#!/usr/bin/env ruby
# frozen_string_literal: true

require 'gitlab'
require 'pathname'

# This script saves the diffs of changes in an MR to the directory specified as the first argument
#
# It exits with a success code if diffs are found and saved, or if there are no changes, including if the script runs in
# a pipeline that is not for a merge request.

gitlab_token = ENV.fetch('PROJECT_TOKEN_FOR_CI_SCRIPTS_API_USAGE')
gitlab_endpoint = ENV.fetch('CI_API_V4_URL')
mr_project_path = ENV['CI_MERGE_REQUEST_PROJECT_PATH']
mr_iid = ENV['CI_MERGE_REQUEST_IID']

puts "CI_MERGE_REQUEST_PROJECT_PATH is missing." if mr_project_path.to_s.empty?
puts "CI_MERGE_REQUEST_IID is missing." if mr_iid.to_s.empty?

unless mr_project_path && mr_iid
  puts "Exiting as this does not appear to be a merge request pipeline."
  exit
end

abort("ERROR: Please specify a directory to write MR diffs into.") if ARGV.empty?
output_diffs_dir = Pathname.new(ARGV.shift).expand_path

Gitlab.configure do |config|
  config.endpoint       = gitlab_endpoint
  config.private_token  = gitlab_token
end

Gitlab.merge_request_changes(mr_project_path, mr_iid).changes.each do |change|
  next if change['diff'].empty?

  output_diffs_dir.join(File.dirname(change['new_path'])).mkpath
  output_diffs_dir.join("#{change['new_path']}.diff").write(change['diff'])
end