CST-agent/src/model_registry.c

#include "cst_models.h"

#include "cJSON.h"
#include "os_compat.h"

#include <ctype.h>
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>

static const char BUILTIN[] = {
#include "models_builtin.inc"
    0};

const char *cst_models_builtin_json(void) { return BUILTIN; }

#define MAX_PROV 32
#define MAX_PMODELS 16
#define MAX_RULES 256

typedef struct {
  cst_provider_t pub; /* points into the buffers below */
  char name[64];
  char api_base[256];
  char model[128];
  char key_env[64];
  int passback, prefix;
  char effort[16]; /* "", "passthrough", "openai" */
  char models[MAX_PMODELS][128];
  int nmodels;
  const char *source;
} prov_t;

enum { F_CONTEXT = 1, F_VISION = 2, F_CACHE = 4, F_REASONING = 8, F_PRICE = 16 };

typedef struct {
  char match[128]; /* lowercase */
  int spec;        /* literal characters: higher is more specific */
  unsigned has;    /* F_* set by this rule */
  long context;
  int vision, cache, reasoning;
  cst_price_t price;
} rule_t;

typedef struct {
  char provider[64];
  long fetched_at;
  cst_model_meta_t m;
} cached_t;

static pthread_mutex_t g_mu = PTHREAD_MUTEX_INITIALIZER;

static struct {
  int loaded;
  prov_t prov[MAX_PROV];
  int nprov;
  rule_t builtin[MAX_RULES];
  int nbuiltin;
  rule_t user[MAX_RULES];
  int nuser;
  cached_t *cache;
  int ncache;
  char err[1400];
} R;

/* --- parsing ------------------------------------------------------------- */

static void lower_copy(char *out, size_t n, const char *s) {
  size_t i = 0;
  for (; s && s[i] && i + 1 < n; i++)
    out[i] = (char)tolower((unsigned char)s[i]);
  out[i] = 0;
}

static const char *jstr(const cJSON *o, const char *k) {
  const cJSON *v = cJSON_GetObjectItemCaseSensitive(o, k);
  return cJSON_IsString(v) ? v->valuestring : NULL;
}

static void fix_pub(prov_t *p) {
  p->pub.name = p->name;
  p->pub.api_base = p->api_base;
  p->pub.model = p->model;
  p->pub.key_env = p->key_env;
}

static prov_t *prov_by_name(const char *name) {
  for (int i = 0; i < R.nprov; i++)
    if (strcmp(R.prov[i].name, name) == 0)
      return &R.prov[i];
  return NULL;
}

static void parse_providers(const cJSON *obj, const char *source) {
  const cJSON *it = NULL;
  cJSON_ArrayForEach(it, obj) {
    if (!cJSON_IsObject(it) || !it->string || !it->string[0])
      continue;
    prov_t *p = prov_by_name(it->string);
    if (!p) {
      if (R.nprov >= MAX_PROV)
        continue;
      p = &R.prov[R.nprov++];
      memset(p, 0, sizeof(*p));
      snprintf(p->name, sizeof(p->name), "%s", it->string);
      fix_pub(p);
    }
    p->source = source;
    const char *s;
    if ((s = jstr(it, "api_base")))
      snprintf(p->api_base, sizeof(p->api_base), "%s", s);
    if ((s = jstr(it, "key_env")))
      snprintf(p->key_env, sizeof(p->key_env), "%s", s);
    if ((s = jstr(it, "default_model")))
      snprintf(p->model, sizeof(p->model), "%s", s);
    if ((s = jstr(it, "effort")))
      snprintf(p->effort, sizeof(p->effort), "%s", s);
    const cJSON *b = cJSON_GetObjectItemCaseSensitive(it, "reasoning_passback");
    if (cJSON_IsBool(b))
      p->passback = cJSON_IsTrue(b);
    b = cJSON_GetObjectItemCaseSensitive(it, "prefix_completion");
    if (cJSON_IsBool(b))
      p->prefix = cJSON_IsTrue(b);
    const cJSON *ms = cJSON_GetObjectItemCaseSensitive(it, "models");
    if (cJSON_IsArray(ms)) {
      p->nmodels = 0;
      const cJSON *m = NULL;
      cJSON_ArrayForEach(m, ms) {
        if (cJSON_IsString(m) && m->valuestring[0] && p->nmodels < MAX_PMODELS)
          snprintf(p->models[p->nmodels++], 128, "%s", m->valuestring);
      }
    }
  }
}

static int parse_price(const cJSON *o, cst_price_t *pr) {
  const cJSON *miss = cJSON_GetObjectItemCaseSensitive(o, "miss");
  const cJSON *out = cJSON_GetObjectItemCaseSensitive(o, "out");
  if (!cJSON_IsNumber(miss) || !cJSON_IsNumber(out))
    return -1;
  memset(pr, 0, sizeof(*pr));
  pr->miss = miss->valuedouble;
  pr->out = out->valuedouble;
  const cJSON *v = cJSON_GetObjectItemCaseSensitive(o, "hit");
  pr->hit = cJSON_IsNumber(v) ? v->valuedouble : pr->miss;
  v = cJSON_GetObjectItemCaseSensitive(o, "write");
  pr->write = cJSON_IsNumber(v) ? v->valuedouble : pr->miss;
  const char *c = jstr(o, "currency");
  snprintf(pr->currency, sizeof(pr->currency), "%s", c ? c : "$");
  pr->offpeak_half =
      cJSON_IsTrue(cJSON_GetObjectItemCaseSensitive(o, "offpeak_half"));
  return 0;
}

static int parse_rule(const cJSON *o, rule_t *r) {
  const char *m = jstr(o, "match");
  if (!m || !m[0])
    return -1;
  memset(r, 0, sizeof(*r));
  lower_copy(r->match, sizeof(r->match), m);
  for (const char *q = r->match; *q; q++)
    if (*q != '*')
      r->spec++;
  const cJSON *v = cJSON_GetObjectItemCaseSensitive(o, "context");
  if (cJSON_IsNumber(v) && v->valuedouble > 0) {
    r->context = (long)v->valuedouble;
    r->has |= F_CONTEXT;
  }
  v = cJSON_GetObjectItemCaseSensitive(o, "vision");
  if (cJSON_IsBool(v)) {
    r->vision = cJSON_IsTrue(v);
    r->has |= F_VISION;
  }
  v = cJSON_GetObjectItemCaseSensitive(o, "reasoning");
  if (cJSON_IsBool(v)) {
    r->reasoning = cJSON_IsTrue(v);
    r->has |= F_REASONING;
  }
  const char *c = jstr(o, "cache");
  if (c) {
    if (strcmp(c, "openai") == 0)
      r->cache = CST_CACHE_OPENAI;
    else if (strcmp(c, "anthropic") == 0)
      r->cache = CST_CACHE_ANTHROPIC;
    else
      r->cache = CST_CACHE_AUTO;
    r->has |= F_CACHE;
  }
  v = cJSON_GetObjectItemCaseSensitive(o, "price");
  if (cJSON_IsObject(v) && parse_price(v, &r->price) == 0)
    r->has |= F_PRICE;
  return 0;
}

static int parse_doc(const char *json, int user, char *err, size_t err_sz) {
  cJSON *doc = cJSON_Parse(json);
  if (!cJSON_IsObject(doc)) {
    cJSON_Delete(doc);
    snprintf(err, err_sz, "not a JSON object");
    return -1;
  }
  parse_providers(cJSON_GetObjectItemCaseSensitive(doc, "providers"),
                  user ? "user" : "built-in");
  rule_t *rules = user ? R.user : R.builtin;
  int *n = user ? &R.nuser : &R.nbuiltin;
  const cJSON *it = NULL;
  cJSON_ArrayForEach(it, cJSON_GetObjectItemCaseSensitive(doc, "models")) {
    if (*n < MAX_RULES && parse_rule(it, &rules[*n]) == 0)
      (*n)++;
  }
  cJSON_Delete(doc);
  return 0;
}

static char *read_file(const char *path) {
  FILE *f = fopen(path, "rb");
  if (!f)
    return NULL;
  char *buf = NULL;
  size_t len = 0;
  char chunk[8192];
  size_t got;
  while ((got = fread(chunk, 1, sizeof(chunk), f)) > 0 && len < (8u << 20)) {
    char *nb = realloc(buf, len + got + 1);
    if (!nb)
      break;
    buf = nb;
    memcpy(buf + len, chunk, got);
    len += got;
  }
  fclose(f);
  if (buf)
    buf[len] = 0;
  return buf;
}

static int cache_path(const char *provider, char *out, size_t n) {
  char dir[1024];
  if (!provider || !provider[0] || os_config_dir(dir, sizeof(dir)) != 0)
    return -1;
  for (const char *q = provider; *q; q++)
    if (!isalnum((unsigned char)*q) && !strchr("._-", *q))
      return -1;
  int w = snprintf(out, n, "%s/models-cache/%s.json", dir, provider);
  return w > 0 && (size_t)w < n ? 0 : -1;
}

static void meta_from_json(const cJSON *o, cst_model_meta_t *m) {
  memset(m, 0, sizeof(*m));
  m->vision = -1;
  const char *id = jstr(o, "id");
  snprintf(m->id, sizeof(m->id), "%s", id ? id : "");
  const cJSON *v = cJSON_GetObjectItemCaseSensitive(o, "context");
  if (cJSON_IsNumber(v) && v->valuedouble > 0)
    m->context = (long)v->valuedouble;
  v = cJSON_GetObjectItemCaseSensitive(o, "vision");
  if (cJSON_IsBool(v))
    m->vision = cJSON_IsTrue(v);
  v = cJSON_GetObjectItemCaseSensitive(o, "price");
  cst_price_t pr;
  if (cJSON_IsObject(v) && parse_price(v, &pr) == 0) {
    m->has_price = 1;
    m->miss = pr.miss;
    m->hit = pr.hit;
    m->write = pr.write;
    m->out = pr.out;
  }
}

/* Appends provider's cache file to R.cache (caller holds the lock). */
static void load_cache(const char *provider) {
  char path[1100];
  if (cache_path(provider, path, sizeof(path)) != 0)
    return;
  char *txt = read_file(path);
  cJSON *doc = txt ? cJSON_Parse(txt) : NULL;
  free(txt);
  const cJSON *fa = cJSON_GetObjectItemCaseSensitive(doc, "fetched_at");
  long at = cJSON_IsNumber(fa) ? (long)fa->valuedouble : 0;
  const cJSON *it = NULL;
  cJSON_ArrayForEach(it, cJSON_GetObjectItemCaseSensitive(doc, "models")) {
    cst_model_meta_t m;
    meta_from_json(it, &m);
    if (!m.id[0])
      continue;
    cached_t *nc = realloc(R.cache, (size_t)(R.ncache + 1) * sizeof(*nc));
    if (!nc)
      break;
    R.cache = nc;
    cached_t *c = &R.cache[R.ncache++];
    snprintf(c->provider, sizeof(c->provider), "%s", provider);
    c->fetched_at = at;
    c->m = m;
  }
  cJSON_Delete(doc);
}

static void drop_cache(const char *provider) {
  int w = 0;
  for (int i = 0; i < R.ncache; i++)
    if (provider && strcmp(R.cache[i].provider, provider) != 0)
      R.cache[w++] = R.cache[i];
  R.ncache = w;
}

static void reset_locked(void) {
  R.nprov = 0;
  R.nbuiltin = 0;
  R.nuser = 0;
  drop_cache(NULL);
  R.err[0] = 0;
}

static void load_caches_locked(void) {
  for (int i = 0; i < R.nprov; i++)
    load_cache(R.prov[i].name);
}

int cst_models_user_path(char *out, size_t out_sz) {
  char dir[1024];
  if (os_config_dir(dir, sizeof(dir)) != 0)
    return -1;
  int w = snprintf(out, out_sz, "%s/models.json", dir);
  return w > 0 && (size_t)w < out_sz ? 0 : -1;
}

static void load_default_locked(void) {
  reset_locked();
  char e[128];
  if (parse_doc(BUILTIN, 0, e, sizeof(e)) != 0)
    snprintf(R.err, sizeof(R.err), "built-in model data: %s", e);
  char path[1100];
  char *user = cst_models_user_path(path, sizeof(path)) == 0
                   ? read_file(path)
                   : NULL;
  if (user && parse_doc(user, 1, e, sizeof(e)) != 0)
    snprintf(R.err, sizeof(R.err), "%s: %s", path, e);
  free(user);
  load_caches_locked();
  R.loaded = 1;
}

static void ensure_locked(void) {
  if (!R.loaded)
    load_default_locked();
}

void cst_models_reload(void) {
  pthread_mutex_lock(&g_mu);
  load_default_locked();
  pthread_mutex_unlock(&g_mu);
}

int cst_models_load_json(const char *builtin_json, const char *user_json,
                         char *err, size_t err_sz) {
  char dummy[8];
  if (!err || !err_sz) {
    err = dummy;
    err_sz = sizeof(dummy);
  }
  err[0] = 0;
  pthread_mutex_lock(&g_mu);
  reset_locked();
  int rc = 0;
  if (builtin_json && parse_doc(builtin_json, 0, err, err_sz) != 0)
    rc = -1;
  if (rc == 0 && user_json && parse_doc(user_json, 1, err, err_sz) != 0)
    rc = -1;
  load_caches_locked();
  R.loaded = 1;
  pthread_mutex_unlock(&g_mu);
  return rc;
}

const char *cst_models_load_error(void) {
  pthread_mutex_lock(&g_mu);
  ensure_locked();
  pthread_mutex_unlock(&g_mu);
  return R.err;
}

/* --- providers ----------------------------------------------------------- */

const cst_provider_t *cst_provider_find(const char *name) {
  if (!name || !name[0])
    return NULL;
  pthread_mutex_lock(&g_mu);
  ensure_locked();
  prov_t *p = prov_by_name(name);
  pthread_mutex_unlock(&g_mu);
  return p ? &p->pub : NULL;
}

const cst_provider_t *cst_provider_default(void) {
  const cst_provider_t *p = cst_provider_find(getenv("CST_PROVIDER"));
  return p ? p : cst_provider_at(0);
}

int cst_provider_count(void) {
  pthread_mutex_lock(&g_mu);
  ensure_locked();
  int n = R.nprov;
  pthread_mutex_unlock(&g_mu);
  return n;
}

const cst_provider_t *cst_provider_at(int i) {
  pthread_mutex_lock(&g_mu);
  ensure_locked();
  const cst_provider_t *p = i >= 0 && i < R.nprov ? &R.prov[i].pub : NULL;
  pthread_mutex_unlock(&g_mu);
  return p;
}

const char *cst_provider_source(const cst_provider_t *p) {
  for (int i = 0; p && i < MAX_PROV; i++)
    if (p == &R.prov[i].pub)
      return R.prov[i].source ? R.prov[i].source : "built-in";
  return "";
}

int cst_provider_models(const cst_provider_t *p, char out[][128], int max) {
  int n = 0;
  pthread_mutex_lock(&g_mu);
  for (int i = 0; p && i < R.nprov; i++) {
    if (p != &R.prov[i].pub)
      continue;
    for (int k = 0; k < R.prov[i].nmodels && n < max; k++)
      snprintf(out[n++], 128, "%s", R.prov[i].models[k]);
  }
  pthread_mutex_unlock(&g_mu);
  return n;
}

static int push_name(char out[][128], int *n, int max, const char *name) {
  if (!name || !name[0] || *n >= max)
    return 0;
  for (int i = 0; i < *n; i++)
    if (strcmp(out[i], name) == 0)
      return 0;
  snprintf(out[(*n)++], 128, "%s", name);
  return 1;
}

int cst_models_list(const char *current, char out[][128], int max_out) {
  if (!out || max_out <= 0)
    return 0;
  int n = 0;
  const char *env = getenv("CST_MODELS");
  if (env && env[0]) {
    char buf[1024];
    snprintf(buf, sizeof(buf), "%s", env);
    for (char *tok = buf; *tok;) {
      while (*tok == ':' || *tok == ',' || *tok == ' ')
        tok++;
      char *end = tok;
      while (*end && *end != ':' && *end != ',')
        end++;
      char save = *end;
      *end = 0;
      char *t = end;
      while (t > tok && (t[-1] == ' ' || t[-1] == '\t'))
        *--t = 0;
      push_name(out, &n, max_out, tok);
      *end = save;
      tok = *end ? end + 1 : end;
    }
  } else {
    pthread_mutex_lock(&g_mu);
    ensure_locked();
    for (int i = 0; i < R.nprov; i++)
      for (int k = 0; k < R.prov[i].nmodels; k++)
        push_name(out, &n, max_out, R.prov[i].models[k]);
    pthread_mutex_unlock(&g_mu);
  }
  push_name(out, &n, max_out, current);
  return n;
}

/* --- model lookup -------------------------------------------------------- */

/* '*' matches any run; without one the pattern is a prefix. */
static int glob(const char *p, const char *s) {
  if (!strchr(p, '*'))
    return strncmp(s, p, strlen(p)) == 0;
  while (*p) {
    if (*p == '*') {
      while (*p == '*')
        p++;
      if (!*p)
        return 1;
      for (; *s; s++)
        if (glob(p, s))
          return 1;
      return 0;
    }
    if (*p != *s)
      return 0;
    p++;
    s++;
  }
  return !*s;
}

static void set_field(cst_model_info_t *o, unsigned f, const rule_t *r) {
  switch (f) {
  case F_CONTEXT:
    o->context = r->context;
    break;
  case F_VISION:
    o->vision = r->vision;
    break;
  case F_CACHE:
    o->cache_style = r->cache;
    break;
  case F_REASONING:
    o->reasoning = r->reasoning;
    break;
  case F_PRICE:
    o->price = r->price;
    o->has_price = 1;
    break;
  }
}

static void add_source(cst_model_info_t *o, const char *src) {
  if (strstr(o->source, src))
    return;
  size_t l = strlen(o->source);
  snprintf(o->source + l, sizeof(o->source) - l, "%s%s", l ? "+" : "", src);
}

static void apply_rules(const rule_t *rules, int n, const char *full,
                        const char *bare, unsigned *have, cst_model_info_t *o,
                        const char *src) {
  for (unsigned f = 1; f <= F_PRICE; f <<= 1) {
    if (*have & f)
      continue;
    const rule_t *best = NULL;
    for (int i = 0; i < n; i++) {
      const rule_t *r = &rules[i];
      if (!(r->has & f) || (best && r->spec <= best->spec))
        continue;
      if (glob(r->match, strchr(r->match, '/') ? full : bare))
        best = r;
    }
    if (best) {
      set_field(o, f, best);
      *have |= f;
      add_source(o, src);
    }
  }
}

static void apply_cache(const char *provider, const char *model,
                        unsigned *have, cst_model_info_t *o) {
  for (int i = 0; i < R.ncache; i++) {
    const cached_t *c = &R.cache[i];
    if ((provider && strcmp(c->provider, provider) != 0) ||
        strcmp(c->m.id, model) != 0)
      continue;
    unsigned before = *have;
    if (!(*have & F_CONTEXT) && c->m.context > 0) {
      o->context = c->m.context;
      *have |= F_CONTEXT;
    }
    if (!(*have & F_VISION) && c->m.vision >= 0) {
      o->vision = c->m.vision;
      *have |= F_VISION;
    }
    if (!(*have & F_PRICE) && c->m.has_price) {
      memset(&o->price, 0, sizeof(o->price));
      snprintf(o->price.currency, sizeof(o->price.currency), "$");
      o->price.miss = c->m.miss;
      o->price.hit = c->m.hit;
      o->price.write = c->m.write;
      o->price.out = c->m.out;
      o->has_price = 1;
      *have |= F_PRICE;
    }
    if (*have != before)
      add_source(o, "api");
    return;
  }
}

static int env_price(cst_price_t *out) {
  const char *e = getenv("CST_PRICE");
  if (!e || !e[0])
    return -1;
  memset(out, 0, sizeof(*out));
  char cur[8] = "";
  int n = sscanf(e, "%lf,%lf,%lf,%lf,%7s", &out->miss, &out->hit, &out->out,
                 &out->write, cur);
  if (n < 3)
    return -1;
  if (n < 4)
    out->write = out->miss;
  snprintf(out->currency, sizeof(out->currency), "%s", cur);
  return 0;
}

void cst_model_info(const char *provider, const char *model,
                    cst_model_info_t *out) {
  memset(out, 0, sizeof(*out));
  out->vision = -1;
  unsigned have = 0;
  const char *e = getenv("CST_CTX_TOKENS");
  if (e && atol(e) > 0) {
    out->context = atol(e);
    have |= F_CONTEXT;
    add_source(out, "env");
  }
  if (env_price(&out->price) == 0) {
    out->has_price = 1;
    have |= F_PRICE;
    add_source(out, "env");
  }
  if (model && model[0]) {
    char full[256], bare[256];
    lower_copy(full, sizeof(full), model);
    const char *slash = strrchr(full, '/');
    snprintf(bare, sizeof(bare), "%s", slash && slash[1] ? slash + 1 : full);
    pthread_mutex_lock(&g_mu);
    ensure_locked();
    apply_rules(R.user, R.nuser, full, bare, &have, out, "user");
    if (provider && !prov_by_name(provider))
      provider = NULL;
    apply_cache(provider, model, &have, out);
    apply_rules(R.builtin, R.nbuiltin, full, bare, &have, out, "built-in");
    pthread_mutex_unlock(&g_mu);
  }
  if (!(have & F_CONTEXT)) {
    out->context = 128000;
    add_source(out, "default");
  }
}

void cst_model_info_label(const cst_model_info_t *mi, char *out, size_t n) {
  char ctx[32];
  if (mi->context >= 1000000)
    snprintf(ctx, sizeof(ctx), "%.0fM", (double)mi->context / 1e6);
  else
    snprintf(ctx, sizeof(ctx), "%ldK", (mi->context + 500) / 1000);
  snprintf(out, n, "%s%s", ctx,
           mi->vision == 1   ? " · vision"
           : mi->vision == 0 ? " · text only"
                             : "");
}

/* --- wrappers kept for the rest of the code ------------------------------ */

long cst_model_context_tokens(const char *model) {
  cst_model_info_t i;
  cst_model_info(NULL, model, &i);
  return i.context;
}

int cst_model_price(const char *model, cst_price_t *out) {
  cst_model_info_t i;
  cst_model_info(NULL, model, &i);
  *out = i.price;
  if (!i.has_price)
    memset(out, 0, sizeof(*out));
  return i.has_price ? 0 : -1;
}

/* "https://api.deepseek.com/v1" -> "api.deepseek.com" */
static void host_of(const char *url, char *out, size_t n) {
  const char *s = strstr(url, "://");
  s = s ? s + 3 : url;
  size_t i = 0;
  for (; s[i] && s[i] != '/' && i + 1 < n; i++)
    out[i] = s[i];
  out[i] = 0;
}

void cst_model_caps(const char *provider, const char *api_base,
                    const char *model, cst_model_caps_t *out) {
  memset(out, 0, sizeof(*out));
  pthread_mutex_lock(&g_mu);
  ensure_locked();
  /* provider extensions follow the provider, or its host behind any name */
  for (int i = 0; i < R.nprov; i++) {
    const prov_t *p = &R.prov[i];
    if (!p->passback && !p->prefix)
      continue;
    char host[256];
    host_of(p->api_base, host, sizeof(host));
    if ((provider && strcmp(provider, p->name) == 0) ||
        (api_base && host[0] && strstr(api_base, host))) {
      out->reasoning_passback |= p->passback;
      out->prefix_completion |= p->prefix;
    }
  }
  pthread_mutex_unlock(&g_mu);
  cst_model_info_t mi;
  cst_model_info(provider, model, &mi);
  out->vision = mi.vision;
  const char *e = getenv("CST_NO_CACHE_HINTS");
  if ((e && e[0] == '1') || !model)
    return;
  out->cache_style = mi.cache_style;
}

const char *cst_effort_wire(const char *provider, const char *model,
                            const char *effort) {
  if (!cst_effort_valid(effort) || !provider || !model)
    return NULL;
  char mode[16] = "";
  pthread_mutex_lock(&g_mu);
  ensure_locked();
  const prov_t *p = prov_by_name(provider);
  if (p)
    snprintf(mode, sizeof(mode), "%s", p->effort);
  pthread_mutex_unlock(&g_mu);
  if (strcmp(mode, "passthrough") == 0)
    return effort;
  if (strcmp(mode, "openai") == 0) {
    cst_model_info_t mi;
    cst_model_info(provider, model, &mi);
    if (mi.reasoning)
      return strcmp(effort, "max") == 0 ? "high" : effort;
  }
  return NULL;
}

/* --- fetched cache ------------------------------------------------------- */

int cst_models_cache_save(const char *provider, const char *api_base,
                          const cst_model_meta_t *list, int n) {
  char path[1100];
  if (!list || n < 0 || cache_path(provider, path, sizeof(path)) != 0)
    return -1;
  char dir[1100];
  snprintf(dir, sizeof(dir), "%s", path);
  char *sl = strrchr(dir, '/');
  if (sl)
    *sl = 0;
  os_mkdir_p(dir, 0700);

  long now = (long)time(NULL);
  cJSON *doc = cJSON_CreateObject();
  cJSON_AddNumberToObject(doc, "fetched_at", (double)now);
  if (api_base)
    cJSON_AddStringToObject(doc, "api_base", api_base);
  cJSON *arr = cJSON_AddArrayToObject(doc, "models");
  for (int i = 0; i < n; i++) {
    const cst_model_meta_t *m = &list[i];
    cJSON *o = cJSON_CreateObject();
    cJSON_AddStringToObject(o, "id", m->id);
    if (m->context > 0)
      cJSON_AddNumberToObject(o, "context", (double)m->context);
    if (m->vision >= 0)
      cJSON_AddBoolToObject(o, "vision", m->vision);
    if (m->has_price) {
      cJSON *p = cJSON_AddObjectToObject(o, "price");
      cJSON_AddStringToObject(p, "currency", "$");
      cJSON_AddNumberToObject(p, "miss", m->miss);
      cJSON_AddNumberToObject(p, "hit", m->hit);
      cJSON_AddNumberToObject(p, "write", m->write);
      cJSON_AddNumberToObject(p, "out", m->out);
    }
    cJSON_AddItemToArray(arr, o);
  }
  char *txt = cJSON_Print(doc);
  cJSON_Delete(doc);
  if (!txt)
    return -1;
  char tmp[1200];
  snprintf(tmp, sizeof(tmp), "%s.tmp", path);
  FILE *f = fopen(tmp, "wb");
  int rc = -1;
  if (f) {
    size_t len = strlen(txt);
    rc = fwrite(txt, 1, len, f) == len ? 0 : -1;
    if (fclose(f) != 0)
      rc = -1;
    if (rc == 0)
      rc = os_rename_replace(tmp, path);
    if (rc != 0)
      remove(tmp);
  }
  free(txt);
  if (rc == 0) {
    pthread_mutex_lock(&g_mu);
    ensure_locked();
    drop_cache(provider);
    load_cache(provider);
    pthread_mutex_unlock(&g_mu);
  }
  return rc;
}

int cst_models_cache_load(const char *provider, cst_model_meta_t *out, int max,
                          long *age_s) {
  if (age_s)
    *age_s = 0;
  if (!provider)
    return -1;
  pthread_mutex_lock(&g_mu);
  ensure_locked();
  int n = 0, found = 0;
  for (int i = 0; i < R.ncache; i++) {
    const cached_t *c = &R.cache[i];
    if (strcmp(c->provider, provider) != 0)
      continue;
    if (!found && age_s)
      *age_s = (long)time(NULL) - c->fetched_at;
    found = 1;
    if (out && n < max)
      out[n++] = c->m;
  }
  pthread_mutex_unlock(&g_mu);
  return found ? n : -1;
}