class RGL::BellmanFordAlgorithm

def init(source)
  @visitor.set_source(source)
end

def initialize(graph, edge_weights_map, visitor)
  @graph            = graph
  @edge_weights_map = EdgePropertiesMap.new(edge_weights_map, @graph.directed?)
  @visitor          = visitor
end

def relax_edge(u, v)
  @visitor.handle_examine_edge(u, v)
  new_v_distance = @visitor.distance_map[u] + @edge_weights_map.edge_property(u, v)
  if new_v_distance < @visitor.distance_map[v]
    @visitor.distance_map[v] = new_v_distance
    @visitor.parents_map[v]  = u
    @visitor.handle_edge_relaxed(u, v)
  else
    @visitor.handle_edge_not_relaxed(u, v)
  end
end

def relax_edges
  (@graph.size - 1).times do
    @graph.each_edge do |u, v|
      relax_edge(u, v)
      relax_edge(v, u) unless @graph.directed?
    end
  end
  @graph.each_edge do |u, v|
    if @visitor.distance_map[u] + @edge_weights_map.edge_property(u, v) < @visitor.distance_map[v]
      @visitor.handle_edge_not_minimized(u, v)
    else
      @visitor.handle_edge_minimized(u, v)
    end
  end
end

def shortest_paths(source)
  init(source)
  relax_edges
  PathBuilder.new(source, @visitor.parents_map).paths(@graph.vertices)
end