# -*- coding: UTF-8 -*-

require 'mj/tools/subprocess'
require 'mj/error'

#
#
module MJ; module VCS; module Git;

    @git_available = nil

    # Is the git executable available?
    def self.git_available?()
        return @git_available unless @git_available.nil?
        %x( git --version 2>&1 )
        @git_available = $?.success?
        return @git_available
    end

    # Thrown if git signals a problem
    class GitError < MJ::Error; end

    # A (local) git repository.
    #
    class Repository

        include MJ::Tools::SubProcess

        attr_reader :path

        # Some helper methods that should be factored out somewhere

        # Create directory +dir+ recursively if needed.
        def mkdir_p(dir)
            logger.debug "mkdir -p #{dir}"
            FileUtils.mkdir_p(dir) if !@noop
        end

        # Checkout a branch
        def checkout(opts)
            if ! exist? and ! $noop
                raise GitError, "Repository #{path} does not exist!"
            end
            # Fetch only from remote if specified
            git("checkout " + opts)
        end

        # Clone a repository
        def clone(url, branch = 'master' )
            # Initialize the repository
            init(url)
            remote_add(url, "origin")
            fetch("origin")
            checkout("-b master origin/#{branch}")
        end # def clone

        # Check if the repository exists
        def exist?
            # If path does not exist the repo does not exist
            return false if !path.exist?
            # If the path is not a directory we have a problem
            raise GitError, "#{path.to_s} is not a directory!" if !path.directory?
            # If the path is a directory but no .git directory is found we have a problem too
            if !path.join( ".git" ).exist?
                raise GitError, "#{path.to_s} is not a git repo!"
            end
            return true
        end

        def fetch(remote = nil)
            if ! exist? and ! $noop
                raise GitError, "Repository #{path} does not exist!"
            end
            # Fetch only from remote if specified
            cmd = "fetch"
            if remote
                cmd += " -q #{remote}"
            end
            git(cmd)
        end

        # Execute +command+ from working directory +wd+. If specified call +block+ with every line
        # of command output.
        def git(command, wd = path, &block)
            rc = self.class.execute "git #{command}", wd, &block
            if rc != 0
                raise GitError, "git #{command || "" } failed with error code #{rc}";
            end
            rc
        end

        def init(url)
            # If the repository already exists we cannot initialize
            if exist?
                raise GitError, "Repository #{path} already exists!"
            end
            # Create the repository parent directory if needed
            mkdir_p path
            # Initialize the repository
            git("init")
        end

        # If +noop+ is true no methods invoked on this object actually do any changes. The
        # required actions will be logged but not executed.
        def initialize(path, noop=false)
            @path = path
            @noop = noop
        end

        def log(rev="")
            @lines = Array.new
            git("log #{rev}") do |line|
                @lines << line
            end
            @lines
        end

        def rebase(branch, remote="origin")
            if ! exist? and ! $noop
                raise GitError, "Repository #{path} does not exist!"
            end
            # Fetch only from remote if specified
            cmd = "rebase "
            if remote
                cmd += "#{remote}/#{branch}"
            else
                cmd += "origin/#{branch}"
            end
            git(cmd)
        end

        # Add a new remote
        def remote_add(url, name)
            if ! exist? and ! $noop
                raise GitError, "Repository #{path} does not exist!"
            end
            # Add the origin remote
            git("remote add #{name} #{url.to_s}")
        end


    end # class Git

end; end; end # module BuildTool::VCS::Git