class Bundler::Resolver

def self.resolve(requirements, index, source_requirements = {}, base = [])
  base = SpecSet.new(base) unless base.is_a?(SpecSet)
  resolver = new(index, source_requirements, base)
  result = resolver.start(requirements)
  SpecSet.new(result)
end

def after_resolution
  Bundler.ui.info ''
end

def before_resolution
  Bundler.ui.info 'Resolving dependencies...', false
end

def debug(depth = 0)
  if debug?
    debug_info = yield
    debug_info = debug_info.inspect unless debug_info.is_a?(String)
    STDERR.puts debug_info.split("\n").map { |s| '  ' * depth + s }
  end
end

def debug?
  ENV['DEBUG_RESOLVER'] || ENV['DEBUG_RESOLVER_TREE']
end

def dependencies_for(specification)
  specification.dependencies_for_activated_platforms
end

def indicate_progress
  Bundler.ui.info '.', false
end

def initialize(index, source_requirements, base)
  @index = index
  @source_requirements = source_requirements
  @base = base
  @resolver = Molinillo::Resolver.new(self, self)
  @search_for = {}
  @prereleases_cache = Hash.new { |h,k| h[k] = k.prerelease? }
  @base_dg = Molinillo::DependencyGraph.new
  @base.each { |ls| @base_dg.add_root_vertex ls.name, Dependency.new(ls.name, ls.version) }
end

def name_for(dependency)
  dependency.name
end

def name_for_explicit_dependency_source
  'Gemfile'
end

def name_for_locking_dependency_source
  'Gemfile.lock'
end

def requirement_satisfied_by?(requirement, activated, spec)
  requirement.matches_spec?(spec)
end

def search_for(dependency)
  platform = dependency.__platform
  dependency = dependency.dep unless dependency.is_a? Gem::Dependency
  search = @search_for[dependency] ||= begin
    index = @source_requirements[dependency.name] || @index
    results = index.search(dependency, @base[dependency.name])
    if vertex = @base_dg.vertex_named(dependency.name)
      locked_requirement = vertex.payload.requirement
    end
    if results.any?
      version = results.first.version
      nested  = [[]]
      results.each do |spec|
        if spec.version != version
          nested << []
          version = spec.version
        end
        nested.last << spec
      end
      groups = nested.map { |a| SpecGroup.new(a) }
      !locked_requirement ? groups : groups.select { |sg| locked_requirement.satisfied_by? sg.version }
    else
      []
    end
  end
  search.select { |sg| sg.for?(platform) }.each { |sg| sg.activate_platform(platform) }
end

def sort_dependencies(dependencies, activated, conflicts)
  dependencies.sort_by do |dependency|
    name = name_for(dependency)
    [
      activated.vertex_named(name).payload ? 0 : 1,
      @prereleases_cache[dependency.requirement] ? 0 : 1,
      conflicts[name] ? 0 : 1,
      activated.vertex_named(name).payload ? 0 : search_for(dependency).count,
    ]
  end
end

def start(requirements)
  verify_gemfile_dependencies_are_found!(requirements)
  dg = @resolver.resolve(requirements, @base_dg)
  dg.map(&:payload).map(&:to_specs).flatten
rescue Molinillo::VersionConflict => e
  raise VersionConflict.new(e.conflicts.keys.uniq, e.message)
rescue Molinillo::CircularDependencyError => e
  names = e.dependencies.sort_by(&:name).map { |d| "gem '#{d.name}'"}
  raise CyclicDependencyError, "Your Gemfile requires gems that depend" \
    " on each other, creating an infinite loop. Please remove" \
    " #{names.count > 1 ? 'either ' : '' }#{names.join(' or ')}" \
    " and try again."
end

def verify_gemfile_dependencies_are_found!(requirements)
  requirements.each do |requirement|
    next if requirement.name == 'bundler'
    if search_for(requirement).empty?
      if base = @base[requirement.name] and !base.empty?
        version = base.first.version
        message = "You have requested:\n" \
          "  #{requirement.name} #{requirement.requirement}\n\n" \
          "The bundle currently has #{requirement.name} locked at #{version}.\n" \
          "Try running `bundle update #{requirement.name}`"
      elsif requirement.source
        name = requirement.name
        versions = @source_requirements[name][name].map { |s| s.version }
        message  = "Could not find gem '#{requirement}' in #{requirement.source}.\n"
        if versions.any?
          message << "Source contains '#{name}' at: #{versions.join(', ')}"
        else
          message << "Source does not contain any versions of '#{requirement}'"
        end
      else
        message = "Could not find gem '#{requirement}' "
        if @index.source_types.include?(Bundler::Source::Rubygems)
          message << "in any of the gem sources listed in your Gemfile."
        else
          message << "in the gems available on this machine."
        end
      end
      raise GemNotFound, message
    end
  end
end