import { existsSync, readFileSync, writeFileSync } from 'node:fs';
import { join, resolve } from 'node:path';
import type { Context } from 'hono';
import { createRouter, type HonoVariables } from '@@/create-router';
import * as errors from '@@/custom-errors';
import { TODO_STATUSES, bodyOf, frontmatter, patchFrontmatter, readTree, writeIndex } from './tree';
import { ProjectPathError, addProject, getProject, listProjects, removeProject, safeProjectPath } from './projects';

/**
 * Mounted at `/api/kanban`.
 *
 * ── Every item route takes a project ──
 *
 * That is the extraction, expressed in the URL. The platform's version had no such parameter because it
 * had no such question: there was one folder and it was found from `process.cwd()`.
 *
 * The project is resolved to a row FIRST, scoped by the caller's own user id, and the path used for the
 * filesystem work comes from that row — never from the request. So a caller cannot name a directory,
 * only choose among ones already vetted by `safeProjectPath` when they were added.
 *
 * ── Who may do what ──
 *
 * The manifest makes `/projects` owner-only: pointing this plugin at a folder is a statement about the
 * filesystem. Moving a card is not, so a member granted `kanban` can work the board of any project they
 * can see. Nothing in this file checks again — two places deciding the same thing is how they come to
 * disagree.
 */
export const router = createRouter();

// ── Projects ──

router.get('/projects', async (ctx) => {
  const user = ctx.get('user');
  return ctx.json({ projects: await listProjects(user.id as number) });
});

router.post('/projects', async (ctx) => {
  const user = ctx.get('user');
  const { name, path } = (ctx.get('body') ?? {}) as { name?: string; path?: string };
  if (!name?.trim()) throw errors.BAD_REQUEST('name is required');

  try {
    const resolved = await safeProjectPath(path, user.email as string);
    return ctx.json(await addProject(user.id as number, name.trim(), resolved), 201);
  } catch (error) {
    // A bad path is the caller's words being unusable, not a fault. Anything else is a real failure and
    // is left to the platform's error handler rather than flattened into a 400.
    if (error instanceof ProjectPathError) throw errors.BAD_REQUEST(error.message);
    throw error;
  }
});

router.delete('/projects/:id', async (ctx) => {
  const user = ctx.get('user');
  const removed = await removeProject(user.id as number, Number(ctx.req.param('id')));
  if (!removed) throw errors.NOT_FOUND('no such project');
  // Said plainly, because "delete" next to a folder full of somebody's work deserves to be unambiguous.
  return ctx.json({ ok: true, note: 'The folder and its files were not touched.' });
});

// ── The board ──

/**
 * Resolve `?project=<id>` to a directory this caller owns.
 *
 * Every item route starts here, so there is one place where a request turns into a path on disk.
 */
async function rootFor(ctx: Context<{ Variables: HonoVariables }>): Promise<string> {
  const user = ctx.get('user');
  const id = Number(ctx.req.query('project'));
  if (!Number.isInteger(id)) throw errors.BAD_REQUEST('project is required');

  const project = await getProject(user.id as number, id);
  if (!project) throw errors.NOT_FOUND('no such project');
  return project.path;
}

/** `<theme>/<slug>`, both kebab-case — also the traversal guard, since it admits no dot or slash pair. */
const ID_SHAPE = /^[a-z0-9][a-z0-9-]*\/[a-z0-9][a-z0-9-]*$/;

const fileForId = (root: string, id: string): string => {
  if (!ID_SHAPE.test(id)) throw errors.BAD_REQUEST(`not a todo id: ${id}`);
  const [theme, slug] = id.split('/');
  // Joined onto the ROW's path, which was vetted when the project was added — never onto anything from
  // this request beyond the id, which the shape above has already constrained.
  const path = resolve(root, join(theme!, `${slug}.md`));
  if (!existsSync(path)) throw errors.NOT_FOUND(`no todo at ${id}`);
  return path;
};

/** GET /api/kanban?project=<id> — the whole tree, no bodies. What the board renders. */
router.get('/', async (ctx) => ctx.json(readTree(await rootFor(ctx))));

/** GET /api/kanban/item?project=<id>&id=<theme>/<slug> — one item, body included. */
router.get('/item', async (ctx) => {
  const text = readFileSync(fileForId(await rootFor(ctx), ctx.req.query('id') ?? ''), 'utf8');
  return ctx.json({ meta: frontmatter(text), body: bodyOf(text) });
});

/**
 * PATCH /api/kanban/item — update an item's frontmatter: `{ id, status?, priority?, due?, order? }`.
 *
 * **The body is untouchable through this API, on purpose.** The prose is the owner's; only the machine's
 * half of the file is writable here, and `patchFrontmatter` splices keys without touching a byte past
 * the closing fence.
 */
router.patch('/item', async (ctx) => {
  const root = await rootFor(ctx);
  const { id, status, priority, due, order } = (ctx.get('body') ?? {}) as {
    id: string;
    status?: string;
    priority?: string;
    due?: string;
    order?: number;
  };
  const path = fileForId(root, id);

  const updates: Record<string, string> = {};
  if (status !== undefined) {
    if (!(TODO_STATUSES as readonly string[]).includes(status)) throw errors.BAD_REQUEST(`not a status: ${status}`);
    updates.status = status;
  }
  // `urgent` or nothing — the format deliberately has no scale.
  if (priority !== undefined) {
    if (priority !== '' && priority !== 'urgent') throw errors.BAD_REQUEST(`not a priority: ${priority}`);
    updates.priority = priority;
  }
  if (due !== undefined) {
    if (due !== '' && !/^20\d\d-\d\d-\d\d$/.test(due)) throw errors.BAD_REQUEST(`not a date: ${due}`);
    updates.due = due;
  }
  if (order !== undefined) {
    if (!Number.isInteger(order) || order < 0) throw errors.BAD_REQUEST(`not an order: ${order}`);
    updates.order = String(order);
  }
  if (Object.keys(updates).length === 0) throw errors.BAD_REQUEST('nothing to update');

  writeFileSync(path, patchFrontmatter(readFileSync(path, 'utf8'), updates));
  // The generated map, regenerated on every write so it cannot drift from the tree it describes.
  writeIndex(root);
  return ctx.json({ ok: true });
});