/* -*- 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.
 */

#include <assert.h>
#include <limits>
#include "s_expression.h"

s_symbol::s_symbol(const char *str, size_t n)
{
   /* Assume the given string is already nul-terminated and in memory that
    * will live as long as this node.
    */
   assert(str[n] == '\0');
   this->str = str;
}

s_list::s_list()
{
}

static void
skip_whitespace(const char *&src, char *&symbol_buffer)
{
   size_t n = strspn(src, " \v\t\r\n");
   src += n;
   symbol_buffer += n;
   /* Also skip Scheme-style comments: semi-colon 'til end of line */
   if (src[0] == ';') {
      n = strcspn(src, "\n");
      src += n;
      symbol_buffer += n;
      skip_whitespace(src, symbol_buffer);
   }
}

static s_expression *
read_atom(void *ctx, const char *&src, char *&symbol_buffer)
{
   s_expression *expr = NULL;

   skip_whitespace(src, symbol_buffer);

   size_t n = strcspn(src, "( \v\t\r\n);");
   if (n == 0)
      return NULL; // no atom

   // Check for the special symbol '+INF', which means +Infinity.  Note: C99
   // requires strtof to parse '+INF' as +Infinity, but we still support some
   // non-C99-compliant compilers (e.g. MSVC).
   if (n == 4 && strncmp(src, "+INF", 4) == 0) {
      expr = new(ctx) s_float(std::numeric_limits<float>::infinity());
   } else {
      // Check if the atom is a number.
      char *float_end = NULL;
      float f = glsl_strtof(src, &float_end);
      if (float_end != src) {
         char *int_end = NULL;
         int i = strtol(src, &int_end, 10);
         // If strtof matched more characters, it must have a decimal part
         if (float_end > int_end)
            expr = new(ctx) s_float((float)f);
         else
            expr = new(ctx) s_int(i);
      } else {
         // Not a number; return a symbol.
         symbol_buffer[n] = '\0';
         expr = new(ctx) s_symbol(symbol_buffer, n);
      }
   }

   src += n;
   symbol_buffer += n;

   return expr;
}

static s_expression *
__read_expression(void *ctx, const char *&src, char *&symbol_buffer)
{
   s_expression *atom = read_atom(ctx, src, symbol_buffer);
   if (atom != NULL)
      return atom;

   skip_whitespace(src, symbol_buffer);
   if (src[0] == '(') {
      ++src;
      ++symbol_buffer;

      s_list *list = new(ctx) s_list;
      s_expression *expr;

      while ((expr = __read_expression(ctx, src, symbol_buffer)) != NULL) {
	 list->subexpressions.push_tail(expr);
      }
      skip_whitespace(src, symbol_buffer);
      if (src[0] != ')') {
	 printf("Unclosed expression (check your parenthesis).\n");
	 return NULL;
      }
      ++src;
      ++symbol_buffer;
      return list;
   }
   return NULL;
}

s_expression *
s_expression::read_expression(void *ctx, const char *&src)
{
   assert(src != NULL);

   /* When we encounter a Symbol, we need to save a nul-terminated copy of
    * the string.  However, ralloc_strndup'ing every individual Symbol is
    * extremely expensive.  We could avoid this by simply overwriting the
    * next character (guaranteed to be whitespace, parens, or semicolon) with
    * a nul-byte.  But overwriting non-whitespace would mess up parsing.
    *
    * So, just copy the whole buffer ahead of time.  Walk both, leaving the
    * original source string unmodified, and altering the copy to contain the
    * necessary nul-bytes whenever we encounter a symbol.
    */
   char *symbol_buffer = ralloc_strdup(ctx, src);
   return __read_expression(ctx, src, symbol_buffer);
}

void s_int::print()
{
   printf("%d", this->val);
}

void s_float::print()
{
   printf("%f", this->val);
}

void s_symbol::print()
{
   printf("%s", this->str);
}

void s_list::print()
{
   printf("(");
   foreach_in_list(s_expression, expr, &this->subexpressions) {
      expr->print();
      if (!expr->next->is_tail_sentinel())
	 printf(" ");
   }
   printf(")");
}

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

bool
s_pattern::match(s_expression *expr)
{
   switch (type)
   {
   case EXPR:   *p_expr = expr; break;
   case LIST:   if (expr->is_list())   *p_list   = (s_list *)   expr; break;
   case SYMBOL: if (expr->is_symbol()) *p_symbol = (s_symbol *) expr; break;
   case NUMBER: if (expr->is_number()) *p_number = (s_number *) expr; break;
   case INT:    if (expr->is_int())    *p_int    = (s_int *)    expr; break;
   case STRING:
      s_symbol *sym = SX_AS_SYMBOL(expr);
      if (sym != NULL && strcmp(sym->value(), literal) == 0)
	 return true;
      return false;
   };

   return *p_expr == expr;
}

bool
s_match(s_expression *top, unsigned n, s_pattern *pattern, bool partial)
{
   s_list *list = SX_AS_LIST(top);
   if (list == NULL)
      return false;

   unsigned i = 0;
   foreach_in_list(s_expression, expr, &list->subexpressions) {
      if (i >= n)
	 return partial; /* More actual items than the pattern expected */

      if (expr == NULL || !pattern[i].match(expr))
	 return false;

      i++;
   }

   if (i < n)
      return false; /* Less actual items than the pattern expected */

   return true;
}
