# -*- coding: utf-8 -*-
##############################################################################
# Name: peg_peg.py
# Purpose: PEG parser definition using PEG itself.
# Author: Igor R. Dejanovic <igor DOT dejanovic AT gmail DOT com>
# Copyright: (c) 2009 Igor R. Dejanovic <igor DOT dejanovic AT gmail DOT com>
# License: MIT License
#
# PEG can be used to describe PEG.
# This example demonstrates building PEG parser using PEG based grammar of PEG
# grammar definition language.
##############################################################################
from arpeggio import *
from arpeggio.export import PMDOTExporter, PTDOTExporter
from arpeggio.peg import ParserPEG

# Semantic actions
from arpeggio.peg import SemGrammar, SemRule, SemOrderedChoice, SemSequence,\
    SemPrefix, SemSufix, SemExpression, SemRegEx, SemIdentifier, SemLiteral,\
    SemTerminal

sem_actions = {
    "grammar":         SemGrammar(),
    "rule":            SemRule(),
    "ordered_choice":  SemOrderedChoice(),
    "sequence":        SemSequence(),
    "prefix":          SemPrefix(),
    "sufix":           SemSufix(),
    "expression":      SemExpression(),
    "regex":           SemRegEx(),
    "identifier":      SemIdentifier(),
    "literal":         SemLiteral()
}

for sem in ["LEFT_ARROW", "SLASH", "STAR", "QUESTION", "PLUS", "AND", "NOT",
            "OPEN", "CLOSE"]:
    sem_actions[sem] = SemTerminal()


# PEG defined using PEG itself.
peg_grammar = r"""
 grammar <- rule+ EndOfFile;
 rule <- identifier LEFT_ARROW ordered_choice ';';
 ordered_choice <- sequence (SLASH sequence)*;
 sequence <- prefix+;
 prefix <- (AND/NOT)? sufix;
 sufix <- expression (QUESTION/STAR/PLUS)?;
 expression <- regex / (identifier !LEFT_ARROW)
                / ("(" ordered_choice ")") / literal;

 identifier <- r'[a-zA-Z_]([a-zA-Z_]|[0-9])*';
 regex <- 'r\'' r'(\\\'|[^\'])*' '\'';
 literal <- r'\'(\\\'|[^\'])*\'|"[^"]*"';
 LEFT_ARROW <- '<-';
 SLASH <- '/';
 AND <- '&';
 NOT <- '!';
 QUESTION <- '?';
 STAR <- '*';
 PLUS <- '+';
 OPEN <- '(';
 CLOSE <- ')';
 DOT <- '.';
 comment <- '//' r'.*\n';
"""


# ParserPEG will use ParserPython to parse peg_grammar definition and
# create parser_model for parsing PEG based grammars
parser = ParserPEG(peg_grammar, 'grammar', debug=True)

# Exporting parser model to dot file for visualization.
PMDOTExporter().exportFile(parser.parser_model,
                         "peg_peg_parser_model.dot")

# Now we will use created parser to parse the same peg_grammar used for
# parser initialization. We can parse peg_grammar because it is specified
# using PEG itself.
parser.parse(peg_grammar)

# Again we export parse tree in dot file for vizualization.
PTDOTExporter().exportFile(parser.parse_tree,
                         "peg_peg_parse_tree.dot")

# ASG should be the same as parser.parser_model because semantic
# actions will create PEG parser (tree of ParsingExpressions).
asg = parser.getASG(sem_actions)

# This graph should be the same as peg_peg_parser_model.dot because
# they define the same parser.
PMDOTExporter().exportFile(asg,
                         "peg_peg_asg.dot")

# If we replace parser_mode with ASG constructed parser it will still
# parse PEG grammars
parser.parser_model = asg
parser.parse(peg_grammar)