import optparse
import sys
import distutils.version
import os
import shutil
import logging.handlers
import errno
import tempfile
import itertools

from wizard import app, command, deploy, shell, util

def main(argv, baton):
    options, args = parse_args(argv, baton)
    if args:
        dir = args[0]
    else:
        dir = "."
    shell.drop_priviledges(dir, options.log_file)
    util.chdir(dir)
    if os.path.exists(".scripts/blacklisted"):
        raise BlacklistedError()
    sh = shell.Shell()
    util.set_git_env()
    use_shm = False # if you are running --continue, this is guaranteed to be False
    if options.continue_:
        temp_wc_dir = os.getcwd()
        user_commit, next_commit = open(".git/WIZARD_PARENTS", "r").read().split()
        repo = open(".git/WIZARD_REPO", "r").read()
        version = open(".git/WIZARD_UPGRADE_VERSION", "r").read()
        util.chdir(sh.eval("git", "config", "remote.origin.url"))
        d = deploy.Deployment(".")
        try:
            sh.call("git", "status")
            raise LocalChangesError()
        except shell.CallError:
            pass
    else:
        d = deploy.Deployment(".")
        d.verify()
        d.verifyTag(options.srv_path)
        d.verifyGit(options.srv_path)
        d.verifyConfigured()
        d.verifyVersion()
        if not options.dry_run:
            d.verifyWeb()
        repo = d.application.repository(options.srv_path)
        version = calculate_newest_version(sh, repo)
        if version == d.app_version.scripts_tag and not options.force:
            # don't log this error
            # XXX: maybe we should build this in as a flag to add
            # to exceptions w/ our exception handler
            sys.stderr.write("Traceback:\n  (n/a)\nAlreadyUpgraded\n")
            sys.exit(1)
        logging.info("Upgrading %s" % os.getcwd())
        if not options.dry_run:
            perform_pre_commit(sh)
        # If /dev/shm exists, it's a tmpfs and we can use it
        # to do a fast git merge. Don't forget to move it to
        # /tmp if it fails.
        # XXX: git merge-tree is another possibility for
        # reducing filesystem interactions, and also probably
        # works better with extra merging functionality.  However,
        # I don't know how I would put the results back in the
        # working tree.
        use_shm = os.path.exists("/dev/shm")
        temp_dir, temp_wc_dir = perform_tmp_clone(sh, use_shm)
        with util.ChangeDirectory(temp_wc_dir):
            sh.call("git", "remote", "add", "scripts", repo)
            sh.call("git", "fetch", "-q", "scripts")
            user_commit, next_commit = calculate_parents(sh, version)
            # save variables so that --continue will work
            # yeah yeah no trailing newline whatever
            open(".git/WIZARD_REPO", "w").write(repo)
            open(".git/WIZARD_UPGRADE_VERSION", "w").write(version)
            open(".git/WIZARD_PARENTS", "w").write("%s\n%s" % (user_commit, next_commit))
            perform_merge(sh, repo, d, version, use_shm)
    # variables: version, user_commit, next_commit, temp_wc_dir
    with util.ChangeDirectory(temp_wc_dir):
        try:
            sh.call("git", "status")
            sh.call("git", "commit", "-m", "throw-away commit")
        except shell.CallError:
            pass
        message = make_commit_message(version)
        new_tree = sh.eval("git", "rev-parse", "HEAD^{tree}")
        final_commit = sh.eval("git", "commit-tree", new_tree,
                "-p", user_commit, "-p", next_commit, input=message, log=True)
        # a master branch may not necessarily exist if the user
        # was manually installed to an earlier version
        try:
            sh.call("git", "checkout", "-q", "-b", "master", "--")
        except shell.CallError:
            sh.call("git", "checkout", "-q", "master", "--")
        sh.call("git", "reset", "-q", "--hard", final_commit)
        # This is a quick sanity check to make sure we didn't completely
        # mess up the merge
        d.verifyVersion()
    # Till now, all of our operations were in a tmp sandbox.
    if options.dry_run:
        logging.info("Dry run, bailing.  See results at %s" % temp_wc_dir)
        return
    # perform database backup
    backup = d.backup(options)
    # XXX: frob .htaccess to make site inaccessible
    with util.IgnoreKeyboardInterrupts():
        with util.LockDirectory(".scripts-upgrade-lock"):
            # git merge (which performs a fast forward)
            sh.call("git", "pull", "-q", temp_wc_dir, "master")
            # after the pull is successful, the directory now
            # has the objects for this commit, so we can safely
            # nuke the shm directory.  We refrain from nuking the
            # tmp directory in case we messed up the merge resolution
            # and want to be able to use it again.
            if use_shm:
                shutil.rmtree(temp_dir)
            version_obj = distutils.version.LooseVersion(version.partition('-')[2])
            try:
                # run update script
                d.upgrade(version_obj, options)
                d.verifyWeb()
            except app.UpgradeFailure:
                logging.warning("Upgrade failed: rolling back")
                perform_restore(d, backup)
                raise
            except deploy.WebVerificationError as e:
                logging.warning("Web verification failed: rolling back")
                logging.info("Web page that was output was:\n\n%s" % e.contents)
                perform_restore(d, backup)
                raise app.UpgradeVerificationFailure("Upgrade caused website to become inaccessible; site was rolled back")
    # XXX: frob .htaccess to make site accessible
    #       to do this, check if .htaccess changed, first.  Upgrade
    #       process might have frobbed it.  Don't be
    #       particularly worried if the segment disappeared

def perform_restore(d, backup):
    # You don't want d.restore() because it doesn't perform
    # the file level backup
    shell.Shell().call("wizard", "restore", backup)
    try:
        d.verifyWeb()
    except deploy.WebVerificationError:
        logging.critical("Web verification failed after rollback")

def make_commit_message(version):
    message = "Upgraded autoinstall in %s to %s.\n\n%s" % (util.get_dir_owner(), version, util.get_git_footer())
    try:
        message += "\nUpgraded-by: " + util.get_operator_git()
    except util.NoOperatorInfo:
        pass
    return message

def calculate_newest_version(sh, repo):
    # XXX: put this in Application
    return sh.eval("git", "--git-dir="+repo, "describe", "--tags", "master")

def calculate_parents(sh, version):
    user_commit = sh.eval("git", "rev-parse", "HEAD")
    next_commit = sh.eval("git", "rev-parse", version)
    return user_commit, next_commit

def perform_pre_commit(sh):
    message = "Pre-commit of %s locker before autoinstall upgrade.\n\n%s" % (util.get_dir_owner(), util.get_git_footer())
    try:
        message += "\nPre-commit-by: " + util.get_operator_git()
    except util.NoOperatorInfo:
        pass
    try:
        sh.call("git", "commit", "-a", "-m", message)
    except shell.CallError:
        logging.info("No changes detected")

def perform_tmp_clone(sh, use_shm):
    if use_shm:
        dir = "/dev/shm/wizard"
        if not os.path.exists(dir):
            os.mkdir(dir)
    else:
        dir = None
    temp_dir = tempfile.mkdtemp(prefix="wizard", dir=dir)
    temp_wc_dir = os.path.join(temp_dir, "repo")
    logging.info("Using temporary directory: " + temp_wc_dir)
    sh.call("git", "clone", "-q", "--shared", ".", temp_wc_dir)
    return temp_dir, temp_wc_dir

def perform_merge(sh, repo, d, version, use_shm):
    # naive merge algorithm:
    # sh.call("git", "merge", "-m", message, "scripts/master")
    # crazy merge algorithm:
    def make_virtual_commit(tag, parents = []):
        """WARNING: Changes state of Git repository"""
        sh.call("git", "checkout", "-q", tag, "--")
        d.parametrize(".")
        for file in d.application.parametrized_files:
            try:
                sh.call("git", "add", "--", file)
            except shell.CallError:
                pass
        virtual_tree = sh.eval("git", "write-tree", log=True)
        parent_args = itertools.chain(*(["-p", p] for p in parents))
        virtual_commit = sh.eval("git", "commit-tree", virtual_tree,
                *parent_args, input="", log=True)
        sh.call("git", "reset", "--hard")
        return virtual_commit
    user_tree = sh.eval("git", "rev-parse", "HEAD^{tree}")
    base_virtual_commit = make_virtual_commit(d.app_version.scripts_tag)
    next_virtual_commit = make_virtual_commit(version, [base_virtual_commit])
    user_virtual_commit = sh.eval("git", "commit-tree", user_tree,
            "-p", base_virtual_commit, input="", log=True)
    sh.call("git", "checkout", user_virtual_commit, "--")
    try:
        sh.call("git", "merge", next_virtual_commit)
    except shell.CallError:
        # Run the application's specific merge resolution algorithms
        # and see if we can salvage it
        curdir = os.getcwd()
        if d.application.resolveConflicts(curdir):
            logging.info("Resolved conflicts with application specific knowledge")
            sh.call("git", "commit", "-a", "-m", "merge")
            return
        logging.info("Conflict info:\n", sh.eval("git", "diff"))
        if use_shm:
            # Keeping all of our autoinstalls in shared memory is
            # a recipe for disaster, so let's move them to slightly
            # less volatile storage (a temporary directory)
            os.chdir(tempfile.gettempdir())
            newdir = tempfile.mkdtemp(prefix="wizard")
            # shutil, not os; at least on Ubuntu os.move fails
            # with "[Errno 18] Invalid cross-device link"
            shutil.move(curdir, newdir)
            shutil.rmtree(os.path.dirname(curdir))
            curdir = os.path.join(newdir, "repo")
        print curdir
        raise MergeFailed

def parse_args(argv, baton):
    usage = """usage: %prog upgrade [ARGS] [DIR]

Upgrades an autoinstall to the latest version.  This involves
updating files and running .scripts/update.

WARNING: This is still experimental."""
    parser = command.WizardOptionParser(usage)
    parser.add_option("--dry-run", dest="dry_run", action="store_true",
            default=False, help="Prints would would be run without changing anything")
    # notice trailing underscore
    parser.add_option("--continue", dest="continue_", action="store_true",
            default=False, help="Continues an upgrade that has had its merge manually "
            "resolved using the current working directory as the resolved copy.")
    parser.add_option("--force", dest="force", action="store_true",
            default=False, help="Force running upgrade even if it's already at latest version.")
    baton.push(parser, "srv_path")
    options, args = parser.parse_all(argv)
    if len(args) > 1:
        parser.error("too many arguments")
    return options, args

class Error(command.Error):
    """Base exception for all exceptions raised by upgrade"""
    pass

class AlreadyUpgraded(Error):
    def __str__(self):
        return """

ERROR: This autoinstall is already at the latest version."""

class MergeFailed(Error):
    def __str__(self):
        return """

ERROR: Merge failed.  Resolve the merge by cd'ing to the
temporary directory, finding conflicted files with `git status`,
resolving the files, adding them using `git add` and then
running `wizard upgrade --continue`."""

class LocalChangesError(Error):
    def __str__(self):
        return """

ERROR: Local changes occurred in the install while the merge was
being processed so that a pull would not result in a fast-forward.
The best way to resolve this is probably to attempt an upgrade again,
with git rerere to remember merge resolutions (XXX: not sure if
this actually works)."""

class BlacklistedError(Error):
    def __str__(self):
        return """

ERROR: This autoinstall was manually blacklisted against errors;
if the user has not been notified of this, please send them
mail."""