add post

app/controllers/posts_controller.rb

@@ -0,0 +1,53 @@
+class PostsController < ApplicationController
+  before_action :set_post, only: %i[ show update destroy ]
+
+  # GET /posts
+  # GET /posts.json
+  def index
+    @posts = Post.all
+  end
+
+  # GET /posts/1
+  # GET /posts/1.json
+  def show
+  end
+
+  # POST /posts
+  # POST /posts.json
+  def create
+    @post = Post.new(post_params)
+
+    if @post.save
+      render :show, status: :created, location: @post
+    else
+      render json: @post.errors, status: :unprocessable_entity
+    end
+  end
+
+  # PATCH/PUT /posts/1
+  # PATCH/PUT /posts/1.json
+  def update
+    if @post.update(post_params)
+      render :show, status: :ok, location: @post
+    else
+      render json: @post.errors, status: :unprocessable_entity
+    end
+  end
+
+  # DELETE /posts/1
+  # DELETE /posts/1.json
+  def destroy
+    @post.destroy
+  end
+
+  private
+    # Use callbacks to share common setup or constraints between actions.
+    def set_post
+      @post = Post.find(params[:id])
+    end
+
+    # Only allow a list of trusted parameters through.
+    def post_params
+      params.require(:post).permit(:content, :user_id, :quoted_post_id)
+    end
+end

app/models/post.rb

@@ -0,0 +1,27 @@
+class Post < ApplicationRecord
+  belongs_to :user
+  belongs_to :quoted_post, optional: true, class_name: 'Post'
+
+  validates :content, length: { maximum: 777 }
+  validates :content, presence: true, if: :quoted_post?
+
+  def kind
+    if quoted_post?
+      :quoted_post
+    elsif repost?
+      :repost
+    else
+      :post
+    end
+  end
+
+  private
+
+  def quoted_post?
+    content.present? && quoted_post_id
+  end
+
+  def repost?
+    content.blank? && quoted_post_id
+  end
+end

app/views/posts/_post.json.jbuilder

@@ -0,0 +1,4 @@
+json.extract! post, :id, :content, :user_id, :created_at, :updated_at
+json.url post_url(post, format: :json)
+
+json.quoted_post(post.quoted_post)

app/views/posts/index.json.jbuilder

@@ -0,0 +1 @@
+json.array! @posts, partial: "posts/post", as: :post

app/views/posts/show.json.jbuilder

@@ -0,0 +1 @@
+json.partial! "posts/post", post: @post