require 'zlib'
require 'json'

module Gitlab
  module Ci
    module Build
      module Artifacts
        class Metadata
          class ParserError < StandardError; end

          VERSION_PATTERN = /^[\w\s]+(\d+\.\d+\.\d+)/
          INVALID_PATH_PATTERN = %r{(^\.?\.?/)|(/\.?\.?/)}

          attr_reader :file, :path, :full_version

          def initialize(file, path)
            @file, @path = file, path
            @full_version = read_version
          end

          def version
            @full_version.match(VERSION_PATTERN)[1]
          end

          def errors
            gzip do |gz|
              read_string(gz) # version
              errors = read_string(gz)
              raise ParserError, 'Errors field not found!' unless errors

              begin
                JSON.parse(errors)
              rescue JSON::ParserError
                raise ParserError, 'Invalid errors field!'
              end
            end
          end

          def find_entries!
            gzip do |gz|
              2.times { read_string(gz) } # version and errors fields
              match_entries(gz)
            end
          end

          def to_entry
            entries = find_entries!
            Entry.new(@path, entries)
          end

          private

          def match_entries(gz)
            entries = {}
            match_pattern = %r{^#{Regexp.escape(@path)}[^/]*/?$}

            until gz.eof? do
              begin
                path = read_string(gz).force_encoding('UTF-8')
                meta = read_string(gz).force_encoding('UTF-8')
               
                next unless path.valid_encoding? && meta.valid_encoding?
                next unless path =~ match_pattern
                next if path =~ INVALID_PATH_PATTERN

                entries[path] = JSON.parse(meta, symbolize_names: true)
              rescue JSON::ParserError, Encoding::CompatibilityError
                next
              end
            end

            entries
          end

          def read_version
            gzip do |gz|
              version_string = read_string(gz)

              unless version_string
                raise ParserError, 'Artifacts metadata file empty!'
              end

              unless version_string =~ VERSION_PATTERN
                raise ParserError, 'Invalid version!'
              end

              version_string.chomp
            end
          end

          def read_uint32(gz)
            binary = gz.read(4)
            binary.unpack('L>')[0] if binary
          end

          def read_string(gz)
            string_size = read_uint32(gz)
            return nil unless string_size
            gz.read(string_size)
          end

          def gzip(&block)
            Zlib::GzipReader.open(@file, &block)
          end
        end
      end
    end
  end
end