require 'mj/tools/subprocess'

module BuildTool

    #
    # Encapsulates all environment related options for a build
    #
    class Environment

        include MJ::Tools::SubProcess

        # Name for the environment
        attr_reader :name

        # Parent environment
        attr_accessor :parent

        attr_accessor :feature

        # Create a environment object
        def initialize( name )
            raise StandardError.new "Environment.name has to be set" if name.nil?
            @name = name
            @vars = Hash.new
            @parent = nil
            @feature = nil
        end

        def active?
            if @feature.nil?
                true
            else
                @feature.active?
            end
        end


        # Set a environment variable
        def append( name, value )
            if @vars.has_key?(name.to_s) and !@vars[name.to_s].empty?
                @vars[name.to_s] = "#{@vars[name.to_s]}:#{value.to_s}"
            else
                set( name, "$#{name.to_s}:#{value}" )
            end
        end

        # Execute command in a shell with the environment set.
        def execute( command, wd = nil, envadd = nil )
            env = Hash.new
            for var in vars do
                env[var] = self[var]
            end
            env.merge!( envadd ) if envadd
            return self.class.execute( command.to_s, wd, env )
        end

        # Prepend +value+ to variable +name+. A ':' is added when necessary.
        def prepend( name, value )
            if @vars.has_key?(name.to_s) and !@vars[name.to_s].empty?
                @vars[name.to_s] = "#{value.to_s}:#{@vars[name.to_s]}"
            else
                set( name, "#{value}:$#{name.to_s}" )
            end
        end

        def set( name, value )
            @vars[name.to_s] = value.to_s
        end

        # Open a shell with the environment set.
        #
        # It sets an environment variable *BUILD_TOOL_ENV* with the name of
        # the environment set. This can be used to add this information to
        # the prompt.
        def shell( wd = nil )
            begin
                ENV['BUILD_TOOL_ENV'] = name
                self.class.adjust_environment( wd, values ) {
                    logger.info "Starting #{ENV['SHELL']}"
                    system( ENV['SHELL'] )
                    logger.info "#{ENV['SHELL']} stopped."
                    return 0;
                }
            ensure
                ENV['BUILD_TOOL_ENV'] = nil
            end
        end

        def vars
            if @parent
                ( @vars.keys + @parent.vars ).uniq
            else
                @vars.keys
            end
        end

        def values
            vals = {}
            vars.each do |var|
                vals[var] = self[var]
            end
            vals
        end

        # Get the value of a environment variable
        def []( name )
            parentval = ""
            # Get the value from the parent
            if @parent
                parentval = @parent[name]
            end
            # If we don't know the var or the env is not active return the parents value
            if !@vars.has_key?( name.to_s ) or !active?
                return parentval
            end
            if parentval.empty?
                val = @vars[name.to_s].sub( ":$#{name.to_s}:", "" )
                val.sub!( ":$#{name.to_s}", "" )
                val.sub!( "$#{name.to_s}:", "" )
                return val
            else
                return @vars[name.to_s].sub( "$#{name.to_s}", parentval )
            end
        end

        def to_s
            "Environment: #{name}"
        end

    end # class Environment

end # module BuildTool