require 'ostruct'
require 'set'

require 'fig/logging'

# Copies files from the project directories in FIG_HOME to the user's working
# directory. It keeps track of which files have already been copied, and which
# package/versions they came from, and deletes files as necessary to ensure
# that we never have files from two different versions of the same package in
# the user's working directory.
class Retriever
  def initialize(base_dir)
    @base_dir = base_dir
    @configs = {}
    @fig_dir = File.join(@base_dir, '.fig')

    file = File.join(@fig_dir, 'retrieve')
    if File.exist?(file)
      load(file)
    end
  end

  def with_package_config(name, version)
    if name and version
      @config = @configs[name]
      if @config && @config.version != version
        @config.files.each do |relpath|
          Fig::Logging.info "- [#{@config.name}/#{@config.version}] #{relpath}"
          FileUtils.rm_f(File.join(@base_dir, relpath))
        end
        @config = nil
      end
      if not @config
        @config = new_package_config(name, version)
        @configs[name] = @config
      end
    else
      @config = nil
    end
    yield
  end

  def retrieve(source, relpath)
    copy(source, relpath)
  end

  def save
    FileUtils.mkdir_p(@fig_dir)
    File.open(File.join(@fig_dir, 'retrieve'), 'w') do |f|
      @configs.each do |name,config|
        config.files.each do |target|
          f << target << '=' << config.name << '/' << config.version << "\n"
        end
      end
    end
  end

  private

  def load(file)
    File.open(file).each_line do |line|
      line = line.strip()
      if line =~ /^(.+)=(.+)\/(.+)$/
        target = $1
        config_name = $2
        config_version = $3
        config = @configs[config_name]
        if config
          if config.version != config_version
            raise 'version mismatch in .figretrieve'
          end
        else
          config = new_package_config(config_name, config_version)
          @configs[config_name] = config
        end
        config.files << target
      else
        raise "parse error in #{file}: #{line}"
      end
    end
  end

  def new_package_config(name, version)
    config = OpenStruct.new
    config.name = name
    config.version = version
    config.files = Set.new()
    return config
  end

  def copy(source, relpath)
    target = File.join(@base_dir, relpath)
    if File.directory?(source)
      FileUtils.mkdir_p(target)
      Dir.foreach(source) do |child|
        if child != '.' and child != '..'
          source_file = File.join(source, child)
          target_file = File.join(relpath, child)
          Fig::Logging.debug "Copying #{source_file} to #{target_file}."
          copy(source_file, target_file)
        end
      end
    else
      if !File.exist?(target) || File.mtime(source) > File.mtime(target)
        if Fig::Logging.debug?
          Fig::Logging.debug "Copying package [#{@config.name}/#{@config.version}] from #{source} to #{target}."
        else
          Fig::Logging.info "+ [#{@config.name}/#{@config.version}] #{relpath}"
        end
        FileUtils.mkdir_p(File.dirname(target))

        FileUtils.cp(source, target, :preserve => true)
      end
      @config.files << relpath if @config
    end
  end
end