space_game_server/lib/game/ship.rb

# Represents a space-faring vessel owned by a player.
# Handles movement and validation of ship creation.

require 'securerandom'

# Load the ships into a constant:
require 'yaml'
# Configuration data for all available ships
SHIP_DATA = File.open('lib/game/data/ships.yaml', 'r') do |fi|
  YAML.safe_load(fi.read())
end

# Represents a space-faring vessel owned by a player.
class Ship

  attr_reader :owner, :position

  # Ships are built by a player so we should *always* know what player is
  # owning a ship
  #
  # @param player [Player] The player who owns the ship
  # @param position_x [Float] The starting x position of the ship.
  # @param position_y [Float] The starting y position of the ship.
  # @param position_z [Float] The starting z position of the ship.
  def initialize(player, position_x, position_y, position_z, name)
    @owner = player
    @ship_id = SecureRandom.hex
    @position = [position_x, position_y, position_z]
    @target = @position
    @speed = 1
    @ship_info = validate_creation(name)
  end

  # Validates that the ship name exists and it is unlocked by the player (Has
  # the right buildings and tech to actually create). This means that you might
  # be able to start a ship however when it is 'finished' if a required
  # building has been removed it will fail to finish properly. In this case the
  # player resources should be refunded (with some lost) and the ship creation
  # will raise an error.
  def validate_creation(name)
    ship = SHIP_DATA[name]
    raise ShipError, "invalid ship name '#{name}'" if ship.nil?
    # Validate that the owner has the correct tech:
    ship['required_tech'].each do |tech_needed|
      if !(@owner.researched_tech.include? tech_needed)
        raise ShipError, "Player needs the tech of '#{tech_needed}'"
      end
    end
    # Validate the buildings:
    ship['required_buildings'].each do |building_needed|
      if !(@owner.buildings.include? building_needed)
        raise ShipError, "Player needs the building of '#{building_needed}' to build this ship"
      end
    end
    return ship
  end

  # Teleport the ship to a given position. Really only should be used for admin
  # stuff.
  #
  # @param position_x [Float] The new x position of the ship.
  # @param position_y [Float] The new y position of the ship.
  # @param position_z [Float] The new z position of the ship.
  def teleport(position_x, position_y, position_z)
    @position = [position_x, position_y, position_z]
  end

  # Sets the target position of a ship.
  #
  # @param position_x [Float] The new x position of the ship.
  # @param position_y [Float] The new y position of the ship.
  # @param position_z [Float] The new z position of the ship.
  def move(position_x, position_y, position_z)
    @target = [position_x, position_y, position_z]
  end

  # Contains the logic to move a ship
  #
  # @param delta_time [Float] The delta time elapsed in the game
  def update(delta_time)
    # Movement logic:
    if @position == @target
      # Do nothing
    else
      # Calculate the difference of the position and the target
      x_dist = @target[0] - @position[0]
      y_dist = @target[1] - @position[1]
      z_dist = @target[2] - @position[2]
      total_dist = Math.sqrt(x_dist**2 + y_dist**2 + z_dist**2)
      speed = (@speed/total_dist) * delta_time

      new_x = @position[0] + (x_dist * speed)
      new_y = @position[1] + (y_dist * speed)
      new_z = @position[2] + (z_dist * speed)

      if x_dist > 0 # Going right
        if new_x > @target[0]
          new_x = @target[0]
        end
      elsif x_dist < 0 # Going left
        if new_x < @target[0]
          new_x = @target[0]
        end
      end

      if y_dist > 0 # Going right
        if new_y > @target[1]
          new_y = @target[1]
        end
      elsif y_dist < 0 # Going left
        if new_y < @target[1]
          new_y = @target[1]
        end
      end

      if z_dist > 0 # Going right
        if new_z > @target[2]
          new_z = @target[2]
        end
      elsif z_dist < 0 # Going left
        if new_z < @target[2]
          new_z = @target[2]
        end
      end
      @position = [new_x, new_y, new_z]
    end
  end

  # Save a player to a file
  def save_to_file
    File.open("game_data/#{self.planet_id}.save", 'wb') do |fi|
      # Load resources for the player:
      fi.write(Marshal.dump(self))
    end
    return self.planet_id
  end

  # Load a player from a file
  def self.load_from_save(fname)
    File.open("game_data/#{fname}_ship_.save", 'rb') do |fi|
      # Load resources for the player:
      Marshal.load(fi.read)
    end
  end
end

# Error class for ships
# Represents a space-faring vessel owned by a player.
class ShipError < StandardError
end