# 安装 Rails
gem install rails

# 验证
rails --version

# 创建新项目
rails new myapp
rails new myapp --database=postgresql
rails new myapp --api  # API 模式
rails new myapp --skip-test --skip-system-test

# 启动服务器
rails server
rails s

# 控制台
rails console
rails c

# 数据库
rails db:create
rails db:migrate
rails db:seed
rails db:rollback

# 生成器
rails generate model User name:string email:string
rails generate controller Users index show
rails generate migration AddAgeToUsers age:integer
rails generate scaffold Post title:string body:text

# 路由
rails routes
rails routes | grep users

# 测试
rails test
rails test:system

# config/routes.rb
Rails.application.routes.draw do
  # 基本路由
  get "/about", to: "pages#about"
  post "/contact", to: "pages#contact"
  
  # 多个 HTTP 方法
  match "/path", to: "controller#action", via: [:get, :post]
  
  # 资源路由（RESTful）
  resources :users
  
  # 有限资源
  resources :posts, only: [:index, :show, :create]
  resources :comments, except: [:destroy]
  
  # 嵌套资源
  resources :users do
    resources :posts
  end
  
  # 命名空间
  namespace :admin do
    resources :users
    resources :posts
  end
  
  # 自定义路由
  get "search", to: "search#index"
  post "login", to: "sessions#create"
  delete "logout", to: "sessions#destroy"
  
  # 根路由
  root "pages#home"
end

resources :users
# 生成以下路由：
# GET    /users          → users#index
# GET    /users/new      → users#new
# POST   /users          → users#create
# GET    /users/:id      → users#show
# GET    /users/:id/edit → users#edit
# PATCH  /users/:id      → users#update
# DELETE /users/:id      → users#destroy

# 辅助方法
# users_path        → /users
# user_path(@user)  → /users/1
# new_user_path     → /users/new
# edit_user_path(@user) → /users/1/edit

# app/controllers/users_controller.rb
class UsersController < ApplicationController
  before_action :set_user, only: [:show, :edit, :update, :destroy]

  def index
    @users = User.all
    @users = @users.where(active: true) if params[:active]
    @users = @users.order(created_at: :desc).page(params[:page])
  end

  def show
  end

  def new
    @user = User.new
  end

  def create
    @user = User.new(user_params)

    if @user.save
      redirect_to @user, notice: "User created successfully."
    else
      render :new, status: :unprocessable_entity
    end
  end

  def edit
  end

  def update
    if @user.update(user_params)
      redirect_to @user, notice: "User updated successfully."
    else
      render :edit, status: :unprocessable_entity
    end
  end

  def destroy
    @user.destroy
    redirect_to users_path, notice: "User deleted."
  end

  private

  def set_user
    @user = User.find(params[:id])
  end

  def user_params
    params.require(:user).permit(:name, :email, :age, :active)
  end
end

class PagesController < ApplicationController
  def home
    # 默认渲染 app/views/pages/home.html.erb
  end

  def about
    render :about  # 显式渲染
  end

  def search
    @results = Search.perform(params[:q])
    
    respond_to do |format|
      format.html  # 渲染 HTML 模板
      format.json { render json: @results }
      format.xml  { render xml: @results }
    end
  end

  def redirect_example
    redirect_to root_path
    redirect_to user_path(@user), status: :moved_permanently
    redirect_back(fallback_location: root_path)
  end
end

# app/models/user.rb
class User < ApplicationRecord
  # 关联
  has_many :posts, dependent: :destroy
  has_many :comments, through: :posts
  belongs_to :organization, optional: true

  # 验证
  validates :name, presence: true, length: { minimum: 2, maximum: 50 }
  validates :email, presence: true, uniqueness: true, format: { with: URI::MailTo::EMAIL_REGEXP }
  validates :age, numericality: { greater_than: 0, less_than: 150 }, allow_nil: true

  # 回调
  before_save :normalize_email
  after_create :send_welcome_email

  # 作用域
  scope :active, -> { where(active: true) }
  scope :adults, -> { where("age >= ?", 18) }
  scope :recent, -> { where("created_at > ?", 1.week.ago) }

  # 类方法
  def self.search(query)
    where("name LIKE ? OR email LIKE ?", "%#{query}%", "%#{query}%")
  end

  # 实例方法
  def full_name
    "#{first_name} #{last_name}"
  end

  private

  def normalize_email
    self.email = email.downcase.strip
  end

  def send_welcome_email
    UserMailer.welcome(self).deliver_later
  end
end

# 基本查询
User.all
User.find(1)
User.find_by(email: "alice@example.com")
User.where(active: true)
User.where("age > ?", 18)

# 链式查询
User.active.adults.recent.order(name: :asc).limit(10)

# 聚合
User.count
User.average(:age)
User.maximum(:age)
User.minimum(:age)
User.group(:role).count

# 复杂查询
User.includes(:posts).where(posts: { published: true })
User.joins(:posts).where("posts.created_at > ?", 1.month.ago)
User.left_joins(:comments).group("users.id").having("COUNT(comments.id) > ?", 5)

# 原始 SQL
User.find_by_sql("SELECT * FROM users WHERE age > 18")

# 分页
User.page(1).per(25)  # Kaminari
User.where(active: true).page(params[:page])

# 创建
user = User.new(name: "Alice", email: "alice@example.com")
user.save

User.create(name: "Alice", email: "alice@example.com")
User.create!(name: "Alice", email: "alice@example.com")  # 失败时抛异常

# 读取
User.find(1)
User.find_by(email: "alice@example.com")
User.first
User.last
User.where(active: true)

# 更新
user.update(name: "Bob")
user.update!(name: "Bob")
user.update_columns(name: "Bob")  # 跳过验证和回调
User.update_all(active: true)

# 删除
user.destroy
user.destroy!
User.destroy_all
User.delete_all  # 跳过回调

# 生成迁移
rails generate migration CreateUsers name:string email:string age:integer
rails generate migration AddRoleToUsers role:string
rails generate migration AddIndexToUsersEmail

# db/migrate/20240115120000_create_users.rb
class CreateUsers < ActiveRecord::Migration[7.1]
  def change
    create_table :users do |t|
      t.string :name, null: false
      t.string :email, null: false
      t.integer :age
      t.string :role, default: "user"
      t.boolean :active, default: true
      t.timestamps
    end

    add_index :users, :email, unique: true
    add_index :users, :role
  end
end

# db/migrate/20240116120000_add_posts_table.rb
class AddPostsTable < ActiveRecord::Migration[7.1]
  def change
    create_table :posts do |t|
      t.references :user, null: false, foreign_key: true
      t.string :title, null: false
      t.text :body
      t.boolean :published, default: false
      t.datetime :published_at
      t.timestamps
    end

    add_index :posts, :published
    add_index :posts, [:user_id, :published]
  end
end

# 复杂迁移
class MigrateUserData < ActiveRecord::Migration[7.1]
  def up
    User.find_each do |user|
      user.update_columns(
        first_name: user.name.split(" ").first,
        last_name: user.name.split(" ").last
      )
    end
  end

  def down
    User.find_each do |user|
      user.update_columns(name: "#{user.first_name} #{user.last_name}")
    end
  end
end

# 运行迁移
rails db:migrate

# 回滚
rails db:rollback
rails db:rollback STEP=3  # 回滚 3 步

# 重置数据库
rails db:reset  # drop + create + migrate + seed

# 迁移状态
rails db:migrate:status

# 生成迁移时指定类型
rails generate migration AddIndex \
  field:type{options} \
  --no-test-framework

rails new blog
cd blog
rails generate scaffold Post title:string body:text
rails db:migrate
rails server

rails generate model Comment post:references body:text
rails db:migrate
# 实现嵌套路由和表单

# 为 Post 模型添加验证
# 编写集成测试