# encoding: utf-8

require 'forwardable'

module TTY
  class Prompt
    class Reader
      class Line
        extend Forwardable

        def_delegators :@text, :size, :length, :to_s, :inspect,
                       :slice!, :empty?

        attr_accessor :text

        attr_accessor :cursor

        def initialize(text = "")
          @text = text
          @cursor = [0, @text.length].max
          yield self if block_given?
        end

        # Check if cursor reached beginning of the line
        #
        # @return [Boolean]
        #
        # @api public
        def start?
          @cursor == 0
        end

        # Check if cursor reached end of the line
        #
        # @return [Boolean]
        #
        # @api public
        def end?
          @cursor == @text.length
        end

        # Move line position to the left by n chars
        #
        # @api public
        def left(n = 1)
          @cursor = [0, @cursor - n].max
        end

        # Move line position to the right by n chars
        #
        # @api public
        def right(n = 1)
          @cursor = [@text.length, @cursor + n].min
        end

        # Move cursor to beginning position
        #
        # @api public
        def move_to_start
          @cursor = 0
        end

        # Move cursor to end position
        #
        # @api public
        def move_to_end
          @cursor = @text.length # put cursor outside of text
        end

        # Insert characters inside a line. When the lines exceeds
        # maximum length, an extra space is added to accomodate index.
        #
        # @param [Integer] i
        #   the index to insert at
        #
        # @example
        #   text = 'aaa'
        #   line[5]= 'b'
        #   => 'aaa  b'
        #
        # @api public
        def []=(i, chars)
          if i.is_a?(Range)
            @text[i] = chars
            @cursor += chars.length
            return
          end

          if i <= 0
            before_text = ''
            after_text = @text.dup
          elsif i == @text.length - 1
            before_text = @text.dup
            after_text = ''
          elsif i > @text.length - 1
            before_text = @text.dup
            after_text = ?\s * (i - @text.length)
            @cursor += after_text.length
          else
            before_text = @text[0..i-1].dup
            after_text  = @text[i..-1].dup
          end

          if i > @text.length - 1
            @text = before_text << after_text << chars
          else
            @text = before_text << chars << after_text
          end

          @cursor = i + chars.length
        end

        # Read character
        #
        # @api public
        def [](i)
          @text[i]
        end

        # Replace current line with new text
        #
        # @param [String] text
        #
        # @api public
        def replace(text)
          @text = text
          @cursor = @text.length # put cursor outside of text
        end

        # Insert char(s) at cursor position
        #
        # @api public
        def insert(chars)
          self[@cursor] = chars
        end

        # Add char and move cursor
        #
        # @api public
        def <<(char)
          @text << char
          @cursor += 1
        end

        # Remove char from the line at current position
        #
        # @api public
        def delete
          @text.slice!(@cursor, 1)
        end

        # Remove char from the line in front of the cursor
        #
        # @api public
        def remove
          left
          @text.slice!(@cursor, 1)
        end
      end # Line
    end # Reader
  end # Prompt
end # TTY