import { Router, Request, Response, NextFunction } from 'express';
import multer from 'multer';
import { promises as fs } from 'fs';
import { randomUUID } from 'crypto';
import { PoolClient } from 'pg';
import { pool, requireRow } from '../db';
import { ADMIN_ITEM_SELECT, AdminItemRow, ItemRecord } from '../itemSelect';
import { ItemStatus } from '../types';
import { asyncRoute } from '../asyncRoute';
import { parseItemFilters, buildItemFilterSql, FilterError } from '../itemFilters';
import { tagColorFor } from '../utils';
import {
  ALLOWED_IMAGE_TYPES,
  SIGNATURE_BYTES,
  extensionFor,
  isAllowedImageType,
  signatureMatches
} from '../uploadTypes';
import { notifyFavoritersOfSale, notifyFavoritersOfRemoval, collectFavoriteRecipients } from '../favoriteAlerts';

const router = Router();

/** The next image slot, from a COALESCE'd MAX so it is never null. */
interface MaxSortRow {
  max_sort: number;
}

/** Just the status column, read before deciding whether a transition is legal. */
interface ItemStatusRow {
  status: ItemStatus;
}

const UPLOADS_DIR = process.env.UPLOADS_DIR || '/app/uploads';

// Multer writes to disk with no size cap unless one is given, so a single
// request could fill the uploads volume. Bound every dimension of the
// multipart body: image count, bytes per image, and the small text fields
// (name/description/price) that accompany them.
const MAX_IMAGES_PER_REQUEST = 6;
// 8 MB, not 8 MiB — this is the ceiling S5693 treats as safe, and 8 * 1024 *
// 1024 sits just over it. Plenty for a product photo either way.
const MAX_IMAGE_BYTES = 8_000_000;
const MAX_TEXT_FIELDS = 8;
const MAX_TEXT_FIELD_BYTES = 64 * 1024;

// Refused before a byte is written. This catches the honest mistake — picking a
// PDF by accident — and nothing more, because file.mimetype is whatever the
// caller wrote in the multipart headers. The bytes are checked after the write;
// see verifyUploadedImages.
class UnsupportedImageTypeError extends Error {}

const storage = multer.diskStorage({
  destination: UPLOADS_DIR,
  // Stored names come from a CSPRNG rather than a timestamp plus Math.random,
  // which is predictable enough that a caller could guess (or collide with)
  // another upload's path.
  //
  // The extension comes from the validated content type rather than from
  // path.extname(file.originalname), so the name on disk cannot disagree with
  // what the file claims to be — a caller cannot get `.html` onto the uploads
  // volume by naming their file that way.
  filename: (_req, file, cb) => {
    const ext = extensionFor(file.mimetype);
    if (!ext) {
      // Unreachable while fileFilter runs first, and here so that it stays
      // unreachable rather than silently writing a file with no extension.
      cb(new UnsupportedImageTypeError(`unsupported image type ${file.mimetype}`), '');
      return;
    }
    cb(null, `${randomUUID()}${ext}`);
  }
});

const upload = multer({
  storage,
  limits: {
    fileSize: MAX_IMAGE_BYTES,
    files: MAX_IMAGES_PER_REQUEST,
    fields: MAX_TEXT_FIELDS,
    fieldSize: MAX_TEXT_FIELD_BYTES
  },
  fileFilter: (_req, file, cb) => {
    if (!isAllowedImageType(file.mimetype)) {
      cb(new UnsupportedImageTypeError(
        `${file.mimetype} is not an accepted image type — allowed: ${ALLOWED_IMAGE_TYPES.join(', ')}`
      ));
      return;
    }
    cb(null, true);
  }
});

// Reads only the leading bytes — enough to identify a format, not enough to
// care how large the file is. The handle is closed before anything is unlinked,
// because an open handle makes the unlink fail on Windows.
async function readHead(filePath: string): Promise<Buffer> {
  const handle = await fs.open(filePath, 'r');
  try {
    const buffer = Buffer.alloc(SIGNATURE_BYTES);
    const { bytesRead } = await handle.read(buffer, 0, SIGNATURE_BYTES, 0);
    return buffer.subarray(0, bytesRead);
  } finally {
    await handle.close();
  }
}

// Best effort: a file that cannot be removed should not turn a 400 into a 500,
// but it must not be left behind quietly either.
async function discardUploads(files: Express.Multer.File[]): Promise<void> {
  await Promise.all(
    files.map((file) =>
      fs.unlink(file.path).catch((err: unknown) => {
        console.error(`[upload] could not remove rejected file ${file.path}:`, err);
      })
    )
  );
}

/**
 * Confirms each stored file actually is what it was declared to be.
 *
 * This cannot happen in multer's fileFilter, which runs before the stream has
 * been read — there are no bytes to look at yet. So the check runs after the
 * write, and a failure removes *every* file from the request rather than only
 * the offending one: a half-accepted upload would leave files on the volume
 * that the request was refused for.
 *
 * Returns the message to refuse with, or null when everything checks out.
 */
async function verifyUploadedImages(req: Request): Promise<string | null> {
  const files = (req.files as Express.Multer.File[]) || [];

  for (const file of files) {
    const head = await readHead(file.path);
    if (!signatureMatches(file.mimetype, head)) {
      await discardUploads(files);
      return `${file.originalname} does not contain ${file.mimetype} data`;
    }
  }

  return null;
}

// No error-handling middleware is mounted on the app, so translate multer's
// limit errors here instead of letting them surface as a generic 500.
const uploadImages = (req: Request, res: Response, next: NextFunction) => {
  upload.array('images', MAX_IMAGES_PER_REQUEST)(req, res, (err: unknown) => {
    if (err instanceof UnsupportedImageTypeError) {
      return res.status(400).json({ error: err.message });
    }
    if (err instanceof multer.MulterError) {
      const status = err.code === 'LIMIT_FILE_SIZE' ? 413 : 400;
      return res.status(status).json({ error: err.message });
    }
    if (err) {
      return next(err);
    }

    verifyUploadedImages(req)
      .then((problem) => {
        if (problem) {
          res.status(400).json({ error: problem });
          return;
        }
        next();
      })
      .catch(next);
  });
};

// The multipart body carries category_id and tags as text fields. An absent
// field means "leave as-is" on update, which is why these return undefined
// rather than null for a missing value.
function readCategoryId(value: unknown): number | null | undefined {
  if (value === undefined) return undefined;
  if (value === null || value === '') return null;
  const parsed = Number(value);
  if (!Number.isSafeInteger(parsed) || parsed < 1) return undefined;
  return parsed;
}

function readTagNames(value: unknown): string[] | undefined {
  if (value === undefined) return undefined;
  if (typeof value !== 'string' || value.trim() === '') return [];
  try {
    const parsed = JSON.parse(value);
    if (!Array.isArray(parsed)) return undefined;
    return parsed.filter((name): name is string => typeof name === 'string');
  } catch {
    return undefined;
  }
}

// Tags typed into the item form may not exist yet. Look each name up
// case-insensitively — matching the unique index — and create the missing ones
// inside the caller's transaction so a later failure rolls them back too.
async function resolveTagIds(client: PoolClient, names: string[]): Promise<number[]> {
  const ids: number[] = [];
  for (const raw of names) {
    const name = raw.trim();
    if (!name) continue;

    const existing = await client.query(`SELECT id FROM tags WHERE lower(name) = lower($1)`, [name]);
    if (existing.rows.length) {
      if (!ids.includes(existing.rows[0].id)) ids.push(existing.rows[0].id);
      continue;
    }

    const inserted = await client.query(
      `INSERT INTO tags (name, color) VALUES ($1, $2) RETURNING id`,
      [name, tagColorFor(name)]
    );
    ids.push(inserted.rows[0].id);
  }
  return ids;
}

// Tags are replaced wholesale rather than merged — the form submits the full
// set it wants, so removing a chip has to actually remove the row.
async function setItemTags(client: PoolClient, itemId: number, tagIds: number[]): Promise<void> {
  await client.query(`DELETE FROM item_tags WHERE item_id = $1`, [itemId]);
  for (const tagId of tagIds) {
    await client.query(`INSERT INTO item_tags (item_id, tag_id) VALUES ($1, $2)`, [itemId, tagId]);
  }
}

router.get('/items', asyncRoute(async (req: Request, res: Response) => {
  // Same parser and query builder as the storefront, so admin filtering cannot
  // drift from what customers see. The one addition is `status`, which is how
  // the Inventory tab surfaces Reserved.
  let filters;
  try {
    filters = parseItemFilters(req.query as Record<string, unknown>);
  } catch (err) {
    if (err instanceof FilterError) {
      return res.status(400).json({ error: err.message });
    }
    throw err;
  }

  // Favorites belong to a customer, and the admin inventory view is not
  // browsing as one. Refused rather than ignored so the mistake is visible.
  if (filters.favoritesOnly) {
    return res.status(400).json({ error: 'favorites is not a valid inventory filter' });
  }

  const { clauses, params } = buildItemFilterSql(filters, 1, null);
  const where = clauses.length ? `WHERE ${clauses.join(' AND ')}` : '';
  const { rows } = await pool.query<AdminItemRow>(`${ADMIN_ITEM_SELECT} ${where} ORDER BY i.created_at DESC`, params);
  res.json(rows);
}));

router.post('/items', uploadImages, asyncRoute(async (req: Request, res: Response) => {
  const { name, description, price } = req.body;

  const categoryId = readCategoryId(req.body.category_id);
  if (categoryId === undefined && req.body.category_id !== undefined) {
    return res.status(400).json({ error: 'invalid category_id' });
  }
  const tagNames = readTagNames(req.body.tags);
  if (tagNames === undefined && req.body.tags !== undefined) {
    return res.status(400).json({ error: 'invalid tags' });
  }

  const files = (req.files as Express.Multer.File[]) || [];
  const client = await pool.connect();
  try {
    await client.query('BEGIN');
    const { rows } = await client.query<ItemRecord>(
      `INSERT INTO items (name, description, price_cents, category_id) VALUES ($1, $2, $3, $4) RETURNING *`,
      [name, description, Math.round(parseFloat(price) * 100), categoryId ?? null]
    );
    const item = requireRow(rows, 'the item INSERT');
    for (let i = 0; i < files.length; i++) {
      await client.query(
        `INSERT INTO item_images (item_id, image_path, sort_order) VALUES ($1, $2, $3)`,
        [item.id, `/uploads/${files[i]?.filename ?? ''}`, i]
      );
    }
    if (tagNames) {
      await setItemTags(client, item.id, await resolveTagIds(client, tagNames));
    }
    await client.query('COMMIT');
    const { rows: full } = await pool.query<AdminItemRow>(`${ADMIN_ITEM_SELECT} WHERE i.id = $1`, [item.id]);
    res.json(requireRow(full, 'the item just inserted'));
  } catch (err) {
    await client.query('ROLLBACK');
    console.error(err);
    res.status(500).json({ error: 'internal error' });
  } finally {
    client.release();
  }
}));

router.put('/items/:id', uploadImages, asyncRoute(async (req: Request, res: Response) => {
  const { name, description, price } = req.body;

  const categoryId = readCategoryId(req.body.category_id);
  if (categoryId === undefined && req.body.category_id !== undefined) {
    return res.status(400).json({ error: 'invalid category_id' });
  }
  const tagNames = readTagNames(req.body.tags);
  if (tagNames === undefined && req.body.tags !== undefined) {
    return res.status(400).json({ error: 'invalid tags' });
  }

  const files = (req.files as Express.Multer.File[]) || [];
  const client = await pool.connect();
  try {
    await client.query('BEGIN');
    await client.query(
      `UPDATE items SET name=$1, description=$2, price_cents=$3 WHERE id=$4`,
      [name, description, Math.round(parseFloat(price) * 100), req.params.id]
    );
    // Only touch the category when the field was actually submitted, so a
    // caller that omits it doesn't silently uncategorize the item.
    if (categoryId !== undefined) {
      await client.query(`UPDATE items SET category_id=$1 WHERE id=$2`, [categoryId, req.params.id]);
    }
    if (tagNames) {
      await setItemTags(client, Number(req.params.id), await resolveTagIds(client, tagNames));
    }
    if (files.length) {
      const { rows: existing } = await client.query<MaxSortRow>(
        `SELECT COALESCE(MAX(sort_order), -1) AS max_sort FROM item_images WHERE item_id = $1`,
        [req.params.id]
      );
      // COALESCE'd MAX, so the aggregate always returns exactly one row.
      let nextSort = requireRow(existing, 'the MAX(sort_order) aggregate').max_sort + 1;
      for (const file of files) {
        await client.query(
          `INSERT INTO item_images (item_id, image_path, sort_order) VALUES ($1, $2, $3)`,
          [req.params.id, `/uploads/${file.filename}`, nextSort++]
        );
      }
    }
    await client.query('COMMIT');
    const { rows: full } = await pool.query<AdminItemRow>(`${ADMIN_ITEM_SELECT} WHERE i.id = $1`, [req.params.id]);
    res.json(full[0]);
  } catch (err) {
    await client.query('ROLLBACK');
    console.error(err);
    res.status(500).json({ error: 'internal error' });
  } finally {
    client.release();
  }
}));

router.delete('/items/:id', asyncRoute(async (req: Request, res: Response) => {
  const itemId = Number(req.params.id);

  // Collected before the delete: favorites cascade with the item, so after it
  // is gone there is no record of who was watching. Restricted to unsold items
  // because anyone watching a sold one has already been told it went.
  const recipients = await collectFavoriteRecipients([itemId], null, true);

  await pool.query(`DELETE FROM items WHERE id = $1`, [itemId]);

  // Sent only once the delete has succeeded, so nobody hears about a withdrawal
  // that did not happen.
  await notifyFavoritersOfRemoval(recipients);
  res.status(204).end();
}));

router.delete('/items/:id/images/:imageId', asyncRoute(async (req: Request, res: Response) => {
  await pool.query(`DELETE FROM item_images WHERE id = $1 AND item_id = $2`, [req.params.imageId, req.params.id]);
  res.status(204).end();
}));

router.post('/items/:id/mark-sold', asyncRoute(async (req: Request, res: Response) => {
  const { rows } = await pool.query<ItemRecord>(
    `UPDATE items SET status='sold', sold_at=now() WHERE id=$1 RETURNING *`,
    [req.params.id]
  );
  // No buyer to exclude: an admin marking an item sold has no associated
  // customer, so everyone watching it hears about it.
  await notifyFavoritersOfSale([Number(req.params.id)], null);
  res.json(rows[0]);
}));

// Publishing is the existing mark-available: it already sets status='available'
// and clears sold_at, reserved_until and paypal_order_id, all of which are
// no-ops on a pending item. A second endpoint running the same UPDATE would be
// duplication, so the admin UI labels that button "Publish" when the item is
// pending. This is the reverse, and it is not symmetrical — see the guard.
router.post('/items/:id/unpublish', asyncRoute(async (req: Request, res: Response) => {
  const { rows } = await pool.query<ItemStatusRow>(`SELECT status FROM items WHERE id = $1`, [req.params.id]);
  if (!rows.length) {
    return res.status(404).json({ error: 'not found' });
  }

  const status = requireRow(rows, 'the item status lookup').status;
  if (status === 'pending') {
    return res.status(400).json({ error: 'this item is already pending' });
  }
  // Reserved and sold are not drafts. A reserved item is in someone's cart
  // right now and hiding it would strand them mid-checkout; a sold item is a
  // record of something that happened, and pulling it back would quietly
  // rewrite that. Both are refused by name so the reason is on screen rather
  // than left to be guessed from a generic error.
  if (status === 'reserved') {
    return res.status(400).json({ error: 'a customer is holding this item — it cannot be unpublished' });
  }
  if (status === 'sold') {
    return res.status(400).json({ error: 'a sold item cannot be unpublished' });
  }

  const { rows: updated } = await pool.query<ItemRecord>(
    `UPDATE items SET status='pending' WHERE id=$1 RETURNING *`,
    [req.params.id]
  );
  res.json(updated[0]);
}));

router.post('/items/:id/mark-available', asyncRoute(async (req: Request, res: Response) => {
  const { rows } = await pool.query<ItemRecord>(
    `UPDATE items SET status='available', sold_at=NULL, reserved_until=NULL, paypal_order_id=NULL
     WHERE id=$1 RETURNING *`,
    [req.params.id]
  );
  res.json(rows[0]);
}));

export default router;