# CodeQ: an online programming tutor.
# Copyright (C) 2015 UL FRI
#
# This program is free software: you can redistribute it and/or modify it under
# the terms of the GNU Affero General Public License as published by the Free
# Software Foundation, either version 3 of the License, or (at your option) any
# later version.
#
# 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 Affero General Public License for more
# details.
#
# You should have received a copy of the GNU Affero General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.

import sys
import importlib.machinery
import threading
import os.path
import logging

_path_prefix = os.environ.get('CODEQ_PROBLEMS') or '/var/local/codeq-problems'
_module_loading_lock = threading.RLock()  # TODO: make a more fine-grained locking import machinery

def load_module(fullname):
#   return importlib.import_module(fullname)
    with _module_loading_lock:
        mod = sys.modules.get(fullname, None)
        if mod is None:
            parts = fullname.split('.')
            d = os.path.join(_path_prefix, *parts[:-1])
            ff = importlib.machinery.FileFinder(d, (importlib.machinery.SourceFileLoader, ['.py']))
            spec = ff.find_spec(fullname)
            if spec is None:
                logging.error('ERROR: there is no problem module {0}'.format(fullname))
                return None
            mod = type(sys)(fullname)
            mod.__loader__ = spec.loader
            mod.__package__ = spec.parent
            mod.__spec__ = spec
            if spec.has_location:
                mod.__file__ = spec.origin
                mod.__cached__ = spec.cached
            sys.modules[fullname] = mod
            try:
                spec.loader.exec_module(mod)
            except:
                try:
                    del sys.modules[fullname]
                except KeyError:
                    pass
                raise
        return mod

def load_language(language, tail_module):
    return load_module('{0}.{1}'.format(language, tail_module))

def load_group(language, problem_group, tail_module):
    return load_module('{0}.problems.{1}.{2}'.format(language, problem_group, tail_module))

def load_problem(language, problem_group, problem, tail_module):
    return load_module('{0}.problems.{1}.{2}.{3}'.format(language, problem_group, problem, tail_module))

def load_facts(language, fact_module):
    return load_module('{0}.facts.{1}'.format(language, fact_module))

def load_file(language, group, problem, name):
    path = os.path.join(_path_prefix, language, 'problems', group, problem, name)
    try:
        with open(path, 'r') as f:
            return f.read()
    except:
        return None

def load_problems(language, tuples, tail_module):
    modules = []
    for problem_group, problem in tuples:
        mod = '{0}.problems.{1}.{2}.{3}'.format(language, problem_group, problem, tail_module)
        modules.append(load_module(mod))
    return modules

def get_facts(language, problem_module):
    try:
        facts = problem_module.facts
    except AttributeError as e:
        return ''
    if facts is None:
        return ''
    module = load_facts(language, facts)
    if module:
        try:
            return module.facts
        except AttributeError as e:
            return ''
    return ''

def solutions_for_problems(language, tuples):
    if not tuples:
        return ''
    modules = load_problems(language, tuples, 'common')
    solutions = []
    for module in modules:
        try:
            solutions.append(module.solution)
        except AttributeError as me:
            pass
    return '\n'.join(solutions)