class Bundler::Molinillo::Resolver::Resolution

def activate_spec
  conflicts.delete(name)
  debug(depth) { 'Activated ' + name + ' at ' + possibility.to_s }
  vertex = activated.vertex_named(name)
  vertex.payload = possibility
  require_nested_dependencies_for(possibility)
end

def attempt_to_activate
  debug(depth) { 'Attempting to activate ' + possibility.to_s }
  existing_node = activated.vertex_named(name)
  if existing_node.payload
    debug(depth) { "Found existing spec (#{existing_node.payload})" }
    attempt_to_activate_existing_spec(existing_node)
  else
    attempt_to_activate_new_spec
  end
end

def attempt_to_activate_existing_spec(existing_node)
  existing_spec = existing_node.payload
  if requirement_satisfied_by?(requirement, activated, existing_spec)
    new_requirements = requirements.dup
    push_state_for_requirements(new_requirements)
  else
    return if attempt_to_swap_possibility
    create_conflict
    debug(depth) { "Unsatisfied by existing spec (#{existing_node.payload})" }
    unwind_for_conflict
  end
end

def attempt_to_activate_new_spec
  satisfied = begin
    locked_requirement = locked_requirement_named(name)
    requested_spec_satisfied = requirement_satisfied_by?(requirement, activated, possibility)
    locked_spec_satisfied = !locked_requirement ||
      requirement_satisfied_by?(locked_requirement, activated, possibility)
    debug(depth) { 'Unsatisfied by requested spec' } unless requested_spec_satisfied
    debug(depth) { 'Unsatisfied by locked spec' } unless locked_spec_satisfied
    requested_spec_satisfied && locked_spec_satisfied
  end
  if satisfied
    activate_spec
  else
    create_conflict
    unwind_for_conflict
  end
end

def attempt_to_swap_possibility
  swapped = activated.dup
  swapped.vertex_named(name).payload = possibility
  return unless swapped.vertex_named(name).requirements.
      all? { |r| requirement_satisfied_by?(r, swapped, possibility) }
  attempt_to_activate_new_spec
end

def create_conflict
  vertex = activated.vertex_named(name)
  requirements = {
    name_for_explicit_dependency_source => vertex.explicit_requirements,
    name_for_locking_dependency_source => Array(locked_requirement_named(name)),
  }
  vertex.incoming_edges.each { |edge| (requirements[edge.origin.payload] ||= []).unshift(*edge.requirements) }
  conflicts[name] = Conflict.new(
    requirement,
    Hash[requirements.select { |_, r| !r.empty? }],
    vertex.payload,
    possibility,
    locked_requirement_named(name),
    requirement_trees
  )
end

def debug(depth = 0, &block)
  resolver_ui.debug(depth, &block)
end

def end_resolution
  resolver_ui.after_resolution
  debug do
    "Finished resolution (#{@iteration_counter} steps) " \
    "(Took #{(ended_at = Time.now) - @started_at} seconds) (#{ended_at})"
  end
  debug { 'Unactivated: ' + Hash[activated.vertices.reject { |_n, v| v.payload }].keys.join(', ') } if state
  debug { 'Activated: ' + Hash[activated.vertices.select { |_n, v| v.payload }].keys.join(', ') } if state
end

def find_state_for(requirement)
  return nil unless requirement
  states.reverse_each.find { |i| requirement == i.requirement && i.is_a?(DependencyState) }
end

def indicate_progress
  @iteration_counter += 1
  @progress_rate ||= resolver_ui.progress_rate
  if iteration_rate.nil?
    if Time.now - started_at >= @progress_rate
      self.iteration_rate = @iteration_counter
    end
  end
  if iteration_rate && (@iteration_counter % iteration_rate) == 0
    resolver_ui.indicate_progress
  end
end

def initial_state
  graph = DependencyGraph.new.tap do |dg|
    original_requested.each { |r| dg.add_root_vertex(name_for(r), nil).tap { |v| v.explicit_requirements << r } }
  end
  requirements = sort_dependencies(original_requested, graph, {})
  initial_requirement = requirements.shift
  DependencyState.new(
    initial_requirement && name_for(initial_requirement),
    requirements,
    graph,
    initial_requirement,
    initial_requirement && search_for(initial_requirement),
    0,
    {}
  )
end

def initialize(specification_provider, resolver_ui, requested, base)
  @specification_provider = specification_provider
  @resolver_ui = resolver_ui
  @original_requested = requested
  @base = base
  @states = []
  @iteration_counter = 0
end

def locked_requirement_named(requirement_name)
  vertex = base.vertex_named(requirement_name)
  vertex && vertex.payload
end

def parent_of(requirement)
  return nil unless requirement
  seen = false
  state = states.reverse_each.find do |s|
    seen ||= s.requirement == requirement
    seen && s.requirement != requirement && !s.requirements.include?(requirement)
  end
  state && state.requirement
end

def possibility
  possibilities.last
end

def process_topmost_state
  if possibility
    attempt_to_activate
  else
    create_conflict if state.is_a? PossibilityState
    unwind_for_conflict until possibility && state.is_a?(DependencyState)
  end
end

def push_state_for_requirements(new_requirements)
  new_requirements = sort_dependencies(new_requirements.uniq, activated, conflicts)
  new_requirement = new_requirements.shift
  states.push DependencyState.new(
    new_requirement ? name_for(new_requirement) : '',
    new_requirements,
    activated.dup,
    new_requirement,
    new_requirement ? search_for(new_requirement) : [],
    depth,
    conflicts.dup
  )
end

def require_nested_dependencies_for(activated_spec)
  nested_dependencies = dependencies_for(activated_spec)
  debug(depth) { "Requiring nested dependencies (#{nested_dependencies.map(&:to_s).join(', ')})" }
  nested_dependencies.each { |d|  activated.add_child_vertex name_for(d), nil, [name_for(activated_spec)], d }
  push_state_for_requirements(requirements + nested_dependencies)
end

def requirement_for_existing_name(name)
  return nil unless activated.vertex_named(name).payload
  states.reverse_each.find { |s| !s.activated.vertex_named(name).payload }.requirement
end