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#include "formula.h"
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
struct parser {
const char *p;
double x;
char err[128];
};
static void skip_ws(struct parser *ps)
{
while (*ps->p == ' ' || *ps->p == '\t')
ps->p++;
}
static int parse_expr(struct parser *ps, double *out);
static int parse_primary(struct parser *ps, double *out)
{
skip_ws(ps);
if (*ps->p == '(') {
ps->p++;
if (parse_expr(ps, out) != 0)
return -1;
skip_ws(ps);
if (*ps->p != ')') {
snprintf(ps->err, sizeof ps->err, "saknar ')'");
return -1;
}
ps->p++;
return 0;
}
if (*ps->p == 'x' || *ps->p == 'X') {
ps->p++;
*out = ps->x;
return 0;
}
if ((*ps->p >= '0' && *ps->p <= '9') || *ps->p == '.') {
char *end = NULL;
double v = strtod(ps->p, &end);
if (!end || end == ps->p) {
snprintf(ps->err, sizeof ps->err, "ogiltigt tal");
return -1;
}
ps->p = end;
*out = v;
return 0;
}
snprintf(ps->err, sizeof ps->err, "förväntade tal, x eller '('");
return -1;
}
static int parse_factor(struct parser *ps, double *out)
{
skip_ws(ps);
if (*ps->p == '-') {
ps->p++;
if (parse_factor(ps, out) != 0)
return -1;
*out = -*out;
return 0;
}
if (*ps->p == '+') {
ps->p++;
return parse_factor(ps, out);
}
return parse_primary(ps, out);
}
static int parse_term(struct parser *ps, double *out)
{
double left;
if (parse_factor(ps, &left) != 0)
return -1;
for (;;) {
skip_ws(ps);
char op = *ps->p;
if (op != '*' && op != '/')
break;
ps->p++;
double right;
if (parse_factor(ps, &right) != 0)
return -1;
if (op == '*') {
left *= right;
} else {
if (right == 0.0) {
snprintf(ps->err, sizeof ps->err, "division med noll");
return -1;
}
left /= right;
}
}
*out = left;
return 0;
}
static int parse_expr(struct parser *ps, double *out)
{
double left;
if (parse_term(ps, &left) != 0)
return -1;
for (;;) {
skip_ws(ps);
char op = *ps->p;
if (op != '+' && op != '-')
break;
ps->p++;
double right;
if (parse_term(ps, &right) != 0)
return -1;
if (op == '+')
left += right;
else
left -= right;
}
*out = left;
return 0;
}
int formula_eval(const char *formula, double x, double *out_kr, char *errbuf,
size_t errlen)
{
if (errbuf && errlen)
errbuf[0] = '\0';
if (!formula || !*formula) {
if (errbuf)
snprintf(errbuf, errlen, "tom formel");
return -1;
}
struct parser ps;
ps.p = formula;
ps.x = x;
ps.err[0] = '\0';
double out = 0;
if (parse_expr(&ps, &out) != 0) {
if (errbuf)
snprintf(errbuf, errlen, "%s", ps.err);
return -1;
}
skip_ws(&ps);
if (*ps.p) {
if (errbuf)
snprintf(errbuf, errlen, "oväntat tecken '%c'", *ps.p);
return -1;
}
if (!isfinite(out)) {
if (errbuf)
snprintf(errbuf, errlen, "ogiltigt resultat");
return -1;
}
*out_kr = out;
return 0;
}
int formula_valid(const char *formula)
{
double v;
return formula_eval(formula, 1.0, &v, NULL, 0) == 0;
}
int formula_resolve_rows(const struct template_row *rows, size_t nrows,
double x, struct resolved_row *out, size_t *out_n,
char *errbuf, size_t errlen)
{
if (errbuf && errlen)
errbuf[0] = '\0';
size_t n = 0;
for (size_t i = 0; i < nrows; i++) {
double kr = 0;
char err[128] = "";
if (formula_eval(rows[i].formula, x, &kr, err, sizeof err) != 0) {
if (errbuf)
snprintf(errbuf, errlen, "rad %zu: %s", i + 1, err);
return -1;
}
int64_t ore = (int64_t)llround(kr * 100.0);
if (ore == 0)
continue;
struct resolved_row *r = &out[n++];
memset(r, 0, sizeof *r);
snprintf(r->account, sizeof r->account, "%s", rows[i].account);
if (ore > 0)
r->debit_ore = ore;
else
r->credit_ore = -ore;
if (rows[i].description)
snprintf(r->description, sizeof r->description, "%s",
rows[i].description);
}
if (n < 2) {
if (errbuf)
snprintf(errbuf, errlen,
"mallen gav färre än två rader med belopp");
return -1;
}
int64_t sum_d = 0, sum_c = 0;
for (size_t i = 0; i < n; i++) {
sum_d += out[i].debit_ore;
sum_c += out[i].credit_ore;
}
int64_t diff = sum_d - sum_c;
if (diff != 0) {
/* the rounding remainder goes to the largest row */
size_t biggest = 0;
int64_t best = -1;
for (size_t i = 0; i < n; i++) {
int64_t amount = out[i].debit_ore ? out[i].debit_ore
: out[i].credit_ore;
if (amount > best) {
best = amount;
biggest = i;
}
}
struct resolved_row *r = &out[biggest];
if (r->debit_ore) {
r->debit_ore -= diff;
if (r->debit_ore < 0) {
r->credit_ore = -r->debit_ore;
r->debit_ore = 0;
}
} else {
r->credit_ore += diff;
if (r->credit_ore < 0) {
r->debit_ore = -r->credit_ore;
r->credit_ore = 0;
}
}
if (r->debit_ore == 0 && r->credit_ore == 0) {
if (errbuf)
snprintf(errbuf, errlen,
"kunde inte balansera avrundningen");
return -1;
}
}
*out_n = n;
return 0;
}
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