/*
  * simple arithmetic expression evaluator
  *

  * Copyright (c) 2002-2006 Michael Niedermayer <michaelni@gmx.at>

  * Copyright (c) 2006 Oded Shimon <ods15@ods15.dyndns.org>

  *

  * This file is part of FFmpeg.
  *
  * FFmpeg is free software; you can redistribute it and/or

  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation; either

  * version 2.1 of the License, or (at your option) any later version.

  *

  * FFmpeg 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
  * Lesser General Public License for more details.
  *
  * You should have received a copy of the GNU Lesser General Public

  * License along with FFmpeg; if not, write to the Free Software

  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

  */
 

 /**

  * @file libavcodec/eval.c

  * simple arithmetic expression evaluator.
  *

  * see http://joe.hotchkiss.com/programming/eval/eval.html
  */
 

 #include "avcodec.h"

 #include "eval.h"

 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <math.h>
 

 #ifndef NAN

   #define NAN 0.0/0.0

 #endif
 

 #ifndef M_PI
 #define M_PI 3.14159265358979323846
 #endif
 

 typedef struct Parser{
     int stack_index;
     char *s;

     const double *const_value;
     const char * const *const_name;          // NULL terminated

     double (**func1)(void *, double a); // NULL terminated

     const char **func1_name;          // NULL terminated

     double (**func2)(void *, double a, double b); // NULL terminated

     const char **func2_name;          // NULL terminated

     void *opaque;

     const char **error;

 #define VARS 10
     double var[VARS];

 } Parser;
 

 static const int8_t si_prefixes['z' - 'E' + 1]={

     ['y'-'E']= -24,
     ['z'-'E']= -21,
     ['a'-'E']= -18,
     ['f'-'E']= -15,
     ['p'-'E']= -12,
     ['n'-'E']= - 9,
     ['u'-'E']= - 6,
     ['m'-'E']= - 3,
     ['c'-'E']= - 2,
     ['d'-'E']= - 1,
     ['h'-'E']=   2,
     ['k'-'E']=   3,
     ['K'-'E']=   3,
     ['M'-'E']=   6,
     ['G'-'E']=   9,
     ['T'-'E']=  12,
     ['P'-'E']=  15,
     ['E'-'E']=  18,
     ['Z'-'E']=  21,
     ['Y'-'E']=  24,
 };
 
 /** strtod() function extended with 'k', 'M', 'G', 'ki', 'Mi', 'Gi' and 'B'
  * postfixes.  This allows using f.e. kB, MiB, G and B as a postfix. This
  * function assumes that the unit of numbers is bits not bytes.
  */
 static double av_strtod(const char *name, char **tail) {
     double d;
     char *next;
     d = strtod(name, &next);
     /* if parsing succeeded, check for and interpret postfixes */
     if (next!=name) {
 
         if(*next >= 'E' && *next <= 'z'){
             int e= si_prefixes[*next - 'E'];
             if(e){
                 if(next[1] == 'i'){
                     d*= pow( 2, e/0.3);
                     next+=2;
                 }else{
                     d*= pow(10, e);
                     next++;
                 }
             }
         }
 
         if(*next=='B') {
             d*=8;

             next++;

         }
     }
     /* if requested, fill in tail with the position after the last parsed
        character */
     if (tail)
         *tail = next;
     return d;
 }
 

 static int strmatch(const char *s, const char *prefix){

     int i;
     for(i=0; prefix[i]; i++){
         if(prefix[i] != s[i]) return 0;
     }
     return 1;
 }
 

 struct ff_expr_s {
     enum {
         e_value, e_const, e_func0, e_func1, e_func2,

         e_squish, e_gauss, e_ld,

         e_mod, e_max, e_min, e_eq, e_gt, e_gte,
         e_pow, e_mul, e_div, e_add,

         e_last, e_st, e_while,

     } type;
     double value; // is sign in other types
     union {
         int const_index;
         double (*func0)(double);
         double (*func1)(void *, double);
         double (*func2)(void *, double, double);
     } a;
     AVEvalExpr * param[2];
 };
 
 static double eval_expr(Parser * p, AVEvalExpr * e) {
     switch (e->type) {
         case e_value:  return e->value;
         case e_const:  return e->value * p->const_value[e->a.const_index];
         case e_func0:  return e->value * e->a.func0(eval_expr(p, e->param[0]));
         case e_func1:  return e->value * e->a.func1(p->opaque, eval_expr(p, e->param[0]));
         case e_func2:  return e->value * e->a.func2(p->opaque, eval_expr(p, e->param[0]), eval_expr(p, e->param[1]));
         case e_squish: return 1/(1+exp(4*eval_expr(p, e->param[0])));
         case e_gauss: { double d = eval_expr(p, e->param[0]); return exp(-d*d/2)/sqrt(2*M_PI); }

         case e_ld:     return e->value * p->var[av_clip(eval_expr(p, e->param[0]), 0, VARS-1)];

         case e_while: {

             double d = NAN;

             while(eval_expr(p, e->param[0]))
                 d=eval_expr(p, e->param[1]);
             return d;
         }

         default: {
             double d = eval_expr(p, e->param[0]);
             double d2 = eval_expr(p, e->param[1]);
             switch (e->type) {
                 case e_mod: return e->value * (d - floor(d/d2)*d2);
                 case e_max: return e->value * (d >  d2 ?   d : d2);
                 case e_min: return e->value * (d <  d2 ?   d : d2);
                 case e_eq:  return e->value * (d == d2 ? 1.0 : 0.0);
                 case e_gt:  return e->value * (d >  d2 ? 1.0 : 0.0);
                 case e_gte: return e->value * (d >= d2 ? 1.0 : 0.0);
                 case e_pow: return e->value * pow(d, d2);
                 case e_mul: return e->value * (d * d2);
                 case e_div: return e->value * (d / d2);
                 case e_add: return e->value * (d + d2);

                 case e_last:return e->value * d2;

                 case e_st : return e->value * (p->var[av_clip(d, 0, VARS-1)]= d2);

             }
         }
     }
     return NAN;
 }
 
 static AVEvalExpr * parse_expr(Parser *p);
 
 void ff_eval_free(AVEvalExpr * e) {
     if (!e) return;
     ff_eval_free(e->param[0]);
     ff_eval_free(e->param[1]);
     av_freep(&e);
 }
 
 static AVEvalExpr * parse_primary(Parser *p) {
     AVEvalExpr * d = av_mallocz(sizeof(AVEvalExpr));

     char *next= p->s;
     int i;
 
     /* number */

     d->value = av_strtod(p->s, &next);

     if(next != p->s){

         d->type = e_value;

         p->s= next;

         return d;

     }

     d->value = 1;

     /* named constants */

     for(i=0; p->const_name && p->const_name[i]; i++){

         if(strmatch(p->s, p->const_name[i])){
             p->s+= strlen(p->const_name[i]);

             d->type = e_const;
             d->a.const_index = i;
             return d;

         }
     }

     p->s= strchr(p->s, '(');
     if(p->s==NULL){

         *p->error = "undefined constant or missing (";

         p->s= next;

         ff_eval_free(d);
         return NULL;

     }
     p->s++; // "("

     if (*next == '(') { // special case do-nothing
         av_freep(&d);
         d = parse_expr(p);
         if(p->s[0] != ')'){
             *p->error = "missing )";
             ff_eval_free(d);
             return NULL;
         }
         p->s++; // ")"
         return d;
     }
     d->param[0] = parse_expr(p);

     if(p->s[0]== ','){
         p->s++; // ","

         d->param[1] = parse_expr(p);

     }

     if(p->s[0] != ')'){

         *p->error = "missing )";

         ff_eval_free(d);
         return NULL;

     }
     p->s++; // ")"

     d->type = e_func0;
          if( strmatch(next, "sinh"  ) ) d->a.func0 = sinh;
     else if( strmatch(next, "cosh"  ) ) d->a.func0 = cosh;
     else if( strmatch(next, "tanh"  ) ) d->a.func0 = tanh;
     else if( strmatch(next, "sin"   ) ) d->a.func0 = sin;
     else if( strmatch(next, "cos"   ) ) d->a.func0 = cos;
     else if( strmatch(next, "tan"   ) ) d->a.func0 = tan;
     else if( strmatch(next, "atan"  ) ) d->a.func0 = atan;
     else if( strmatch(next, "asin"  ) ) d->a.func0 = asin;
     else if( strmatch(next, "acos"  ) ) d->a.func0 = acos;
     else if( strmatch(next, "exp"   ) ) d->a.func0 = exp;
     else if( strmatch(next, "log"   ) ) d->a.func0 = log;
     else if( strmatch(next, "abs"   ) ) d->a.func0 = fabs;
     else if( strmatch(next, "squish") ) d->type = e_squish;
     else if( strmatch(next, "gauss" ) ) d->type = e_gauss;
     else if( strmatch(next, "mod"   ) ) d->type = e_mod;
     else if( strmatch(next, "max"   ) ) d->type = e_max;
     else if( strmatch(next, "min"   ) ) d->type = e_min;
     else if( strmatch(next, "eq"    ) ) d->type = e_eq;
     else if( strmatch(next, "gte"   ) ) d->type = e_gte;

     else if( strmatch(next, "gt"    ) ) d->type = e_gt;

     else if( strmatch(next, "lte"   ) ) { AVEvalExpr * tmp = d->param[1]; d->param[1] = d->param[0]; d->param[0] = tmp; d->type = e_gt; }

     else if( strmatch(next, "lt"    ) ) { AVEvalExpr * tmp = d->param[1]; d->param[1] = d->param[0]; d->param[0] = tmp; d->type = e_gte; }

     else if( strmatch(next, "ld"    ) ) d->type = e_ld;
     else if( strmatch(next, "st"    ) ) d->type = e_st;

     else if( strmatch(next, "while" ) ) d->type = e_while;

     else {

         for(i=0; p->func1_name && p->func1_name[i]; i++){
             if(strmatch(next, p->func1_name[i])){

                 d->a.func1 = p->func1[i];
                 d->type = e_func1;
                 return d;

             }
         }
 
         for(i=0; p->func2_name && p->func2_name[i]; i++){
             if(strmatch(next, p->func2_name[i])){

                 d->a.func2 = p->func2[i];
                 d->type = e_func2;
                 return d;

             }
         }
 

         *p->error = "unknown function";

         ff_eval_free(d);
         return NULL;

     }

     return d;

 }

 static AVEvalExpr * new_eval_expr(int type, int value, AVEvalExpr *p0, AVEvalExpr *p1){
     AVEvalExpr * e = av_mallocz(sizeof(AVEvalExpr));
     e->type     =type   ;
     e->value    =value  ;
     e->param[0] =p0     ;
     e->param[1] =p1     ;
     return e;
 }
 

 static AVEvalExpr * parse_pow(Parser *p, int *sign){

     *sign= (*p->s == '+') - (*p->s == '-');
     p->s += *sign&1;

     return parse_primary(p);

 }
 

 static AVEvalExpr * parse_factor(Parser *p){

     int sign, sign2;

     AVEvalExpr * e = parse_pow(p, &sign);

     while(p->s[0]=='^'){
         p->s++;

         e= new_eval_expr(e_pow, 1, e, parse_pow(p, &sign2));
         if (e->param[1]) e->param[1]->value *= (sign2|1);

     }

     if (e) e->value *= (sign|1);
     return e;

 }
 

 static AVEvalExpr * parse_term(Parser *p){
     AVEvalExpr * e = parse_factor(p);

     while(p->s[0]=='*' || p->s[0]=='/'){

         int c= *p->s++;
         e= new_eval_expr(c == '*' ? e_mul : e_div, 1, e, parse_factor(p));

     }

     return e;

 }
 

 static AVEvalExpr * parse_subexpr(Parser *p) {
     AVEvalExpr * e = parse_term(p);
     while(*p->s == '+' || *p->s == '-') {
         e= new_eval_expr(e_add, 1, e, parse_term(p));
     };
 
     return e;
 }
 

 static AVEvalExpr * parse_expr(Parser *p) {
     AVEvalExpr * e;

     if(p->stack_index <= 0) //protect against stack overflows

         return NULL;

     p->stack_index--;
 

     e = parse_subexpr(p);

     while(*p->s == ';') {
         p->s++;
         e= new_eval_expr(e_last, 1, e, parse_subexpr(p));

     };

 
     p->stack_index++;
 

     return e;

 }
 

 static int verify_expr(AVEvalExpr * e) {
     if (!e) return 0;
     switch (e->type) {
         case e_value:
         case e_const: return 1;
         case e_func0:
         case e_func1:
         case e_squish:

         case e_ld:

         case e_gauss: return verify_expr(e->param[0]);
         default: return verify_expr(e->param[0]) && verify_expr(e->param[1]);
     }
 }
 

 AVEvalExpr * ff_parse(const char *s, const char * const *const_name,

                double (**func1)(void *, double), const char **func1_name,

                double (**func2)(void *, double, double), const char **func2_name,

                const char **error){

     Parser p;

     AVEvalExpr * e;

     char w[strlen(s) + 1], * wp = w;
 
     while (*s)
         if (!isspace(*s++)) *wp++ = s[-1];
     *wp++ = 0;

     p.stack_index=100;

     p.s= w;

     p.const_name = const_name;
     p.func1      = func1;
     p.func1_name = func1_name;
     p.func2      = func2;
     p.func2_name = func2_name;

     p.error= error;

     e = parse_expr(&p);
     if (!verify_expr(e)) {
         ff_eval_free(e);
         return NULL;
     }
     return e;
 }
 

 double ff_parse_eval(AVEvalExpr * e, const double *const_value, void *opaque) {

     Parser p;
 
     p.const_value= const_value;
     p.opaque     = opaque;
     return eval_expr(&p, e);
 }
 

 double ff_eval2(const char *s, const double *const_value, const char * const *const_name,

                double (**func1)(void *, double), const char **func1_name,

                double (**func2)(void *, double, double), const char **func2_name,

                void *opaque, const char **error){

     AVEvalExpr * e = ff_parse(s, const_name, func1, func1_name, func2, func2_name, error);
     double d;
     if (!e) return NAN;
     d = ff_parse_eval(e, const_value, opaque);
     ff_eval_free(e);
     return d;

 }

 
 #ifdef TEST

 #undef printf

 static double const_values[]={
     M_PI,
     M_E,
     0
 };
 static const char *const_names[]={
     "PI",
     "E",
     0
 };

 int main(void){

     int i;

     printf("%f == 12.7\n", ff_eval2("1+(5-2)^(3-1)+1/2+sin(PI)-max(-2.2,-3.1)", const_values, const_names, NULL, NULL, NULL, NULL, NULL, NULL));
     printf("%f == 0.931322575\n", ff_eval2("80G/80Gi", const_values, const_names, NULL, NULL, NULL, NULL, NULL, NULL));

     for(i=0; i<1050; i++){
         START_TIMER

             ff_eval2("1+(5-2)^(3-1)+1/2+sin(PI)-max(-2.2,-3.1)", const_values, const_names, NULL, NULL, NULL, NULL, NULL, NULL);
         STOP_TIMER("ff_eval2")

     }

     return 0;

 }
 #endif