#:  * `man` [`--fail-if-changed`]:
#:    Generate Homebrew's manpages.
#:
#:    If `--fail-if-changed` is passed, the command will return a failing
#:    status code if changes are detected in the manpage outputs.
#:    This can be used for CI to be notified when the manpages are out of date.
#:    Additionally, the date used in new manpages will match those in the existing
#:    manpages (to allow comparison without factoring in the date).

require "formula"
require "erb"
require "ostruct"
require "cli_parser"
require "dev-cmd/audit"
require "dev-cmd/bottle"
require "dev-cmd/bump-formula-pr"
require "dev-cmd/create"
require "dev-cmd/edit"
require "dev-cmd/formula"
require "dev-cmd/irb"
require "dev-cmd/linkage"
require "dev-cmd/mirror"
require "dev-cmd/pull"
require "dev-cmd/extract"
require "dev-cmd/release-notes"
require "dev-cmd/tap-new"
require "dev-cmd/tests"
require "dev-cmd/update-test"

module Homebrew
  module_function

  SOURCE_PATH = HOMEBREW_LIBRARY_PATH/"manpages"
  TARGET_MAN_PATH = HOMEBREW_REPOSITORY/"manpages"
  TARGET_DOC_PATH = HOMEBREW_REPOSITORY/"docs"

  def man_args
    Homebrew::CLI::Parser.new do
      usage_banner <<~EOS
        `man` [<options>]:

        Generate Homebrew's manpages.
      EOS
      switch "--fail-if-changed",
        description: "Return a failing status code if changes are detected in the manpage outputs. This "\
                     "can be used for CI to be notified when the manpages are out of date. Additionally, "\
                     "the date used in new manpages will match those in the existing manpages (to allow "\
                     "comparison without factoring in the date)."
      switch "--link",
        description: "It is now done automatically by `brew update`."
    end
  end

  def man
    man_args.parse

    raise UsageError unless ARGV.named.empty?

    if args.link?
      odie "`brew man --link` is now done automatically by `brew update`."
    end

    regenerate_man_pages

    if system "git", "-C", HOMEBREW_REPOSITORY, "diff", "--quiet", "docs/Manpage.md", "manpages"
      puts "No changes to manpage output detected."
    elsif args.fail_if_changed?
      Homebrew.failed = true
    end
  end

  def regenerate_man_pages
    Homebrew.install_gem_setup_path! "ronn"

    markup = build_man_page
    convert_man_page(markup, TARGET_DOC_PATH/"Manpage.md")
    convert_man_page(markup, TARGET_MAN_PATH/"brew.1")

    cask_markup = (SOURCE_PATH/"brew-cask.1.md").read
    convert_man_page(cask_markup, TARGET_MAN_PATH/"brew-cask.1")
  end

  def path_glob_commands(glob)
    Pathname.glob(glob)
            .map(&:read).map(&:lines)
            .map { |lines| lines.grep(/^#:/).map { |line| line.slice(2..-1) }.join }
            .reject { |s| s.strip.empty? || s.include?("@hide_from_man_page") }
  end

  def build_man_page
    template = (SOURCE_PATH/"brew.1.md.erb").read
    variables = OpenStruct.new

    variables[:commands] = path_glob_commands("#{HOMEBREW_LIBRARY_PATH}/cmd/*.{rb,sh}")

    variables[:developer_commands] = generate_cmd_manpages("#{HOMEBREW_LIBRARY_PATH}/dev-cmd/*.{rb,sh}")
    variables[:global_options] = global_options_manpage_lines
    readme = HOMEBREW_REPOSITORY/"README.md"
    variables[:lead_maintainer] =
      readme.read[/(Homebrew's lead maintainer .*\.)/, 1]
            .gsub(/\[([^\]]+)\]\([^)]+\)/, '\1')
    variables[:leadership] =
      readme.read[/(Homebrew's project leadership committee .*\.)/, 1]
            .gsub(/\[([^\]]+)\]\([^)]+\)/, '\1')
    variables[:brew_maintainers] =
      readme.read[%r{(Homebrew/brew's other current maintainers .*\.)}, 1]
            .gsub(/\[([^\]]+)\]\([^)]+\)/, '\1')
    variables[:linux_maintainers] =
      readme.read[%r{(Homebrew/brew's Linux support \(and Linuxbrew\) maintainers are .*\.)}, 1]
            .gsub(/\[([^\]]+)\]\([^)]+\)/, '\1')
    variables[:core_maintainers] =
      readme.read[%r{(Homebrew/homebrew-core's other current maintainers .*\.)}, 1]
            .gsub(/\[([^\]]+)\]\([^)]+\)/, '\1')
    variables[:former_maintainers] =
      readme.read[/(Former maintainers .*\.)/, 1]
            .gsub(/\[([^\]]+)\]\([^)]+\)/, '\1')

    variables[:homebrew_bundle] = help_output(:bundle)
    variables[:homebrew_services] = help_output(:services)

    ERB.new(template, nil, ">").result(variables.instance_eval { binding })
  end

  def sort_key_for_path(path)
    # Options after regular commands (`~` comes after `z` in ASCII table).
    path.basename.to_s.sub(/\.(rb|sh)$/, "").sub(/^--/, "~~")
  end

  def convert_man_page(markup, target)
    manual = target.basename(".1")
    organisation = "Homebrew"

    # Set the manpage date to the existing one if we're checking for changes.
    # This avoids the only change being e.g. a new date.
    date = if args.fail_if_changed? &&
              target.extname == ".1" && target.exist?
      /"(\d{1,2})" "([A-Z][a-z]+) (\d{4})" "#{organisation}" "#{manual}"/ =~ target.read
      Date.parse("#{Regexp.last_match(1)} #{Regexp.last_match(2)} #{Regexp.last_match(3)}")
    else
      Date.today
    end
    date = date.strftime("%Y-%m-%d")

    shared_args = %W[
      --pipe
      --organization=#{organisation}
      --manual=#{target.basename(".1")}
      --date=#{date}
    ]

    format_flag, format_desc = target_path_to_format(target)

    puts "Writing #{format_desc} to #{target}"
    Utils.popen(["ronn", format_flag] + shared_args, "rb+") do |ronn|
      ronn.write markup
      ronn.close_write
      ronn_output = ronn.read
      odie "Got no output from ronn!" unless ronn_output
      ronn_output.gsub!(%r{</var>`(?=[.!?,;:]?\s)}, "").gsub!(%r{</?var>}, "`") if format_flag == "--markdown"
      unless format_flag == "--markdown"
        ronn_output = ronn_output.gsub(%r{<code>(.*?)</code>}, "\\fB\\1\\fR")
                                 .gsub(%r{<var>(.*?)</var>}, "\\fI\\1\\fR")
      end
      target.atomic_write ronn_output
    end
  end

  def help_output(command)
    tap = Tap.fetch("Homebrew/homebrew-#{command}")
    tap.install unless tap.installed?
    command_help_lines(which("brew-#{command}.rb", Tap.cmd_directories))
  end

  def target_path_to_format(target)
    case target.basename
    when /\.md$/    then ["--markdown", "markdown"]
    when /\.\d$/    then ["--roff", "man page"]
    else
      odie "Failed to infer output format from '#{target.basename}'."
    end
  end

  def generate_cmd_manpages(glob)
    cmd_paths = Pathname.glob(glob)
    man_page_lines = []
    cmd_paths.each do |cmd_path|
      begin
        cmd_parser = Homebrew.send(cmd_arg_parser(cmd_path))
        man_page_lines << cmd_manpage_lines(cmd_parser).join
      rescue NoMethodError
        man_page_lines << path_glob_commands(cmd_path.to_s).first
      end
    end
    man_page_lines
  end

  def cmd_arg_parser(cmd_path)
    "#{cmd_path.basename.to_s.gsub(".rb", "").tr("-", "_")}_args".to_sym
  end

  def cmd_manpage_lines(cmd_parser)
    lines = [format_usage_banner(cmd_parser.usage_banner_text)]
    lines += cmd_parser.processed_options.map do |short, long, _, desc|
      next if !long.nil? && cmd_parser.global_option?(cmd_parser.option_to_name(long))
      generate_option_doc(short, long, desc)
    end
    lines
  end

  def global_options_manpage_lines
    lines = ["These options are applicable across all sub-commands.\n"]
    lines += Homebrew::CLI::Parser.global_options.values.map do |names, _, desc|
      short, long = names
      generate_option_doc(short, long, desc)
    end
    lines
  end

  def generate_option_doc(short, long, desc)
    "* #{format_short_opt(short)} #{format_long_opt(long)}:" + "\n" + desc + "\n"
  end

  def format_short_opt(opt)
    "`#{opt}`, " unless opt.nil?
  end

  def format_long_opt(opt)
    "`#{opt}`"
  end

  def format_usage_banner(usage_banner)
    usage_banner.sub(/^/, "###")
  end
end