#!/usr/bin/env python3

# Copyright 2022, Jan Danielzick (aka. BodgeMaster)
#
# This program is free software: you can redistribute it and/or modify it
# under the terms of the GNU General Public License as published
# by the Free Software Foundation, version 3.
#
# 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 General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# version 3 along with this program.
# If not, see https://www.gnu.org/licenses/gpl-3.0.en.html

import re, time

debug_mode = False

def debug_message(text):
    if debug_mode:
        print("DEBUG: ", end="")
        print(text)


cursor_north = 'Λ'
cursor_south = 'V'
cursor_west  = '<'
cursor_east  = '>'

cursor_current = ' '

field = [
    " _________________ ",
    "|                 |",
    "|                 |",
    "|                 |",
    "|                 |",
    "|                 |",
    "|                 |",
    "|                 |",
    "|                 |",
    " ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ "
]

wall  = '#'
apple = 'ó'
goal  = '$'

cursor_position = [0, 0]

command_delay = 0.3

def clear_field():
    field = [
        " _________________ ",
        "|                 |",
        "|                 |",
        "|                 |",
        "|                 |",
        "|                 |",
        "|                 |",
        "|                 |",
        "|                 |",
        " ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ "
    ]

def draw_field():
    print("\033[2J\033[H")
    for row in range(len(field)):
        for column in range(len(field[row])):
            if column==cursor_position[0] and row==cursor_position[1]:
                print(cursor_current, end="")
            else:
                print(field[row][column], end="")
        print("")


# returns "" or error message
# Parsed code is the result of running the parser,
# though at this point the input is assumed to be valid
# and no additional checks are performed on what the parser produced.
def run_code(parsed_code):
    for i in range(len(parsed_code[0])):
        result = parsed_code[0][i](*parsed_code[1][i])
        if not result=="":
            return result
        draw_field()
        time.sleep(command_delay)
    return ""


def condition_facing_north(inverted):
    if inverted:
        return not cursor_current == cursor_north
    return cursor_current == cursor_north

def condition_facing_south(inverted):
    if inverted:
        return not cursor_current == cursor_south
    return cursor_current == cursor_south

def condition_facing_east(inverted):
    if inverted:
        return not cursor_current == cursor_east
    return cursor_current == cursor_east

def condition_facing_west(inverted):
    if inverted:
        return not cursor_current == cursor_west
    return cursor_current == cursor_west

def condition_in_front_of_wall(inverted):
    if condition_facing_north(False):
        result = field[cursor_position[1]-1][cursor_position[0]]==wall or field[cursor_position[1]-1][cursor_position[0]]=='_'
    elif condition_facing_south(False):
        result = field[cursor_position[1]+1][cursor_position[0]]==wall or field[cursor_position[1]+1][cursor_position[0]]=='¯'
    elif condition_facing_east(False):
        result = field[cursor_position[1]][cursor_position[0]+1]==wall or field[cursor_position[1]][cursor_position[0]+1]=='|'
    elif condition_facing_west(False):
        result = field[cursor_position[1]][cursor_position[0]-1]==wall or field[cursor_position[1]][cursor_position[0]-1]=='|'
    else:
        result = False
    if inverted:
        return not result
    return result

def condition_goal_reached(inverted):
    if inverted:
        return not field[cursor_position[1]][cursor_position[0]]==goal
    return field[cursor_position[1]][cursor_position[0]]==goal

def condition_on_apple(inverted):
    if inverted:
        return not field[cursor_position[1]][cursor_position[0]]==apple
    return field[cursor_position[1]][cursor_position[0]]==apple

# return value: "" or error message
def command_step():
    if condition_in_front_of_wall(False):
        return "You stepped into a wall."

    if condition_facing_north(False):
        cursor_position[1] = cursor_position[1]-1
    elif condition_facing_south(False):
        cursor_position[1] = cursor_position[1]+1
    elif condition_facing_east(False):
        cursor_position[0] = cursor_position[0]+1
    elif condition_facing_west(False):
        cursor_position[0] = cursor_position[0]-1
    else:
        return "Cannot step because direction is unknown."
    return ""

def command_left():
    global cursor_current
    if condition_facing_north(False):
        cursor_current = cursor_west
    elif condition_facing_south(False):
        cursor_current = cursor_east
    elif condition_facing_east(False):
        cursor_current = cursor_north
    elif condition_facing_west(False):
        cursor_current = cursor_south
    else:
        return "Cannot turn left because direction is unknown."
    return ""

def command_right():
    global cursor_current
    if condition_facing_north(False):
        cursor_current = cursor_east
    elif condition_facing_south(False):
        cursor_current = cursor_west
    elif condition_facing_east(False):
        cursor_current = cursor_south
    elif condition_facing_west(False):
        cursor_current = cursor_north
    else:
        return "Cannot turn right because direction is unknown."
    return ""

def command_take():
    if condition_on_apple(True):
        # Note: condition is inverted
        return "Cannot take apple, there is no apple here."
    field[cursor_position[1]] = field[cursor_position[1]][:cursor_position[0]]+" "+field[cursor_position[1]][cursor_position[0]+1:]
    return ""

def command_repeat(number, parsed_code):
    for i in range(number):
        result = run_code(parsed_code)
        if not result=="":
            return result
    return ""

def command_while(parsed_condition, parsed_code):
    while parsed_condition[0](parsed_condition[1]):
        result = run_code(parsed_code)
        if not result=="":
            return result
    return ""

def command_if(parsed_condition, parsed_then_code, parsed_else_code):
    if parsed_condition[0](parsed_condition[1]):
        result = run_code(parsed_then_code)
        if not result=="":
            return result
    elif not parsed_else_code==None:
        result = run_code(parsed_else_code)
        if not result=="":
            return result
    return ""


# returns -1 for generic error
# returns -2 if end can’t be found
def get_length_of_condition(code):
    if len(code)==0:
        return -1
    if code[0] == '<':
        length = 0
        while length<len(code) and code[length]!='>':
            length = length+1
        if length==len(code) and code[-1]!='>':
            return -2
        return length+1
    else:
        return -1


# returns -1 for generic error
# returns -2 if end can’t be found
def get_length_of_contained_code(code):
    if len(code)==0:
        return -1
    if code[0] == '(':
        length = 1
        nesting_level = 1
        while length<len(code) and nesting_level>0:
            if code[length] == '(':
                nesting_level = nesting_level+1
            elif code[length] == ')':
                nesting_level = nesting_level-1
            length = length+1
        if length==len(code) and nesting_level > 0:
            return -2
        return length
    else:
        return -1

# clean up whitespace
def format_code(code):
    regex_pattern = re.compile(r'\s+')
    code = " ".join(re.sub(regex_pattern, ' ', code).lower().split())
    code = code.replace(" (", "(")
    code = code.replace("( ", "(")
    code = code.replace(" )", ")")
    code = code.replace(") ", ")")
    code = code.replace(" <", "<")
    code = code.replace("< ", "<")
    code = code.replace(" >", ">")
    code = code.replace("< ", "<")
    code = code.replace("! ", "!")
    # add spaces back after closing parenthesis
    code = code.replace(")", ") ")
    code = code.replace(") )", "))")
    code = code.replace(") )", "))")
    if len(code)>0 and code[-1]==' ':
        return code[:-1]
    return code

# returns [function, inverted?, error message]
def parse_condition(condition_code, allowed_conditions):
    inverted = False
    condition = None
    if len(condition_code)==0:
        debug_message("  No condition specified")
        return [condition, inverted, "Syntax error: No condition specified"]
    if condition_code[0]=='!':
        debug_message("  Condition is inverted")
        inverted = True
        condition_code = condition_code[1:]
        if len(condition_code)==0:
            debug_message("  No condition specified")
            return [condition, inverted, "Syntax error: No condition specified"]

    if condition_code == "in front of wall":
        condition = condition_in_front_of_wall
    elif condition_code == "goal reached":
        condition = condition_goal_reached
    elif condition_code == "on apple":
        condition = condition_on_apple
    elif condition_code == "facing north":
        condition = condition_facing_north
    elif condition_code == "facing south":
        condition = condition_facing_south
    elif condition_code == "facing east":
        condition = condition_facing_east
    elif condition_code == "facing west":
        condition = condition_facing_west
    else:
        debug_message("  Unknown condition: "+condition_code)
        return [condition, inverted, "Unknown condition: "+condition_code]
    return [condition, inverted, ""]

# returns [[functions], [arguments], -1, ""] or [[], [], error_position, "error message"]
def parse_code(code, allowed_commands, allowed_conditions, unformatted_code=True):
    if unformatted_code:
        code = format_code(code)
        debug_message("Formatted code: "+code)

    parse_position = 0
    parsed_code = [[], [], -1, "", code]
    while parse_position < len(code):
        # find next command
        next_space = code.find(' ', parse_position)
        next_condition = code.find('<', parse_position)
        if next_space == -1:
            next_space = len(code)
        if next_condition == -1:
            next_condition = len(code)
        # Are we working with a simple command?
        if next_condition>next_space or next_condition==next_space:
            next_command = code[parse_position:next_space]
            debug_message("Next command is: "+next_command)

            parsed_code[1].append(())
            #TODO: add function to to the function list
            if next_command == "step":
                parsed_code[0].append(command_step)
            elif next_command == "left":
                parsed_code[0].append(command_left)
            elif next_command == "right":
                parsed_code[0].append(command_right)
            elif next_command == "take":
                parsed_code[0].append(command_take)
            elif next_command == "repeat":
                return [[], [], next_space, "Syntax error: Number of repetitions missing", code]
            elif next_command == "while":
                return [[], [], next_space, "Syntax error: Condition missing", code]
            elif next_command == "if":
                return [[], [], next_space, "Syntax error: Condition missing", code]
            elif next_command[0:4] == "else":
                return [[], [], parse_position, "Syntax error: Else without if statement", code]
            else:
                #TODO: better error message (especially when special chars are detected inside next_command or a known command)
                return [[], [], parse_position, "Unknown command: "+next_command, code]
            parse_position = next_space+1
        else:
            debug_message("Found control structure...")
            control_structure = code[parse_position:next_condition]
            if control_structure == "repeat":
                debug_message("  Type: repeat loop")
                parse_position = next_condition
                repetitions_length = get_length_of_condition(code[parse_position:])
                if repetitions_length == -2:
                    debug_message("  Mismatched <>")
                    return [[], [], parse_position, "Syntax error: Cannot not find matching '>' for this '<'", code]
                repetitions = code[parse_position:parse_position+repetitions_length]
                debug_message("  Number of repetitions: "+repetitions)
                repetitions_int = 0
                try:
                    repetitions_int = int(repetitions[1:-1])
                except ValueError:
                    return [[], [], parse_position, "Not a valid number: "+repetitions[1:-1], code]
                parse_position = parse_position+len(repetitions)
                contained_code_length = get_length_of_contained_code(code[parse_position:])
                if contained_code_length == -1:
                    debug_message("  Missing (")
                    return [[], [], parse_position, "Syntax error: Cannot not find '(' for contained code", code]
                if contained_code_length == -2:
                    debug_message("  Mismatched ()")
                    return [[], [], parse_position, "Syntax error: Cannot not find matching ')' for this '('", code]
                contained_code = code[parse_position:parse_position+contained_code_length]
                debug_message("  Contained code: "+contained_code)
                parsed_contained_code = parse_code(contained_code[1:-1], allowed_commands, allowed_conditions, unformatted_code=False)
                if not parsed_contained_code[2]==-1:
                    debug_message("  Error while parsing contained code")
                    return [[], [], parse_position+1+parsed_contained_code[2], parsed_contained_code[3], code]
                parse_position = parse_position+contained_code_length+1

                parsed_code[1].append((repetitions_int, parsed_contained_code))
                parsed_code[0].append(command_repeat)
                continue
            elif control_structure == "if":
                debug_message("  Type: if statement")
                parse_position = next_condition
                condition_length = get_length_of_condition(code[parse_position:])
                if condition_length == -2:
                    debug_message("  Mismatched <>")
                    return [[], [], parse_position, "Syntax error: Cannot not find matching '>' for this '<'", code]
                condition = code[parse_position:parse_position+condition_length]
                debug_message("  Condition is: "+condition)
                parsed_condition = parse_condition(condition[1:-1], allowed_conditions)
                if not parsed_condition[2]=="":
                    return [[], [], parse_position, parsed_condition[2], code]
                parse_position = parse_position+len(condition)
                then_code_length = get_length_of_contained_code(code[parse_position:])
                if then_code_length == -1:
                    debug_message("  Missing (")
                    return [[], [], parse_position, "Syntax error: Cannot not find '(' for then-code", code]
                if then_code_length == -2:
                    debug_message("  Mismatched ()")
                    return [[], [], parse_position, "Syntax error: Cannot not find matching ')' for this '('", code]
                then_code = code[parse_position:parse_position+then_code_length]
                debug_message("  Then-code: "+then_code)
                parsed_then_code = parse_code(then_code[1:-1], allowed_commands, allowed_conditions, unformatted_code=False)
                if not parsed_then_code[2]==-1:
                    debug_message("  Error while parsing then-code")
                    return [[], [], parse_position+1+parsed_then_code[2], parsed_then_code[3], code]
                parse_position = parse_position+then_code_length+1
                parsed_else_code = None
                if parse_position<len(code)+4 and code[parse_position:parse_position+4]=="else":
                    parse_position = parse_position+4
                    else_code_length = get_length_of_contained_code(code[parse_position:])
                    if else_code_length == -1:
                        debug_message("  Missing (")
                        return [[], [], parse_position, "Syntax error: Cannot not find '(' for else-code", code]
                    if else_code_length == -2:
                        debug_message("  Mismatched ()")
                        return [[], [], parse_position, "Syntax error: Cannot not find matching ')' for this '('", code]
                    else_code = code[parse_position:parse_position+else_code_length]
                    debug_message("  Else-code: "+else_code)
                    parsed_else_code = parse_code(else_code[1:-1], allowed_commands, allowed_conditions, unformatted_code=False)
                    parse_position = parse_position+else_code_length+1

                parsed_code[1].append((parsed_condition, parsed_then_code, parsed_else_code))
                parsed_code[0].append(command_if)
                continue
            elif control_structure == "while":
                debug_message("  Type: while loop")
                parse_position = next_condition
                condition_length = get_length_of_condition(code[parse_position:])
                if condition_length == -2:
                    debug_message("  Mismatched <>")
                    return [[], [], parse_position, "Syntax error: Cannot not find matching '>' for this '<'", code]
                condition = code[parse_position:parse_position+condition_length]
                debug_message("  Condition is: "+condition)
                parsed_condition = parse_condition(condition[1:-1], allowed_conditions)
                if not parsed_condition[2]=="":
                    return [[], [], parse_position, parsed_condition[2], code]
                parse_position = parse_position+len(condition)
                contained_code_length = get_length_of_contained_code(code[parse_position:])
                if contained_code_length == -1:
                    debug_message("  Missing (")
                    return [[], [], parse_position, "Syntax error: Cannot not find '(' for contained code", code]
                if contained_code_length == -2:
                    debug_message("  Mismatched ()")
                    return [[], [], parse_position, "Syntax error: Cannot not find matching ')' for this '('", code]
                contained_code = code[parse_position:parse_position+contained_code_length]
                debug_message("  Contained code: "+contained_code)
                parsed_contained_code = parse_code(contained_code[1:-1], allowed_commands, allowed_conditions, unformatted_code=False)
                if not parsed_contained_code[2]==-1:
                    debug_message("  Error while parsing contained code")
                    return [[], [], parse_position+1+parsed_contained_code[2], parsed_contained_code[3], code]
                parse_position = parse_position+contained_code_length+1

                parsed_code[1].append((parsed_condition, parsed_contained_code))
                parsed_code[0].append(command_while)
            else:
                debug_message("  Type: unknown control structure: "+control_structure)
                #TODO: better error message (especially when special chars are detected inside control_structure or a known command)
                return [[], [], parse_position, "Syntax error: Unknown control structure: "+control_structure, code]
    return parsed_code

# A wrapper for run_code that deals with potential errors produced by the parser.
# returns success or error message
def evaluate_parser_result(parsed_code):
    if not parsed_code[2]==-1:
        # parser error
        return parsed_code[3] + "\n" + (" "*parsed_code[2]) + "↓\n" + parsed_code[4]
    outcome = run_code(parsed_code)
    if not outcome=="":
        # runtime error
        # TODO: pass back information about where the error occurred
        return outcome
    #TODO: check if goal reached
    return "Success!"


def debug_setup():
    global cursor_position
    cursor_position = [1,1]
    global cursor_current
    cursor_current = cursor_south
    draw_field()

if __name__ == "__main__":
    pass