require "extend/pathname"
require "keg_relocate"
require "lock_file"
require "ostruct"

class Keg
  class AlreadyLinkedError < RuntimeError
    def initialize(keg)
      super <<~EOS
        Cannot link #{keg.name}
        Another version is already linked: #{keg.linked_keg_record.resolved_path}
        EOS
    end
  end

  class LinkError < RuntimeError
    attr_reader :keg, :src, :dst

    def initialize(keg, src, dst, cause)
      @src = src
      @dst = dst
      @keg = keg
      @cause = cause
      super(cause.message)
      set_backtrace(cause.backtrace)
    end
  end

  class ConflictError < LinkError
    def suggestion
      conflict = Keg.for(dst)
    rescue NotAKegError, Errno::ENOENT
      "already exists. You may want to remove it:\n  rm '#{dst}'\n"
    else
      <<~EOS
        is a symlink belonging to #{conflict.name}. You can unlink it:
          brew unlink #{conflict.name}
      EOS
    end

    def to_s
      s = []
      s << "Could not symlink #{src}"
      s << "Target #{dst}" << suggestion
      s << <<~EOS
        To force the link and overwrite all conflicting files:
          brew link --overwrite #{keg.name}

        To list all files that would be deleted:
          brew link --overwrite --dry-run #{keg.name}
        EOS
      s.join("\n")
    end
  end

  class DirectoryNotWritableError < LinkError
    def to_s
      <<~EOS
        Could not symlink #{src}
        #{dst.dirname} is not writable.
      EOS
    end
  end

  # locale-specific directories have the form language[_territory][.codeset][@modifier]
  LOCALEDIR_RX = %r{(locale|man)/([a-z]{2}|C|POSIX)(_[A-Z]{2})?(\.[a-zA-Z\-0-9]+(@.+)?)?}
  INFOFILE_RX = %r{info/([^.].*?\.info|dir)$}
  TOP_LEVEL_DIRECTORIES = %w[bin etc include lib sbin share var Frameworks].freeze
  ALL_TOP_LEVEL_DIRECTORIES = (TOP_LEVEL_DIRECTORIES + %w[lib/pkgconfig share/locale share/man opt]).freeze
  PRUNEABLE_DIRECTORIES = %w[bin etc include lib sbin share opt Frameworks LinkedKegs var/homebrew/linked].map do |dir|
    case dir
    when "LinkedKegs"
      HOMEBREW_LIBRARY/dir
    else
      HOMEBREW_PREFIX/dir
    end
  end

  # These paths relative to the keg's share directory should always be real
  # directories in the prefix, never symlinks.
  SHARE_PATHS = %w[
    aclocal doc info java locale man
    man/man1 man/man2 man/man3 man/man4
    man/man5 man/man6 man/man7 man/man8
    man/cat1 man/cat2 man/cat3 man/cat4
    man/cat5 man/cat6 man/cat7 man/cat8
    applications gnome gnome/help icons
    mime-info pixmaps sounds postgresql
  ].freeze

  # Given an array of kegs, this method will try to find some other kegs
  # that depend on them.
  #
  # If it does, it returns:
  # - some kegs in the passed array that have installed dependents
  # - some installed dependents of those kegs.
  #
  # If it doesn't, it returns nil.
  #
  # Note that nil will be returned if the only installed dependents
  # in the passed kegs are other kegs in the array.
  #
  # For efficiency, we don't bother trying to get complete data.
  def self.find_some_installed_dependents(kegs)
    # First, check in the tabs of installed Formulae.
    kegs.each do |keg|
      # Don't include dependencies of kegs that were in the given array.
      dependents = keg.installed_dependents - kegs
      dependents.map! { |d| "#{d.name} #{d.version}" }
      return [keg], dependents if dependents.any?
    end

    # Some kegs won't have modern Tabs with the dependencies listed.
    # In this case, fall back to Formula#missing_dependencies.

    # Find formulae that didn't have dependencies saved in all of their kegs,
    # so need them to be calculated now.
    #
    # This happens after the initial dependency check because it's sloooow.
    remaining_formulae = Formula.installed.select do |f|
      installed_kegs = f.installed_kegs

      # Don't include dependencies of kegs that were in the given array.
      next false if (installed_kegs - kegs).empty?

      installed_kegs.any? { |k| Tab.for_keg(k).runtime_dependencies.nil? }
    end

    keg_names = kegs.map(&:name)
    kegs_by_source = kegs.group_by do |keg|
      begin
        # First, attempt to resolve the keg to a formula
        # to get up-to-date name and tap information.
        f = keg.to_formula
        [f.name, f.tap]
      rescue FormulaUnavailableError
        # If the formula for the keg can't be found,
        # fall back to the information in the tab.
        [keg.name, Tab.for_keg(keg).tap]
      end
    end

    remaining_formulae.each do |dependent|
      required = dependent.missing_dependencies(hide: keg_names)

      required_kegs = required.map do |f|
        f_kegs = kegs_by_source[[f.name, f.tap]]
        next unless f_kegs

        f_kegs.sort_by(&:version).last
      end.compact

      next unless required_kegs.any?

      return required_kegs, [dependent.to_s]
    end

    nil
  end

  # if path is a file in a keg then this will return the containing Keg object
  def self.for(path)
    path = path.realpath
    until path.root?
      return Keg.new(path) if path.parent.parent == HOMEBREW_CELLAR.realpath
      path = path.parent.realpath # realpath() prevents root? failing
    end
    raise NotAKegError, "#{path} is not inside a keg"
  end

  def self.all
    Formula.racks.flat_map(&:subdirs).map { |d| new(d) }
  end

  attr_reader :path, :name, :linked_keg_record, :opt_record
  protected :path

  extend Forwardable

  def_delegators :path,
    :to_s, :hash, :abv, :disk_usage, :file_count, :directory?, :exist?, :/,
    :join, :rename, :find

  def initialize(path)
    path = path.resolved_path if path.to_s.start_with?("#{HOMEBREW_PREFIX}/opt/")
    raise "#{path} is not a valid keg" unless path.parent.parent.realpath == HOMEBREW_CELLAR.realpath
    raise "#{path} is not a directory" unless path.directory?
    @path = path
    @name = path.parent.basename.to_s
    @linked_keg_record = HOMEBREW_LINKED_KEGS/name
    @opt_record = HOMEBREW_PREFIX/"opt/#{name}"
    @require_relocation = false
  end

  def rack
    path.parent
  end

  alias to_path to_s

  def inspect
    "#<#{self.class.name}:#{path}>"
  end

  def ==(other)
    instance_of?(other.class) && path == other.path
  end
  alias eql? ==

  def empty_installation?
    Pathname.glob("#{path}/*") do |file|
      return false if file.directory? && !file.children.reject(&:ds_store?).empty?
      basename = file.basename.to_s
      next if Metafiles.copy?(basename)
      next if %w[.DS_Store INSTALL_RECEIPT.json].include?(basename)
      return false
    end

    true
  end

  def require_relocation?
    @require_relocation
  end

  def linked?
    linked_keg_record.symlink? &&
      linked_keg_record.directory? &&
      path == linked_keg_record.resolved_path
  end

  def remove_linked_keg_record
    linked_keg_record.unlink
    linked_keg_record.parent.rmdir_if_possible
  end

  def optlinked?
    opt_record.symlink? && path == opt_record.resolved_path
  end

  def remove_old_aliases
    opt = opt_record.parent

    tap = begin
      to_formula.tap
    rescue FormulaUnavailableError, TapFormulaAmbiguityError,
           TapFormulaWithOldnameAmbiguityError
      # If the formula can't be found, just ignore aliases for now.
      nil
    end

    if tap
      bad_tap_opt = opt/tap.user
      FileUtils.rm_rf bad_tap_opt if bad_tap_opt.directory?
    end

    aliases.each do |a|
      alias_symlink = opt/a
      alias_symlink.delete if alias_symlink.symlink? || alias_symlink.exist?
    end

    Pathname.glob("#{opt_record}@*").each do |a|
      a = a.basename
      next if aliases.include?(a)

      alias_symlink = opt/a
      if alias_symlink.symlink? && alias_symlink.exist?
        next if rack != alias_symlink.realpath.parent
      end

      alias_symlink.delete
    end
  end

  def remove_opt_record
    opt_record.unlink
    opt_record.parent.rmdir_if_possible
  end

  def uninstall
    path.rmtree
    path.parent.rmdir_if_possible
    remove_opt_record if optlinked?
    remove_old_aliases
    remove_oldname_opt_record
  end

  def unlink(mode = OpenStruct.new)
    ObserverPathnameExtension.reset_counts!

    dirs = []

    TOP_LEVEL_DIRECTORIES.map { |d| path/d }.each do |dir|
      next unless dir.exist?
      dir.find do |src|
        dst = HOMEBREW_PREFIX + src.relative_path_from(path)
        dst.extend(ObserverPathnameExtension)

        dirs << dst if dst.directory? && !dst.symlink?

        # check whether the file to be unlinked is from the current keg first
        next unless dst.symlink? && src == dst.resolved_path
        if mode.dry_run
          puts dst
          Find.prune if src.directory?
          next
        end

        dst.uninstall_info if dst.to_s =~ INFOFILE_RX
        dst.unlink
        remove_old_aliases
        Find.prune if src.directory?
      end
    end

    unless mode.dry_run
      remove_linked_keg_record if linked?
      dirs.reverse_each(&:rmdir_if_possible)
    end

    ObserverPathnameExtension.n
  end

  def lock
    FormulaLock.new(name).with_lock do
      if oldname_opt_record
        FormulaLock.new(oldname_opt_record.basename.to_s).with_lock { yield }
      else
        yield
      end
    end
  end

  def completion_installed?(shell)
    dir = case shell
    when :bash then path/"etc/bash_completion.d"
    when :zsh
      dir = path/"share/zsh/site-functions"
      dir if dir.directory? && dir.children.any? { |f| f.basename.to_s.start_with?("_") }
    when :fish then path/"share/fish/vendor_completions.d"
    end
    dir&.directory? && !dir.children.empty?
  end

  def functions_installed?(shell)
    case shell
    when :fish
      dir = path/"share/fish/vendor_functions.d"
      dir.directory? && !dir.children.empty?
    when :zsh
      # Check for non completion functions (i.e. files not started with an underscore),
      # since those can be checked separately
      dir = path/"share/zsh/site-functions"
      dir.directory? && dir.children.any? { |f| !f.basename.to_s.start_with?("_") }
    end
  end

  def plist_installed?
    !Dir["#{path}/*.plist"].empty?
  end

  def python_site_packages_installed?
    (path/"lib/python2.7/site-packages").directory?
  end

  def python_pth_files_installed?
    !Dir["#{path}/lib/python2.7/site-packages/*.pth"].empty?
  end

  def apps
    app_prefix = optlinked? ? opt_record : path
    Pathname.glob("#{app_prefix}/{,libexec/}*.app")
  end

  def elisp_installed?
    return false unless (path/"share/emacs/site-lisp"/name).exist?
    (path/"share/emacs/site-lisp"/name).children.any? { |f| %w[.el .elc].include? f.extname }
  end

  def version
    require "pkg_version"
    PkgVersion.parse(path.basename.to_s)
  end

  def to_formula
    Formulary.from_keg(self)
  end

  def installed_dependents
    return [] unless optlinked?
    tap = Tab.for_keg(self).source["tap"]
    Keg.all.select do |keg|
      tab = Tab.for_keg(keg)
      next if tab.runtime_dependencies.nil?
      tab.runtime_dependencies.any? do |dep|
        # Resolve formula rather than directly comparing names
        # in case of conflicts between formulae from different taps.
        begin
          dep_formula = Formulary.factory(dep["full_name"])
          dep_formula == to_formula
        rescue FormulaUnavailableError
          next dep["full_name"] == "#{tap}/#{name}"
        end
      end
    end
  end

  def oldname_opt_record
    @oldname_opt_record ||= if (opt_dir = HOMEBREW_PREFIX/"opt").directory?
      opt_dir.subdirs.detect do |dir|
        dir.symlink? && dir != opt_record && path.parent == dir.resolved_path.parent
      end
    end
  end

  def link(mode = OpenStruct.new)
    raise AlreadyLinkedError, self if linked_keg_record.directory?

    ObserverPathnameExtension.reset_counts!

    optlink(mode) unless mode.dry_run

    # yeah indeed, you have to force anything you need in the main tree into
    # these dirs REMEMBER that *NOT* everything needs to be in the main tree
    link_dir("etc", mode) { :mkpath }
    link_dir("bin", mode) { :skip_dir }
    link_dir("sbin", mode) { :skip_dir }
    link_dir("include", mode) { :link }

    link_dir("share", mode) do |relative_path|
      case relative_path.to_s
      when "locale/locale.alias" then :skip_file
      when INFOFILE_RX then :info
      when LOCALEDIR_RX then :mkpath
      when %r{^icons/.*/icon-theme\.cache$} then :skip_file
      # all icons subfolders should also mkpath
      when %r{^icons/} then :mkpath
      when /^zsh/ then :mkpath
      when /^fish/ then :mkpath
      # Lua, Lua51, Lua53 all need the same handling.
      when %r{^lua/} then :mkpath
      when %r{^guile/} then :mkpath
      when *SHARE_PATHS then :mkpath
      else :link
      end
    end

    link_dir("lib", mode) do |relative_path|
      case relative_path.to_s
      when "charset.alias" then :skip_file
      # pkg-config database gets explicitly created
      when "pkgconfig" then :mkpath
      # cmake database gets explicitly created
      when "cmake" then :mkpath
      # lib/language folders also get explicitly created
      when "dtrace" then :mkpath
      when /^gdk-pixbuf/ then :mkpath
      when "ghc" then :mkpath
      when /^gio/ then :mkpath
      when "lua" then :mkpath
      when /^mecab/ then :mkpath
      when /^node/ then :mkpath
      when /^ocaml/ then :mkpath
      when /^perl5/ then :mkpath
      when "php" then :mkpath
      when /^python[23]\.\d/ then :mkpath
      when /^R/ then :mkpath
      when /^ruby/ then :mkpath
      # Everything else is symlinked to the cellar
      else :link
      end
    end

    link_dir("Frameworks", mode) do |relative_path|
      # Frameworks contain symlinks pointing into a subdir, so we have to use
      # the :link strategy. However, for Foo.framework and
      # Foo.framework/Versions we have to use :mkpath so that multiple formulae
      # can link their versions into it and `brew [un]link` works.
      if relative_path.to_s =~ %r{[^/]*\.framework(/Versions)?$}
        :mkpath
      else
        :link
      end
    end

    make_relative_symlink(linked_keg_record, path, mode) unless mode.dry_run
  rescue LinkError
    unlink
    raise
  else
    ObserverPathnameExtension.n
  end

  def remove_oldname_opt_record
    return unless oldname_opt_record
    return unless oldname_opt_record.resolved_path == path
    @oldname_opt_record.unlink
    @oldname_opt_record.parent.rmdir_if_possible
    @oldname_opt_record = nil
  end

  def aliases
    Tab.for_keg(self).aliases || []
  end

  def optlink(mode = OpenStruct.new)
    opt_record.delete if opt_record.symlink? || opt_record.exist?
    make_relative_symlink(opt_record, path, mode)
    aliases.each do |a|
      alias_opt_record = opt_record.parent/a
      alias_opt_record.delete if alias_opt_record.symlink? || alias_opt_record.exist?
      make_relative_symlink(alias_opt_record, path, mode)
    end

    return unless oldname_opt_record
    oldname_opt_record.delete
    make_relative_symlink(oldname_opt_record, path, mode)
  end

  def delete_pyc_files!
    find { |pn| pn.delete if %w[.pyc .pyo].include?(pn.extname) }
  end

  private

  def resolve_any_conflicts(dst, mode)
    return unless dst.symlink?

    src = dst.resolved_path

    # src itself may be a symlink, so check lstat to ensure we are dealing with
    # a directory, and not a symlink pointing at a directory (which needs to be
    # treated as a file). In other words, we only want to resolve one symlink.

    begin
      stat = src.lstat
    rescue Errno::ENOENT
      # dst is a broken symlink, so remove it.
      dst.unlink unless mode.dry_run
      return
    end

    return unless stat.directory?
    begin
      keg = Keg.for(src)
    rescue NotAKegError
      if ARGV.verbose?
        puts "Won't resolve conflicts for symlink #{dst} as it doesn't resolve into the Cellar"
      end
      return
    end

    dst.unlink unless mode.dry_run
    keg.link_dir(src, mode) { :mkpath }
    true
  end

  def make_relative_symlink(dst, src, mode)
    if dst.symlink? && src == dst.resolved_path
      puts "Skipping; link already exists: #{dst}" if ARGV.verbose?
      return
    end

    # cf. git-clean -n: list files to delete, don't really link or delete
    if mode.dry_run && mode.overwrite
      if dst.symlink?
        puts "#{dst} -> #{dst.resolved_path}"
      elsif dst.exist?
        puts dst
      end
      return
    end

    # list all link targets
    if mode.dry_run
      puts dst
      return
    end

    dst.delete if mode.overwrite && (dst.exist? || dst.symlink?)
    dst.make_relative_symlink(src)
  rescue Errno::EEXIST => e
    raise ConflictError.new(self, src.relative_path_from(path), dst, e) if dst.exist?
    if dst.symlink?
      dst.unlink
      retry
    end
  rescue Errno::EACCES => e
    raise DirectoryNotWritableError.new(self, src.relative_path_from(path), dst, e)
  rescue SystemCallError => e
    raise LinkError.new(self, src.relative_path_from(path), dst, e)
  end

  protected

  # symlinks the contents of path+relative_dir recursively into #{HOMEBREW_PREFIX}/relative_dir
  def link_dir(relative_dir, mode)
    root = path/relative_dir
    return unless root.exist?
    root.find do |src|
      next if src == root
      dst = HOMEBREW_PREFIX + src.relative_path_from(path)
      dst.extend ObserverPathnameExtension

      if src.symlink? || src.file?
        Find.prune if File.basename(src) == ".DS_Store"
        Find.prune if src.resolved_path == dst
        # Don't link pyc or pyo files because Python overwrites these
        # cached object files and next time brew wants to link, the
        # file is in the way.
        if %w[.pyc .pyo].include?(src.extname) && src.to_s.include?("/site-packages/")
          Find.prune
        end

        case yield src.relative_path_from(root)
        when :skip_file, nil
          Find.prune
        when :info
          next if File.basename(src) == "dir" # skip historical local 'dir' files
          make_relative_symlink dst, src, mode
          dst.install_info
        else
          make_relative_symlink dst, src, mode
        end
      elsif src.directory?
        # if the dst dir already exists, then great! walk the rest of the tree tho
        next if dst.directory? && !dst.symlink?
        # no need to put .app bundles in the path, the user can just use
        # spotlight, or the open command and actual mac apps use an equivalent
        Find.prune if src.extname == ".app"

        case yield src.relative_path_from(root)
        when :skip_dir
          Find.prune
        when :mkpath
          dst.mkpath unless resolve_any_conflicts(dst, mode)
        else
          unless resolve_any_conflicts(dst, mode)
            make_relative_symlink dst, src, mode
            Find.prune
          end
        end
      end
    end
  end
end