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# frozen_string_literal: false
require 'set'
require 'tsort'
module Gem::Resolver::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
vertices.values.each { |v| yield v }
end
include TSort
alias_method :tsort_each_node, :each
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
def initialize
@vertices = {}
end
# Initializes a copy of a {DependencyGraph}, ensuring that all {#vertices}
# are properly copied.
def initialize_copy(other)
super
@vertices = {}
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
# @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
vertices.each do |name, vertex|
other_vertex = other.vertex_named(name)
return false unless other_vertex
return false unless other_vertex.successors.map(&:name).to_set == vertex.successors.map(&:name).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)
vertex = add_vertex(name, payload)
parent_names.each do |parent_name|
unless parent_name
vertex.root = true
next
end
parent_node = vertex_named(parent_name)
add_edge(parent_node, vertex, requirement)
end
vertex
end
# @param [String] name
# @param [Object] payload
# @return [Vertex] the vertex that was added to `self`
def add_vertex(name, payload, root = false)
vertex = vertices[name] ||= Vertex.new(name, payload)
vertex.payload ||= payload
vertex.root ||= root
vertex
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 [void]
def detach_vertex_named(name)
return unless vertex = vertices.delete(name)
vertex.outgoing_edges.each do |e|
v = e.destination
v.incoming_edges.delete(e)
detach_vertex_named(v.name) unless v.root? || v.predecessors.any?
end
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([origin, destination])
end
add_edge_no_circular(origin, destination, requirement)
end
private
def add_edge_no_circular(origin, destination, requirement)
edge = Edge.new(origin, destination, requirement)
origin.outgoing_edges << edge
destination.incoming_edges << edge
edge
end
# A vertex in a {DependencyGraph} that encapsulates a {#name} and a
# {#payload}
class Vertex
# @return [String] the name of the vertex
attr_accessor :name
# @return [Object] the payload the vertex holds
attr_accessor :payload
# @return [Arrary<Object>] the explicit requirements that required
# this vertex
attr_reader :explicit_requirements
# @return [Boolean] whether the vertex is considered a root vertex
attr_accessor :root
alias_method :root?, :root
# @param [String] name see {#name}
# @param [Object] payload see {#payload}
def initialize(name, payload)
@name = name
@payload = payload
@explicit_requirements = []
@outgoing_edges = []
@incoming_edges = []
end
# @return [Array<Object>] all of the requirements that required
# this vertex
def requirements
incoming_edges.map(&:requirement) + explicit_requirements
end
# @return [Array<Edge>] the edges of {#graph} that have `self` as their
# {Edge#origin}
attr_accessor :outgoing_edges
# @return [Array<Edge>] the edges of {#graph} that have `self` as their
# {Edge#destination}
attr_accessor :incoming_edges
# @return [Array<Vertex>] the vertices of {#graph} that have an edge with
# `self` as their {Edge#destination}
def predecessors
incoming_edges.map(&:origin)
end
# @return [Array<Vertex>] the vertices of {#graph} where `self` is a
# {#descendent?}
def recursive_predecessors
vertices = predecessors
vertices += vertices.map(&:recursive_predecessors).flatten(1)
vertices.uniq!
vertices
end
# @return [Array<Vertex>] the vertices of {#graph} that have an edge with
# `self` as their {Edge#origin}
def successors
outgoing_edges.map(&:destination)
end
# @return [Array<Vertex>] the vertices of {#graph} where `self` is an
# {#ancestor?}
def recursive_successors
vertices = successors
vertices += vertices.map(&:recursive_successors).flatten(1)
vertices.uniq!
vertices
end
# @return [String] a string suitable for debugging
def inspect
"#{self.class}:#{name}(#{payload.inspect})"
end
# @return [Boolean] whether the two vertices are equal, determined
# by a recursive traversal of each {Vertex#successors}
def ==(other)
shallow_eql?(other) &&
successors.to_set == other.successors.to_set
end
# @return [Boolean] whether the two vertices are equal, determined
# solely by {#name} and {#payload} equality
def shallow_eql?(other)
other &&
name == other.name &&
payload == other.payload
end
alias_method :eql?, :==
# @return [Fixnum] a hash for the vertex based upon its {#name}
def hash
name.hash
end
# Is there a path from `self` to `other` following edges in the
# dependency graph?
# @return true iff there is a path following edges within this {#graph}
def path_to?(other)
equal?(other) || successors.any? { |v| v.path_to?(other) }
end
alias_method :descendent?, :path_to?
# Is there a path from `other` to `self` following edges in the
# dependency graph?
# @return true iff there is a path following edges within this {#graph}
def ancestor?(other)
other.path_to?(self)
end
alias_method :is_reachable_from?, :ancestor?
end
end
end
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