# QFactory is a class that can generate question instances, e.g. by shuffling
# options, running a script to generate the question, etc.
#
# To generate an instance of a question we use the method generate() where
# the argument is the reference of the question we wish to produce.
#
# Example:
#
#   # read question from file
#   qdict = tools.load_yaml(filename)
#   qfactory = QFactory(question)
#   question = qfactory.generate()
#
#   # experiment answering one question and correct it
#   question.updateAnswer('42')      # insert answer
#   grade = question.correct()       # correct answer

# An instance of an actual question is an object that inherits from Question()
#
# Question          - base class inherited by other classes
# QuestionRadio     - single choice from a list of options
# QuestionCheckbox  - multiple choice, equivalent to multiple true/false
# QuestionText      - line of text compared to a list of acceptable answers
# QuestionTextRegex - line of text matched against a regular expression
# QuestionTextArea  - corrected by an external program
# QuestionInformation - not a question, just a box with content

import random
import re
from os import path
import logging
import sys

# setup logger for this module
logger = logging.getLogger(__name__)

try:
    import yaml
except ImportError:
    logger.critical('Python package missing. See README.md for instructions.')
    sys.exit(1)
else:
    # allow regular expressions in yaml files, for example
    #       correct: !regex '[aA]zul'
    yaml.add_constructor('!regex', lambda l, n: re.compile(l.construct_scalar(n)))

from tools import load_yaml, run_script


# ===========================================================================
# Questions derived from Question are already instantiated and ready to be
# presented to students.
# ===========================================================================
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 __init__(self, q):
        super().__init__(q)

        # add these if missing
        self.set_defaults({
            'title': '',
            'answer': None,
            'files': {},
            })

    def updateAnswer(answer=None):
        self['answer'] = answer

    def correct(self, answer=None):
        if answer is not None:
            self['answer'] = answer
        self['grade'] = 0.0
        self['comments'] = ''
        return 0.0

    def set_defaults(self, d):
        'Add k:v pairs from default dict d for nonexistent keys'
        for k,v in d.items():
            self.setdefault(k, v)


# ===========================================================================
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):
        super().__init__(q)

        # set defaults if missing
        self.set_defaults({
            'text': '',
            'correct': 0,
            'shuffle': True,
            'discount': True,
            })

        n = len(self['options'])

        # always convert to list, e.g.  correct: 2 --> correct: [0,0,1,0,0]
        # correctness levels from 0.0 to 1.0 (no discount here!)
        if isinstance(self['correct'], int):
            self['correct'] = [1.0 if x==self['correct'] else 0.0 for x in range(n)]

        if len(self['correct']) != n:
            logger.error('Options and correct mismatch in "{1}", file "{0}".'.format(self['filename'], self['ref']))

        # generate random permutation, e.g. [2,1,4,0,3]
        # and apply to `options` and `correct`
        if self['shuffle']:
            perm = list(range(n))
            random.shuffle(perm)
            self['options'] = [ str(self['options'][i]) for i in perm ]
            self['correct'] = [ float(self['correct'][i]) for i in perm ]

    #------------------------------------------------------------------------
    # can return negative values for wrong answers
    def correct(self, answer=None):
        super().correct(answer)

        if self['answer']:
            x = self['correct'][int(self['answer'][0])]
            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 self['grade']


# ===========================================================================
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):
        super().__init__(q)

        n = len(self['options'])

        # set defaults if missing
        self.set_defaults({
            'text': '',
            'correct': [0.0] * n,     # useful for questionaries
            'shuffle': True,
            'discount': True,
            })

        if len(self['correct']) != n:
            logger.error('Options and correct mismatch in "{1}", file "{0}".'.format(self['filename'], self['ref']))

        # generate random permutation, e.g. [2,1,4,0,3]
        # and apply to `options` and `correct`
        if self['shuffle']:
            perm = list(range(n))
            random.shuffle(perm)
            self['options'] = [ str(self['options'][i]) for i in perm ]
            self['correct'] = [ float(self['correct'][i]) for i in perm ]

    #------------------------------------------------------------------------
    # can return negative values for wrong answers
    def correct(self, answer=None):
        super().correct(answer)

        if self['answer'] is not None:
            sum_abs = sum(abs(p) for p in self['correct'])
            if sum_abs < 1e-6:  # case correct [0,...,0] avoid div-by-zero
                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 QuestionText will always have the keys:
        type (str)
        text (str)
        correct (list of str)
        answer (None or an actual answer)
    '''

    #------------------------------------------------------------------------
    def __init__(self, q):
        super().__init__(q)

        self.set_defaults({
            'text': '',
            'correct': [],
            })

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

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

    #------------------------------------------------------------------------
    # can return negative values for wrong answers
    def correct(self, answer=None):
        super().correct(answer)

        if self['answer']:
            self['grade'] = 1.0 if self['answer'][0] in self['correct'] else 0.0

        return self['grade']


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

    #------------------------------------------------------------------------
    def __init__(self, q):
        super().__init__(q)

        self.set_defaults({
            'text': '',
            'correct': '$.^',   # will always return false
            })

    #------------------------------------------------------------------------
    # can return negative values for wrong answers
    def correct(self, answer=None):
        super().correct(answer)
        if self['answer']:
            try:
                self['grade'] = 1.0 if re.match(self['correct'], self['answer'][0]) else 0.0
            except TypeError:
                logger.error('While matching regex {0} with answer {1}.'.format(self['correct'], self['answer'][0]))

        return self['grade']


# ===========================================================================
class QuestionTextNumeric(Question):
    '''An instance of QuestionTextNumeric will always have the keys:
        type (str)
        text (str)
        correct (list [lower bound, upper bound])
        answer (None or an actual answer)
    An answer is correct if it's in the closed interval.
    '''

    #------------------------------------------------------------------------
    def __init__(self, q):
        super().__init__(q)

        self.set_defaults({
            'text': '',
            'correct': [1.0, -1.0],   # will always return false
            })

    #------------------------------------------------------------------------
    # can return negative values for wrong answers
    def correct(self, answer=None):
        super().correct(answer)
        if self['answer']:
            lower, upper = self['correct']
            try:
                self['grade'] = 1.0 if lower <= float(self['answer'][0]) <= upper else 0.0
            except TypeError:
                logger.error('While matching regex {0} with answer {1}.'.format(self['correct'], self['answer'][0]))
            except ValueError:
                self['comments'] = f'A resposta "{self["answer"][0]}" não é numérica.'
        return self['grade']


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

    #------------------------------------------------------------------------
    def __init__(self, q):
        logger.debug('QuestionTextArea.__init__()')
        super().__init__(q)

        self.set_defaults({
            'text': '',
            'lines': 8,
            'timeout': 5,  # seconds
            'correct': ''  # trying to execute this will fail => grade 0.0
            })

        self['correct'] = path.abspath(path.normpath(path.join(self['path'], self['correct'])))

    #------------------------------------------------------------------------
    # can return negative values for wrong answers
    def correct(self, answer=None):
        super().correct(answer)

        if self['answer']:
            # correct answer
            out = run_script(
                script=self['correct'],
                stdin=self['answer'][0],
                timeout=self['timeout']
                )
            if type(out) in (int, float):
                self['grade'] = float(out)

            elif isinstance(out, dict):
                self['comments'] = out.get('comments', '')
                try:
                    self['grade'] = float(out['grade'])
                except ValueError:
                    logger.error('Correction script of "{0}" returned nonfloat.'.format(self['ref']))
                except KeyError:
                    logger.error('Correction script of "{0}" returned no "grade" key.'.format(self['ref']))

        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):
        super().__init__(q)
        self.set_defaults({
            'text': '',
            })

    #------------------------------------------------------------------------
    # can return negative values for wrong answers
    def correct(self, answer=None):
        super().correct(answer)
        self['grade'] = 1.0  # always "correct" but points should be zero!
        return self['grade']




# ===========================================================================
# Question Factory
# ===========================================================================
class QFactory(object):
    # Depending on the type of question, a different question class will be
    # instantiated. All these classes derive from the base class `Question`.
    _types = {
        'radio'     : QuestionRadio,
        'checkbox'  : QuestionCheckbox,
        'text'      : QuestionText,
        'text_regex': QuestionTextRegex,
        'text_numeric': QuestionTextNumeric,
        'textarea'  : QuestionTextArea,
        # -- informative panels --
        'information': QuestionInformation,
        'info'      : QuestionInformation, # same as 'information'
        'warning'   : QuestionInformation,
        'alert'     : QuestionInformation,
        'success'   : QuestionInformation,
        }

    def __init__(self, question_dict):
        self.question = question_dict

    # -----------------------------------------------------------------------
    # Given a ref returns an instance of a descendent of Question(),
    # i.e. a question object (radio, checkbox, ...).
    # -----------------------------------------------------------------------
    def generate(self):
        logger.debug(f'Generating "{self.question["ref"]}"')
        # Shallow copy so that script generated questions will not replace
        # the original generators
        q = self.question.copy()

        # If question is of generator type, an external program will be run
        # which will print a valid question in yaml format to stdout. This
        # output is then yaml parsed into a dictionary `q`.
        if q['type'] == 'generator':
            logger.debug(f'Running script "{q["script"]}"...')
            q.setdefault('arg', '') # optional arguments will be sent to stdin
            script = path.join(q['path'], q['script'])
            out = run_script(script=script, stdin=q['arg'])
            q.update(out)
            # try:
            #     q.update(out)
            # except:
            #     logger.error(f'Question generator "{q["ref"]}"')
            #     q.update({
            #         'type': 'alert',
            #         'title': 'Erro interno',
            #         'text': 'Ocorreu um erro a gerar esta pergunta.'
            #         })

        # Finally we create an instance of Question()
        try:
            qinstance = self._types[q['type']](q)   # instance with correct class
        except KeyError as e:
            logger.error(f'Failed to generate question "{q["ref"]}"')
            raise e
        else:
            return qinstance