lighttroupe/luz

#
# History implements a basic browser-like forward/backward history with change notification.
#
require 'callbacks'

class History
    callback :navigation

    def initialize
        @list = []
        @index = -1
    end

    #
    # Status
    #
    def can_go_back?
        @index > 0
    end

    def current?
        @index > -1
    end

    def current
        @list[@index] if current?
    end

    def can_go_forward?
        @index < (@list.size - 1)
    end

    #
    # Navigation
    #
    def back!
        if can_go_back?
            @index -= 1
            navigation_notify(current)
            true
        end
    end

    def forward!
        if can_go_forward?
            @index += 1
            navigation_notify(current)
            true
        end
    end

    #
    # Manipulation
    #
    def add(item)
        @index += 1
        @list[@index] = item
        @list = @list.first(@index+1)        # chop off all history after this index
    end

    def remove(item)
        return unless (index = @list.index(item))
        @index -= 1 if index <= @index
        @list.delete(item)
    end
end