require "date"
def validate(*a)
  # Check arguments against either a list of acceptable classes or just a class
  raise ArgumentError, "expected an even number of arguments" if a.count%2 != 0 
  for i in (0..a.count-1).step(2) do
    if a[i+1].kind_of?(Class) then
      raise TypeError, "expected argument #{i/2} of type #{a[i+1].to_s}" unless a[i].kind_of?(a[i+1])
    elsif a[i+1].kind_of?(Array) then
      raise TypeError, "expected argument #{i/2} of any of the types #{a[i+1].to_s}" unless a[i+1].include?(a[i].class)
    end
  end
end
module Heimdall
  # Core protocol
  class NetEntity
    # Abstraction that stores basic object properties
    @createdAt
    def initialize()
      @createdAt = DateTime.new
    end
    attr_reader :createdAt
  end
  
  class User < NetEntity
    # User abstraction (not bound to a group chat)
    @username
    @nickname
    def initialize(username,nickname = nil)
      validate(
        username, String,
        nickname, [String,NilClass]
      )
      super()
      nickname = username if not nickname
      @username = username
      @nickname = nickname
    end
    attr_reader :username
    attr_accessor :nickname
  end

  class Channel < NetEntity
    # Channel abstraction (not bound to a group)
    # Practically acts as a message stack
    # Read access to all elements
    # Write access only to top 
    @messages
    def initialize()
      validate(
        id, String
      )
      super()
      @messages = []
    end
    def [](index)
      @messages[id]
    end
    def <<(message)
      @messages.append(message)
    end
    def top(count = 1)
      return @messages[-1] if count == 1
      @messages[(-1*count)..-1]
    end
    def filter(&block)
      @messages.filter(block)
    end
    def snapshot()
      @messages.clone
    end
  end

  class Message < NetEntity
    # Message abstraction with edits and content history (not bound to a group)
    @content
    @author
    @editedAt
    @contentHist
    def initialize(content,author,channel) 
      validate(
        content, String,
        author, Heimdall::User,
        channel, Heimdall::Channel
      )
      super()
      @editedAt = DateTime.new
      @contentHist = [content]
      @content = content
      @author = author
    end
    def edit(content)
      @content = content
      @editedAt = DateTime.new
      @contentHist.append(content)
    end
    attr_reader :content
    attr_reader :author
    attr_reader :contentHist
    attr_reader :editedAt
  end
end