#!/usr/bin/env python3

import importlib
import os
import re
import pathlib
import traceback

from argparse import ArgumentParser

PATH = pathlib.Path(__file__).parent
INPUT_PATH = PATH / 'input'

class Tests(list):
    """
    Test cases class. A test case is a tuple of the form
    (puzzle_input, partI_result, partII_result).
    """

    def add(self, test_input, partI=None, partII=None):
        """Add a test case"""
        self.append((str(test_input), partI, partII))

def testf(tests, f, part):
    """
    Tests a function f on test cases tests and compares the result
    to test_case[part]. The test is not run if test_case[part] == None.
    """
    tests = [(t[0], t[part]) for t in tests if t[part] != None]
    if tests == []:
        return "No tests"
    for i, (case, sol) in enumerate(tests):
        if sol == None:
            continue
        r = f(case)
        if r == sol:
            continue
        return "Failed on test {}. Expected {}. Got {}".format(i+1, sol, r)
    return "OK" 



class Solver:
    """
    Solver class. A solver is a module with functions partI and partII,
    an optional preprocessing function preproc, and an optional variable
    tests of type Tests.
    """

    def __init__(self, mod):
        """Initilizes the solver instance of module mod."""
        def unpack(name, default):
            """Returns mod.name if it exists and default otherwise."""
            return getattr(mod, name) if name in dir(mod) else default

        dn_pattern = re.compile("\d\d?")
        self.preproc = unpack('preproc', NotImplemented)
        self.tests = unpack('tests', [])
        self.partI = getattr(mod, 'partI')
        self.partII = getattr(mod, 'partII')


    def solve(self, puzzle_input):
        """Solves puzzle input and returns pair of solutions"""
        puzzle_input = puzzle_input.rstrip()
        if self.preproc != NotImplemented:
            puzzle_input = self.preproc(puzzle_input)
        ptI = self.partI(puzzle_input)
        ptII = self.partII(puzzle_input)
        return ptI, ptII

    def test(self):
        """Tests the solver and returns pair of test results."""
        tests = self.tests
        if self.preproc != NotImplemented:
            tests = [(self.preproc(str(t)), s1, s2)
                    for (t, s1, s2) in tests]
        ptI  = testf(tests, self.partI, 1)
        ptII = testf(tests, self.partII, 2)
        return ptI, ptII



        return r


parser = ArgumentParser()

parser.description = \
"""Solves Advent of Code 2019 puzzle of day {}.
   The puzzle is available at https://adventofcode.com/2019/day/{}"""

parser.add_argument('-d', '--day',
                    action='store',
                    type=str,
                    metavar='DAY[-DAY]',
                    help='solve puzzle of day DAY or of range DAY-DAY')

parser.add_argument('-i', '--input',
                    action='store',
                    type=str,
                    metavar='INPUT',
                    default=INPUT_PATH,
                    help='use INPUT as puzzle input')



parser.add_argument('-t', '--test',
                    action='store_true',
                    help="run tests")

def parse_day_arg(s, mind, maxd):
    """Parses day argument. Returns a list of days."""
    split = s.split('-')
    if len(split) == 1:
        return [int(split[0])]
    elif len(split) == 2:
        d, D = map(int, split)
        return list(range(max(1, d), min(D+1, 26)))
    raise ValueError


def main():
    solver_pattern = re.compile("day(\d\d?).py")
    matches = map(solver_pattern.fullmatch, os.listdir(PATH))
    solvers = {int(s.group(1)) : s.group(0) for s in matches if s != None}
    
    mind, maxd = min(solvers), max(solvers)
    days = sorted(solvers.keys())

    args = parser.parse_args()
    #Handle day argument
    if args.day != None:
        try:
            days = parse_day_arg(args.day, mind, maxd)
        except ValueError:
            return 'invalid format of argument -d/--day'

    #Handle input argument
    inputs = {}
    input_path = pathlib.Path('.') 
    num_pattern = re.compile(r'\d\d?')
    try:
        fs = os.listdir(args.input)
        input_path /= args.input
        for fn in fs:
            ns = num_pattern.findall(fn)
            if ns == []:
                print('warning : ignoring input file {}'.format(fn))
                continue
            n = int(ns[0])
            inputs[n] = fn
    except FileNotFoundError:
        return "input directory or file doesn't exist"
    except NotADirectoryError:
        if len(days) > 1:
            return "input is file"
        day = days[0]
        inputs[day] = args.input

    #Solve days
    for d in days:
        print("=" * 6 + "  Day {}  ".format(d) + "=" * 6)
        if d not in solvers:
            return "no solver for day {}".format(d)
        mod_name = solvers[d][:-3]
        try:
            mod = importlib.import_module(mod_name)
            solver = Solver(mod)
        except:
            return "bad solver\n\n{}".format(traceback.format_exc())
        try:
            if args.test:
                ptI, ptII = solver.test()
            else:
                if d not in inputs:
                    return 'no input file'
                with open(input_path / inputs[d]) as f:
                    puzzle_input = f.read()
                ptI, ptII = solver.solve(puzzle_input)
            print("Part One : {}".format(ptI))
            print("Part Two : {}".format(ptII))
        except:
            return "error in solver\n\n{}".format(traceback.format_exc())

if __name__ == '__main__':
    error = main()
    if error != None:
        print('error : {}'.format(error))