typedef struct Exp Exp;

%{
typedef struct Exp Exp;
enum {
NUM,
DOT,
DOLLAR,
ADD,
SUB,
MUL,
DIV,
FRAC,
NEG,
};

struct Exp {
int ty;
long long n;
Exp *e1;
Exp *e2;
};

typedef Exp* Expptr;
#define YYSTYPE Expptr
Exp *yyexp;
%}

%token NUMBER

%left '+' '-'
%left '*' '/'
%left UNARYMINUS '%'
%%
top: expr { yyexp = $1; return 0; }

expr: NUMBER
| '.' { $$ = mkOP(DOT, nil, nil); }
| '$' { $$ = mkOP(DOLLAR, nil, nil); }
| '(' expr ')' { $$ = $2; }
| expr '+' expr { $$ = mkOP(ADD, $1, $3); }
| expr '-' expr { $$ = mkOP(SUB, $1, $3); }
| expr '*' expr { $$ = mkOP(MUL, $1, $3); }
| expr '/' expr { $$ = mkOP(DIV, $1, $3); }
| expr '%' { $$ = mkOP(FRAC, $1, nil); }
| '-' expr %prec UNARYMINUS { $$ = mkOP(NEG, $2, nil); }
;

%%

#include <u.h>
#include <libc.h>
#include <ctype.h>
#include "disk.h"
#include "edit.h"

static Exp*
mkNUM(vlong x)
{
Exp *n;

n = emalloc(sizeof *n);

n->ty = NUM;
n->n = x;
return n;
}

static Exp*
mkOP(int ty, Exp *e1, Exp *e2)
{
Exp *n;

n = emalloc(sizeof *n);
n->ty = ty;
n->e1 = e1;
n->e2 = e2;

return n;
}

static char *inp;
static jmp_buf jmp;
static vlong dot, size, dollar;

static int
yylex(void)
{
while(isspace(*inp))
inp++;

if(*inp == 0)
return 0;

if(isdigit(*inp)) {
yylval = mkNUM(strtoll(inp, &inp, 0));
return NUMBER;
}

return *inp++;
}

static void
yyerror(char *s)
{
longjmp(jmp, (int)s);
}

static vlong
eval(Exp *e)
{
vlong i;

switch(e->ty) {
case NUM:
return e->n;
case DOT:
return dot;
case DOLLAR:
return dollar;
case ADD:
return eval(e->e1)+eval(e->e2);
case SUB:
return eval(e->e1)-eval(e->e2);
case MUL:
return eval(e->e1)*eval(e->e2);
case DIV:
i = eval(e->e2);
if(i == 0)
yyerror("division by zero");
return eval(e->e1)/i;
case FRAC:
return (size*eval(e->e1))/100;
case NEG:
return -eval(e->e1);
}
assert(0);
return 0;
}

int yyparse(void);

char*
parseexpr(char *s, vlong xdot, vlong xdollar, vlong xsize, vlong *result)
{
char *err;

if(err = (char*)setjmp(jmp))
return err;

inp = s;
dot = xdot;
size = xsize;
dollar = xdollar;
yyparse();
if(yyexp == nil)
return "nil yylval?";
*result = eval(yyexp);
return nil;
}

#ifdef TEST
void
main(int argc, char **argv)
{
int i;
vlong r;
char *e;

for(i=1; i<argc; i++)
if(e = parseexpr(argv[i], 1000, 1000000, 1000000, &r))
print("%s\n", e);
else
print("%lld\n", r);
}
#endif