gerbeur/api/services/category-service.ts

/**
 * Stores the categories and which dumps belong to them. The category routes
 * manage and list them, the dump service files each dump it writes under its
 * categories, and every service that lists dumps fills in their `categoryIds`.
 *
 * @module
 */

import { APIException } from "../lib/api-exception.ts";
import type {
  Category,
  CreateCategoryRequest,
  UpdateCategoryRequest,
} from "../../shared/category.ts";
import type { Dump } from "../../shared/dump.ts";
import { categoryRowToApi, isCategoryRow } from "../model/category.ts";
import { db, transaction } from "../db/connection.ts";
import {
  DUMP_SELECT_COLUMNS_ALIASED as SELECT_COLS_ALIASED,
  dumpRowToApi,
  isDumpRow,
} from "../model/dump.ts";
import { type Page, pageOf } from "../lib/pagination.ts";
import { isReservedSlug } from "../lib/reserved-slugs.ts";
import { validateSlug } from "../lib/slugify.ts";
import { VALIDATION } from "../../shared/validation.ts";
import { parseRows } from "../model/rows.ts";

/**
 * Throws a 400 unless `slug` is a valid category slug: a slug within a
 * category's length, and none of the top-level paths other pages hold
 * (reserved-slugs.ts), since a category's feed lives at the URL root.
 */
function validateCategorySlug(slug: string): void {
  validateSlug(slug, VALIDATION.CATEGORY_SLUG_MAX);
  if (isReservedSlug(slug)) {
    throw new APIException(400, `Slug "${slug}" is reserved`);
  }
}

function requireName(name: string): string {
  const trimmed = name.trim();
  if (!trimmed) {
    throw new APIException(400, "Name is required");
  }
  if (trimmed.length > VALIDATION.CATEGORY_NAME_MAX) {
    throw new APIException(
      400,
      `Name must be at most ${VALIDATION.CATEGORY_NAME_MAX} characters`,
    );
  }
  return trimmed;
}

/**
 * Rethrows a UNIQUE violation from SQLite as a 409 naming the slug or name
 * that is taken, and any other error as is. SQLite's message names the
 * column, so this matches on it.
 */
function uniqueConflict(err: unknown, slug: string, name: string): never {
  const msg = err instanceof Error ? err.message : String(err);
  if (msg.includes("categories.name")) {
    throw new APIException(409, `Name "${name}" is already in use`);
  }
  if (msg.includes("UNIQUE") || msg.includes("unique")) {
    throw new APIException(409, `Slug "${slug}" is already in use`);
  }
  throw err as Error;
}

/**
 * Returns category `id`, for {@link updateCategory}.
 *
 * @throws {APIException} 404 when there is no such category.
 */
export function getCategoryById(id: string): Category {
  const row = db.prepare(`SELECT * FROM categories WHERE id = ?;`).get(id);
  if (!row || !isCategoryRow(row)) {
    throw new APIException(404, "Category not found");
  }
  return categoryRowToApi(row);
}

/**
 * Returns the category at `slug`, for {@link listDumpsByCategory}.
 *
 * @throws {APIException} 404 when there is no such category.
 */
export function getCategoryBySlug(slug: string): Category {
  const row = db.prepare(`SELECT * FROM categories WHERE slug = ?;`).get(slug);
  if (!row || !isCategoryRow(row)) {
    throw new APIException(404, "Category not found");
  }
  return categoryRowToApi(row);
}

/**
 * Returns the id of the category at `slug`, or undefined when there is none.
 * The follows routes use it for their `?category=` feed filter.
 */
export function getCategoryIdBySlug(slug: string): string | undefined {
  const row = db.prepare(`SELECT id FROM categories WHERE slug = ?;`).get(slug);
  return row && typeof (row as { id?: unknown }).id === "string"
    ? (row as { id: string }).id
    : undefined;
}

/**
 * Returns every category, by position then slug, for `GET /api/categories`.
 */
export function listCategories(): Category[] {
  const rows = db.prepare(
    `SELECT * FROM categories ORDER BY position ASC, slug ASC;`,
  ).all();
  return parseRows(rows, isCategoryRow, categoryRowToApi);
}

/**
 * Creates a category, for `POST /api/categories`. The name is stored trimmed,
 * and the position defaults to 0.
 *
 * @throws {APIException} 400 when the slug or name is invalid, 409 when
 * either is taken.
 */
export function createCategory(req: CreateCategoryRequest): Category {
  validateCategorySlug(req.slug);
  const name = requireName(req.name);

  const id = crypto.randomUUID();
  const createdAt = new Date();
  try {
    db.prepare(
      `INSERT INTO categories (id, slug, name, position, created_at)
       VALUES (?, ?, ?, ?, ?);`,
    ).run(
      id,
      req.slug,
      name,
      req.position ?? 0,
      createdAt.toISOString(),
    );
  } catch (err) {
    uniqueConflict(err, req.slug, name);
  }

  return {
    id,
    slug: req.slug,
    name,
    position: req.position ?? 0,
    createdAt,
  };
}

/**
 * Applies `req` to category `id`, for `PUT /api/categories/:id`, and returns
 * the category as it now is. Fields `req` leaves out keep their value.
 *
 * @throws {APIException} 404 when there is no such category, 400 when the new
 * slug or name is invalid, 409 when either is taken.
 */
export function updateCategory(
  id: string,
  req: UpdateCategoryRequest,
): Category {
  const existing = getCategoryById(id);

  const newSlug = req.slug ?? existing.slug;
  if (req.slug !== undefined && req.slug !== existing.slug) {
    validateCategorySlug(req.slug);
  }
  const newName = req.name !== undefined
    ? requireName(req.name)
    : existing.name;
  const newPosition = req.position ?? existing.position;
  const now = new Date();

  try {
    db.prepare(
      `UPDATE categories SET slug = ?, name = ?, position = ?, updated_at = ? WHERE id = ?;`,
    ).run(
      newSlug,
      newName,
      newPosition,
      now.toISOString(),
      id,
    );
  } catch (err) {
    uniqueConflict(err, newSlug, newName);
  }

  return {
    ...existing,
    slug: newSlug,
    name: newName,
    position: newPosition,
    updatedAt: now,
  };
}

/**
 * Deletes category `id`, for `DELETE /api/categories/:id`. Its dumps stay, and
 * lose it from their `categoryIds`.
 *
 * @throws {APIException} 404 when there is no such category.
 */
export function deleteCategory(id: string): void {
  const result = db.prepare(`DELETE FROM categories WHERE id = ?;`).run(id);
  if (result.changes === 0) {
    throw new APIException(404, "Category not found");
  }
}

/**
 * Checks that every id in `categoryIds` names a category. The dump service
 * runs it before it writes a dump row or stores an uploaded file, so a bad id
 * fails the request before anything is written.
 *
 * @throws {APIException} 400 when an id names no category.
 */
export function assertCategoriesExist(categoryIds: string[]): void {
  const unique = [...new Set(categoryIds)];

  if (unique.length > 0) {
    const placeholders = unique.map(() => "?").join(", ");
    const found = db.prepare(
      `SELECT COUNT(*) as count FROM categories WHERE id IN (${placeholders});`,
    ).get(...unique) as { count: number } | undefined;
    if ((found?.count ?? 0) !== unique.length) {
      throw new APIException(400, "One or more categories do not exist");
    }
  }
}

/**
 * Replaces the categories of dump `dumpId` with `categoryIds`, duplicates
 * dropped. An empty list takes the dump out of every category. Called inside
 * the dump service's transaction, it joins that one.
 *
 * @throws {APIException} 400 when an id names no category.
 */
export function setDumpCategories(
  dumpId: string,
  categoryIds: string[],
): void {
  assertCategoriesExist(categoryIds);
  const unique = [...new Set(categoryIds)];

  transaction(() => {
    db.prepare(`DELETE FROM dump_categories WHERE dump_id = ?;`).run(dumpId);
    const insert = db.prepare(
      `INSERT INTO dump_categories (dump_id, category_id) VALUES (?, ?);`,
    );
    for (const categoryId of unique) {
      insert.run(dumpId, categoryId);
    }
  });
}

/**
 * Sets `categoryIds` on each of `dumps` in place, in one query. The dump row
 * doesn't carry them, so every service that returns dumps calls this first.
 */
export function attachCategoryIds(dumps: Dump[]): void {
  if (dumps.length === 0) return;
  const ids = dumps.map((d) => d.id);
  const placeholders = ids.map(() => "?").join(", ");
  const rows = db.prepare(
    `SELECT dump_id, category_id FROM dump_categories WHERE dump_id IN (${placeholders});`,
  ).all(...ids) as Array<{ dump_id: string; category_id: string }>;

  const byDump = new Map<string, string[]>();
  for (const { dump_id, category_id } of rows) {
    const list = byDump.get(dump_id) ?? [];
    list.push(category_id);
    byDump.set(dump_id, list);
  }
  for (const dump of dumps) {
    dump.categoryIds = byDump.get(dump.id) ?? [];
  }
}

/**
 * Returns a page of the dumps in the category at `slug`, newest first, for
 * `GET /api/dumps?category=`. Private dumps are left out, except
 * `requestingUserId`'s own.
 *
 * @throws {APIException} 404 when there is no such category.
 */
export function listDumpsByCategory(
  slug: string,
  page: number,
  limit: number,
  requestingUserId?: string,
): Page<Dump> {
  const category = getCategoryBySlug(slug);
  const offset = (page - 1) * limit;

  const privacyClause = requestingUserId
    ? "(d.is_private = 0 OR d.user_id = ?)"
    : "d.is_private = 0";
  const privacyParams = requestingUserId ? [requestingUserId] : [];

  const rows = db.prepare(
    `SELECT ${SELECT_COLS_ALIASED}
     FROM dumps d
     INNER JOIN dump_categories dc ON dc.dump_id = d.id
     WHERE dc.category_id = ? AND ${privacyClause}
     ORDER BY d.created_at DESC LIMIT ? OFFSET ?;`,
  ).all(category.id, ...privacyParams, limit + 1, offset);

  const items = parseRows(rows, isDumpRow, dumpRowToApi);
  attachCategoryIds(items);
  return pageOf(items, limit);
}