# Copyright (C) 2010 by Intevation GmbH
# Authors:
# Andre Heinecke <aheinecke@intevation.de>
#
# This program is free software under the GPL (>=v2)
# Read the file COPYING coming with the software for details.

"""Collection of Git utility code"""

import os
import shutil
import re
import StringIO

import run
from cmdexpand import cmdexpand
from util import extract_value_for_key


class GitError(Exception):

    """Base class for Git specific errors raised by TreePKG"""

def checkout(url, localdir, branch=None):
    """Clones the repository at url into the localdir"""
    run.call(cmdexpand("git clone $url $localdir", **locals()))
    if branch:
        run.call(cmdexpand("git checkout --track -b local $branch",
                            **locals()), cwd=localdir)
    else:
        run.call(cmdexpand("git checkout --track -b local master"),
                            cwd=localdir)

def update(localdir, revision=None):
    """Runs git pull on the localdir."""
    run.call(cmdexpand("git pull -q"), cwd=localdir)

def export(src, dest):
    """Exports the local branch from src to dest"""
    dest = dest + os.sep
    run.call(cmdexpand("git checkout-index -a -f --prefix=$dest", **locals()),
             cwd=src)

def last_changed_revision(git_working_copy):
    """Return the SHA1 sum of the latest commit"""
    output = run.capture_output(cmdexpand("git rev-parse HEAD"),
                                cwd=git_working_copy)
    if output is None:
        raise GitError("Cannot determine last changed revision for %r"
                       % git_working_copy)
    return output.strip()

class GitRepository(object):

    """Describes a git repository"""

    def __init__(self, url, branch=None):
        """Initialize the git repository description
        Parameters:
          url -- The url of the repository

          branch -- The name of the remote Branch to track
                    defaults to master
        """
        self.url = url
        self.branch = branch

    def checkout(self, localdir):
        """Checks out the repository into localdir."""
        checkout(self.url , localdir, self.branch)
        update(localdir)

    def export(self, localdir, destdir):
        """Exports the working copy in localdir to destdir"""
        export(localdir, destdir)

    def last_changed_revision(self, localdir):
        """Returns the last changed revision of the working copy in localdir"""
        return last_changed_revision(localdir)

    def check_working_copy(self, localdir):
        """FIXME STUB: Not implemented for git"""
        return None

class GitWorkingCopy(object):

    """Represents a checkout of a git repository"""

    def __init__(self, repository, localdir, logger=None):
        """
        Initialize the working copy.
        Parameters:
          repository -- The GitRepository instance describing the
                        repository
          localdir -- The directory for the working copy
          logger -- logging object to use for some info/debug messages
        """
        self.repository = repository
        self.localdir = localdir
        self.logger = logger

    def log_info(self, *args):
        if self.logger is not None:
            self.logger.info(*args)

    def update_or_checkout(self, revision=0):
        """Updates the working copy or creates by checking out the repository.
           Revision number included for compatibility
        """
        if os.path.exists(self.localdir):
            self.log_info("Updating the working copy in %r", self.localdir)
            update(self.localdir, self.repository.branch)
        else:
            self.log_info("The working copy in %r doesn't exist yet."
                          "  Checking out from %r",
                          self.localdir, self.repository.url)
            self.repository.checkout(self.localdir)

    def export(self, destdir):
        """Exports the working copy to destdir"""
        self.repository.export(self.localdir, destdir)

    def last_changed_revision(self):
        """Returns the last changed rev of the working copy"""
        return self.repository.last_changed_revision(self.localdir)

    def list_tags(self, pattern):
        output = run.capture_output(cmdexpand("git tag -l $pattern",
            pattern=pattern), cwd=self.localdir)
        return output.splitlines()

    def get_revision(self, refname="HEAD"):
        """Return the SHA1 sum of the latest commit"""
        output = run.capture_output(cmdexpand("git rev-parse $id",
            refname=refname), cwd=git_working_copy)
        if output is None:
            raise GitError("Cannot determine revision for %r"
                           % git_working_copy)
        return output.strip()

class TagDetector:

    """Class to detect tags from a git repository

    The tags are found using the parameters:
      url -- The url of the git repository to use
      pattern -- A regular expression matching the tags
    """

    def __init__(self, url, pattern, localdir):
        self.url = url
        self.pattern = pattern
        repo = GitRepository(url)
        self.workingcopy = GitWorkingCopy(repo, localdir)

    def newest_tag_revision(self):
        self.workingcopy.update_or_checkout()
        candidates = self.workingcopy.list_tags(self.pattern)
        candidates = sorted(candidates)
        urlrev = (None, None)
        if candidates:
            newest = candidates[-1]
            try:
                rev = self.workingcopy.get_revision(newest)
                urlrev = (newest, rev)
            except GitError:
                pass
        return urlrev