#!/usr/bin/env python3

import os;
import readline
import argparse
import pickle;
import sys;

def parse_args(argv):
    parser = argparse.ArgumentParser(prog = '4-variable-simplifier');
    
    parser.add_argument('-c', '--command', help = '''
        Provide a boolean expression to simpliy on the command-line.
        Without this option, boolean expressions are read stdin.
    ''')
    
    parser.add_argument('-e', '--extended-operators', action='store_true', help='''
        Use more than just the standard three boolean operators (not, or, and).
        This options allows use of: nor, nand, xor, nxor, andn, orn.
    ''')
    
    parser.add_argument('-o', '--custom-operators', help='''
        Pick and choose which operators the simplifier can use. Comma seperated.
        You can refer to them using their names or their symbols.
    ''')
    
    parser.add_argument("-n", '--use-names', help='''
        Print the operator's names in the expression tree, rather than the
        symbols.
    ''')
    
    parser.add_argument('-p', "--printout", action = 'store_true', help='''
        Print out all simplified expressions for the given expressions and
        quit.
    ''')
    
    parser.add_argument("--simplifications-file", \
        default = ".simplifications.bin", help='''
        Path to pickle file that stores the cached simplifications.
    ''')
    
    parser.add_argument("-y", "--yes", action = 'store_true', help='''
        Do not ask before generating simplification cache.
    ''')
    
    parser.add_argument("-q", "--quiet", action = 'store_true', help='''
        Do not print anything but the simplification. Assumes '--yes'.
    ''')
    
    parser.add_argument("-C", "--color", default = 'auto', \
        choices = ["off", "on", "auto"], help='''
        Select whether to use terminal colors. Default is to use if it is
        supported. use '--color=on' to force it on. '--color=off' otherwise.
    ''')
    
    return parser.parse_args(argv[1:]);

symbol_to_name = {
    "!": "not",
    "||": "or",
    "&&": "and",
    "!|": "nor",
    "!&": "nand",
    "!=": "xor",
    "==": "nxor",
    "|!": "orn",
    "&!": "andn",
};

def determine_available_operators(args):
    standard = ("!", "||", "&&");
    
    extended = ("!|", "!&", "!=", "==", "|!", "&!");
    
    if args.extended_operators:
        return set(standard + extended);
    elif args.custom_operators:
        available_operators = set();
        
        for o in args.custom_operators.split(","):
            if o in symbol_to_name:
                available_operators.add(o);
            elif o in symbol_to_name.values():
                for k, v in symbol_to_name.items():
                    if v == o:
                        available_operators.add(k);
            else:
                raise BaseException(f"not an operator: '{o}'");
        
        return available_operators;
    else:
        return set(standard);

def pretty(exp):
    match exp:
        case ("literal", x):
            return str(x);
        
        case ("variable", x):
            return x
        
        case (op, inner):
            return f"({op}{pretty(inner)})"
        
        case (op, left, right):
            return f"({pretty(left)} {op} {pretty(right)})"
        
        case _:
            print(exp);
            assert(not "TODO");

W = 0b0101_0101_0101_0101
X = 0b0011_0011_0011_0011
Y = 0b0000_1111_0000_1111
Z = 0b0000_0000_1111_1111

M = 0b1111_1111_1111_1111

def calculate_simplifications(args, available_operators):
    print(f'available_operators = {available_operators}')
    
    lookup = dict() # truthtable -> expression

    costs = dict() # truthtable -> cost

    todo = [set() for _ in range(100)] # indexed by cost, set of truthtables.
    
    todo_count = [0]; # I have to wrap in an array because python is dumb.
    
    def prequeue(truthtable, expression, cost):
        lookup[truthtable] = expression;
        costs[truthtable] = cost;
        todo[cost].add(truthtable);
        todo_count[0] += 1;
    
    # literals:
    prequeue(0b1111_1111_1111_1111, ("literal", 1), cost = 1);
    prequeue(0b0000_0000_0000_0000, ("literal", 0), cost = 1);

    # variables:
    prequeue(W, ("variable", "w"), cost = 0);
    prequeue(X, ("variable", "x"), cost = 0);
    prequeue(Y, ("variable", "y"), cost = 0);
    prequeue(Z, ("variable", "z"), cost = 0);
    
    # Completely unnecessary critera, alphabetical variables is more
    # aesthetically pleasing. Thanks Benson.
    def is_aesthetically_better(this, that):
        def extract_variables(exp):
            match exp:
                case ("literal", x):
                    return ();
                case ("variable", x):
                    return (x, )
                case (_, inner):
                    return extract_variables(inner);
                case (_, left, right):
                    return extract_variables(left) + extract_variables(right);
                case _:
                    print(exp);
                    assert(not "TODO");

        return extract_variables(this) < extract_variables(that);

    unary_operators = {
        '!': lambda x: ~x,
    }

    binary_operators = {
        '||': lambda x, y: (x | y) & M,
        '&&': lambda x, y: (x & y) & M,

        '!|': lambda x, y: ~(x | y) & M,
        '!&': lambda x, y: ~(x & y) & M,

        '&!': lambda x, y: (~x & y) & M,
        '|!': lambda x, y: (~x | y) & M,

        '!=': lambda x, y: (x ^ y) & M,
        '==': lambda x, y: (~(x ^ y)) & M,
    }
    
    def print_status():
        numerator = 65536 - todo_count[0];
        denominator = 65536
        
        line = f'{numerator} of 65536';
        line += f' ({numerator / denominator * 100:.2f}%):'
        line += f' [{my_cost}]';
        line += f' {pretty(my_expression)}';
        
        print(line);
    
    min_cost = 0;
    
    while todo_count[0]:
        truthtables = todo[min_cost];

        if not truthtables:
            min_cost += 1;
            continue;

        assert(todo_count[0] <= 65536);

        my_truthtable = min(truthtables);
        truthtables.discard(my_truthtable);
        my_cost = min_cost;
        my_expression = lookup[my_truthtable];
        todo_count[0] -= 1;
        
        if not args.quiet:
            print_status();
        
        def consider(new_truthtable, new_expression, new_cost):
            if new_truthtable not in costs:
                todo[new_cost].add(new_truthtable);

                costs[new_truthtable] = new_cost
                lookup[new_truthtable] = new_expression
                
                todo_count[0] += 1;
            elif new_cost < costs[new_truthtable] or \
                    (new_cost == costs[new_truthtable] and \
                        is_aesthetically_better(new_expression, \
                            lookup[new_truthtable])):
                current_cost = costs[new_truthtable];

                assert(new_cost >= min_cost);

                todo[current_cost].discard(new_truthtable);
                todo[new_cost].add(new_truthtable);

                costs[new_truthtable] = new_cost
                lookup[new_truthtable] = new_expression

        # consider unary operators:
        for name, function in sorted(unary_operators.items()):
            if name in available_operators:
                unary_truthtable = function(my_truthtable) & M;
                unary_expression = (name, my_expression);
                unary_cost = my_cost + 1;

                consider(unary_truthtable, unary_expression, unary_cost);

        # consider binary operators:
        for name, function in sorted(binary_operators.items()):
            if name in available_operators:
                for other_truthtable, other_expression in sorted(lookup.items()):
                    # x + y
                    binary_truthtable = function(my_truthtable, other_truthtable);
                    binary_truthtable = binary_truthtable & M
                    binary_expression = (name, my_expression, other_expression);
                    binary_cost = my_cost + 1 + costs[other_truthtable];

                    consider(binary_truthtable, binary_expression, binary_cost);

                    # y + x
                    binary_truthtable = function(other_truthtable, my_truthtable);
                    binary_truthtable = binary_truthtable & M
                    binary_expression = (name, other_expression, my_expression);
                    binary_cost = my_cost + 1 + costs[other_truthtable];

                    consider(binary_truthtable, binary_expression, binary_cost);

    return costs, lookup

pathname = "simplifications.bin"

def get_simplifications(args, available_operators):
    available_operators = tuple(sorted(available_operators));
    
    try:
        with open(pathname, "rb") as stream:
            cache = pickle.load(stream);
    except FileNotFoundError:
        cache = dict();
    
    if available_operators not in cache:
        if not args.quiet:
            print("Oh! looks like you're running this for the first time");
            print("I'll have to build up my cache of simplifications");
            print("This may take a while.");
            print("I'll only have to do this once.");

            if not args.yes:
                print();
                input("any input to start:");
                print();
        
        bundle = calculate_simplifications(args, available_operators);
        
        if not args.quiet:
            print();
            print("done!");
            print();
        
        cache[available_operators] = bundle;
        
        with open(pathname, "wb") as stream:
            pickle.dump(cache, stream);
        
        if not args.quiet:
            print();
            print("saved!");
            print();
    
    return cache[available_operators];

def create_parser():
    import pyparsing as pp

    from pyparsing import Forward, Suppress, Keyword, Group, ZeroOrMore, Optional, Literal

    root = Forward()

    literal = pp.Word('01');

    variable = pp.Word('wxyz')

    highest = literal | variable | (Suppress('(') + root + Suppress(')'));

    prefix_expression = Group(Literal("!") + highest) | highest

    relational_expression = \
          Group(prefix_expression + Literal('<=')  + prefix_expression) \
        | Group(prefix_expression + Literal('>=')  + prefix_expression) \
        | Group(prefix_expression + Literal('>') + prefix_expression) \
        | Group(prefix_expression + Literal('<') + prefix_expression) \
        | Group(prefix_expression + Literal('==') + prefix_expression) \
        | Group(prefix_expression + Literal('!=') + prefix_expression) \
        | prefix_expression;

    logical_and_expression = Forward();
    logical_and_expression <<= \
          Group(relational_expression + Literal('&&') + logical_and_expression) \
        | Group(relational_expression + Literal('!&') + logical_and_expression) \
        | Group(relational_expression + Literal('&!') + logical_and_expression) \
        | relational_expression;

    logical_or_expression = Forward()
    logical_or_expression <<= \
          Group(logical_and_expression + Literal('||') + logical_or_expression) \
        | Group(logical_and_expression + Literal('!|') + logical_or_expression) \
        | Group(logical_and_expression + Literal('|!') + logical_or_expression) \
        | logical_and_expression;

    root <<= logical_or_expression;
    
    return root;


def parse(parser, text):
    return parser.parseString(text, parseAll = True).asList()[0]

def evaluate(expr):
    match expr:
        case "0":
            return 0;
        case "1":
            return M;
        case "w":
            return W;
        case "x":
            return X;
        case "y":
            return Y;
        case "z":
            return Z;
        case ("!", subexp):
            return ~evaluate(subexp) & M;
        case (left, "||", right):
            return evaluate(left) | evaluate(right);
        case (left, "!|", right):
            return ~(evaluate(left) | evaluate(right)) & M;
        case (left, "|!", right):
            return (~evaluate(left) | evaluate(right)) & M;
        case (left, "&&", right):
            return evaluate(left) & evaluate(right);
        case (left, "!&", right):
            return ~(evaluate(left) & evaluate(right)) & M;
        case (left, "&!", right):
            return (~evaluate(left) & evaluate(right)) & M;
        case (left, "<", right):
            return (~evaluate(left) & evaluate(right)) & M;
        case (left, "<=", right):
            return (~evaluate(left) | evaluate(right)) & M;
        case (left, ">", right):
            return (evaluate(left) & ~evaluate(right)) & M;
        case (left, ">=", right):
            return (evaluate(left) | ~evaluate(right)) & M;
        case (left, "==", right):
            return ~(evaluate(left) ^ evaluate(right)) & M;
        case (left, "!=", right):
            return evaluate(left) ^ evaluate(right);
        case _:
            print(exp);
            assert(not "TODO");

def repl(args, cost, lookup):
    import readline;
    
    print("""
Give a boolean expression using the variables 'w', 'x', 'y' and 'z'.
Operations: not ('!'), or ('||'), and ('&&').
Extended operations: nor ('!|'), orn ('|!'), nand ('!&'), andn ('&!'), xor ('!='),
Extended operations: nxor ('==')
    """);
    
    # print(f'I can do anything in {max(cost.values())} operations.')
    # print();
    
    parser = create_parser();
    
    while True:
        try:
            line = input(">>> ");
        except EOFError:
            return;
            
        truthtable = evaluate(parse(parser, line));
        
        if truthtable in lookup:
            print(f'{cost[truthtable]}: {pretty(lookup[truthtable])}')
        else:
            print('unreachable.')

def main(args):
    available_operators = determine_available_operators(args);
    
    match args.color:
        case 'off': args.color = False;
        case 'on': args.color = True;
        case 'auto': args.color = os.isatty(1);
    
    cost, lookup = get_simplifications(args, available_operators);
    
    if args.printout:
        for truthtable, exp in sorted(lookup.items()):
            print(f'{truthtable:016b}: {pretty(exp)}');
    elif args.command:
        truthtable = evaluate(parse(create_parser(), args.command));
        
        if truthtable in lookup:
            print(pretty(lookup[truthtable]));
        else:
            print('unreachable.')
    else:
        repl(args, cost, lookup);
    
    return 0;


exit(main(parse_args(sys.argv)))