# ***************************************************************************
# *   Copyright (c) 2020 Werner Mayer <wmayer[at]users.sourceforge.net>     *
# *                                                                         *
# *   This file is part of the FreeCAD CAx development system.              *
# *                                                                         *
# *   This program is free software; you can redistribute it and/or modify  *
# *   it under the terms of the GNU Lesser General Public License (LGPL)    *
# *   as published by the Free Software Foundation; either version 2 of     *
# *   the License, or (at your option) any later version.                   *
# *   for detail see the LICENCE text file.                                 *
# *                                                                         *
# *   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 Library General Public License for more details.                  *
# *                                                                         *
# *   You should have received a copy of the GNU Library General Public     *
# *   License along with this program; if not, write to the Free Software   *
# *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  *
# *   USA                                                                   *
# *                                                                         *
# ***************************************************************************

__title__ = "FEM Utilities"
__author__ = "Werner Mayer"
__url__ = "https://www.freecad.org"

tokens = (
    'NAME',
    'FLOAT',
    'INT',
    'PLUS',
    'MINUS',
    'TIMES',
    'DIVIDE',
    'EQUALS',
    'LPAREN',
    'RPAREN',
    'POWER'
)

# Tokens

t_PLUS = r'\+'
t_MINUS = r'-'
t_TIMES = r'\*'
t_DIVIDE = r'/'
t_EQUALS = r'='
t_LPAREN = r'\('
t_RPAREN = r'\)'
t_POWER = r'\^'
t_NAME = r'[a-zA-Z_][a-zA-Z0-9_]*'


def t_FLOAT(t):
    r'\d+\.(\d+)?([eE][-+]?\d+)?'
    t.value = float(t.value)
    return t


def t_INT(t):
    r'\d+'
    t.value = int(t.value)
    return t


# Ignored characters
t_ignore = " \t"


def t_COMMENT(t):
    r'\#.*'
    pass


def t_newline(t):
    r'\n+'
    t.lexer.lineno += t.value.count("\n")


def t_error(t):
    print("Illegal character '%s'" % t.value[0])
    t.lexer.skip(1)


# Build the lexer
import ply.lex as lex
lex.lex()


# Precedence rules for the arithmetic operators
precedence = (
    ('left', 'PLUS', 'MINUS'),
    ('left', 'TIMES', 'DIVIDE'),
    ('left', 'POWER'),
    ('right', 'UMINUS')
)

# dictionary of names (for storing variables)
names = {}


def p_statement_assign(p):
    'statement : NAME EQUALS expression'
    names[p[1]] = p[3]


def p_statement_expr(p):
    'statement : expression'
    print(p[1])


def p_expression_binop(p):
    '''expression : expression PLUS expression
                  | expression MINUS expression
                  | expression TIMES expression
                  | expression DIVIDE expression
                  | expression POWER expression'''
    if p[2] == '+'  : p[0] = p[1] + p[3]
    elif p[2] == '-': p[0] = p[1] - p[3]
    elif p[2] == '*': p[0] = p[1] * p[3]
    elif p[2] == '/': p[0] = p[1] / p[3]
    elif p[2] == '^': p[0] = p[1] ** p[3]


def p_expression_uminus(p):
    'expression : MINUS expression %prec UMINUS'
    p[0] = -p[2]


def p_expression_group(p):
    'expression : LPAREN expression RPAREN'
    p[0] = p[2]


def p_expression_float(p):
    'expression : FLOAT'
    p[0] = p[1]


def p_expression_int(p):
    'expression : INT'
    p[0] = p[1]


def p_expression_name(p):
    'expression : NAME'
    try:
        p[0] = names[p[1]]
    except LookupError:
        print("Undefined name '%s'" % p[1])
        p[0] = 0


def p_error(p):
    print("Syntax error at '%s'" % p.value)


import ply.yacc as yacc
yacc.yacc(debug=False, write_tables=False)