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

from wizard import command, deploy, shell, util

# XXX: need errors for history sanity checking (if the user is on a completely
# different history tree, we should abort, and manually figure out the
# appropriate rebase)
# $(git merge-base P C) == $(git rev-parse P)

def main(argv, baton):
    options, args = parse_args(argv, baton)
    if args:
        command.chdir(args[0])
    sh = shell.Shell()
    util.set_git_env()
    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()
        command.chdir(sh.eval("git", "config", "remote.origin.url"))
        d = make_deployment_from_cwd()
    else:
        d = make_deployment_from_cwd()
        repo = d.application.repository(options.srv_path)
        version = calculate_newest_version(sh, repo)
        if not options.dry_run:
            perform_pre_commit(sh)
        temp_wc_dir = perform_tmp_clone(sh)
        with util.ChangeDirectory(temp_wc_dir):
            if options.dry_run:
                # we delayed performing the pre upgrade commit
                # until we're in the temporary directory
                perform_pre_commit(sh)
            sh.call("git", "remote", "add", "scripts", repo)
            sh.call("git", "fetch", "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)
    # variables: version, user_commit, next_commit, temp_wc_dir
    with util.ChangeDirectory(temp_wc_dir):
        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", "-b", "master", "--")
        except shell.CallError:
            sh.call("git", "checkout", "master", "--")
        sh.call("git", "reset", "--hard", final_commit)
    # 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
    # XXX: frob .htaccess to make site inaccessible
    # XXX: need locking
    # git merge (which performs a fast forward)
    #   - merge could fail (race); that's /really/ dangerous.
    sh.call("git", "pull", temp_wc_dir, "master")
    # run update script
    d.application.upgrade(options)
    # XXX: frob .htaccess to make site accessible
    # XXX:  - check if .htaccess changed, first.  Upgrade
    #       process might have frobbed it.  Don't be
    #       particularly worried if the segment dissappeared

def make_deployment_from_cwd():
    if not os.path.isdir(".git"):
        raise NotAutoinstallError()
    try:
        d = deploy.Deployment(".")
    except IOError as e:
        if e.errno == errno.ENOENT:
            raise NotAutoinstallError()
        else: raise e
    return d

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):
    temp_dir = tempfile.mkdtemp(prefix="wizard")
    temp_wc_dir = os.path.join(temp_dir, "repo")
    logging.info("Using temporary directory: " + temp_wc_dir)
    sh.call("git", "clone", "--shared", ".", temp_wc_dir)
    return temp_wc_dir

def perform_merge(sh, repo, d, version):
    # 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", 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:
        print os.getcwd()
        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.")
    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 NotAutoinstallError(Error):
    def __str__(self):
        return """

ERROR: Could not find .git file. Are you sure
this is an autoinstalled application? Did you remember
to migrate it?"""

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
committing your changes with `git commit` (your log message
will be ignored), and then running `wizard upgrade --continue`."""