# module: git
 
class Git < Thor
  
  class NoRepositoryError < RuntimeError; end
  class GitError < RuntimeError; end
  class GitRebaseError < GitError; end
  class GitBranchDeleteError < GitError; end
 
 
  desc "open [NAME]", "Create a new branch off master, named NAME"
  def open(name=nil)
    newbranch = name if name && !name.empty?
    newbranch ||= begin
      require "readline"
      print "* Name your branch: "
      Readline.readline.chomp
    end
    branch = git_branch
    if git_branches.include?(newbranch)
      if newbranch == branch
        puts "* Already on branch \"#{newbranch}\""
      else
        puts "* Switching to existing branch \"#{newbranch}\""
        git_checkout(newbranch, :silent => true)
        system "git log --pretty=oneline --abbrev-commit master..HEAD"
      end
      exit(0)
    end
    unless branch == "master"
      puts "* Switching to master"
      git_checkout("master")
    end
    git_checkout(newbranch, :create_branch => true)
    unless $?.exitstatus.zero?
      puts "* Couldn't create branch #{newbranch}, switching back to #{branch}"
      git_checkout(branch)
      exit(1)
    end
    exit(0)
  end
  
  desc "close [NAME]", "Delete the current branch and switch back to master"
  def close(name=nil)
    branch = name if name && !name.empty?
    branch ||= git_branch
    current = git_branch
    if branch == "master"
      $stderr.puts "* Cannot delete master branch"
      exit(1)
    end
    if current == branch
      puts "* Switching to master"
      git_checkout("master")
    end
    puts "* Deleting branch #{branch}"
    git_branch(branch, :delete => true)
    if $?.exitstatus == 1
      $stderr.puts "* Branch #{branch} isn't a strict subset of master, quitting"
      git_checkout(current)
      exit(1)
    end
    git_checkout(current) unless current == branch
    exit(0)
  end
 
  desc "fold", "Merge the current branch into the master branch."
  def fold
    branch = git_branch
    if branch == "master"
      $stderr.puts "* Cannot fold master branch"
      exit(1)
    end
    puts "* Switching to master"
    git_checkout("master")
    puts "* Merging #{branch}"
    @merge_flags ||= {}
    git_merge(branch, @merge_flags)
    if $?.exitstatus == 1
      $stderr.puts "* Merge had errors -- see to your friend"
      exit(1)
    end
    puts "* Switching to #{branch}"
    git_checkout(branch)
  end
 
  desc "ify", "Converts an existing Subversion Repo into a Git Repository"
  method_options :stdlayout => :boolean
  def ify(opts)
    unless File.directory?("./.svn")
      $stderr.puts "This task can only be executed in an existing working copy! (No .svn-Folder found)"
      exit(1)
    end
    svnurl = `svn info`.grep(/^URL:/).first.gsub("URL: ", "").chomp
 
    # Remove "trunk" from the svnurl if we use the stdlayout option
    svnurl.slice!(-5, 5) if opts[:stdlayout] && svnurl =~ /trunk$/
 
    project = "../#{File.basename(Dir.pwd)}.git"
    puts(cmd = "git svn clone #{"--stdlayout" if opts[:stdlayout]} #{svnurl} #{project}")
    `#{cmd}`
  end
 
  desc "push", "Push local commits into the remote repository"
  def push
    git_stash do
      puts "* Pushing changes..."
      git_push
      branch = git_branch
      if branch != "master"
        git_checkout("master")
        puts "* Porting changes into master"
        git_rebase
        git_checkout(branch)
      end
    end
  end
 
  desc "squash", "Squash the current branch into the master branch."
  def squash
    @merge_flags = {:squash => true}
    fold
  end
 
  desc "update", "Pull new commits from the repository"
  def update
    git_stash do
      branch = git_branch
      if branch == "master"
        switch = false
      else
        switch = true
        git_checkout("master")
        puts "* Switching back to master..."
      end
      puts "* Pulling in new commits..."
      git_fetch
      git_rebase
      if switch
        puts "* Porting changes into #{branch}..."
        git_checkout(branch)
        git_rebase(branch)
      end
    end
  end
 
  desc "all", "Update all branches"
  def all
    git_stash do
      branch = git_branch
      switch = true
      git_branches.each do |b|
        puts "* Updating branch #{b}"
        begin
          git_rebase(b)
        rescue GitRebaseError => e
          puts "* Couldn't rebase #{b}, aborting so you can clean it up"
          switch = false
          break
        end
      end
      git_checkout(branch) if switch
    end
  end
 
  private
  
  def git_branch(what = nil, opts = {})
    # If no name is given, return the name of the current branch
    return `git branch`.grep(/^\*/).first.strip[(2..-1)] if what.nil?
    
    delete = opts[:delete] ? "-d" : ""
    force_delete = opts[:force_delete] ? "-D" : ""
    
    `git branch #{delete} #{force_delete} #{what}`
    assert_branch_delete_succeeded(what)
  end
  
  def git_branches
    `git branch`.to_a.map { |b| b[(2..-1)].chomp }
  end
  
  def git_merge(what, opts = {})
    squash = opts[:squash] ? "--squash" : ""
    
    `git merge #{squash} #{what}`
  end
  
  def git?
    `git status`
    $?.exitstatus != 128
  end
  
  def git_stash
    `git diff-files --quiet --ignore-submodules`
    if $?.exitstatus == 1
      stash = true
      clear = (`git stash list`.scan("\n").size == 0)
      puts "* Saving changes..."
      `git stash save`
    else
      stash = false
    end
    begin
      yield
    rescue => e
      puts "* Encountered an error (#{e}), backing out..."
    ensure
      if stash
        puts "* Applying changes..."
        `git stash apply`
        `git stash clear` if clear
      end
    end
  end
 
  def git_checkout(what = nil, opts = {})
    silent = opts[:silent] ? "-q" : ""
    create_branch = opts[:create_branch] ? "-b" : ""
    
    branch = git_branch
    `git checkout #{silent} #{create_branch} #{what}` if branch != what
    if block_given?
      yield
      `git checkout #{silent} #{create_branch} #{branch}` if branch != what
    end
  end
 
  def git_fetch
    `git#{" svn" if git_svn?} fetch`
  end
 
  def assert_command_succeeded(*args)
    raise(*args) unless $?.exitstatus == 0
  end
 
  def assert_rebase_succeeded(what = nil)
    assert_command_succeeded(GitRebaseError, "conflict while rebasing branch #{what}")
  end
  
  def assert_branch_delete_succeeded(what = nil)
    assert_command_succeeded(GitBranchDeleteError, "branch #{what} could not be deleted")
  end
  
  def git_rebase(what = nil)
    if git_svn?
      git_checkout(what) do
        `git svn rebase --local`
        assert_rebase_succeeded(what)
      end
    else
      `git rebase origin/master #{what}`
      assert_rebase_succeeded(what)
    end
  end
  
  def git_push
    git_svn? ? (`git svn dcommit`) : (`git push`)
  end
  
  def chroot
    # store cwd
    dir = Dir.pwd
    
    # find .git
    until File.directory?('.git') || File.expand_path('.') == '/'
      Dir.chdir('..')
    end
    is_git = File.directory?('.git')
    
    raise NoRepositoryError, "No repository found containing #{dir}" unless is_git
  end
  
  def git_svn?
    chroot
    (not File.readlines(".git/config").grep(/^\[svn-remote "svn"\]\s*$/).empty?)
  end
end