#!/usr/bin/env ruby
# encoding: UTF-8
# 
# Fast-forward all local branches to their remote counterparts.
# 
# Inspired from http://stackoverflow.com/questions/5147537/how-do-i-fast-forward-other-tracking-branches-in-git
# 
require 'ostruct'
require 'optparse'
require 'term/ansicolor'
require 'git-whistles/logger'
require 'git-whistles/app'

############################################################################


class App < Git::Whistles::App

  def initialize
    super
    @local_branches  = {}
    @remote_branches = {}
    @current_branch  = nil
  end


  def main(args)
    super
    log.level = options.loglevel

    if options.fetch
      run "git fetch"
    end

    load_refs
    local_branches.each_pair do |branch_name, _|
      process_branch(branch_name)
    end
  end



  private

  def defaults
    {
      :fetch    => false,
      :dry_run  => false,
      :remote   => 'origin',
      :loglevel => Logger::WARN
    }
  end


  attr :local_branches
  attr :remote_branches
  attr :current_branch


  def process_branch(branch_name)
    unless remote_branches[branch_name]
      log.debug("skipping #{branch_name} (not on remote)")
      return
    end

    old_head = local_branches[branch_name]
    new_head = remote_branches[branch_name]
    if old_head == new_head
      log.debug("skipping #{branch_name} (up-to-date)")
      return
    end

    if branch_name == current_branch
      if run!('git status --porcelain').strip.empty?
        flag = (options.loglevel > Logger::INFO) ? '-q' : ''
        run!("git merge --ff-only #{flag} #{new_head}") unless options.dry_run
      else
        log.warn('not merging current branch as it has local changes')
        return
      end
    else
      merge_base = run!("git merge-base #{old_head} #{new_head}").strip
      if merge_base != old_head
        log.warn("cannot fast-forward #{branch_name}")
        return
      end
      run!("git update-ref refs/heads/#{branch_name} #{new_head} #{old_head}")
    end

    log.info("#{branch_name}: #{short_sha old_head} -> #{short_sha new_head}")
  end


  def option_parser
    @option_parser ||= OptionParser.new do |op|
      op.banner = "Usage: git ff-all-branches [options]"

      op.on("-v", "--verbose", "Run verbosely (add twice for more verbosity)") do |v|
        options.loglevel -= 1
      end

      op.on("-q", "--quiet", "Run silently") do |v|
        options.loglevel = Logger::UNKNOWN
      end

      op.on("-r", "--remote REMOTE", "Set the remote [origin]") do |remote|
        options.remote = remote
      end

      op.on("-f", "--fetch", "Run git fetch beforehand") do |v|
        options.fetch = v
      end

      op.on("-p", "--dry-run", "Don't actually do anything") do |v|
        options.dry_run = v
      end
    end
  end


  def parse_args!(args)
    super

    if args.any?
      die "this command does not take any argument besides flags", :usage => true
    end
  end


  def load_refs
    @current_branch = run!("git symbolic-ref HEAD").strip.gsub(%r(^refs/heads/), '')

    run!('git show-ref').strip.split(/\n+/).each do |line|
      line =~ %r(([a-f0-9]{40}) refs/(remotes/#{options.remote}|heads)/(.*)) or next
      if $2 == 'heads'
        @local_branches[$3] = $1
      else
        @remote_branches[$3] = $1
      end
    end
  end

  def short_sha(sha)
    sha[0..7]
  end
end

############################################################################

App.run!