lib/molinillo/dependency_graph.rb
# frozen_string_literal: true
require 'tsort'
require_relative 'dependency_graph/log'
require_relative 'dependency_graph/vertex'
module Molinillo
# A directed acyclic graph that is tuned to hold named dependencies
class DependencyGraph
include Enumerable
# Enumerates through the vertices of the graph.
# @return [Array<Vertex>] The graph's vertices.
def each
return vertices.values.each unless block_given?
vertices.values.each { |v| yield v }
end
include TSort
# @!visibility private
alias tsort_each_node each
# @!visibility private
def tsort_each_child(vertex, &block)
vertex.successors.each(&block)
end
# Topologically sorts the given vertices.
# @param [Enumerable<Vertex>] vertices the vertices to be sorted, which must
# all belong to the same graph.
# @return [Array<Vertex>] The sorted vertices.
def self.tsort(vertices)
TSort.tsort(
lambda { |b| vertices.each(&b) },
lambda { |v, &b| (v.successors & vertices).each(&b) }
)
end
# A directed edge of a {DependencyGraph}
# @attr [Vertex] origin The origin of the directed edge
# @attr [Vertex] destination The destination of the directed edge
# @attr [Object] requirement The requirement the directed edge represents
Edge = Struct.new(:origin, :destination, :requirement)
# @return [{String => Vertex}] the vertices of the dependency graph, keyed
# by {Vertex#name}
attr_reader :vertices
# @return [Log] the op log for this graph
attr_reader :log
# Initializes an empty dependency graph
def initialize
@vertices = {}
@log = Log.new
end
# Tags the current state of the dependency as the given tag
# @param [Object] tag an opaque tag for the current state of the graph
# @return [Void]
def tag(tag)
log.tag(self, tag)
end
# Rewinds the graph to the state tagged as `tag`
# @param [Object] tag the tag to rewind to
# @return [Void]
def rewind_to(tag)
log.rewind_to(self, tag)
end
# Initializes a copy of a {DependencyGraph}, ensuring that all {#vertices}
# are properly copied.
# @param [DependencyGraph] other the graph to copy.
def initialize_copy(other)
super
@vertices = {}
@log = other.log.dup
traverse = lambda do |new_v, old_v|
return if new_v.outgoing_edges.size == old_v.outgoing_edges.size
old_v.outgoing_edges.each do |edge|
destination = add_vertex(edge.destination.name, edge.destination.payload)
add_edge_no_circular(new_v, destination, edge.requirement)
traverse.call(destination, edge.destination)
end
end
other.vertices.each do |name, vertex|
new_vertex = add_vertex(name, vertex.payload, vertex.root?)
new_vertex.explicit_requirements.replace(vertex.explicit_requirements)
traverse.call(new_vertex, vertex)
end
end
# @return [String] a string suitable for debugging
def inspect
"#{self.class}:#{vertices.values.inspect}"
end
# @param [Hash] options options for dot output.
# @return [String] Returns a dot format representation of the graph
def to_dot(options = {})
edge_label = options.delete(:edge_label)
raise ArgumentError, "Unknown options: #{options.keys}" unless options.empty?
dot_vertices = []
dot_edges = []
vertices.each do |n, v|
dot_vertices << " #{n} [label=\"{#{n}|#{v.payload}}\"]"
v.outgoing_edges.each do |e|
label = edge_label ? edge_label.call(e) : e.requirement
dot_edges << " #{e.origin.name} -> #{e.destination.name} [label=#{label.to_s.dump}]"
end
end
dot_vertices.uniq!
dot_vertices.sort!
dot_edges.uniq!
dot_edges.sort!
dot = dot_vertices.unshift('digraph G {').push('') + dot_edges.push('}')
dot.join("\n")
end
# @param [DependencyGraph] other
# @return [Boolean] whether the two dependency graphs are equal, determined
# by a recursive traversal of each {#root_vertices} and its
# {Vertex#successors}
def ==(other)
return false unless other
return true if equal?(other)
vertices.each do |name, vertex|
other_vertex = other.vertex_named(name)
return false unless other_vertex
return false unless vertex.payload == other_vertex.payload
return false unless other_vertex.successors.to_set == vertex.successors.to_set
end
end
# @param [String] name
# @param [Object] payload
# @param [Array<String>] parent_names
# @param [Object] requirement the requirement that is requiring the child
# @return [void]
def add_child_vertex(name, payload, parent_names, requirement)
root = !parent_names.delete(nil) { true }
vertex = add_vertex(name, payload, root)
vertex.explicit_requirements << requirement if root
parent_names.each do |parent_name|
parent_vertex = vertex_named(parent_name)
add_edge(parent_vertex, vertex, requirement)
end
vertex
end
# Adds a vertex with the given name, or updates the existing one.
# @param [String] name
# @param [Object] payload
# @return [Vertex] the vertex that was added to `self`
def add_vertex(name, payload, root = false)
log.add_vertex(self, name, payload, root)
end
# Detaches the {#vertex_named} `name` {Vertex} from the graph, recursively
# removing any non-root vertices that were orphaned in the process
# @param [String] name
# @return [Array<Vertex>] the vertices which have been detached
def detach_vertex_named(name)
log.detach_vertex_named(self, name)
end
# @param [String] name
# @return [Vertex,nil] the vertex with the given name
def vertex_named(name)
vertices[name]
end
# @param [String] name
# @return [Vertex,nil] the root vertex with the given name
def root_vertex_named(name)
vertex = vertex_named(name)
vertex if vertex && vertex.root?
end
# Adds a new {Edge} to the dependency graph
# @param [Vertex] origin
# @param [Vertex] destination
# @param [Object] requirement the requirement that this edge represents
# @return [Edge] the added edge
def add_edge(origin, destination, requirement)
if destination.path_to?(origin)
raise CircularDependencyError.new(path(destination, origin))
end
add_edge_no_circular(origin, destination, requirement)
end
# Deletes an {Edge} from the dependency graph
# @param [Edge] edge
# @return [Void]
def delete_edge(edge)
log.delete_edge(self, edge.origin.name, edge.destination.name, edge.requirement)
end
# Sets the payload of the vertex with the given name
# @param [String] name the name of the vertex
# @param [Object] payload the payload
# @return [Void]
def set_payload(name, payload)
log.set_payload(self, name, payload)
end
private
# Adds a new {Edge} to the dependency graph without checking for
# circularity.
# @param (see #add_edge)
# @return (see #add_edge)
def add_edge_no_circular(origin, destination, requirement)
log.add_edge_no_circular(self, origin.name, destination.name, requirement)
end
# Returns the path between two vertices
# @raise [ArgumentError] if there is no path between the vertices
# @param [Vertex] from
# @param [Vertex] to
# @return [Array<Vertex>] the shortest path from `from` to `to`
def path(from, to)
distances = Hash.new(vertices.size + 1)
distances[from.name] = 0
predecessors = {}
each do |vertex|
vertex.successors.each do |successor|
if distances[successor.name] > distances[vertex.name] + 1
distances[successor.name] = distances[vertex.name] + 1
predecessors[successor] = vertex
end
end
end
path = [to]
while before = predecessors[to]
path << before
to = before
break if to == from
end
unless path.last.equal?(from)
raise ArgumentError, "There is no path from #{from.name} to #{to.name}"
end
path.reverse
end
end
end