# Copyright (C) 2012-2015  Codethink Limited
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; version 2 of the License.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License along
# with this program.  If not, see <http://www.gnu.org/licenses/>.


import cliapp
import contextlib
import glob
import logging
import os
import shutil

import morphlib


class BranchAndMergePlugin(cliapp.Plugin):

    '''Add subcommands for handling workspaces and system branches.'''

    def enable(self):
        self.app.add_subcommand('init', self.init, arg_synopsis='[DIR]')
        self.app.add_subcommand('workspace', self.workspace, arg_synopsis='')
        self.app.add_subcommand(
            'checkout', self.checkout, arg_synopsis='REPO BRANCH')
        self.app.add_subcommand(
            'branch', self.branch, arg_synopsis='REPO NEW [OLD]')
        self.app.add_subcommand(
            'show-system-branch', self.show_system_branch, arg_synopsis='')
        self.app.add_subcommand(
            'show-branch-root', self.show_branch_root, arg_synopsis='')
        self.app.add_subcommand('status', self.status,
                                arg_synopsis='')
        self.app.add_subcommand('branch-from-image', self.branch_from_image,
                                arg_synopsis='BRANCH')
        group_branch = 'Branching Options'
        self.app.settings.string(['metadata-dir'],
                                  'Set metadata location for branch-from-image'
                                  ' (default: /baserock)',
                                  metavar='DIR',
                                  default='/baserock',
                                  group=group_branch)

    def disable(self):
        pass

    def init(self, args):
        '''Initialize a workspace directory.

        Command line argument:

        * `DIR` is the directory to use as a workspace, and defaults to
          the current directory.

        This creates a workspace, either in the current working directory,
        or if `DIR` is given, in that directory. If the directory doesn't
        exist, it is created. If it does exist, it must be empty.

        You need to run `morph init` to initialise a workspace, or none
        of the other system branching tools will work: they all assume
        an existing workspace. Note that a workspace only exists on your
        machine, not on the git server.

        Example:

            morph init /src/workspace
            cd /src/workspace

        '''

        if not args:
            args = ['.']
        elif len(args) > 1:
            raise morphlib.Error('init must get at most one argument')

        ws = morphlib.workspace.create(args[0])
        self.app.status(msg='Initialized morph workspace', chatty=True)

    def workspace(self, args):
        '''Show the toplevel directory of the current workspace.'''

        ws = morphlib.workspace.open('.')
        self.app.output.write('%s\n' % ws.root)

    # TODO: Move this somewhere nicer
    @contextlib.contextmanager
    def _initializing_system_branch(self, ws, root_url, system_branch,
                                    cached_repo, base_ref):
        '''A context manager for system branches under construction.

        The purpose of this context manager is to factor out the branch
        cleanup code for if an exception occurs while a branch is being
        constructed.

        This could be handled by a higher order function which takes
        a function to initialize the branch as a parameter, but with
        statements look nicer and are more obviously about resource
        cleanup.

        '''
        root_dir = ws.get_default_system_branch_directory_name(system_branch)
        try:
            sb = morphlib.sysbranchdir.create(
                root_dir, root_url, system_branch)
            gd = sb.clone_cached_repo(cached_repo, base_ref)

            yield (sb, gd)

            gd.update_submodules(self.app)
            gd.update_remotes()

        except morphlib.sysbranchdir.SystemBranchDirectoryAlreadyExists as e:
            logging.error('Caught exception: %s' % str(e))
            raise
        except BaseException as e:
            # Oops. Clean up.
            logging.error('Caught exception: %s' % str(e))
            logging.info('Removing half-finished branch %s' % system_branch)
            self._remove_branch_dir_safe(ws.root, root_dir)
            raise

    def checkout(self, args):
        '''Check out an existing system branch.

        Command line arguments:

        * `REPO` is the URL to the repository to the root repository of
          a system branch.
        * `BRANCH` is the name of the system branch.

        This will check out an existing system branch to an existing
        workspace.  You must create the workspace first. This only checks
        out the root repository, not the repositories for individual
        components. You need to use `morph edit` to check out those.

        Example:

            cd /src/workspace
            morph checkout baserock:baserock/morphs master

        '''

        if len(args) != 2:
            raise cliapp.AppException('morph checkout needs a repo and the '
                                      'name of a branch as parameters')

        root_url = args[0]
        system_branch = args[1]
        base_ref = system_branch

        self._require_git_user_config()

        # Open the workspace first thing, so user gets a quick error if
        # we're not inside a workspace.
        ws = morphlib.workspace.open('.')

        # Make sure the root repository is in the local git repository
        # cache, and is up to date.
        lrc, rrc = morphlib.util.new_repo_caches(self.app)
        cached_repo = lrc.get_updated_repo(root_url)

        # Check the git branch exists.
        cached_repo.resolve_ref_to_commit(system_branch)

        with self._initializing_system_branch(
            ws, root_url, system_branch, cached_repo, base_ref) as (sb, gd):

            if gd.has_fat():
                gd.fat_init()
                gd.fat_pull()


    def branch(self, args):
        '''Create a new system branch.

        Command line arguments:

        * `REPO` is a repository URL.
        * `NEW` is the name of the new system branch.
        * `OLD` is the point from which to branch, and defaults to `master`.

        This creates a new system branch. It needs to be run in an
        existing workspace (see `morph workspace`). It creates a new
        git branch in the clone of the repository in the workspace. The
        system branch will not be visible on the git server until you
        push your changes to the repository.

        Example:

            cd /src/workspace
            morph branch baserock:baserock/morphs jrandom/new-feature

        '''

        if len(args) not in [2, 3]:
            raise cliapp.AppException(
                'morph branch needs name of branch as parameter')

        root_url = args[0]
        system_branch = args[1]
        base_ref = 'master' if len(args) == 2 else args[2]
        origin_base_ref = 'origin/%s' % base_ref

        self._require_git_user_config()

        # Open the workspace first thing, so user gets a quick error if
        # we're not inside a workspace.
        ws = morphlib.workspace.open('.')

        # Make sure the root repository is in the local git repository
        # cache, and is up to date.
        lrc, rrc = morphlib.util.new_repo_caches(self.app)
        cached_repo = lrc.get_updated_repo(root_url)

        # Make sure the system branch doesn't exist yet.
        if cached_repo.ref_exists(system_branch):
            raise cliapp.AppException(
                'branch %s already exists in repository %s' %
                (system_branch, root_url))

        # Make sure the base_ref exists.
        cached_repo.resolve_ref_to_commit(base_ref)

        with self._initializing_system_branch(
            ws, root_url, system_branch, cached_repo, base_ref) as (sb, gd):

            gd.branch(system_branch, base_ref)
            gd.checkout(system_branch)
            if gd.has_fat():
                gd.fat_init()
                gd.fat_pull()

    def _save_dirty_morphologies(self, loader, sb, morphs):
        logging.debug('Saving dirty morphologies: start')
        for morph in morphs:
            if morph.dirty:
                logging.debug(
                    'Saving morphology: %s %s %s' %
                        (morph.repo_url, morph.ref, morph.filename))
                loader.unset_defaults(morph)
                loader.save_to_file(
                    sb.get_filename(morph.repo_url, morph.filename), morph)
                morph.dirty = False
        logging.debug('Saving dirty morphologies: done')

    def show_system_branch(self, args):
        '''Show the name of the current system branch.'''

        ws = morphlib.workspace.open('.')
        sb = morphlib.sysbranchdir.open_from_within('.')
        self.app.output.write('%s\n' % sb.system_branch_name)

    def show_branch_root(self, args):
        '''Show the name of the repository holding the system morphologies.

        This would, for example, write out something like:

            /src/ws/master/baserock/baserock/definitions

        when the master branch of the `baserock/baserock/definitions`
        repository is checked out.

        '''

        ws = morphlib.workspace.open('.')
        sb = morphlib.sysbranchdir.open_from_within('.')
        repo_url = sb.get_config('branch.root')
        self.app.output.write('%s\n' % sb.get_git_directory_name(repo_url))

    def _remove_branch_dir_safe(self, workspace_root, system_branch_root):
        # This function avoids throwing any exceptions, so it is safe to call
        # inside an 'except' block without altering the backtrace.

        def handle_error(function, path, excinfo):
            logging.warning ("Error while trying to clean up %s: %s" %
                             (path, excinfo))

        shutil.rmtree(system_branch_root, onerror=handle_error)

        # Remove parent directories that are empty too, avoiding exceptions
        parent = os.path.dirname(system_branch_root)
        while parent != os.path.abspath(workspace_root):
            if len(os.listdir(parent)) > 0 or os.path.islink(parent):
                break
            os.rmdir(parent)
            parent = os.path.dirname(parent)

    def _require_git_user_config(self):
        '''Warn if the git user.name and user.email variables are not set.'''

        keys = {
            'user.name': 'My Name',
            'user.email': 'me@example.com',
        }

        try:
            morphlib.git.check_config_set(self.app.runcmd, keys)
        except morphlib.git.ConfigNotSetException as e:
            self.app.status(
                msg="WARNING: %(message)s",
                message=str(e), error=True)

    def _load_all_sysbranch_morphologies(self, sb, loader):
        '''Read in all the morphologies in the root repository.'''
        self.app.status(msg='Loading in all morphologies')
        morphs = morphlib.morphset.MorphologySet()
        for morph in sb.load_all_morphologies():
            morphs.add_morphology(morph)
        return morphs

    def status(self, args):
        '''Show information about the current system branch or workspace

        This shows the status of every local git repository of the
        current system branch. This is similar to running `git status`
        in each repository separately.

        If run in a Morph workspace, but not in a system branch checkout,
        it lists all checked out system branches in the workspace.

        '''

        if args:
            raise cliapp.AppException('morph status takes no arguments')

        ws = morphlib.workspace.open('.')
        try:
            sb = morphlib.sysbranchdir.open_from_within('.')
        except morphlib.sysbranchdir.NotInSystemBranch:
            self._workspace_status(ws)
        else:
            self._branch_status(ws, sb)

    def _workspace_status(self, ws):
        '''Show information about the current workspace

        This lists all checked out system branches in the workspace.

        '''
        self.app.output.write("System branches in current workspace:\n")
        branches = sorted(ws.list_system_branches(),
                          key=lambda x: x.root_directory)
        for sb in branches:
            self.app.output.write("    %s\n" % sb.get_config('branch.name'))

    def _branch_status(self, ws, sb):
        '''Show information about the current branch

        This shows the status of every local git repository of the
        current system branch. This is similar to running `git status`
        in each repository separately.

        '''
        branch = sb.get_config('branch.name')
        root = sb.get_config('branch.root')

        self.app.output.write("On branch %s, root %s\n" % (branch, root))

        has_uncommitted_changes = False
        for gd in sorted(sb.list_git_directories(), key=lambda x: x.dirname):
            try:
                repo = gd.get_config('morph.repository')
            except cliapp.AppException:
                self.app.output.write(
                    '    %s: not part of system branch\n' % gd.dirname)
            # TODO: make this less vulnerable to a branch using
            #       refs/heads/foo instead of foo
            head = gd.HEAD
            if head != branch:
                self.app.output.write(
                    '    %s: unexpected ref checked out %r\n' % (repo, head))
            if any(gd.get_index().get_uncommitted_changes()):
                has_uncommitted_changes = True
                self.app.output.write('    %s: uncommitted changes\n' % repo)

        if not has_uncommitted_changes:
            self.app.output.write("\nNo repos have outstanding changes.\n")

    def branch_from_image(self, args):
        '''Produce a branch of an existing system image.

        Given the metadata specified by --metadata-dir, create a new
        branch then petrify it to the state of the commits at the time
        the system was built.

        If --metadata-dir is not specified, it defaults to your currently
        running system.

        '''
        if len(args) != 1:
            raise cliapp.AppException(
                "branch-from-image needs exactly 1 argument "
                "of the new system branch's name")
        system_branch = args[0]
        metadata_path = self.app.settings['metadata-dir']
        alias_resolver = morphlib.repoaliasresolver.RepoAliasResolver(
            self.app.settings['repo-alias'])

        self._require_git_user_config()

        ws = morphlib.workspace.open('.')

        system, metadata = self._load_system_metadata(metadata_path)
        resolved_refs = dict(self._resolve_refs_from_metadata(alias_resolver,
                                                              metadata))
        self.app.status(msg='Resolved refs: %r' % resolved_refs)
        base_ref = system['sha1']
        # The previous version would fall back to deducing this from the repo
        # url and the repo alias resolver, but this does not always work, and
        # new systems always have repo-alias in the metadata
        root_url = system['repo-alias']

        lrc, rrc = morphlib.util.new_repo_caches(self.app)
        cached_repo = lrc.get_updated_repo(root_url)


        with self._initializing_system_branch(
            ws, root_url, system_branch, cached_repo, base_ref) as (sb, gd):

            # TODO: It's nasty to clone to a sha1 then create a branch
            #       of that sha1 then check it out, a nicer API may be the
            #       initial clone not checking out a branch at all, then
            #       the user creates and checks out their own branches
            gd.branch(system_branch, base_ref)
            gd.checkout(system_branch)

            loader = sb.get_morphology_loader()
            morphs = self._load_all_sysbranch_morphologies(sb, loader)

            morphs.repoint_refs(sb.root_repository_url,
                                sb.system_branch_name)

            morphs.petrify_chunks(resolved_refs)

            self._save_dirty_morphologies(loader, sb, morphs.morphologies)

    @staticmethod
    def _load_system_metadata(path):
        '''Load all metadata in `path` corresponding to a single System.
        '''

        smd = morphlib.systemmetadatadir.SystemMetadataDir(path)
        metadata = smd.values()
        systems = [md for md in metadata
                   if 'kind' in md and md['kind'] == 'system']

        if not systems:
            raise cliapp.AppException(
                'Metadata directory does not contain any systems.')
        if len(systems) > 1:
            raise cliapp.AppException(
                'Metadata directory contains multiple systems.')
        system_metadatum = systems[0]
    
        metadata_cache_id_lookup = dict((md['cache-key'], md)
                                        for md in metadata
                                        if 'cache-key' in md)

        return system_metadatum, metadata_cache_id_lookup

    @staticmethod
    def _resolve_refs_from_metadata(alias_resolver, metadata):
        '''Pre-resolve a set of refs from existing metadata.

        Given the metadata, generate a mapping of all the (repo, ref)
        pairs defined in the metadata and the commit id they resolved to.

        '''
        for md in metadata.itervalues():
            repourls = set((md['repo-alias'], md['repo']))
            repourls.update(alias_resolver.aliases_from_url(md['repo']))
            for repourl in repourls:
                yield ((repourl, md['original_ref']), md['sha1'])