#!/usr/bin/env ruby
#
# Generate a feature flag entry file in the correct location.
#
# Automatically stages the file and amends the previous commit if the `--amend`
# argument is used.

require 'optparse'
require 'yaml'
require 'fileutils'
require 'uri'
require 'readline'

require_relative '../lib/feature/shared' unless defined?(Feature::Shared)

module FeatureFlagHelpers
  Abort = Class.new(StandardError)
  Done = Class.new(StandardError)

  def capture_stdout(cmd)
    output = IO.popen(cmd, &:read)
    fail_with "command failed: #{cmd.join(' ')}" unless $?.success?
    output
  end

  def fail_with(message)
    raise Abort, "\e[31merror\e[0m #{message}"
  end
end

class FeatureFlagOptionParser
  extend FeatureFlagHelpers
  extend ::Feature::Shared

  Options = Struct.new(
    :name,
    :type,
    :group,
    :milestone,
    :ee,
    :amend,
    :dry_run,
    :force,
    :introduced_by_url,
    :rollout_issue_url
  )

  class << self
    def parse(argv)
      options = Options.new

      parser = OptionParser.new do |opts|
        opts.banner = "Usage: #{__FILE__} [options] <feature-flag>\n\n"

        # Note: We do not provide a shorthand for this in order to match the `git
        # commit` interface
        opts.on('--amend', 'Amend the previous commit') do |value|
          options.amend = value
        end

        opts.on('-f', '--force', 'Overwrite an existing entry') do |value|
          options.force = value
        end

        opts.on('-m', '--introduced-by-url [string]', String, 'URL of merge request introducing the Feature Flag') do |value|
          options.introduced_by_url = value
        end

        opts.on('-M', '--milestone [string]', String, 'Milestone in which the Feature Flag was introduced') do |value|
          options.milestone = value
        end

        opts.on('-i', '--rollout-issue-url [string]', String, 'URL of Issue rolling out the Feature Flag') do |value|
          options.rollout_issue_url = value
        end

        opts.on('-n', '--dry-run', "Don't actually write anything, just print") do |value|
          options.dry_run = value
        end

        opts.on('-g', '--group [string]', String, "The group introducing a feature flag, like: `group::apm`") do |value|
          options.group = value if value.start_with?('group::')
        end

        opts.on('-t', '--type [string]', String, "The category of the feature flag, valid options are: #{TYPES.keys.map(&:to_s).join(', ')}") do |value|
          options.type = value.to_sym if TYPES[value.to_sym]
        end

        opts.on('-e', '--ee', 'Generate a feature flag entry for GitLab EE') do |value|
          options.ee = value
        end

        opts.on('-h', '--help', 'Print help message') do
          $stdout.puts opts
          raise Done.new
        end
      end

      parser.parse!(argv)

      unless argv.one?
        $stdout.puts parser.help
        $stdout.puts
        raise Abort, 'Feature flag name is required'
      end

      # Name is a first name
      options.name = argv.first.downcase.gsub(/-/, '_')

      options
    end

    def read_group
      $stdout.puts
      $stdout.puts ">> Specify the group introducing the feature flag, like `group::apm`:"

      loop do
        group = Readline.readline('?> ', false)&.strip
        group = nil if group.empty?
        return group if group.nil? || group.start_with?('group::')

        $stderr.puts "The group needs to include `group::`"
      end
    end

    def read_type
      # if there's only one type, do not ask, return
      return TYPES.first.first if TYPES.one?

      $stdout.puts
      $stdout.puts ">> Specify the feature flag type:"
      $stdout.puts
      TYPES.each do |type, data|
        next if data[:deprecated]

        $stdout.puts "#{type.to_s.rjust(15)}#{' '*6}#{data[:description]}"
      end

      loop do
        type = Readline.readline('?> ', false)&.strip&.to_sym
        return type if TYPES[type] && !TYPES[type][:deprecated]

        $stderr.puts "Invalid type specified '#{type}'"
      end
    end

    def read_introduced_by_url
      $stdout.puts
      $stdout.puts ">> URL of the MR introducing the feature flag (enter to skip):"

      loop do
        introduced_by_url = Readline.readline('?> ', false)&.strip
        introduced_by_url = nil if introduced_by_url.empty?
        return introduced_by_url if introduced_by_url.nil? || introduced_by_url.start_with?('https://')

        $stderr.puts "URL needs to start with https://"
      end
    end

    def read_ee_only(options)
      TYPES.dig(options.type, :ee_only)
    end

    def read_rollout_issue_url(options)
      return unless TYPES.dig(options.type, :rollout_issue)

      url = "https://gitlab.com/gitlab-org/gitlab/-/issues/new"
      title = "[Feature flag] Rollout of `#{options.name}`"

      params = {
        'issue[title]' => "[Feature flag] Rollout of `#{options.name}`",
        'issuable_template' => 'Feature Flag Roll Out',
      }
      issue_new_url = url + "?" + URI.encode_www_form(params)

      $stdout.puts
      $stdout.puts ">> Open this URL and fill in the rest of the details:"
      $stdout.puts issue_new_url
      $stdout.puts

      $stdout.puts ">> URL of the rollout issue (enter to skip):"

      loop do
        created_url = Readline.readline('?> ', false)&.strip
        created_url = nil if created_url.empty?
        return created_url if created_url.nil? || created_url.start_with?('https://')

        $stderr.puts "URL needs to start with https://"
      end
    end

    def read_milestone
      milestone = File.read('VERSION')
      milestone.gsub(/^(\d+\.\d+).*$/, '\1').chomp
    end

    def read_default_enabled(options)
      TYPES.dig(options.type, :default_enabled)
    end
  end
end

class FeatureFlagCreator
  include FeatureFlagHelpers

  attr_reader :options

  def initialize(options)
    @options = options
  end

  def execute
    assert_feature_branch!
    assert_name!
    assert_existing_feature_flag!

    # Read type from stdin unless is already set
    options.type ||= FeatureFlagOptionParser.read_type
    options.ee ||= FeatureFlagOptionParser.read_ee_only(options)
    options.group ||= FeatureFlagOptionParser.read_group
    options.introduced_by_url ||= FeatureFlagOptionParser.read_introduced_by_url
    options.rollout_issue_url ||= FeatureFlagOptionParser.read_rollout_issue_url(options)
    options.milestone ||= FeatureFlagOptionParser.read_milestone

    $stdout.puts "\e[32mcreate\e[0m #{file_path}"
    $stdout.puts contents

    unless options.dry_run
      write
      amend_commit if options.amend
    end

    if editor
      system("#{editor} '#{file_path}'")
    end
  end

  private

  def contents
    # Slice is used to ensure that YAML keys
    # are always ordered in a predictable way
    config_hash.slice(
      *::Feature::Shared::PARAMS.map(&:to_s)
    ).to_yaml
  end

  def config_hash
    {
      'name'              => options.name,
      'introduced_by_url' => options.introduced_by_url,
      'rollout_issue_url' => options.rollout_issue_url,
      'milestone'         => options.milestone,
      'group'             => options.group,
      'type'              => options.type.to_s,
      'default_enabled'   => FeatureFlagOptionParser.read_default_enabled(options)
    }
  end

  def write
    FileUtils.mkdir_p(File.dirname(file_path))
    File.write(file_path, contents)
  end

  def editor
    ENV['EDITOR']
  end

  def amend_commit
    fail_with "git add failed" unless system(*%W[git add #{file_path}])

    Kernel.exec(*%w[git commit --amend])
  end

  def assert_feature_branch!
    return unless branch_name == 'master'

    fail_with "Create a branch first!"
  end

  def assert_existing_feature_flag!
    existing_path = all_feature_flag_names[options.name]
    return unless existing_path
    return if options.force

    fail_with "#{existing_path} already exists! Use `--force` to overwrite."
  end

  def assert_name!
    return if options.name.match(/\A[a-z0-9_-]+\Z/)

    fail_with "Provide a name for the feature flag that is [a-z0-9_-]"
  end

  def file_path
    feature_flags_paths.last
      .sub('**', options.type.to_s)
      .sub('*.yml', options.name + '.yml')
  end

  def all_feature_flag_names
    @all_feature_flag_names ||=
      feature_flags_paths.map do |glob_path|
        Dir.glob(glob_path).map do |path|
          [File.basename(path, '.yml'), path]
        end
      end.flatten(1).to_h
  end

  def feature_flags_paths
    paths = []
    paths << File.join('config', 'feature_flags', '**', '*.yml')
    paths << File.join('ee', 'config', 'feature_flags', '**', '*.yml') if ee?
    paths
  end

  def ee?
    options.ee
  end

  def branch_name
    @branch_name ||= capture_stdout(%w[git symbolic-ref --short HEAD]).strip
  end
end

if $0 == __FILE__
  begin
    options = FeatureFlagOptionParser.parse(ARGV)
    FeatureFlagCreator.new(options).execute
  rescue FeatureFlagHelpers::Abort => ex
    $stderr.puts ex.message
    exit 1
  rescue FeatureFlagHelpers::Done
    exit
  end
end

# vim: ft=ruby