import { createRouter } from '@@/create-router';
import { db } from 'officerdb/db';
import { and, desc, eq } from 'drizzle-orm';
import { m3eCanvasDocuments } from '../db/schema';

/**
 * Mounted at `/api/m3e-canvas`.
 *
 * Documents, and the handoff. Everything is scoped to the calling user by `userId` on every query —
 * the multi-user answer being a property of each statement rather than a filter to remember.
 */
export const router = createRouter();

const userIdOf = (ctx: { get: (k: 'user') => { id: number } | undefined }): number | null =>
  ctx.get('user')?.id ?? null;

// ── documents ─────────────────────────────────────────────────────────────────────────────────────

router.get('/documents', async (ctx) => {
  const userId = userIdOf(ctx);
  if (!userId) return ctx.json({ error: 'unauthenticated' }, 401);

  const rows = await db
    .select({
      id: m3eCanvasDocuments.id,
      title: m3eCanvasDocuments.title,
      updatedAt: m3eCanvasDocuments.updatedAt,
    })
    .from(m3eCanvasDocuments)
    .where(eq(m3eCanvasDocuments.userId, userId))
    .orderBy(desc(m3eCanvasDocuments.updatedAt));

  // The list never carries the documents themselves. A `Doc` with a few screens of parts is large,
  // and a sidebar that ships every design to draw a list of titles gets slower with every design.
  return ctx.json(rows);
});

/** What the canvas opens when no `?doc=` is named — the last thing worked on. */
router.get('/documents/latest', async (ctx) => {
  const userId = userIdOf(ctx);
  if (!userId) return ctx.json({ error: 'unauthenticated' }, 401);

  const rows = await db
    .select()
    .from(m3eCanvasDocuments)
    .where(eq(m3eCanvasDocuments.userId, userId))
    .orderBy(desc(m3eCanvasDocuments.updatedAt))
    .limit(1);

  return ctx.json(rows[0] ?? null);
});

router.get('/documents/:id', async (ctx) => {
  const userId = userIdOf(ctx);
  if (!userId) return ctx.json({ error: 'unauthenticated' }, 401);

  const id = Number(ctx.req.param('id'));
  if (!Number.isInteger(id)) return ctx.json({ error: 'not a document id' }, 400);

  const rows = await db
    .select()
    .from(m3eCanvasDocuments)
    // The userId is in the WHERE, not checked after the read: another person's design is "not found"
    // rather than "forbidden", so the id space cannot be probed.
    .where(and(eq(m3eCanvasDocuments.id, id), eq(m3eCanvasDocuments.userId, userId)))
    .limit(1);

  const row = rows[0];
  return row ? ctx.json(row) : ctx.json({ error: 'no such design' }, 404);
});

type Body = { title?: string; doc?: unknown; ui?: unknown };

/**
 * How large one design may be.
 *
 * The title was capped at 200 and the document at nothing at all, which is the wrong way round: the
 * document is the part that grows without anybody deciding to make it grow, and it is stored per user
 * with no quota above it. A real design with several screens of parts measures in the tens of
 * kilobytes, so this is far above anything the editor produces and far below anything that would hurt.
 *
 * Measured on the serialised form rather than guessed at from the object, because that is the thing
 * the column actually holds.
 */
const MAX_DOC_BYTES = 4 * 1024 * 1024;

/** Null when it fits, a message when it does not. */
const tooLarge = (doc: unknown, ui: unknown): string | null => {
  // Bytes, not string length: `.length` counts UTF-16 units, and a design full of non-Latin labels
  // would measure well under what it actually stores.
  const size = Buffer.byteLength(JSON.stringify({ doc, ui }), 'utf8');
  return size > MAX_DOC_BYTES ? `design is too large (${Math.round(size / 1024)} KB)` : null;
};

router.post('/documents', async (ctx) => {
  const userId = userIdOf(ctx);
  if (!userId) return ctx.json({ error: 'unauthenticated' }, 401);

  const body = (await ctx.req.json().catch(() => null)) as Body | null;
  if (!body?.doc) return ctx.json({ error: 'doc is required' }, 400);

  const oversize = tooLarge(body.doc, body.ui);
  if (oversize) return ctx.json({ error: oversize }, 413);

  const [row] = await db
    .insert(m3eCanvasDocuments)
    .values({
      userId,
      title: (body.title ?? 'Untitled').slice(0, 200),
      doc: body.doc,
      ui: body.ui ?? null,
    })
    .returning();

  return ctx.json(row, 201);
});

/**
 * A save. Only what is SENT is written.
 *
 * `title` and `ui` were unconditional — omitting either renamed the design to "Untitled" and nulled
 * the editor state. The only caller today sends both every time, so nothing was losing anything; it
 * was a trap set for the second caller, and the panel's own comment calls `ui` the cheaper of the two
 * things to lose, which is a reason to be careful with it rather than a reason not to be.
 */
router.put('/documents/:id', async (ctx) => {
  const userId = userIdOf(ctx);
  if (!userId) return ctx.json({ error: 'unauthenticated' }, 401);

  const id = Number(ctx.req.param('id'));
  if (!Number.isInteger(id)) return ctx.json({ error: 'not a document id' }, 400);

  const body = (await ctx.req.json().catch(() => null)) as Body | null;
  if (!body?.doc) return ctx.json({ error: 'doc is required' }, 400);

  const oversize = tooLarge(body.doc, body.ui);
  if (oversize) return ctx.json({ error: oversize }, 413);

  const [row] = await db
    .update(m3eCanvasDocuments)
    .set({
      ...(body.title === undefined ? {} : { title: body.title.slice(0, 200) }),
      ...(body.ui === undefined ? {} : { ui: body.ui }),
      doc: body.doc,
      updatedAt: new Date(),
    })
    .where(and(eq(m3eCanvasDocuments.id, id), eq(m3eCanvasDocuments.userId, userId)))
    .returning();

  return row ? ctx.json(row) : ctx.json({ error: 'no such design' }, 404);
});

router.delete('/documents/:id', async (ctx) => {
  const userId = userIdOf(ctx);
  if (!userId) return ctx.json({ error: 'unauthenticated' }, 401);

  const id = Number(ctx.req.param('id'));
  if (!Number.isInteger(id)) return ctx.json({ error: 'not a document id' }, 400);

  const rows = await db
    .delete(m3eCanvasDocuments)
    .where(and(eq(m3eCanvasDocuments.id, id), eq(m3eCanvasDocuments.userId, userId)))
    .returning({ id: m3eCanvasDocuments.id });

  return rows[0] ? ctx.json({ deleted: rows[0].id }) : ctx.json({ error: 'no such design' }, 404);
});

// ── the handoff ───────────────────────────────────────────────────────────────────────────────────

/**
 * Where a generated prompt goes instead of the clipboard.
 *
 * **This is the reason the plugin exists, and it is the one part that is not finished.** What is here
 * takes the prompt and holds it; what is missing is the platform hook that starts a chat session with
 * it already in the composer.
 *
 * The reason it is missing rather than merely unwritten: `/api/chat` has **no session-creation route**.
 * A session is created by the browser opening `/api/chat/ws` and sending its first message, so there is
 * nothing a plugin can POST to. Making this work needs one small platform change — a way for
 * `/chat/new` to pick up a prompt by reference — and that is a platform decision rather than a
 * plugin's to invent. `docs/handoff.md` states the shape it would need.
 *
 * Until then this route is the seam: it validates, it holds the prompt in memory against a one-time
 * id, and the panel falls back to the clipboard so the feature is degraded rather than absent.
 *
 * Owner-only by the manifest — starting an agent runs as the owner and writes to the owner's disk,
 * which is not a thing to hand out with a drawing tool.
 */
type PendingHandoff = { prompt: string; title: string; userId: number; at: number };

const pending = new Map<string, PendingHandoff>();
const HANDOFF_TTL_MS = 10 * 60 * 1000;

/** Kept small and swept on write: this is a hand-off desk, not storage. */
const sweep = () => {
  const cutoff = Date.now() - HANDOFF_TTL_MS;
  for (const [id, held] of pending) if (held.at < cutoff) pending.delete(id);
};

router.post('/_handoff', async (ctx) => {
  const userId = userIdOf(ctx);
  if (!userId) return ctx.json({ error: 'unauthenticated' }, 401);

  const body = (await ctx.req.json().catch(() => null)) as { prompt?: string; title?: string } | null;
  const prompt = body?.prompt?.trim();
  if (!prompt) return ctx.json({ error: 'prompt is required' }, 400);

  sweep();
  const id = crypto.randomUUID();
  pending.set(id, { prompt, title: body?.title ?? 'Untitled', userId, at: Date.now() });

  return ctx.json({
    id,
    // The panel navigates here. Nothing reads the parameter yet — see docs/handoff.md.
    chatUrl: `/chat/new?handoff=${id}`,
    ready: false,
  });
});

/** How the chat side would collect a held prompt, once something calls it. */
router.get('/_handoff/:id', async (ctx) => {
  const userId = userIdOf(ctx);
  if (!userId) return ctx.json({ error: 'unauthenticated' }, 401);

  const held = pending.get(ctx.req.param('id'));
  // A handoff belongs to whoever made it; another user asking is told nothing.
  if (!held || held.userId !== userId) return ctx.json({ error: 'no such handoff' }, 404);

  pending.delete(ctx.req.param('id')); // one-time: collected once, then gone
  return ctx.json({ prompt: held.prompt, title: held.title });
});