#!/usr/bin/env ruby

################################
# Requires
################################

require 'fileutils'
require 'open3'
require 'optparse'
require 'erb'

################################
# Options
################################

@options = {
  branch: 'HEAD',
  iterations: 5,
  skip_clean: false,
  verbose: false
}

OptionParser.new do |opts|
  opts.on('--branch BRANCH', "compares the performance of BRANCH against 'master'") do |branch|
    @options[:branch] = branch
  end
  opts.on('--iterations N', Integer, 'iterates lint N times on each repositories') do |iterations|
    @options[:iterations] = iterations
  end
  opts.on('--skip-clean', 'skip cleaning on completion') do |skip_clean|
    @options[:skip_clean] = skip_clean
  end
  opts.on('-v', '--[no-]verbose', 'Run verbosely') do |v|
    @options[:verbose] = v
  end
end.parse!

################################
# Classes
################################

class Repo
  attr_accessor :name
  attr_accessor :github_location
  attr_accessor :commit_hash
  attr_accessor :branch_exit_value
  attr_accessor :branch_duration
  attr_accessor :master_exit_value
  attr_accessor :master_duration

  def initialize(name, github_location)
    @name = name
    @github_location = github_location
  end

  def git_url
    "https://github.com/#{github_location}"
  end

  def to_s
    @name
  end

  def duration_report
    percent_change = 100 * (@master_duration - @branch_duration) / @master_duration
    faster_slower = nil
    if @branch_duration < @master_duration
      faster_slower = 'faster'
    else
      faster_slower = 'slower'
      percent_change *= -1
    end
    "Linting #{self} with this PR took #{@branch_duration}s " \
    "vs #{@master_duration}s on master (#{percent_change.to_i}\% #{faster_slower})"
  end
end

################################
# Methods
################################

def message(str)
  $stderr.puts('Message: ' + str)
end

def warn(str)
  $stderr.puts('Warning: ' + str)
end

def fail(str)
  $stderr.puts('Error: ' + str)
  exit
end

def perform(*args)
  commands = args
  if @options[:verbose]
    commands.each do |x|
      puts(x)
      system(x)
    end
  else
    commands.each { |x| `#{x}` }
  end
end

def validate_state_to_run
  if `git symbolic-ref HEAD --short`.strip == 'master' && @options[:branch] == 'HEAD'
    fail "can't run osscheck without '--branch' option from 'master' as the script compares " \
         "the performance of this branch against 'master'"
  end
end

def make_directory_structure
  ['branch_reports', 'master_reports'].each do |dir|
    FileUtils.mkdir_p("#{@working_dir}/#{dir}")
  end
end

def convert_to_link(repo, string)
  string.sub!("#{Dir.pwd}/#{@working_dir}/#{repo.name}", '')
  string.sub!('.swift:', '.swift#L')
  string = string.partition(': warning:').first.partition(': error:').first
  "#{repo.git_url}/blob/#{repo.commit_hash}#{string}"
end

def non_empty_lines(path)
  File.read(path).split(/\n+/).reject(&:empty?)
end

def setup_repos
  @repos.each do |repo|
    dir = "#{@working_dir}/#{repo.name}"
    puts "Cloning #{repo}"
    perform("git clone #{repo.git_url} --depth 1 #{dir} 2> /dev/null")
    if repo.name == 'Swift'
      File.open("#{dir}/.swiftlint.yml", 'w') do |file|
        file << 'included: stdlib'
      end
    end
    Dir.chdir(dir) do
      repo.commit_hash = `git rev-parse HEAD`.strip
    end
  end
end

def generate_reports(branch)
  @repos.each do |repo|
    Dir.chdir("#{@working_dir}/#{repo.name}") do
      iterations = @options[:iterations]
      print "Linting #{iterations} iterations of #{repo} with #{branch}: 1"
      durations = []
      start = Time.now
      command = '../builds/.build/release/swiftlint lint --no-cache --enable-all-rules --reporter xcode'
      File.open("../#{branch}_reports/#{repo}.txt", 'w') do |file|
        puts "\n#{command}" if @options[:verbose]
        Open3.popen3(command) do |_, stdout, _, wait_thr|
          while line = stdout.gets
            file.puts line
          end
          if branch == 'branch'
            repo.branch_exit_value = wait_thr.value
          else
            repo.master_exit_value = wait_thr.value
          end
        end
      end
      durations << Time.now - start
      for i in 2..iterations
        print "..#{i}"
        start = Time.now
        puts command if @options[:verbose]
        Open3.popen3(command) { |_, stdout, _, _| stdout.read }
        durations << Time.now - start
      end
      puts ''
      average_duration = (durations.reduce(:+) / iterations).round(2)
      if branch == 'branch'
        repo.branch_duration = average_duration
      else
        repo.master_duration = average_duration
      end
    end
  end
end

def build(branch)
  puts "Building #{branch}"

  dir = "#{@working_dir}/builds"
  target = branch == 'master' ? @effective_master_commitish : @options[:branch]
  if File.directory?(dir)
    perform("cd #{dir}; git checkout #{target}")
  else
    perform("git fetch && git worktree add --detach #{dir} #{target}")
  end

  build_command = "cd #{dir}; swift build -c release"

  perform(build_command)
  return if $?.success?

  # Couldn't build, start fresh
  Dir.chdir(dir) do
    FileUtils.rm_rf %w[Packages .build]
  end
  return_value = nil
  puts build_command if @options[:verbose]
  Open3.popen3(build_command) do |_, stdout, _, wait_thr|
    puts stdout.read.chomp
    return_value = wait_thr.value
  end

  fail "Could not build #{branch}" unless return_value.success?
end

def diff_and_report_changes_to_danger
  @repos.each { |repo| message repo.duration_report }

  @repos.each do |repo|
    if repo.master_exit_value != repo.branch_exit_value
      warn "This PR changed the exit value when running on #{repo.name}: " \
           "(#{repo.master_exit_value} to #{repo.branch_exit_value})"
      # If the exit value changed, don't show the fixes or regressions for this
      # repo because it's likely due to a crash, and all violations would be noisy
      next
    end

    branch = non_empty_lines("#{@working_dir}/branch_reports/#{repo.name}.txt")
    master = non_empty_lines("#{@working_dir}/master_reports/#{repo.name}.txt")

    (master - branch).each do |fixed|
      escaped_message = ERB::Util.html_escape fixed
      message "This PR fixed a violation in #{repo.name}: [#{escaped_message}](#{convert_to_link(repo, fixed)})"
    end
    (branch - master).each do |violation|
      escaped_message = ERB::Util.html_escape violation
      warn "This PR introduced a violation in #{repo.name}: [#{escaped_message}](#{convert_to_link(repo, violation)})"
    end
  end
end

def fetch_origin
  perform('git fetch origin')
end

def clean_up
  FileUtils.rm_rf(@working_dir)
  perform('git worktree prune')
end

################################
# Script
################################

# Constants
@working_dir = 'osscheck'
@repos = [
  Repo.new('Aerial', 'JohnCoates/Aerial'),
  Repo.new('Alamofire', 'Alamofire/Alamofire'),
  Repo.new('Firefox', 'mozilla-mobile/firefox-ios'),
  Repo.new('Kickstarter', 'kickstarter/ios-oss'),
  Repo.new('Moya', 'Moya/Moya'),
  Repo.new('Nimble', 'Quick/Nimble'),
  Repo.new('Quick', 'Quick/Quick'),
  Repo.new('Realm', 'realm/realm-cocoa'),
  Repo.new('SourceKitten', 'jpsim/SourceKitten'),
  Repo.new('Sourcery', 'krzysztofzablocki/Sourcery'),
  Repo.new('Swift', 'apple/swift'),
  Repo.new('WordPress', 'wordpress-mobile/WordPress-iOS')
]

# Prep
$stdout.sync = true
validate_state_to_run
setup_repos
make_directory_structure
fetch_origin

@effective_master_commitish = `git merge-base origin/master #{@options[:branch]}`

# Build & generate reports for branch & master
%w[branch master].each do |branch|
  build(branch)
  generate_reports(branch)
end

# Diff and report changes to Danger
diff_and_report_changes_to_danger

# Clean up
clean_up unless @options[:skip_clean]