# frozen_string_literal: true

require "rubygems/resolver/api_set/gem_parser"

class Gem::CompactIndexClient
  class Parser
    # `compact_index` - an object responding to #names, #versions, #info(name, checksum),
    #                   returning the file contents as a string
    def initialize(compact_index)
      @compact_index = compact_index
      @info_checksums = nil
      @versions_by_name = nil
      @available = nil
      @gem_parser = nil
    end

    def names
      lines(@compact_index.names)
    end

    def versions
      @versions_by_name ||= Hash.new {|hash, key| hash[key] = [] }
      @info_checksums = {}

      lines(@compact_index.versions).each do |line|
        name, versions_string, checksum = line.split(" ", 3)
        @info_checksums[name] = checksum || ""
        versions_string.split(",") do |version|
          delete = version.delete_prefix!("-")
          version = version.split("-", 2).unshift(name)
          if delete
            @versions_by_name[name].delete(version)
          else
            @versions_by_name[name] << version
          end
        end
      end

      @versions_by_name
    end

    def info(name)
      parse_info(@compact_index.info(name, info_checksums[name]), name)
    end

    def parse_info(data, name)
      lines(data).map {|line| gem_parser.parse(line).unshift(name) }
    end

    def available?
      return @available unless @available.nil?
      @available = !info_checksums.empty?
    end

    private

    def info_checksums
      @info_checksums ||= lines(@compact_index.versions).each_with_object({}) do |line, checksums|
        parse_version_checksum(line, checksums)
      end
    end

    def lines(data)
      return [] if data.nil? || data.empty?
      lines = data.split("\n")
      header = lines.index("---")
      header ? lines[header + 1..-1] : lines
    end

    def gem_parser
      @gem_parser ||= Gem::Resolver::APISet::GemParser.new
    end

    # This is mostly the same as `split(" ", 3)` but it avoids allocating extra objects.
    # This method gets called at least once for every gem when parsing versions.
    def parse_version_checksum(line, checksums)
      return unless (name_end = line.index(" ")) # Artifactory bug causes blank lines in artifactory index files
      checksum_start = line.index(" ", name_end + 1)
      return unless checksum_start
      checksum_start += 1

      checksum_end = line.size - checksum_start

      line.freeze # allows slicing into the string to not allocate a copy of the line
      name = line[0, name_end]
      checksum = line[checksum_start, checksum_end]
      checksums[name.freeze] = checksum # freeze name since it is used as a hash key
    end
  end
end
