loto/docs/code-standards.md

Code Standards

File Naming & Structure

• Kebab-case for all files: player-board.jsx, game-logic.js.
• Descriptive names: Long names are preferred for self-documentation. Avoid ambiguity.
• Single responsibility: Each file has one primary export (component or utilities).
• Max 200 lines per file: Split larger components into smaller focused ones.

React & JavaScript Conventions

Hooks

• useState: For local UI state (grid, crossed, form inputs).
• useEffect: For side effects (load from localStorage, save to localStorage, detect changes).
• useCallback: For event handlers to stabilize function identity across renders.
• useRef: For mutable values that don't trigger renders (timers, celebratedRows set).

Typing (JSDoc)

• Author types in JSDoc comments — jsconfig.json has checkJs: true, so tsc --noEmit validates them.
• Component props: @typedef {Object} Props { ... } followed by @param {Props} props on the function.
• Layout children: @param {{ children: React.ReactNode }} props.
• Avoid any; use precise types (e.g., number[][] for grid).
• Generics: @template T then reference T in @param / @returns.

Client-Only Constraint

• All interactive pages must have "use client" at the top.
• No server-side data fetching; use localStorage instead.
• No async Server Components.

CSS & Tailwind 4 Patterns

Utilities

• Utility-first: className="px-4 py-2 rounded-lg text-white".
• Responsive: sm:, md:, lg: prefixes for breakpoints.
• Dark mode: dark:bg-slate-800, dark:text-white.
• Animations: Custom keyframes in globals.css, apply via animate-fade-in.

Layout

• Flexbox for alignment: flex flex-col items-center justify-center.
• Grid for game boards: .loto-grid { grid-template-columns: repeat(9, 1fr); }.
• Aspect ratio for square cells: aspect-square.

Gradients

• Player page: from-indigo-500 to-purple-500.
• Host page: from-orange-500 to-red-500.
• Completed rows: bg-emerald-100 + text-emerald-500.
• Shadows: shadow-lg shadow-indigo-500/25.

localStorage Patterns

Saving

/**
 * @param {number[][]} grid
 * @param {string} [prefix]
 */
function saveGrid(grid, prefix = "loto") {
  localStorage.setItem(`${prefix}_grid`, JSON.stringify(grid));
}

Loading

/**
 * @param {string} [prefix]
 * @returns {number[][] | null}
 */
function loadGrid(prefix = "loto") {
  const data = localStorage.getItem(`${prefix}_grid`);
  if (!data) return null;
  try {
    return JSON.parse(data);
  } catch {
    return null;
  }
}

Key Pattern: {prefix}_{key} enables multiple independent boards per component reuse.

Error Handling

• Silent fallback: JSON parse errors return null; caller checks for null.
• No try-catch in render: Keep logic in useEffect or event handlers.
• Confirmation dialogs: confirm("Bạn có muốn...") for destructive actions.

Naming Conventions

Pattern	Example	Usage
camelCase	handleCellClick, storagePrefix	variables, functions, props
PascalCase	PlayerBoard, MasterPage	components, types
UPPER_SNAKE	STORAGE_KEY, NUM_ROWS	constants
kebab-case	player-board.jsx	file names

Comment Style

• Document why, not what. The code shows what it does.
• Use /** JSDoc */ for exported functions.
• Inline comments for complex logic (e.g., weighted random selection in lib/game-logic.js:19–28).

Example

/**
 * Weighted random selection of a column index.
 * @param {number[]} weights
 * @returns {number}
 */
function randomANumberInRow(weights) {
  // Convert weights to cumulative distribution for O(n) lookup
  const tempWeight = [...weights];
  for (let i = 1; i < tempWeight.length; i++) {
    tempWeight[i] += tempWeight[i - 1];
  }
  // ...
}

Import Organization

1. React/Next imports
2. Third-party imports
3. Local component/utility imports

import { useCallback, useState } from "react";
import Link from "next/link";
import PlayerBoard from "@/components/player-board";
import { generateGrid } from "@/lib/game-logic";

Testing (Not Currently Implemented)

Future tests should follow:

• Unit: test game logic (generateGrid, isRowComplete, getWaitingNumber) in isolation.
• Component: mock localStorage, render PlayerBoard with different props.
• E2E: player flow (generate → click → bingo).

Configuration

Environment Variables

• NEXT_DEV_PROFILE: "codeserver" triggers proxy config.
• CODESERVER_HOST: Hostname for HMR (required if NEXT_DEV_PROFILE=codeserver).
• CODESERVER_PORT: Port (defaults to 3000).

Set in .env.local (not committed).

Build Targets

• output: "export": Static HTML export (no Node.js server needed).
• basePath: Configurable per deployment environment.

Last reviewed: 2026-04-26