#!/usr/bin/env ruby -wU

#*******************************************************************************
#
# INTENT
#
# This script codifies the "moment" that someone starts "working" on an issue.
# The goal is leveraging git to capture both the opening and closing moments
# From those moments we can compute the elapsed time for resolving an issue.
#
# The script is "close" to where the developers are working, and is hopefully
# easier to incorporate with developer workflow. Without using this script, we
# have less precise "starting moment", if at all.
#
# The result is that we can now report two time-based attributes for issues:
#
# * Elapsed time: How long an issue took to complete
# * Estimated effort: How much time we think it will take to complete; This is
#   not elapsed time but instead an amount of focused time.
#
# The conjecture is given those two time-based attributes we can begin
# improving the interpretation of our Feature estimates.
#
# Features will likely be comprised of a collection of issues; The estimate for
# a feature is much less precise and I believe is equal parts "Estimated Effort"
# and "Estimated Complexity".
#
#*******************************************************************************

#*******************************************************************************
#
# CONFIGURATION OPTIONS
#
#*******************************************************************************

CONFIG_KEYS = [:REMOTE, :FROM_BRANCH, :REPOSITORY_PATH, :ISSUE_TITLE, :STARTED_ISSUES_FILE].freeze

REPOSITORY_PATH = ENV.fetch('REPOSITORY_PATH') { File.expand_path(File.join(File.dirname(__FILE__), '../')) }
REMOTE = ENV.fetch('REMOTE', 'origin')
FROM_BRANCH = ENV.fetch('FROM_BRANCH', 'master')

issue_title_fetcher = lambda do
  begin
    remote_url = `cd #{REPOSITORY_PATH} && git config --get remote.#{REMOTE}.url`.strip
    match = remote_url.match(/(\w+)\/(\w+)(?:\.git)?\Z/)
    if match
      require 'open-uri'
      require 'json'
      owner, repository = match.captures
      document = open("https://api.github.com/repos/#{owner}/#{repository}/issues/#{ISSUE_NUMBER}.json").read
      json = JSON.parse(document)
      json.fetch('title').gsub(/\W+/, '-')
    else
      'issue-on-github'
    end
  rescue
    'issue-on-github'
  end
end

# TODO: Retrieve the dasherized issue from Github's API
ISSUE_TITLE = ENV.fetch('ISSUE_TITLE', issue_title_fetcher)
STARTED_ISSUES_FILE = ENV.fetch('STARTED_ISSUES_FILE', '.started-issues')

#*******************************************************************************
#
# HELP OPTIONS
#
#*******************************************************************************

if ARGV.grep(/-h/i).size == 1
  $stdout.puts ""
  $stdout.puts "$ ./#{File.basename(__FILE__)} 123"
  $stdout.puts ""
  $stdout.puts "This script will create an issue branch and update the remote repository."
  $stdout.puts ""
  $stdout.puts "* Create a new branch for the given issue number"
  $stdout.puts "* Touch and append the issue number to a tracking file"
  $stdout.puts "* Write a rudimentary commit message"
  $stdout.puts "* Push that commit up to #{REMOTE}"
  $stdout.puts ""
  $stdout.puts "Note: There are steps to insure you have a clean working directory."
  $stdout.puts "Note: If you have spaces in your configuration all bets are off!"
  $stdout.puts ""
  $stdout.puts "Current Configuration:"
  CONFIG_KEYS.each do |key|
    $stdout.puts "\t#{key}='#{Object.const_get(key)}'"
  end
  $stdout.puts ""
  $stdout.puts "You can override the configuration option by adding the corresponding"
  $stdout.puts "ENV variable."
  $stdout.puts ""
  $stdout.puts "Example:"
  $stdout.puts "$ REMOTE=origin ./scripts/#{File.basename(__FILE__)}"
  exit(0)
end

#*******************************************************************************
#
# GUARD
#
#*******************************************************************************

# Guard that I have an issue number

ISSUE_NUMBER = ARGV.shift

unless ISSUE_NUMBER =~ /^\d+$/
  $stderr.puts "Expected first parameter to be an issue number for REPOSITORY.\n\n"
  $stderr.puts "See help for details on specifying an issue number.\n\n"
  $stderr.puts "$ ./#{File.basename(__FILE__)} -h"
  exit!(1)
end

# Capture the issue_title
issue_title = ISSUE_TITLE.respond_to?(:call) ? ISSUE_TITLE.call : ISSUE_TITLE

# Guard that directories exist
[:REPOSITORY_PATH].each do |key|
  repository_path = Object.const_get(key)
  unless File.directory?(repository_path)
    $stderr.puts "Expected directory for #{key} @ #{repository_path} to exist.\n\n"
    $stderr.puts "See help for details on specifying #{key}.\n\n"
    $stderr.puts "$ ./#{File.basename(__FILE__)} -h"
    exit!(2)
  end
end

# Guard that we have a clean working directory
if `cd #{REPOSITORY_PATH} && git status --porcelain`.strip.size > 0
  $stderr.puts "Repository @ #{REPOSITORY_PATH} did not have a clean working directory"
  exit!(3)
end

#*******************************************************************************
#
# DO STUFF
#
#*******************************************************************************

`cd #{REPOSITORY_PATH} && git checkout #{FROM_BRANCH}`
`cd #{REPOSITORY_PATH} && git pull --rebase`

TO_BRANCH = "#{ISSUE_NUMBER}-#{issue_title.gsub(/\W+/, '-')}"
if `cd #{REPOSITORY_PATH} && git branch -l | grep '#{TO_BRANCH}$'`.strip.size > 0
  $stderr.puts "ERROR: Branch #{TO_BRANCH} already exists"
  exit!(4)
end

`cd #{REPOSITORY_PATH} && git checkout -b #{TO_BRANCH} && echo "#{ISSUE_NUMBER}" >> #{STARTED_ISSUES_FILE} && git add #{STARTED_ISSUES_FILE}`

path_to_commit_message = File.expand_path(File.join(REPOSITORY_PATH, '../COMMIT.msg'))
begin
  File.open(path_to_commit_message, 'w+') do |file|
    file.puts "Claiming issue #{ISSUE_NUMBER}"
    file.puts ""
    file.puts "relates to ##{ISSUE_NUMBER}"
    file.puts ""

    message = "$ ./script/#{File.basename(__FILE__)} #{ISSUE_NUMBER}"
    CONFIG_KEYS.each_with_object(message) do |key, mem|
      if ENV.key?(key.to_s)
        mem = "#{key}=\"#{ENV[key.to_s].to_s}\" #{mem}"
      end
      mem
    end
    file.puts message
    file.puts ""
    file.puts "[skip ci]"
  end
  $stdout.puts `cd #{REPOSITORY_PATH} && git commit -F #{path_to_commit_message}`
ensure
  File.unlink(path_to_commit_message) rescue true
end