class Bundler::Resolver

def self.resolve(requirements, index, source_requirements = {}, base = [])
  Bundler.ui.info "Resolving dependencies...", false
  base = SpecSet.new(base) unless base.is_a?(SpecSet)
  resolver = new(index, source_requirements, base)
  result = resolver.start(requirements)
  Bundler.ui.info "" # new line now that dots are done
  SpecSet.new(result)
rescue => e
  Bundler.ui.info "" # new line before the error
  raise e
end

def activate_gem(reqs, activated, requirement, current)
  requirement.required_by.replace current.required_by
  requirement.required_by << current
  activated[requirement.name] = requirement
  debug { "  Activating: #{requirement.name} (#{requirement.version})" }
  debug { requirement.required_by.map { |d| "    * #{d.name} (#{d.requirement})" }.join("\n") }
  dependencies = requirement.activate_platform(current.__platform)
  debug { "    Dependencies"}
  dependencies.each do |dep|
    next if dep.type == :development
    dep.required_by.replace(current.required_by)
    dep.required_by << current
    @gems_size[dep] ||= gems_size(dep)
    reqs << dep
  end
end

def clean_req(req)
  if req.to_s.include?(">= 0")
    req.to_s.gsub(/ \(.*?\)$/, '')
  else
    req.to_s.gsub(/\, (runtime|development)\)$/, ')')
  end
end

def clear_search_cache
  @deps_for = {}
end

def debug
  if ENV['DEBUG_RESOLVER']
    debug_info = yield
    debug_info = debug_info.inspect unless debug_info.is_a?(String)
    $stderr.puts debug_info
  end
end

def dependency_tree(m, requirements)
  requirements.each_with_index do |i, j|
    m << "    " << ("  " * j)
    m << "#{clean_req(i)}"
    m << " depends on\n"
  end
  m << "    " << ("  " * requirements.size)
end

def error_message
  errors.inject("") do |o, (conflict, (origin, requirement))|
    # origin is the SpecSet of specs from the Gemfile that is conflicted with
    if origin
      o << %{Bundler could not find compatible versions for gem "#{origin.name}":\n}
      o << "  In Gemfile:\n"
      required_by = requirement.required_by
      o << gem_message(requirement, required_by)
      # If the origin is "bundler", the conflict is us
      if origin.name == "bundler"
        o << "  Current Bundler version:\n"
        other_bundler_required = !requirement.requirement.satisfied_by?(origin.version)
      # If the origin is a LockfileParser, it does not respond_to :required_by
      elsif !origin.respond_to?(:required_by) || !(origin.required_by.first)
        o << "  In snapshot (Gemfile.lock):\n"
      end
      required_by = origin.required_by[0..-2]
      o << gem_message(origin, required_by)
      # If the bundle wants a newer bundler than the running bundler, explain
      if origin.name == "bundler" && other_bundler_required
        o << "This Gemfile requires a different version of Bundler.\n"
        o << "Perhaps you need to update Bundler by running `gem install bundler`?"
      end
    # origin is nil if the required gem and version cannot be found in any of
    # the specified sources
    else
      # if the gem cannot be found because of a version conflict between lockfile and gemfile,
      # print a useful error that suggests running `bundle update`, which may fix things
      #
      # @base is a SpecSet of the gems in the lockfile
      # conflict is the name of the gem that could not be found
      if locked = @base[conflict].first
        o << "Bundler could not find compatible versions for gem #{conflict.inspect}:\n"
        o << "  In snapshot (Gemfile.lock):\n"
        o << "    #{clean_req(locked)}\n\n"
        o << "  In Gemfile:\n"
        required_by = requirement.required_by
        o << gem_message(requirement, required_by)
        o << "Running `bundle update` will rebuild your snapshot from scratch, using only\n"
        o << "the gems in your Gemfile, which may resolve the conflict.\n"
      # the rest of the time, the gem cannot be found because it does not exist in the known sources
      else
        if requirement.required_by.first
          o << "Could not find gem '#{clean_req(requirement)}', which is required by "
          o << "gem '#{clean_req(requirement.required_by.first)}', in any of the sources."
        else
          o << "Could not find gem '#{clean_req(requirement)} in any of the sources\n"
        end
      end
    end
    o
  end
end

def find_conflict_state(conflict, states)
  return unless conflict
  until states.empty? do
    state = states.pop
    return state if conflict.name == state.name
  end
end

def find_state(current, states)
  states.detect { |i| current && current.name == i.name }
end

def gem_message(requirement, required_by=[])
  m = ""
  # A requirement that is required by itself is actually in the Gemfile, and does
  # not "depend on" itself
  if requirement.required_by.first && requirement.required_by.first.name != requirement.name
    dependency_tree(m, required_by)
    m << "#{clean_req(requirement)}\n"
  else
    m << "    #{clean_req(requirement)}\n"
  end
  m << "\n"
end

def gems_size(dep)
  search(dep).size
end

def handle_conflict(current, states, existing=nil)
  until current.nil? && existing.nil?
    current_state = find_state(current, states)
    existing_state = find_state(existing, states)
    return current if state_any?(current_state)
    return existing if state_any?(existing_state)
    existing = existing.required_by.last if existing
    current = current.required_by.last if current
  end
end

def indicate_progress
  @iteration_counter += 1
  if iteration_rate.nil?
    if ((Time.now - started_at) % 3600).round >= 1
      @iteration_rate = iteration_counter
    end
  else
    if ((iteration_counter % iteration_rate) == 0)
      Bundler.ui.info ".", false
    end
  end
end

def initialize(index, source_requirements, base)
  @errors               = {}
  @base                 = base
  @index                = index
  @deps_for             = {}
  @missing_gems         = Hash.new(0)
  @source_requirements  = source_requirements
  @iteration_counter    = 0
  @started_at           = Time.now
end

def other_possible?(conflict, states)
  return unless conflict
  state = states.detect { |i| i.name == conflict.name }
  state && state.possibles.any?
end

def resolve(reqs, activated)
  states = []
  depth = 0
  conflicts = Set.new
  until reqs.empty?
    indicate_progress
    debug { print "\e[2J\e[f" ; "==== Iterating ====\n\n" }
    reqs = reqs.sort_by do |a|
      [ activated[a.name] ? 0 : 1,
        a.requirement.prerelease? ? 0 : 1,
        @errors[a.name]   ? 0 : 1,
        activated[a.name] ? 0 : @gems_size[a] ]
    end
    debug { "Activated:\n" + activated.values.map {|a| "  #{a}" }.join("\n") }
    debug { "Requirements:\n" + reqs.map {|r| "  #{r}"}.join("\n") }
    current = reqs.shift
    $stderr.puts "#{' ' * depth}#{current}" if ENV['DEBUG_RESOLVER_TREE']
    debug { "Attempting:\n  #{current}"}
    existing = activated[current.name]
    if existing || current.name == 'bundler'
      # Force the current
      if current.name == 'bundler' && !existing
        existing = search(DepProxy.new(Gem::Dependency.new('bundler', VERSION), Gem::Platform::RUBY)).first
        raise GemNotFound, %Q{Bundler could not find gem "bundler" (#{VERSION})} unless existing
        existing.required_by << existing
        activated['bundler'] = existing
      end
      if current.requirement.satisfied_by?(existing.version)
        debug { "    * [SUCCESS] Already activated" }
        @errors.delete(existing.name)
        dependencies = existing.activate_platform(current.__platform)
        reqs.concat dependencies
        dependencies.each do |dep|
          next if dep.type == :development
          @gems_size[dep] ||= gems_size(dep)
        end
        depth += 1
        next
      else
        debug { "    * [FAIL] Already activated" }
        @errors[existing.name] = [existing, current]
        conflicts << current.name
        parent = current.required_by.last
        if existing.respond_to?(:required_by)
          parent = handle_conflict(current, states, existing.required_by[-2]) unless other_possible?(parent, states)
        else
          parent = handle_conflict(current, states) unless other_possible?(parent, states)
        end
        if parent.nil? && !conflicts.empty?
          parent = states.reverse.detect { |i| conflicts.include?(i.name) && state_any?(i)}
        end
        raise version_conflict if parent.nil? || parent.name == 'bundler'
        reqs, activated, depth, conflicts = resolve_conflict(parent, states)
      end
    else
      matching_versions = search(current)
      # If we found no versions that match the current requirement
      if matching_versions.empty?
        # If this is a top-level Gemfile requirement
        if current.required_by.empty?
          if base = @base[current.name] and !base.empty?
            version = base.first.version
            message = "You have requested:\n" \
              "  #{current.name} #{current.requirement}\n\n" \
              "The bundle currently has #{current.name} locked at #{version}.\n" \
              "Try running `bundle update #{current.name}`"
          elsif current.source
            name = current.name
            versions = @source_requirements[name][name].map { |s| s.version }
            message  = "Could not find gem '#{current}' in #{current.source}.\n"
            if versions.any?
              message << "Source contains '#{name}' at: #{versions.join(', ')}"
            else
              message << "Source does not contain any versions of '#{current}'"
            end
          else
            message = "Could not find gem '#{current}' "
            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
          # This is not a top-level Gemfile requirement
        else
          @errors[current.name] = [nil, current]
          parent = handle_conflict(current, states)
          reqs, activated, depth = resolve_conflict(parent, states)
          next
        end
      end
      state = State.new(reqs.dup, activated.dup, current, matching_versions, depth, conflicts)
      states << state
      requirement = state.possibles.pop
      activate_gem(reqs, activated, requirement, current)
    end
  end
  successify(activated)
end

def resolve_conflict(current, states)
  # Find the state where the conflict has occurred
  state = find_conflict_state(current, states)
  debug { "    -> Going to: #{current.name} state" } if current
  # Resolve the conflicts by rewinding the state
  # when the conflicted gem was activated
  reqs, activated, depth, conflicts = resolve_for_conflict(state)
  # Keep the state around if it still has other possibilities
  states << state unless state.possibles.empty?
  clear_search_cache
  return reqs, activated, depth, conflicts
end

def resolve_for_conflict(state)
  raise version_conflict if state.nil? || state.possibles.empty?
  reqs, activated, depth, conflicts = state.reqs.dup, state.activated.dup, state.depth, state.conflicts.dup
  requirement = state.requirement
  possible = state.possibles.pop
  activate_gem(reqs, activated, possible, requirement)
  return reqs, activated, depth, conflicts
end

def search(dep)
  if base = @base[dep.name] and base.any?
    reqs = [dep.requirement.as_list, base.first.version.to_s].flatten.compact
    d = Gem::Dependency.new(base.first.name, *reqs)
  else
    d = dep.dep
  end
  @deps_for[d.hash] ||= begin
    index = @source_requirements[d.name] || @index
    results = index.search(d, @base[d.name])
    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
      deps = nested.map{|a| SpecGroup.new(a) }.select{|sg| sg.for?(dep.__platform) }
    else
      deps = []
    end
  end
end

def start(reqs)
  activated = {}
  @gems_size = Hash[reqs.map { |r| [r, gems_size(r)] }]
  resolve(reqs, activated)
end

def state_any?(state)
  state && state.possibles.any?
end

def successify(activated)
  activated.values.map { |s| s.to_specs }.flatten.compact
end

def version_conflict
  VersionConflict.new(errors.keys, error_message)
end