/* -*- mode: C++; c-basic-offset: 2; indent-tabs-mode: nil -*- */

/*
 *  Main authors:
 *     Jip J. Dekker <jip.dekker@monash.edu>
 */

/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

%define api.header.include {<minizinc/support/regex_parser.tab.hh>}

%{
#include <cstdlib>
#include <cstdio>
#include <memory>
#include <unordered_set>
#include <unordered_map>

#include <gecode/minimodel.hh>
#include <minizinc/values.hh>
using namespace Gecode;
using namespace MiniZinc;

typedef struct yy_buffer_state *YY_BUFFER_STATE;
YY_BUFFER_STATE regex_yy_scan_string ( const char* yy_str );

extern int yylex();
extern FILE* yyin;

typedef struct REContext{
  REG* expr;
  const IntSetVal& dom;
  const std::unordered_map<std::string, int>& idMap;
} REContext;

void yyerror(REContext& ctx, const char* s);
%}

%union {
  int iValue;
  char* sValue;
  std::unordered_set<int>* setValue;
  Gecode::REG* rValue;
}
%parse-param {REContext& ctx}

%token<iValue> R_INTEGER
%token R_GROUP_OPEN "("
%token R_GROUP_CLOSE ")"
%token R_STAR "*"
%token R_PLUS "+"
%token R_ANY "."
%token R_UNION "|"
%token R_OPTIONAL "?"
%token R_QUANT_OPEN "{"
%token R_QUANT_CLOSE "}"
%token R_COMMA ","
%token R_CLASS_OPEN "["
%token R_CLASS_CLOSE "]"
%token R_CLASS_RANGE "-"
%token R_CLASS_NEG "^"
%token<sValue> R_IDENTIFIER

%type<iValue> literal
%type<rValue> regex expression term factor atom
%type<setValue> set_item set_items

%start regex

%%

regex:
  expression
  {
    *ctx.expr = (*$1);
    delete $1;
  }

expression:
    term
  | term "|" expression
    {
      *$1 = *$1 | *$3;
      delete $3;
      $$ = $1;
    }

term:
    factor
  | factor term
    {
      *$1 = *$1 + *$2;
      delete $2;
      $$ = $1;
    }

factor:
    atom
  | atom "*"
    {
      *$1 = *(*$1);
      $$ = $1;
    }
  | atom "+"
    {
      *$1 = +(*$1);
      $$ = $1;
    }
  | atom "?"
    {
      *$1 = (*$1)(0, 1);
      $$ = $1;
    }
  | atom "{" R_INTEGER "}"
    {
      *$1 = (*$1)($3, $3);
      $$ = $1;
    }
  | atom "{" R_INTEGER "," "}"
    {
      *$1 = (*$1)($3);
      $$ = $1;
    }
  | atom "{" R_INTEGER "," R_INTEGER "}"
    {
      *$1 = (*$1)($3, $5);
      $$ = $1;
    }

atom:
    literal
    { $$ = new REG($1); }
  | "."
    {
      IntArgs range = IntArgs::create(ctx.dom.max().toInt() - ctx.dom.min().toInt() + 1, ctx.dom.min().toInt());
      $$ = new REG(range);
    }
  | "[" set_items "]"
    {
      std::vector<int> v;
      v.reserve($2->size());
      for(auto i : *$2) {
        v.push_back(i);
      }
      delete $2;
      $$ = new REG(IntArgs(v));
    }
  | "[" "^" set_items "]"
    {
      std::vector<int> diff;
      std::unordered_set<int> domain;
      for(int i = ctx.dom.min().toInt(); i<=ctx.dom.max().toInt(); ++i) {
        domain.insert(i);
      }
      std::set_difference(
        domain.begin(), domain.end(),
        $3->begin(), $3->end(),
        std::inserter(diff, diff.begin())
      );
      delete $3;
      $$ = new REG(IntArgs(diff));
    }
  | "(" expression ")"
    { $$ = $2; }

set_items:
    set_item
  | set_item set_items
    {
      $$ = $1;
      for (auto i : *$2) {
        $1->insert(i);
      }
      delete $2;
    }

set_item:
    literal
    {
      $$ = new std::unordered_set<int>({$1});
    }
  | literal "-" literal
    {
      int from = $1;
      int to = $3;
      if (to < from) {
        std::swap(from,to);
      }
      $$ = new std::unordered_set<int>;
      for(int i = from; i<=to; ++i) {
        $$->insert(i);
      }
    }

literal:
    R_INTEGER
  | R_IDENTIFIER
    {
      std::string s($1);
      auto find = ctx.idMap.find(s);
      if (find == ctx.idMap.end()) {
        throw std::runtime_error("Unknown identifier: " + s);
      }
      $$ = find->second;
    }

%%

void yyerror(REContext& ctx, const char* s) {
    // TODO: Add error location
    throw std::runtime_error("Cannot parse regular expression: " + std::string(s));
}

std::unique_ptr<REG> regex_from_string(const std::string& regex_str, const IntSetVal& domain, const std::unordered_map<std::string, int>& identifiers) {
    REG* expr = new REG();
    regex_yy_scan_string(regex_str.c_str());
    REContext rctx = REContext{expr, domain, identifiers};
    int err = yyparse(rctx);
    if (err != 0) {
        throw std::runtime_error("Cannot parse regular expression, error code " + std::to_string(err));
    }
    return std::unique_ptr<REG>(expr);
}