exist, and the command starts on a keypress. Keep it on anything expensive,
// so \`sl0ppi up\` across a whole root does not launch a dozen servers at once.
//
// KDL nodes need \`;\` between them on a single line. Just use one line per node.

pane purpose="agent:main" start_suspended=true command="pi"

// A fuller example, for when one pane stops being enough:
//
// pane split_direction="vertical" {
//     pane purpose="agent:main" start_suspended=true command="pi"
//     pane split_direction="horizontal" {
//         pane purpose="service:web" start_suspended=true command="npm" {
//             args "run" "dev"
//         }
//         pane purpose="logs:app" start_suspended=true command="tail" {
//             args "-f" "log/dev.log"
//         }
//     }
// }
`;

export interface InitResult {
  path: string;
  created: boolean;
  /** Set when an existing file was left alone. */
  skipped?: string;
}

export function init(dir: string, options: { force?: boolean } = {}): InitResult {
  const target = resolve(dir);
  if (!existsSync(target)) throw new Error(`no such directory: ${target}`);

  const markerDir = join(target, MARKER_DIR);
  const path = join(markerDir, LAYOUT_FILE);

  if (existsSync(path) && !options.force) {
    return { path, created: false, skipped: "already exists (use --force to overwrite)" };
  }

  mkdirSync(markerDir, { recursive: true });
  writeFileSync(path, TEMPLATE);
  return { path, created: true };
}

export function initMessage(result: InitResult, dir: string): string {
  if (!result.created) return `${result.path}: ${result.skipped}`;
  const name = basename(resolve(dir));
  return [
    `created ${result.path}`,
    ``,
    `${name} is now a project. From its root directory:`,
    `  sl0ppi up      open a tab for it (and every other project there)`,
    `  sl0ppi ls      see what is open`,
  ].join("\n");
}