#!/usr/bin/env ruby

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

require 'erb'
require 'fileutils'
require 'json'
require 'open3'
require 'optparse'
require 'stringio'

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

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

OptionParser.new do |opts|
  opts.on('--branch BRANCH', "Compares the performance of BRANCH against `main`") do |branch|
    @options[:branch] = branch
  end
  opts.on('--iterations N', Integer, 'Runs linting N times on each repository') do |iterations|
    @options[:iterations] = iterations
  end
  opts.on('--skip-clean', 'Skip cleaning upon completion') do |skip_clean|
    @options[:skip_clean] = skip_clean
  end
  opts.on('--force', 'Run oss-check even if binaries are equal') do |force|
    @options[:force] = force
  end
  opts.on('-v', '--[no-]verbose', 'Run verbosely') do |v|
    @options[:verbose] = v
  end
  opts.on('--only-repos REPO1,REPO2', Array, 'Run oss-check only on the specified repositories') do |only_repos|
    @options[:only_repos] = only_repos
  end
end.parse!

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

class Repo
  attr_accessor :name
  attr_accessor :github_location
  attr_accessor :keep_config
  attr_accessor :config
  attr_accessor :commit_hash
  attr_accessor :branch_exit_value
  attr_accessor :branch_duration
  attr_accessor :main_exit_value
  attr_accessor :main_duration

  def initialize(name, github_location, keep_config=false, config=nil)
    @name = name
    @github_location = github_location
    @keep_config = keep_config
    @config = config
  end

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

  def to_s
    @name
  end

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

class ReportEntry < Struct.new(:file, :line, :column, :severity, :message, :rule_id)
  def self.from_xcode(line)
    # /path/to/file.swift:line:column: (warning|error): message (rule_id)
    match = line.match(/^(.*):(\d+):(\d+): (warning|error): (.+) \((\w+)\)$/)
    if match.nil?
      error "Could not parse line '#{line}'"
      return nil
    end
    ReportEntry.new(*match.captures)
  end

  def self.from_json(json)
    ReportEntry.new(json['file'], json['line'], json['character'], json['severity'], json['reason'], json['rule_id'])
  end

  def self.html_escape(str)
    "/#{ERB::Util.url_encode(str.gsub(%r{^/}, ''))}"
  end

  def to_full_message_with_linked_path(repo)
    "#{to_linked_relative_path(repo)}: #{severity}: #{message} (#{rule_id})"
  end

  def to_link(repo)
    "#{repo.git_url}/blob/#{repo.commit_hash}#{ReportEntry.html_escape(file_as_relative_path(repo))}#L#{line}"
  end

  def to_linked_relative_path(repo)
    "[#{file_as_relative_path(repo)}:#{line}:#{column}](#{to_link(repo)})"
  end

  def file_as_relative_path(repo)
    file.sub("#{Dir.pwd}/#{$working_dir}/#{repo.name}", '')
  end

  def equal_to?(other, except = [])
    (members - except).all? { |member| send(member) == other.send(member) }
  end
end

class Change < Struct.new(:category, :new, :old)
  def print_as_diff(repo, into)
    into.puts "- #{new.to_linked_relative_path(repo)}  "
    into.puts "  ```diff"
    into.puts "  - #{old.send(category)}"
    into.puts "  + #{new.send(category)}"
    into.puts "  ```"
    into.puts
  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(command, dir: nil)
  puts command if @options[:verbose]
  if dir
    Dir.chdir(dir) { perform(command) }
  else
    system(command)
  end
end

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

def make_directory_structure
  ['branch_reports', 'main_reports'].each do |dir|
    FileUtils.mkdir_p("#{$working_dir}/#{dir}")
  end
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")
    swiftlint_config = "#{dir}/.swiftlint.yml"
    if !repo.keep_config
      FileUtils.rm_rf(swiftlint_config)
    end
    if repo.config
      File.open(swiftlint_config, 'a') do |file|
        file.puts(repo.config)
      end
    end
    if @only_rules_changed && @rules_changed
      File.open(swiftlint_config, 'a') do |file|
        file.puts('only_rules:')
        file.puts(@rules_changed.map { |rule| "  - #{rule}" })
      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
      perform("git checkout #{repo.commit_hash}")
      iterations = @options[:iterations]
      print "Linting #{iterations} iterations of #{repo} with #{branch}: 1"
      durations = []
      start = Time.now
      command = "../builds/swiftlint-#{branch} lint --no-cache #{'--enable-all-rules' unless @only_rules_changed} --reporter json"
      File.open("../#{branch}_reports/#{repo}.json", 'w') do |file|
        puts "\n#{command}" if @options[:verbose]
        Open3.popen2(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.main_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.popen2(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.main_duration = average_duration
      end
    end
  end
end

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

  dir = "#{$working_dir}/builds"
  target = branch == 'main' ? @effective_main_commitish : @options[:branch]
  if File.directory?(dir)
    perform("git checkout #{target}", dir: dir)
  else
    perform("git worktree add --detach #{dir} #{target}")
  end

  build_command = "bazel build --config=release @SwiftLint//:swiftlint"

  return_value = nil
  puts build_command if @options[:verbose]
  Open3.popen3(build_command, :chdir=>"#{dir}")  do |_, stdout, stderr, wait_thr|
    puts stdout.read.chomp
    puts stderr.read.chomp
    return_value = wait_thr.value
  end

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

  perform("mv bazel-bin/swiftlint swiftlint-#{branch}", dir: dir)
end

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

  summaries = @repos.map do |repo|
    if repo.main_exit_value != repo.branch_exit_value
      warn "This PR changed the exit value from #{repo.main_exit_value} to #{repo.branch_exit_value} when " \
           "running in #{repo.name}."
      # 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 = JSON.parse(File.read("#{$working_dir}/branch_reports/#{repo.name}.json")).map {
      |json| ReportEntry.from_json(json)
    }
    main = JSON.parse(File.read("#{$working_dir}/main_reports/#{repo.name}.json")).map {
      |json| ReportEntry.from_json(json)
    }

    new_violations = branch - main
    fixed_violations = main - branch

    message_changed = []
    severity_changed = []
    rule_id_changed = []
    column_changed = []
    remaining_violations = []

    new_violations.each do |line|
      fixed = fixed_violations.find { |other| line.equal_to?(other, [:message]) }
      if fixed
        next message_changed << Change.new(:message, line, fixed)
      end
      fixed = fixed_violations.find { |other| line.equal_to?(other, [:severity]) }
      if fixed
        next severity_changed << Change.new(:severity, line, fixed)
      end
      fixed = fixed_violations.find { |other| line.equal_to?(other, [:rule_id]) }
      if fixed
        next rule_id_changed << Change.new(:rule_id, line, fixed)
      end
      fixed = fixed_violations.find { |other| line.equal_to?(other, [:column]) }
      if fixed
        next column_changed << Change.new(:column, line, fixed)
      end
      remaining_violations << line
    end

    remaining_fixed = fixed_violations - (message_changed + severity_changed + rule_id_changed + column_changed).map(&:old)

    # Print new and fixed violations to be processed by Danger.
    new_violations.each { |line|
      warn "This PR introduced a violation in #{repo.name}: #{line.to_full_message_with_linked_path(repo)}"
    }
    fixed_violations.each { |line|
      message "This PR fixed a violation in #{repo.name}: #{line.to_full_message_with_linked_path(repo)}"
    }

    # Print report in Markdown format that lists all changes by category.
    summary = StringIO.new

    summary.puts "## #{repo.name}"
    summary.puts
    summary.puts "### Message changed (#{message_changed.count})"
    summary.puts
    message_changed.each { |change| change.print_as_diff(repo, summary) }
    summary.puts
    summary.puts "### Severity changed (#{severity_changed.count})"
    summary.puts
    severity_changed.each { |change| change.print_as_diff(repo, summary) }
    summary.puts
    summary.puts "### Rule ID changed (#{rule_id_changed.count})"
    summary.puts
    rule_id_changed.each { |change| change.print_as_diff(repo, summary) }
    summary.puts
    summary.puts "### Column changed (#{column_changed.count})"
    summary.puts
    column_changed.each { |change| change.print_as_diff(repo, summary) }
    summary.puts
    summary.puts "### Other fixed violations (#{remaining_fixed.count})"
    summary.puts
    remaining_fixed.each { |violation| summary.puts "- #{violation.to_full_message_with_linked_path(repo)}" }
    summary.puts
    summary.puts "### Other new violations (#{remaining_violations.count})"
    summary.puts
    remaining_violations.each { |violation| summary.puts "- #{violation.to_full_message_with_linked_path(repo)}" }
    summary.puts

    summary.string
  end

  File.open("oss-check-summary.md", 'w') do |file|
    file.puts "# Summary"
    file.puts
    file.puts summaries.compact.join("\n")
  end
end

def fetch_origin
  perform('git fetch origin')
end

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

def set_globals
  @effective_main_commitish = `git merge-base origin/main #{@options[:branch]}`.chomp
  @changed_swift_files = `git diff --diff-filter=AMRCU #{@effective_main_commitish} --name-only | grep "\.swift$" || true`.split("\n")
  @changed_rule_files = @changed_swift_files.select do |file|
    file.start_with? 'Source/SwiftLintBuiltInRules/Rules/'
  end
  @rules_changed = @changed_rule_files.map do |path|
    if File.read(path) =~ /^\s+identifier: "(\w+)",$/
      $1
    else
      nil
    end
  end.compact.sort
  # True iff the only Swift files that were changed are SwiftLint rules, and that number is one or greater
  @only_rules_changed = !@rules_changed.empty? && @changed_swift_files.count == @rules_changed.count
end

def print_rules_changed
  if @only_rules_changed
    puts "Only #{@rules_changed.count} rules changed: #{@rules_changed.join(', ')}"
  end
end

def report_binary_size
  size_branch = File.size("#{$working_dir}/builds/swiftlint-branch")
  size_main = File.size("#{$working_dir}/builds/swiftlint-main")
  if size_branch == size_main
    message "Building this branch resulted in the same binary size as when built on `main`."
  else
    percent_change = 100 * (size_branch - size_main) / size_main
    faster_slower = size_branch < size_main ? 'smaller' : 'larger'
    in_kilo_bytes = ->(size) { (size / 1024.0).round(2) }
    msg = "Building this branch resulted in a binary size of #{in_kilo_bytes.call(size_branch)} KiB " \
          "vs #{in_kilo_bytes.call(size_main)} KiB when built on `main` (#{percent_change.to_i}\% #{faster_slower})."
    if percent_change.abs < 2
      message msg
    else
      warn msg
    end
  end
end

def warmup
  %w[branch main].each do |branch|
    perform("../builds/swiftlint-#{branch} lint --no-cache --enable-all-rules", dir: "#{$working_dir}/Aerial")
  end
end

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

# Constants
$working_dir = 'osscheck'
@repos = [
  Repo.new('Aerial', 'JohnCoates/Aerial'),
  Repo.new('Alamofire', 'Alamofire/Alamofire'),
  Repo.new('Brave', 'brave/brave-core', false, 'included: ios/brave-ios'),
  Repo.new('DuckDuckGo', 'duckduckgo/apple-browsers'),
  Repo.new('Firefox', 'mozilla-mobile/firefox-ios'),
  Repo.new('Kickstarter', 'kickstarter/ios-oss'),
  Repo.new('Moya', 'Moya/Moya'),
  Repo.new('NetNewsWire', 'Ranchero-Software/NetNewsWire'),
  Repo.new('Nimble', 'Quick/Nimble'),
  Repo.new('PocketCasts', 'Automattic/pocket-casts-ios'),
  Repo.new('Quick', 'Quick/Quick'),
  Repo.new('Realm', 'realm/realm-swift'),
  Repo.new('Sourcery', 'krzysztofzablocki/Sourcery'),
  Repo.new('Swift', 'apple/swift', false, 'included: stdlib'),
  Repo.new('VLC', 'videolan/vlc-ios'),
  Repo.new('Wire', 'wireapp/wire-ios', false, 'excluded: wire-ios/Templates/Viper'),
  Repo.new('WordPress', 'wordpress-mobile/WordPress-iOS')
].select { |repo| @options[:only_repos].empty? || @options[:only_repos].include?(repo.name) }

# Clean up
clean_up unless @options[:skip_clean]

# Prep
$stdout.sync = true
validate_state_to_run
fetch_origin
set_globals
print_rules_changed
make_directory_structure

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

# Compare binary size of both builds.
report_binary_size

unless @options[:force]
  full_version_branch = `#{$working_dir}/builds/swiftlint-branch version --verbose`
  full_version_main = `#{$working_dir}/builds/swiftlint-main version --verbose`

  if full_version_branch == full_version_main
    message "Skipping OSS check because SwiftLint hasn't changed compared to `main`."
    # Clean up
    clean_up unless @options[:skip_clean]
    exit
  end
end

setup_repos
warmup

%w[branch main].each do |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]