# 用于检查 spec 是否符合当前 Source 要求
require 'cocoapods-core/source/acceptor'
# 记录本地 source 的集合
require 'cocoapods-core/source/aggregate'
# 用于校验 source 的错误和警告
require 'cocoapods-core/source/health_reporter'
# source 管理器
require 'cocoapods-core/source/manager'
# source 元数据
require 'cocoapods-core/source/metadata'

module Pod
  class Source
    # 仓库默认的 Git 分支
    DEFAULT_SPECS_BRANCH = 'master'.freeze
    # 记录仓库的元数据
    attr_reader :metadata
    # 记录仓库的本地地址
    attr_reader :repo
    # repo 仓库地址 ~/.cocoapods/repos/{repo_name}
    def initialize(repo)
      @repo = Pathname(repo).expand_path
      @versions_by_name = {}
      refresh_metadata
    end
    # 读取 Git 仓库中的 remote url 或 .git 目录
    def url
      @url ||= begin
        remote = repo_git(%w(config --get remote.origin.url))
        if !remote.empty?
          remote
        elsif (repo + '.git').exist?
          "file://#{repo}/.git"
        end
      end
    end

    def type
      git? ? 'git' : 'file system'
    end
    # ...
  end
end

def refresh_metadata
  @metadata = Metadata.from_file(metadata_path)
end

def metadata_path
  repo + 'CocoaPods-version.yml'
end

autoload :Digest, 'digest/md5'
require 'active_support/hash_with_indifferent_access'
require 'active_support/core_ext/hash/indifferent_access'

module Pod
  class Source
    class Metadata
      # 最低可支持的 CocoaPods 版本，对应字段 `min`
      attr_reader :minimum_cocoapods_version
      # 最高可支持的 CocoaPods 版本，对应字段 `max`
      attr_reader :maximum_cocoapods_version
      # 最新 CocoaPods 版本，对应字段 `last`
      attr_reader :latest_cocoapods_version
      # 规定截取的关键字段的前缀长度和数量
      attr_reader :prefix_lengths
      # 可兼容的 CocoaPods 最新版本
      attr_reader :last_compatible_versions
      # ...
    end
  end
end

def path_fragment(pod_name, version = nil)
  prefixes = if prefix_lengths.empty?
               []
             else
               hashed = Digest::MD5.hexdigest(pod_name)
               prefix_lengths.map do |length|
                 hashed.slice!(0, length)
               end
             end
  prefixes.concat([pod_name, version]).compact
end

$ Digest::MD5.hexdigest('AFNetworking')
"a75d452377f3996bdc4b623a5df25820"

def versions(name)
  return nil unless specs_dir
  raise ArgumentError, 'No name' unless name
  pod_dir = pod_path(name)
  return unless pod_dir.exist?
  @versions_by_name[name] ||= pod_dir.children.map do |v|
    basename = v.basename.to_s
    begin
      Version.new(basename) if v.directory? && basename[0, 1] != '.'
    rescue ArgumentError
    raise Informative, 'An unexpected version directory ...'
    end
  end.compact.sort.reverse
end

class Version < Pod::Vendor::Gem::Version
  METADATA_PATTERN = '(\+[0-9a-zA-Z\-\.]+)'
  VERSION_PATTERN = "[0-9]+(\\.[0-9a-zA-Z\\-]+)*#{METADATA_PATTERN}?"
  # ...
end

require 'cocoapods-core/source'
# ...
module Pod
  class CDNSource < Source
    def initialize(repo)
      # 标记是否正在同步文件
      @check_existing_files_for_update = false
      # 记录时间用于对比下载文件的新旧程度，以确认是否需要更新保存所下的资源
      @startup_time = Time.new
      # 缓存查询过的 PodSpec 资源
      @version_arrays_by_fragment_by_name = {}
      super(repo)
    end

    def url
      @url ||= File.read(repo.join('.url')).chomp.chomp('/') + '/'
    end

    def type
      'CDN'
    end
    # ...
  end
end

module Pod
  class TrunkSource < CDNSource
    # 新版落盘后仓库名称
    TRUNK_REPO_NAME = 'trunk'.freeze

    TRUNK_REPO_URL = 'https://cdn.cocoapods.org/'.freeze

    def url
      @url ||= TRUNK_REPO_URL
      super
    end
  end
end

module Pod
  class Source
    class Manager
      attr_reader :repos_dir

      def initialize(repos_dir)
        @repos_dir = Pathname(repos_dir).expand_path
      end

      def source_repos
        return [] unless repos_dir.exist?
        repos_dir.children.select(&:directory?).sort_by { |d| d.basename.to_s.downcase }
      end

      def aggregate
        aggregate_with_repos(source_repos)
      end

      def aggregate_with_repos(repos)
        sources = repos.map { |path| source_from_path(path) }
        @aggregates_by_repos ||= {}
        @aggregates_by_repos[repos] ||= Source::Aggregate.new(sources)
      end

      def all
        aggregate.sources
      end
      # ...
    end
  end
end

def source_from_path(path)
  @sources_by_path ||= Hash.new do |hash, key|
    hash[key] = case
                when key.basename.to_s == Pod::TrunkSource::TRUNK_REPO_NAME
                  TrunkSource.new(key)
                when (key + '.url').exist?
                  CDNSource.new(key)
                else
                  Source.new(key)
                end
  end
  @sources_by_path[path]
end

module Pod
  class Source
    class Aggregate
      attr_reader :sources

      def initialize(sources)
        raise "Cannot initialize an aggregate with a nil source: (#{sources})" if sources.include?(nil)
        @sources = sources
      end
      # 查询依赖对应的 specs
      def search(dependency) ... end

      # 查询某个 pod 以发布的 specs
      def search_by_name(query, full_text_search = false) ... end

      # ...
  end
end

source 'https://github.com/CocoaPods/Specs.git'
source 'https://github.com/artsy/Specs.git'

# lib/cocoapods/installer/analyzer.rb

def sources
  @sources ||= begin
    # 省略获取 podfile、plugins、dependencies 的 source url ...
    sources = ...

    result = sources.uniq.map do |source_url|
      sources_manager.find_or_create_source_with_url(source_url)
    end
    unless plugin_sources.empty?
      result.insert(0, *plugin_sources)
      plugin_sources.each do |source|
        sources_manager.add_source(source)
      end
    end
    result
  end
end

# lib/cocoapods/sources_manager.rb

module Pod
  class Source
    class Manager

      def find_or_create_source_with_url(url)
        source_with_url(url) || create_source_with_url(url)
      end

      def create_source_with_url(url)
        name = name_for_url(url)
        is_cdn = cdn_url?(url)
		  # ...
        begin
          if is_cdn
            Command::Repo::AddCDN.parse([name, url]).run
          else
            Command::Repo::Add.parse([name, url]).run
          end
        rescue Informative => e
          raise Informative, # ...
        ensure
          UI.title_level = previous_title_level
        end
        source = source_with_url(url)
        raise "Unable to create a source with URL #{url}" unless source
        source
      end
      # ...
    end
  end
end

# lib/cocoapods-core/source/manager.rb

def source_with_url(url)
  url = canonic_url(url)
  url = 'https://github.com/cocoapods/specs' if url =~ %r{github.com[:/]+cocoapods/specs}
  all.find do |source|
    source.url && canonic_url(source.url) == url
  end
end

def canonic_url(url)
  url.downcase.gsub(/\.git$/, '').gsub(%r{\/$}, '')
end

# lib/cocoapods-core/source/aggregate.rb

def search(dependency)
  found_sources = sources.select { |s| s.search(dependency) }
  unless found_sources.empty?
    Specification::Set.new(dependency.root_name, found_sources)
  end
end

# lib/cocoapods-core/cdn_source.rb

def search(query)
  unless specs_dir
    raise Informative, "Unable to find a source named: `#{name}`"
  end
  if query.is_a?(Dependency)
    query = query.root_name
  end

  fragment = pod_shard_fragment(query)
  ensure_versions_file_loaded(fragment)
  version_arrays_by_name = @version_arrays_by_fragment_by_name[fragment] || {}

  found = version_arrays_by_name[query].nil? ? nil : query

  if found
    set = set(query)
    set if set.specification_name == query
  end
end

def ensure_versions_file_loaded(fragment)
  return if !@version_arrays_by_fragment_by_name[fragment].nil? && !@check_existing_files_for_update

  index_file_name = index_file_name_for_fragment(fragment)
  download_file(index_file_name)
  versions_raw = local_file(index_file_name, &:to_a).map(&:chomp)
  @version_arrays_by_fragment_by_name[fragment] = versions_raw.reduce({}) do |hash, row|
    row = row.split('/')
    pod = row.shift
    versions = row

    hash[pod] = versions
    hash
  end
end

def index_file_name_for_fragment(fragment)
  fragment_joined = fragment.join('_')
  fragment_joined = '_' + fragment_joined unless fragment.empty?
  "all_pods_versions#{fragment_joined}.txt"
end

module Pod
  class Specification
    class Set
      attr_reader :name
      attr_reader :sources

      def specification_name
        versions_by_source.each do |source, versions|
          next unless version = versions.first
          return source.specification(name, version).name
        end
        nil
      end

      def versions_by_source
        @versions_by_source ||= sources.each_with_object({}) do |source, result|
          result[source] = source.versions(name)
        end
      end
      # ...
    end
  end
end

# lib/cocoapods/installer/analyzer.rb

def update_repositories
  sources.each do |source|
    if source.updateable?
      sources_manager.update(source.name, true)
    else
      UI.message "Skipping ..."
    end
  end
  @specs_updated = true
end

# lib/cocoapods/sources_managers.rb

def update(source_name = nil, show_output = false)
  if source_name
    sources = [updateable_source_named(source_name)]
  else
    sources = updateable_sources
  end

  changed_spec_paths = {}

  # Do not perform an update if the repos dir has not been setup yet.
  return unless repos_dir.exist?

  File.open("#{repos_dir}/Spec_Lock", File::CREAT) do |f|
    f.flock(File::LOCK_EX)
    sources.each do |source|
      UI.section "Updating spec repo `#{source.name}`" do
        changed_source_paths = source.update(show_output)
        changed_spec_paths[source] = changed_source_paths if changed_source_paths.count > 0
        source.verify_compatibility!
      end
    end
  end
  update_search_index_if_needed_in_background(changed_spec_paths)
end

def update(show_output)
  return [] if unchanged_github_repo?
  prev_commit_hash = git_commit_hash
  update_git_repo(show_output)
  @versions_by_name.clear
  refresh_metadata
  if version = metadata.last_compatible_version(Version.new(CORE_VERSION))
    tag = "v#{version}"
    CoreUI.warn "Using the ..."
    repo_git(['checkout', tag])
  end
  diff_until_commit_hash(prev_commit_hash)
end

def update(_show_output)
  @check_existing_files_for_update = true
  begin
    preheat_existing_files
  ensure
    @check_existing_files_for_update = false
  end
  []
end

def preheat_existing_files
  files_to_update = files_definitely_to_update + deprecated_local_podspecs - ['deprecated_podspecs.txt']

  concurrent_requests_catching_errors do
    loaders = files_to_update.map do |file|
      download_file_async(file)
    end
    Promises.zip_futures_on(HYDRA_EXECUTOR, *loaders).wait!
  end
end

# lib/cocoapods/command/repo/update.rb

module Pod
  class Command
    class Repo < Command
      class Update < Repo
        def run
          show_output = !config.silent?
          config.sources_manager.update(@name, show_output)
          exclude_repos_dir_from_backup
        end
        # ...
      end
    end
  end
end