#!/usr/bin/env ruby
#/ Usage: git pr [<branch>]
#/ Open the pull request page for <branch>, or the current branch if not
#/ specified. Lands on the new pull request page when no PR exists yet.
#/ The local branch must be tracking the remote branch.

# Based on script from @rtomayko. Translated into ruby and now uses branch
# tracking rather than expecting local and remote branch to have same name

require "json"
require "yaml"

OPEN_SWITCHES = %{-o --open}

def remote_url
  url = chomped_system_call('git config --get remote.origin.url')
  repo_with_owner = url.match(/:(.*)\.git/)

  if repo_with_owner
    repo_with_owner[1]
  else
    die 'Unable to determine repo/owner for remote origin. Using https?'
  end
end

def oauth_token
  hub_config = YAML.load_file(File.expand_path('~/.config/hub'))
  hub_config['github.com'][0]['oauth_token']
end

def open_or_build_pull_request
  auth = "Authorization: token #{oauth_token}"
  pulls_endpoint = "https://api.github.com/repos/#{remote_url}/pulls"
  response = `curl --silent -H '#{auth}' #{pulls_endpoint}`
  pulls = JSON.parse(response)
  pull = pulls.detect { |pull| pull["head"]["ref"] == remote_tracking_branch }
  if !pull.nil?
    system "open-tab --reload #{pull['html_url']}"
  else
    system("open https://github.com/#{remote_url}/pull/#{remote_tracking_branch}")
  end
end

def remote_tracking_branch
  command = 'git rev-parse --abbrev-ref --symbolic-full-name @{u} 2>/dev/null'
  tracking = chomped_system_call(command)

  if tracking == '@{u}'
    die 'Current local branch not setup to track remote branch.'
  else
    branch_without_remote_name(tracking)
  end
end

def branch_without_remote_name(branch_and_remote)
  branch = branch_and_remote.match(/origin\/(.*)/)

  if branch
    branch[1]
  else
    die 'Expected remote to be \'origin\''
  end
end

def chomped_system_call(command)
  `#{command}`.chomp
end

def open_pull_request_for_repo_branch(repo, branch)
  system("open https://github.com/#{repo}/pull/#{branch}")
end

def opening?
  argument = ARGV.pop
  argument && OPEN_SWITCHES.include?(argument)
end

def ensure_published
  if not_published?
    system("git publish")
  end
end

def not_published?
  !system("git upstream > /dev/null 2>&1")
end

def main
  # repo = remote_url
  # branch = remote_tracking_branch
  if opening?
    system 'git log --reverse master..HEAD --format="%H%n%s%n%b" > .git/pr-commits'
    system 'gh compare'
    system 'gh pull-request'
  else
    ensure_published
    open_or_build_pull_request
  end
end

def die(msg)
  puts msg
  exit 1
end

main