svn/view/buffer.rb


module Edmaru
  
  #The instance of this class represents one string sequence.
  class Buffer
    
    #Create a new buffer.
    #
    #=== Argument
    #_name_ :: The unique title of this buffer.
    #
    #=== Return
    #An initialized buffer.
    def initialize(name)
      @name = name
      @lines = Array.new
      @lines.push("")
    end

    #The name of this buffer.
    #
    #=== Return
    #The name of this buffer.
    def name
      @name
    end

    #All lines in this buffer.
    #
    #=== Return
    #An array of string.
    #Each element represents one line of this buffer.
    def lines
      @lines
    end

    #Check if the specified position is valid for this buffer.
    #
    #=== Arguments
    #
    #_row_ :: Row position or line number.
    #_col_ :: Column position.
    #
    #=== Return
    #_true_ if the specified position is valid for this buffer.
    #
    #=== Note
    #
    #The position is between two adjacent characters including line
    #feed character. Thus, this method returns true if _col_ is equal
    #to the size of the specified line, but false if _row_ is equal to
    #the size of Edmaru::Buffer#lines.
    def valid_position?(row, col)
      if row < 0 || row >= @lines.size
        # Invalid row position.
        return false
      elsif col < 0 || col > @lines[row].size
        # Invalid column position.
        return false
      else
        return true
      end
    end

    #Insert the specified string to the specified position
    #
    #=== Arguments
    #
    #_row_ :: Row position or line number.
    #_col_ :: Column position.
    #_str_ :: A string to be inserted.
    def insert(row, col, str)
      if !valid_position?(row, col)
        raise "Invalid position was specified for 'insert' method."
      end

      if str.empty?
        # Nothing to be inserted.
        return
      end

      if str.include?("\n")
        new_lines = str.split(/\n/, -1)
        new_lines[0] =
          @lines[row][0, col] + new_lines[0]
        new_lines[new_lines.size - 1] <<
          @lines[row][col .. -1]
        @lines[row] = new_lines
        @lines.flatten!
      else
        current_line = @lines[row]
        @lines[row] = ""
        if col > 0
          @lines[row] = current_line[0, col]
        end
        @lines[row] << str
        @lines[row] << current_line[col .. -1]
      end
    end

    #Append the specified string to the end of this buffer.
    #
    #=== Argument
    #
    #_str_ :: A string to be appended.
    def append(str)
      row = @lines.size - 1
      insert(row, @lines[row].size, str)
    end

    #Delete all characters in this buffer to make it empty.
    def clear
      @lines.clear
      @lines.push("")
      nil
    end
  end
end