/* -*- c++ -*- */
/*
 * Copyright © 2010 Intel Corporation
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice (including the next
 * paragraph) shall be included in all copies or substantial portions of the
 * Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 * DEALINGS IN THE SOFTWARE.
 */

#pragma once
#ifndef S_EXPRESSION_H
#define S_EXPRESSION_H

#include "main/core.h" /* for Elements */
#include "strtod.h"
#include "list.h"

/* Type-safe downcasting macros (also safe to pass NULL) */
#define SX_AS_(t,x) ((x) && ((s_expression*) x)->is_##t()) ? ((s_##t*) (x)) \
                                                           : NULL
#define SX_AS_LIST(x)   SX_AS_(list, x)
#define SX_AS_SYMBOL(x) SX_AS_(symbol, x)
#define SX_AS_NUMBER(x) SX_AS_(number, x)
#define SX_AS_INT(x)    SX_AS_(int, x)

/* Pattern matching macros */
#define MATCH(list, pat) s_match(list, Elements(pat), pat, false)
#define PARTIAL_MATCH(list, pat) s_match(list, Elements(pat), pat, true)

/* For our purposes, S-Expressions are:
 * - <int>
 * - <float>
 * - symbol
 * - (expr1 expr2 ... exprN)     where exprN is an S-Expression
 *
 * Unlike LISP/Scheme, we do not support (foo . bar) pairs.
 */
class s_expression : public exec_node
{
public:
   /**
    * Read an S-Expression from the given string.
    * Advances the supplied pointer to just after the expression read.
    *
    * Any allocation will be performed with 'ctx' as the ralloc owner.
    */
   static s_expression *read_expression(void *ctx, const char *&src);

   /**
    * Print out an S-Expression.  Useful for debugging.
    */
   virtual void print() = 0;

   virtual bool is_list()   const { return false; }
   virtual bool is_symbol() const { return false; }
   virtual bool is_number() const { return false; }
   virtual bool is_int()    const { return false; }

protected:
   s_expression() { }
};

/* Atoms */

class s_number : public s_expression
{
public:
   bool is_number() const { return true; }

   virtual float fvalue() = 0;

protected:
   s_number() { }
};

class s_int : public s_number
{
public:
   s_int(int x) : val(x) { }

   bool is_int() const { return true; }

   float fvalue() { return float(this->val); }
   int value() { return this->val; }

   void print();

private:
   int val;
};

class s_float : public s_number
{
public:
   s_float(float x) : val(x) { }

   float fvalue() { return this->val; }

   void print();

private:
   float val;
};

class s_symbol : public s_expression
{
public:
   s_symbol(const char *, size_t);

   bool is_symbol() const { return true; }

   const char *value() { return this->str; }

   void print();

private:
   const char *str;
};

/* Lists of expressions: (expr1 ... exprN) */
class s_list : public s_expression
{
public:
   s_list();

   virtual bool is_list() const { return true; }

   void print();

   exec_list subexpressions;
};

// ------------------------------------------------------------

/**
 * Part of a pattern to match - essentially a record holding a pointer to the
 * storage for the component to match, along with the appropriate type.
 */
class s_pattern {
public:
   s_pattern(s_expression *&s) : p_expr(&s),   type(EXPR)   { }
   s_pattern(s_list       *&s) : p_list(&s),   type(LIST)   { }
   s_pattern(s_symbol     *&s) : p_symbol(&s), type(SYMBOL) { }
   s_pattern(s_number     *&s) : p_number(&s), type(NUMBER) { }
   s_pattern(s_int        *&s) : p_int(&s),    type(INT)    { }
   s_pattern(const char *str)  : literal(str), type(STRING) { }

   bool match(s_expression *expr);

private:
   union {
      s_expression **p_expr;
      s_list       **p_list;
      s_symbol     **p_symbol;
      s_number     **p_number;
      s_int        **p_int;
      const char *literal;
   };
   enum { EXPR, LIST, SYMBOL, NUMBER, INT, STRING } type;
};

bool
s_match(s_expression *top, unsigned n, s_pattern *pattern, bool partial);

#endif /* S_EXPRESSION_H */