/*

  * 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

  * simple arithmetic expression evaluator.
  *

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

 #include "avutil.h"

 #include "eval.h"
 

 typedef struct Parser {

     const AVClass *class;

     int stack_index;
     char *s;

     const double *const_values;
     const char * const *const_names;          // NULL terminated
     double (* const *funcs1)(void *, double a);           // NULL terminated
     const char * const *func1_names;          // NULL terminated
     double (* const *funcs2)(void *, double a, double b); // NULL terminated
     const char * const *func2_names;          // NULL terminated

     void *opaque;

     int log_offset;
     void *log_ctx;

 #define VARS 10
     double var[VARS];

 } Parser;
 

 static const AVClass class = { "Eval", av_default_item_name, NULL, LIBAVUTIL_VERSION_INT, offsetof(Parser,log_offset), offsetof(Parser,log_ctx) };
 

 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,
 };
 

 double av_strtod(const char *numstr, char **tail)
 {

     double d;
     char *next;

     if(numstr[0]=='0' && (numstr[1]|0x20)=='x') {

         d = strtoul(numstr, &next, 16);

     } else
         d = strtod(numstr, &next);

     /* if parsing succeeded, check for and interpret postfixes */

     if (next!=numstr) {

         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;
 }
 

 #define IS_IDENTIFIER_CHAR(c) ((c) - '0' <= 9U || (c) - 'a' <= 25U || (c) - 'A' <= 25U || (c) == '_')
 

 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 only if the s identifier is terminated */
     return !IS_IDENTIFIER_CHAR(s[i]);

 }
 

 struct AVExpr {

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

         e_squish, e_gauss, e_ld, e_isnan,

         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, e_floor, e_ceil, e_trunc,

         e_sqrt, e_not,

     } 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;

     struct AVExpr *param[2];

 };
 

 static double eval_expr(Parser *p, AVExpr *e)
 {

     switch (e->type) {
         case e_value:  return e->value;

         case e_const:  return e->value * p->const_values[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_isnan:  return e->value * !!isnan(eval_expr(p, e->param[0]));

         case e_floor:  return e->value * floor(eval_expr(p, e->param[0]));
         case e_ceil :  return e->value * ceil (eval_expr(p, e->param[0]));
         case e_trunc:  return e->value * trunc(eval_expr(p, e->param[0]));

         case e_sqrt:   return e->value * sqrt (eval_expr(p, e->param[0]));

         case e_not:    return e->value * eval_expr(p, e->param[0]) == 0;

         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 int parse_expr(AVExpr **e, Parser *p);

 void av_expr_free(AVExpr *e)

 {

     if (!e) return;

     av_expr_free(e->param[0]);
     av_expr_free(e->param[1]);

     av_freep(&e);
 }
 

 static int parse_primary(AVExpr **e, Parser *p)
 {

     AVExpr *d = av_mallocz(sizeof(AVExpr));

     char *next = p->s, *s0 = p->s;

     int ret, i;

     if (!d)

         return AVERROR(ENOMEM);

     /* number */

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

     if (next != p->s) {

         d->type = e_value;

         p->s= next;

         *e = d;
         return 0;

     }

     d->value = 1;

     /* named constants */

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

             p->s+= strlen(p->const_names[i]);

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

             *e = d;
             return 0;

         }
     }

     p->s= strchr(p->s, '(');

     if (p->s==NULL) {

         av_log(p, AV_LOG_ERROR, "Undefined constant or missing '(' in '%s'\n", s0);

         p->s= next;

         av_expr_free(d);

         return AVERROR(EINVAL);

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

     if (*next == '(') { // special case do-nothing
         av_freep(&d);

         if ((ret = parse_expr(&d, p)) < 0)
             return ret;

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

             av_log(p, AV_LOG_ERROR, "Missing ')' in '%s'\n", s0);

             av_expr_free(d);

             return AVERROR(EINVAL);

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

         *e = d;
         return 0;
     }
     if ((ret = parse_expr(&(d->param[0]), p)) < 0) {

         av_expr_free(d);

         return ret;

     }

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

         p->s++; // ","

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

     }

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

         av_log(p, AV_LOG_ERROR, "Missing ')' or too many args in '%s'\n", s0);

         av_expr_free(d);

         return AVERROR(EINVAL);

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

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

     else if (strmatch(next, "floor" )) d->type = e_floor;
     else if (strmatch(next, "ceil"  )) d->type = e_ceil;
     else if (strmatch(next, "trunc" )) d->type = e_trunc;

     else if (strmatch(next, "sqrt"  )) d->type = e_sqrt;

     else if (strmatch(next, "not"   )) d->type = e_not;

     else if (strmatch(next, "pow"   )) d->type = e_pow;

     else {

         for (i=0; p->func1_names && p->func1_names[i]; i++) {
             if (strmatch(next, p->func1_names[i])) {

                 d->a.func1 = p->funcs1[i];

                 d->type = e_func1;

                 *e = d;
                 return 0;

             }
         }
 

         for (i=0; p->func2_names && p->func2_names[i]; i++) {
             if (strmatch(next, p->func2_names[i])) {

                 d->a.func2 = p->funcs2[i];

                 d->type = e_func2;

                 *e = d;
                 return 0;

             }
         }
 

         av_log(p, AV_LOG_ERROR, "Unknown function in '%s'\n", s0);

         av_expr_free(d);

         return AVERROR(EINVAL);

     }

     *e = d;
     return 0;

 }

 static AVExpr *new_eval_expr(int type, int value, AVExpr *p0, AVExpr *p1)
 {
     AVExpr *e = av_mallocz(sizeof(AVExpr));

     if (!e)
         return NULL;

     e->type     =type   ;
     e->value    =value  ;
     e->param[0] =p0     ;
     e->param[1] =p1     ;
     return e;
 }
 

 static int parse_pow(AVExpr **e, Parser *p, int *sign)
 {

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

     return parse_primary(e, p);

 }
 

 static int parse_factor(AVExpr **e, Parser *p)
 {
     int sign, sign2, ret;
     AVExpr *e0, *e1, *e2;
     if ((ret = parse_pow(&e0, p, &sign)) < 0)
         return ret;

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

         e1 = e0;

         p->s++;

         if ((ret = parse_pow(&e2, p, &sign2)) < 0) {

             av_expr_free(e1);

             return ret;
         }
         e0 = new_eval_expr(e_pow, 1, e1, e2);
         if (!e0) {

             av_expr_free(e1);
             av_expr_free(e2);

             return AVERROR(ENOMEM);
         }
         if (e0->param[1]) e0->param[1]->value *= (sign2|1);

     }

     if (e0) e0->value *= (sign|1);
 
     *e = e0;
     return 0;

 }
 

 static int parse_term(AVExpr **e, Parser *p)
 {
     int ret;
     AVExpr *e0, *e1, *e2;
     if ((ret = parse_factor(&e0, p)) < 0)
         return ret;

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

         int c= *p->s++;

         e1 = e0;
         if ((ret = parse_factor(&e2, p)) < 0) {

             av_expr_free(e1);

             return ret;
         }
         e0 = new_eval_expr(c == '*' ? e_mul : e_div, 1, e1, e2);
         if (!e0) {

             av_expr_free(e1);
             av_expr_free(e2);

             return AVERROR(ENOMEM);
         }

     }

     *e = e0;
     return 0;

 }
 

 static int parse_subexpr(AVExpr **e, Parser *p)
 {
     int ret;
     AVExpr *e0, *e1, *e2;
     if ((ret = parse_term(&e0, p)) < 0)
         return ret;

     while (*p->s == '+' || *p->s == '-') {

         e1 = e0;
         if ((ret = parse_term(&e2, p)) < 0) {

             av_expr_free(e1);

             return ret;
         }
         e0 = new_eval_expr(e_add, 1, e1, e2);
         if (!e0) {

             av_expr_free(e1);
             av_expr_free(e2);

             return AVERROR(ENOMEM);
         }

     };
 

     *e = e0;
     return 0;

 }
 

 static int parse_expr(AVExpr **e, Parser *p)
 {
     int ret;
     AVExpr *e0, *e1, *e2;

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

         return AVERROR(EINVAL);

     p->stack_index--;
 

     if ((ret = parse_subexpr(&e0, p)) < 0)
         return ret;

     while (*p->s == ';') {

         p->s++;

         e1 = e0;
         if ((ret = parse_subexpr(&e2, p)) < 0) {

             av_expr_free(e1);

             return ret;
         }
         e0 = new_eval_expr(e_last, 1, e1, e2);
         if (!e0) {

             av_expr_free(e1);
             av_expr_free(e2);

             return AVERROR(ENOMEM);
         }

     };

 
     p->stack_index++;

     *e = e0;
     return 0;

 }
 

 static int verify_expr(AVExpr *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:

         case e_isnan:
         case e_floor:
         case e_ceil:
         case e_trunc:

         case e_sqrt:

         case e_not:

             return verify_expr(e->param[0]);

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

 int av_expr_parse(AVExpr **expr, const char *s,

                   const char * const *const_names,
                   const char * const *func1_names, double (* const *funcs1)(void *, double),
                   const char * const *func2_names, double (* const *funcs2)(void *, double, double),

                   int log_offset, void *log_ctx)

 {

     Parser p;

     AVExpr *e = NULL;

     char *w = av_malloc(strlen(s) + 1);
     char *wp = w;

     const char *s0 = s;

     int ret = 0;

 
     if (!w)

         return AVERROR(ENOMEM);

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

     p.class      = &class;

     p.stack_index=100;

     p.s= w;

     p.const_names = const_names;
     p.funcs1      = funcs1;
     p.func1_names = func1_names;
     p.funcs2      = funcs2;
     p.func2_names = func2_names;

     p.log_offset = log_offset;
     p.log_ctx    = log_ctx;

     if ((ret = parse_expr(&e, &p)) < 0)
         goto end;

     if (*p.s) {

         av_expr_free(e);

         av_log(&p, AV_LOG_ERROR, "Invalid chars '%s' at the end of expression '%s'\n", p.s, s0);
         ret = AVERROR(EINVAL);
         goto end;
     }

     if (!verify_expr(e)) {

         av_expr_free(e);

         ret = AVERROR(EINVAL);
         goto end;

     }

     *expr = e;

 end:
     av_free(w);

     return ret;

 }
 

 double av_expr_eval(AVExpr *e, const double *const_values, void *opaque)

 {

     Parser p;
 

     p.const_values = const_values;

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

 int av_expr_parse_and_eval(double *d, const char *s,

                            const char * const *const_names, const double *const_values,
                            const char * const *func1_names, double (* const *funcs1)(void *, double),
                            const char * const *func2_names, double (* const *funcs2)(void *, double, double),

                            void *opaque, int log_offset, void *log_ctx)

 {

     AVExpr *e = NULL;

     int ret = av_expr_parse(&e, s, const_names, func1_names, funcs1, func2_names, funcs2, log_offset, log_ctx);

 
     if (ret < 0) {
         *d = NAN;
         return ret;
     }

     *d = av_expr_eval(e, const_values, opaque);
     av_expr_free(e);

     return isnan(*d) ? AVERROR(EINVAL) : 0;

 }

 #if FF_API_OLD_EVAL_NAMES
 int av_parse_expr(AVExpr **expr, const char *s,
                   const char * const *const_names,
                   const char * const *func1_names, double (* const *funcs1)(void *, double),
                   const char * const *func2_names, double (* const *funcs2)(void *, double, double),
                   int log_offset, void *log_ctx)
 {
     return av_expr_parse(expr, s, const_names, func1_names, funcs1, func2_names, funcs2,
                       log_offset, log_ctx);
 }
 
 double av_eval_expr(AVExpr *e, const double *const_values, void *opaque)
 {
     return av_expr_eval(e, const_values, opaque);
 }
 
 int av_parse_and_eval_expr(double *res, const char *s,
                            const char * const *const_names, const double *const_values,
                            const char * const *func1_names, double (* const *funcs1)(void *, double),
                            const char * const *func2_names, double (* const *funcs2)(void *, double, double),
                            void *opaque, int log_offset, void *log_ctx)
 {
     return av_expr_parse_and_eval(res, s, const_names, const_values, func1_names, funcs1, func2_names, funcs2,
                                   opaque, log_offset, log_ctx);
 }
 
 void av_free_expr(AVExpr *e)
 {
     av_expr_free(e);
 }
 #endif /* FF_API_OLD_EVAL_NAMES */
 

 #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;

     double d;

     const char **expr, *exprs[] = {
         "",

         "1;2",

         "-20",
         "-PI",
         "+PI",

         "1+(5-2)^(3-1)+1/2+sin(PI)-max(-2.2,-3.1)",
         "80G/80Gi"
         "1k",
         "1Gi",
         "1gi",
         "1GiFoo",
         "1k+1k",
         "1Gi*3foo",
         "foo",
         "foo(",
         "foo()",
         "foo)",
         "sin",
         "sin(",
         "sin()",
         "sin)",
         "sin 10",
         "sin(1,2,3)",
         "sin(1 )",
         "1",
         "1foo",
         "bar + PI + E + 100f*2 + foo",
         "13k + 12f - foo(1, 2)",
         "1gi",
         "1Gi",

         "st(0, 123)",
         "st(1, 123); ld(1)",
         /* compute 1+2+...+N */
         "st(0, 1); while(lte(ld(0), 100), st(1, ld(1)+ld(0));st(0, ld(0)+1)); ld(1)",
         /* compute Fib(N) */
         "st(1, 1); st(2, 2); st(0, 1); while(lte(ld(0),10), st(3, ld(1)+ld(2)); st(1, ld(2)); st(2, ld(3)); st(0, ld(0)+1)); ld(3)",
         "while(0, 10)",
         "st(0, 1); while(lte(ld(0),100), st(1, ld(1)+ld(0)); st(0, ld(0)+1))",

         "isnan(1)",
         "isnan(NAN)",

         "floor(NAN)",
         "floor(123.123)",
         "floor(-123.123)",
         "trunc(123.123)",
         "trunc(-123.123)",
         "ceil(123.123)",
         "ceil(-123.123)",

         "sqrt(1764)",
         "sqrt(-1)",

         "not(1)",
         "not(NAN)",
         "not(0)",

         "pow(0,1.23)",
         "pow(PI,1.23)",
         "PI^1.23",
         "pow(-1,1.23)",

         NULL
     };
 
     for (expr = exprs; *expr; expr++) {
         printf("Evaluating '%s'\n", *expr);

         av_expr_parse_and_eval(&d, *expr,

                                const_names, const_values,
                                NULL, NULL, NULL, NULL, NULL, 0, NULL);
         printf("'%s' -> %f\n\n", *expr, d);
     }
 

     av_expr_parse_and_eval(&d, "1+(5-2)^(3-1)+1/2+sin(PI)-max(-2.2,-3.1)",

                            const_names, const_values,
                            NULL, NULL, NULL, NULL, NULL, 0, NULL);

     printf("%f == 12.7\n", d);

     av_expr_parse_and_eval(&d, "80G/80Gi",

                            const_names, const_values,

                            NULL, NULL, NULL, NULL, NULL, 0, NULL);

     printf("%f == 0.931322575\n", d);

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

         START_TIMER

             av_expr_parse_and_eval(&d, "1+(5-2)^(3-1)+1/2+sin(PI)-max(-2.2,-3.1)",

                                    const_names, const_values,
                                    NULL, NULL, NULL, NULL, NULL, 0, NULL);

         STOP_TIMER("av_expr_parse_and_eval")

     }

     return 0;

 }
 #endif