#include "json.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

static const char *p;
static int bad;

static void ws(void){ while(*p == ' ' || *p == '\n' || *p == '\r' || *p == '\t') p++; }
static void *xcalloc(size_t n, size_t s){ void *r = calloc(n, s); if(!r){ fprintf(stderr, "out of memory\n"); exit(2); } return r; }

static char *parse_str(void){
  const char *s = ++p;
  char *out, *o;
  while(*p && *p != '"'){ if(*p == '\\' && p[1]) p++; p++; }
  if(*p != '"'){ bad = 1; return NULL; }
  out = o = xcalloc((size_t)(p - s) + 1, 1);
  for(; s < p; s++){ if(*s == '\\') s++; *o++ = *s; }
  p++;
  return out;
}
static jval *parse_val(void);
static void add(jval *v, jval *item){
  v->items = realloc(v->items, sizeof(jval *) * (size_t)(v->n + 1));
  if(!v->items){ fprintf(stderr, "out of memory\n"); exit(2); }
  v->items[v->n++] = item;
}
static jval *parse_val(void){
  jval *v = xcalloc(1, sizeof *v);
  ws();
  if(*p == '{'){
    v->type = J_OBJ; p++; ws();
    if(*p == '}'){ p++; return v; }
    for(;;){
      char *k; jval *item;
      ws(); if(*p != '"'){ bad = 1; return v; }
      k = parse_str(); ws();
      if(*p != ':'){ bad = 1; free(k); return v; }
      p++;
      item = parse_val(); item->key = k; add(v, item);
      ws(); if(*p == ','){ p++; continue; }
      if(*p == '}'){ p++; return v; }
      bad = 1; return v;
    }
  }
  if(*p == '['){
    v->type = J_ARR; p++; ws();
    if(*p == ']'){ p++; return v; }
    for(;;){
      add(v, parse_val());
      ws(); if(*p == ','){ p++; continue; }
      if(*p == ']'){ p++; return v; }
      bad = 1; return v;
    }
  }
  if(*p == '"'){ v->type = J_STR; v->str = parse_str(); return v; }
  if(!strncmp(p, "true", 4)){ v->type = J_BOOL; v->num = 1; p += 4; return v; }
  if(!strncmp(p, "false", 5)){ v->type = J_BOOL; v->num = 0; p += 5; return v; }
  if(!strncmp(p, "null", 4)){ v->type = J_NULL; p += 4; return v; }
  if(*p == '-' || (*p >= '0' && *p <= '9')){
    char *end;
    v->type = J_NUM; v->num = strtoll(p, &end, 10);
    if(*end == '.' || *end == 'e' || *end == 'E') bad = 1;   /* the vectors are integer-only */
    p = end; return v;
  }
  bad = 1; return v;
}

jval *json_parse_file(const char *path){
  FILE *f = fopen(path, "rb");
  long n;
  char *buf;
  jval *v;
  if(!f) return NULL;
  fseek(f, 0, SEEK_END); n = ftell(f); fseek(f, 0, SEEK_SET);
  buf = xcalloc((size_t)n + 1, 1);
  if(fread(buf, 1, (size_t)n, f) != (size_t)n){ fclose(f); free(buf); return NULL; }
  fclose(f);
  p = buf; bad = 0;
  v = parse_val();
  ws();
  if(*p) bad = 1;
  free(buf);
  if(bad){ json_free(v); return NULL; }
  return v;
}
jval *json_get(const jval *o, const char *key){
  int i;
  if(!o || o->type != J_OBJ) return NULL;
  for(i = 0; i < o->n; i++) if(!strcmp(o->items[i]->key, key)) return o->items[i];
  return NULL;
}
jval *json_at(const jval *a, int i){ return (a && (a->type == J_ARR || a->type == J_OBJ) && i >= 0 && i < a->n) ? a->items[i] : NULL; }
void json_free(jval *v){
  int i;
  if(!v) return;
  for(i = 0; i < v->n; i++) json_free(v->items[i]);
  free(v->items); free(v->str); free(v->key); free(v);
}