require 'vedeu/support/esc'
require 'vedeu/support/terminal'

module Vedeu
  InvalidHeight    = Class.new(StandardError)
  InvalidWidth     = Class.new(StandardError)
  OutOfBoundsError = Class.new(StandardError)

  class Geometry
    def initialize(attrs = {})
      @attrs = attrs
    end

    def origin(index = 0)
      Esc.set_position(virtual_y(index), virtual_x)
    end

    def terminal_height
      @terminal_height ||= attrs_terminal_height
    end

    def height
      @height ||= attrs_height
    end

    def y
      @y ||= attrs_y
    end

    def x
      @x ||= attrs_x
    end

    def terminal_width
      @terminal_width ||= attrs_terminal_width
    end

    def width
      @width ||= attrs_width
    end

    def centred
      @centred ||= attrs_centred
    end

    def centre
      [(terminal_height / 2), (terminal_width / 2)]
    end

    def centre_y
      centre.first
    end

    def centre_x
      centre.last
    end

    def top
      if centred
        centre_y - (height / 2)
      else
        y
      end
    end

    def left
      if centred
        centre_x - (width / 2)
      else
        x
      end
    end

    def bottom
      top + height
    end

    def right
      left + width
    end

    def position
      {
        y:       top,
        x:       left,
        height:  height,
        width:   width,
        centred: centred,
        top:     top,
        bottom:  bottom,
        left:    left,
        right:   right,
      }
    end

    private

    attr_reader :attrs

    def attrs_height
      height = attrs.fetch(:height)
      fail_if_less_than_one(height)
      fail_if_out_of_bounds('height', height, terminal_height)
      height
    rescue KeyError
      fail InvalidHeight, 'An Interface must have a height attribute.'
    end

    def attrs_terminal_height
      terminal_height = attrs.fetch(:terminal_height, Terminal.height)
      fail_if_less_than_one(terminal_height)
      fail_if_out_of_bounds('terminal_height', terminal_height, Terminal.height)
      terminal_height
    end

    def attrs_y
      y = attrs.fetch(:y, 1)
      fail_if_less_than_one(y)
      fail_if_out_of_bounds('y', y, terminal_height)
      y
    end

    def attrs_x
      x = attrs.fetch(:x, 1)
      fail_if_less_than_one(x)
      fail_if_out_of_bounds('x', x, terminal_width)
      x
    end

    def attrs_terminal_width
      terminal_width = attrs.fetch(:terminal_width, Terminal.width)
      fail_if_less_than_one(terminal_width)
      fail_if_out_of_bounds('terminal_width',
                            terminal_width,
                            Terminal.width)
      terminal_width
    end

    def attrs_width
      width = attrs.fetch(:width)
      fail_if_less_than_one(width)
      fail_if_out_of_bounds('width', width, terminal_width)
      width
    rescue KeyError
      fail InvalidWidth, 'An Interface must have a width attribute.'
    end

    def attrs_centred
      !!(attrs.fetch(:centred, true))
    end

    def fail_if_less_than_one(value)
      fail OutOfBoundsError,
        'Value must be greater than or equal to 1.' if value < 1
    end

    def fail_if_out_of_bounds(name, attribute, boundary)
      if attribute > boundary
        fail OutOfBoundsError,
          "Cannot set #{name} to be outside the terminal visible area."
      end
    end

    def virtual_x
      left
    end

    def virtual_y(index = 0)
      ((top..bottom).to_a)[index]
    end
  end
end