import yaml
import random
import re
import subprocess
import sys

# Example usage:
#
#   pool = QuestionPool()
#   pool.add_from_file('filename.yaml')
#   pool.add_from_files(['file1.yaml', 'file1.yaml'])
#
#   test = []
#   for q in pool.values():
#       test.append(create_question(q))
#
#   test[0]['answer'] = 42           # insert answer
#   grade = test[0].correct()        # correct answer


# ===========================================================================
class QuestionsPool(dict):
    '''This class contains base questions read from files, but which are
    not ready yet. They have to be instantiated separatly for each student.'''

    #------------------------------------------------------------------------
    def add_from_file(self, filename):
        try:
            with open(filename, 'r') as f:
                questions = yaml.load(f)
        except(FileNotFoundError):
            print('  * Questions file "{0}" not found. Aborting...'.format(filename))
            sys.exit(1)
        except(yaml.parser.ParserError):
            print('  * Error in questions file "{0}". Aborting...'.format(filename))
            sys.exit(1)

        # add defaults if missing from sources
        for i, q in enumerate(questions):
            if not isinstance(q, dict):
                print('  * question with index {0} in file {1} is not a dict. Ignoring...'.format(i, filename))
                continue

            if q['ref'] in self:
                print('  * question "{0}" in file "{1}" already exists in file "{2}". Ignoring...'.format(q['ref'], filename, self[q['ref']]['filename']))

            # filename and index (number in the file, 0 based)
            q['filename'] = filename
            q['index'] = i

            # ref  (if missing, add 'filename.yaml:3')
            q['ref'] = str(q.get('ref', filename + ':' + str(i)))

            # type  (default type is 'information')
            q['type'] = str(q.get('type', 'information'))

            # add question to the pool
            self[q['ref']] = q

    #------------------------------------------------------------------------
    def add_from_files(self, file_list):
        for filename in file_list:
            self.add_from_file(filename)


#============================================================================
# Question Factory
# Given a dictionary returns a question instance.
def create_question(q):
    '''To create a question, q must be a dictionary with at least the
    following keys defined:
        filename
        ref
        type
    The remaing keys depend on the type of question.
    '''

    if q['type'] == 'generator':
        q.update(question_generator(q))
    # at this point the generator question was replaced by an actual question

    types = {
        'radio'     : QuestionRadio,
        'checkbox'  : QuestionCheckbox,
        'text'      : QuestionText,
        'text_regex': QuestionTextRegex,
        # 'text-regex': QuestionTextRegex,
        # 'regex'     : QuestionTextRegex,
        'textarea'  : QuestionTextArea,
        'information': QuestionInformation,
        # 'info'      : QuestionInformation,
        # ''          : QuestionInformation,  # default
    }

    # create instance of given type
    try:
        questiontype = types[q['type']]
    except KeyError:
        print('  * unsupported question type "{0}" in "{1}:{2}".'.format(q['type'], q['filename'], q['ref']))
        questiontype = Question

    # create question instance and return
    try:
        qinstance = questiontype(q)
    except:
        print('  * Error creating question "{0}" from file "{1}".'.format(q['ref'], q['filename']))

    return qinstance


# ---------------------------------------------------------------------------
def question_generator(q):
    '''Run an external script that will generate a question in yaml format.
    This function will return the yaml converted back to a dict.'''

    q['stdin'] = q.get('stdin', '')

    try:
        p = subprocess.Popen([q['script']], stdout=subprocess.PIPE, stdin=subprocess.PIPE, stderr=subprocess.STDOUT)
    except FileNotFoundError:
        print('  * Script "{0}" defined in question "{1}" of file "{2}" could not be found'.format(q['script'], q['ref'], q['filename']))

    try:
        qyaml = p.communicate(input=q['stdin'].encode('utf-8'), timeout=5)[0].decode('utf-8')
    except subprocess.TimeoutExpired:
        p.kill()

    return yaml.load(qyaml)


# ===========================================================================
class Question(dict):
    '''
    Classes derived from this base class are meant to instantiate a question
    to a student.
    Instances can shuffle options, or automatically generate questions.
    '''
    def correct(self):
        self['grade'] = 0.0
        return 0.0


# ===========================================================================
class QuestionRadio(Question):
    '''An instance of QuestionRadio will always have the keys:
        type (str)
        text (str)
        options (list of strings)
        shuffle (bool, default True)
        correct (list of floats)
        discount (bool, default True)
        answer (None or an actual answer)
    '''

    #------------------------------------------------------------------------
    def __init__(self, q):
        # create key/values as given in q
        super().__init__(q)

        self['text'] = self.get('text', '')

        # generate an order for the options, e.g. [0,1,2,3,4]
        n = len(self['options'])
        perm = list(range(n))

        # shuffle the order, e.g. [2,1,4,0,3]
        if self.get('shuffle', True):
            self['shuffle'] = True
            random.shuffle(perm)
        else:
            self['shuffle'] = False

        # sort options in the given order
        options = [None] * n  # will contain list with shuffled options
        for i, v in enumerate(self['options']):
            options[perm[i]] = str(v)  # always convert to string
        self['options'] = options

        # default correct option is the first one
        if 'correct' not in self:
            self['correct'] = 0

        # correct can be either an integer with the correct option
        # or a list of degrees of correction 0..1
        # always convert to list, e.g. [0,0,1,0,0]
        if isinstance(self['correct'], int):
            correct = [0.0] * n
            correct[self['correct']] = 1.0
            self['correct'] = correct

        # sort correct in the given order
        correct = [None] * n
        for i, v in enumerate(self['correct']):
            correct[perm[i]] = float(v)
        self['correct'] = correct
        self['discount'] = bool(self.get('discount', True))
        self['answer'] = None


    #------------------------------------------------------------------------
    # can return negative values for wrong answers
    def correct(self):
        if self['answer'] is None:
            x = 0.0      # zero points if no answer given
        else:
            x = self['correct'][int(self['answer'])]
            if self['discount']:
                n = len(self['options'])  # number of options
                x_aver = sum(self['correct']) / n
                x = (x - x_aver) / (1.0 - x_aver)

        self['grade'] = x
        return x


# ===========================================================================
class QuestionCheckbox(Question):
    '''An instance of QuestionCheckbox will always have the keys:
        type (str)
        text (str)
        options (list of strings)
        shuffle (bool, default True)
        correct (list of floats)
        discount (bool, default True)
        answer (None or an actual answer)
    '''

    #------------------------------------------------------------------------
    def __init__(self, q):
        # create key/values as given in q
        super().__init__(q)

        self['text'] = self.get('text', '')

        # generate an order for the options, e.g. [0,1,2,3,4]
        n = len(self['options'])
        perm = list(range(n))

        # shuffle the order, e.g. [2,1,4,0,3]
        if self.get('shuffle', True):
            self['shuffle'] = True
            random.shuffle(perm)
        else:
            self['shuffle'] = False

        # sort options in the given order
        options = [None] * n  # will contain list with shuffled options
        for i, v in enumerate(self['options']):
            options[perm[i]] = str(v)  # always convert to string
        self['options'] = options

        # default is to give zero to all options [0,0,...,0]
        if 'correct' not in self:
            self['correct'] = [0.0] * n

        # sort correct in the given order
        correct = [None] * n
        for i, v in enumerate(self['correct']):
            correct[perm[i]] = float(v)
        self['correct'] = correct

        self['discount'] = bool(self.get('discount', True))

        self['answer'] = None

    #------------------------------------------------------------------------
    # can return negative values for wrong answers
    def correct(self):
        if self['answer'] is None:
            # not answered
            self['grade'] = 0.0
        else:
            # answered
            sum_abs = sum(abs(p) for p in self['correct'])
            if sum_abs < 1e-6:  # in case correct: [0,0,0,0,0]
                self['grade'] = 0.0

            else:
                x = 0.0

                if self['discount']:
                    for i, p in enumerate(self['correct']):
                        x += p if str(i) in self['answer'] else -p
                else:
                    for i, p in enumerate(self['correct']):
                        x += p if str(i) in self['answer'] else 0.0

                self['grade'] = x / sum_abs

        return self['grade']


# ===========================================================================
class QuestionText(Question):
    '''An instance of QuestionCheckbox will always have the keys:
        type (str)
        text (str)
        correct (list of str)
        answer (None or an actual answer)
    '''

    #------------------------------------------------------------------------
    def __init__(self, q):
        # create key/values as given in q
        super().__init__(q)

        self['text'] = self.get('text', '')

        # make sure its always a list of possible correct answers
        if not isinstance(self['correct'], list):
            self['correct'] = [self['correct']]

        # make sure the elements of the list are strings
        for i, a in enumerate(self['correct']):
            self['correct'][i] = str(a)

        self['answer'] = None

    #------------------------------------------------------------------------
    # can return negative values for wrong answers
    def correct(self):
        if self['answer'] is None:
            # not answered
            self['grade'] = 0.0
        else:
            # answered
            self['grade'] = 1.0 if self['answer'] in self['correct'] else 0.0

        return self['grade']


# ===========================================================================
class QuestionTextRegex(Question):
    '''An instance of QuestionCheckbox will always have the keys:
        type (str)
        text (str)
        correct (str with regex)
        answer (None or an actual answer)
    '''

    #------------------------------------------------------------------------
    def __init__(self, q):
        # create key/values as given in q
        super().__init__(q)
        self['text'] = self.get('text', '')
        self['answer'] = None

    #------------------------------------------------------------------------
    # can return negative values for wrong answers
    def correct(self):
        if self['answer'] is None:
            # not answered
            self['grade'] = 0.0
        else:
            # answered
            self['grade'] = 1.0 if re.match(self['correct'], self['answer']) else 0.0

        return self['grade']


# ===========================================================================
class QuestionTextArea(Question):
    '''An instance of QuestionCheckbox will always have the keys:
        type (str)
        text (str)
        correct (str with script to run)
        answer (None or an actual answer)
    '''

    #------------------------------------------------------------------------
    def __init__(self, q):
        # create key/values as given in q
        super().__init__(q)
        self['text'] = self.get('text', '')
        self['answer'] = None

    #------------------------------------------------------------------------
    # can return negative values for wrong answers
    def correct(self):
        if self['answer'] is None:
            # not answered
            self['grade'] = 0.0
        else:
            # answered

            # The correction program expects data from stdin and prints the result to stdout.
            # The result should be a string that can be parsed to a float.
            try:
                p = subprocess.Popen([self['correct']], stdout=subprocess.PIPE, stdin=subprocess.PIPE, stderr=subprocess.STDOUT)
            except FileNotFoundError as e:
                print('  * Script "{0}" defined in question "{1}" of file "{2}" could not be found'.format(self['correct'], self['ref'], self['filename']))
                raise e

            try:
                value = p.communicate(input=self['answer'].encode('utf-8'), timeout=5)[0].decode('utf-8')  # esta a dar erro!
            except subprocess.TimeoutExpired:
                p.kill()
                # p.communicate() # FIXME parece que este communicate obriga a ficar ate ao final do processo,  mas nao consigo repetir o comportamento num script simples...
                value = 0.0  # student gets a zero if timout occurs
                printf('  * Timeout in correction script')

            # In case the correction program returns a non float value, we assume an error
            # has occurred (for instance, invalid input). We just assume its the student's
            # fault and give him Zero.
            try:
                self['grade'] = float(value)
            except (ValueError):
                self['grade'] = 0.0
                raise Exception('Correction of question "{0}" returned nonfloat "{1}".'.format(self['ref'], value))

        return self['grade']


# ===========================================================================
class QuestionInformation(Question):
    '''An instance of QuestionInformation will always have the keys:
        type (str)
        text (str)
        points (0.0)
    '''
    #------------------------------------------------------------------------
    def __init__(self, q):
        # create key/values as given in q
        super().__init__(q)
        self['text'] = self.get('text', '')
        self['points'] = 0.0  # always override the points

    #------------------------------------------------------------------------
    # can return negative values for wrong answers
    def correct(self):
        self['grade'] = 1.0  # always "correct" but points should be zero!
        return self['grade']