#ifndef _DEFAULT_SOURCE
#define _DEFAULT_SOURCE
#endif

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

#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <time.h>

#ifdef _WIN32
#include <io.h>
#define OS_ACCESS _access
#define OS_F_OK 0
#else
#include <unistd.h>
#define OS_ACCESS access
#define OS_F_OK F_OK
#endif

int cst_agent_store_dir(const char *workspace, char *out, size_t out_sz) {
  if (!workspace || !out || out_sz < 16)
    return -1;
  return os_path_join(out, out_sz, workspace, ".agent/sessions");
}

int cst_agent_store_ensure(const char *workspace) {
  char base[OS_PATH_MAX];
  char sess[OS_PATH_MAX];
  if (cst_agent_store_dir(workspace, sess, sizeof(sess)) != 0)
    return -1;
  if (os_path_join(base, sizeof(base), workspace, ".agent") != 0)
    return -1;
  if (os_mkdir(base, 0755) != 0)
    return -1;
  if (os_mkdir(sess, 0755) != 0)
    return -1;
  /* keep sessions, undo snapshots and exports out of git */
  char gi[OS_PATH_MAX];
  if (os_path_join(gi, sizeof(gi), base, ".gitignore") == 0 &&
      OS_ACCESS(gi, OS_F_OK) != 0) {
    FILE *fp = fopen(gi, "wb");
    if (fp) {
      fputs("*\n", fp);
      fclose(fp);
    }
  }
  return 0;
}

static void make_id(char *out, size_t n) {
  time_t now = time(NULL);
  struct tm tm;
  os_localtime(&now, &tm);
  unsigned r = (unsigned)(os_getpid() ^ (unsigned)now);
  snprintf(out, n, "%04d%02d%02d-%02d%02d%02d-%04x", tm.tm_year + 1900,
           tm.tm_mon + 1, tm.tm_mday, tm.tm_hour, tm.tm_min, tm.tm_sec,
           r & 0xffff);
}

int cst_agent_store_new_id(char *id_out, size_t id_sz) {
  if (!id_out || id_sz < 24)
    return -1;
  make_id(id_out, id_sz);
  return 0;
}

int cst_agent_store_path_for_id(const char *workspace, const char *id,
                                char *out, size_t out_sz) {
  if (!workspace || !id || !out)
    return -1;
  /* Accept bare id or full path. */
  if (strchr(id, '/') || strchr(id, '\\')) {
    snprintf(out, out_sz, "%s", id);
    return 0;
  }
  char dir[OS_PATH_MAX];
  char leaf[160];
  if (cst_agent_store_dir(workspace, dir, sizeof(dir)) != 0)
    return -1;
  snprintf(leaf, sizeof(leaf), "%s.jsonl", id);
  return os_path_join(out, out_sz, dir, leaf);
}

int cst_agent_store_set_current(const char *workspace, const char *id) {
  if (cst_agent_store_ensure(workspace) != 0)
    return -1;
  char dir[OS_PATH_MAX];
  char path[OS_PATH_MAX];
  if (cst_agent_store_dir(workspace, dir, sizeof(dir)) != 0)
    return -1;
  if (os_path_join(path, sizeof(path), dir, "CURRENT") != 0)
    return -1;
  FILE *fp = fopen(path, "wb");
  if (!fp)
    return -1;
  fprintf(fp, "%s\n", id);
  fclose(fp);
  return 0;
}

int cst_agent_store_get_current(const char *workspace, char *id_out,
                                size_t id_sz) {
  char dir[OS_PATH_MAX];
  char path[OS_PATH_MAX];
  if (cst_agent_store_dir(workspace, dir, sizeof(dir)) != 0)
    return -1;
  if (os_path_join(path, sizeof(path), dir, "CURRENT") != 0)
    return -1;
  FILE *fp = fopen(path, "rb");
  if (!fp)
    return -1;
  if (!fgets(id_out, (int)id_sz, fp)) {
    fclose(fp);
    return -1;
  }
  fclose(fp);
  size_t n = strlen(id_out);
  while (n > 0 && (id_out[n - 1] == '\n' || id_out[n - 1] == '\r'))
    id_out[--n] = 0;
  return id_out[0] ? 0 : -1;
}

int cst_agent_store_resolve_default(const char *workspace, char *path_out,
                                    size_t path_sz, char *id_out,
                                    size_t id_sz) {
  if (cst_agent_store_ensure(workspace) != 0)
    return -1;
  char id[128];
  if (cst_agent_store_get_current(workspace, id, sizeof(id)) == 0) {
    char p[OS_PATH_MAX];
    if (cst_agent_store_path_for_id(workspace, id, p, sizeof(p)) == 0 &&
        OS_ACCESS(p, OS_F_OK) == 0) {
      snprintf(path_out, path_sz, "%s", p);
      if (id_out && id_sz)
        snprintf(id_out, id_sz, "%s", id);
      return 0;
    }
  }
  if (cst_agent_store_new_id(id, sizeof(id)) != 0)
    return -1;
  if (cst_agent_store_path_for_id(workspace, id, path_out, path_sz) != 0)
    return -1;
  cst_agent_store_set_current(workspace, id);
  if (id_out && id_sz)
    snprintf(id_out, id_sz, "%s", id);
  return 0;
}

int cst_agent_store_list(const char *workspace, char ids[][128], int max_ids) {
  if (!workspace || !ids || max_ids <= 0)
    return 0;
  char dir[OS_PATH_MAX];
  if (cst_agent_store_dir(workspace, dir, sizeof(dir)) != 0)
    return 0;
  os_dir_t *d = os_dir_open(dir);
  if (!d)
    return 0;
  typedef struct {
    char id[128];
    time_t mtime;
  } ent_t;
  ent_t *ents = calloc((size_t)max_ids * 4, sizeof(ent_t));
  int n = 0, cap = max_ids * 4;
  const os_dirent_t *de;
  while ((de = os_dir_next(d)) != NULL) {
    size_t len = strlen(de->name);
    if (len < 7 || strcmp(de->name + len - 6, ".jsonl") != 0)
      continue;
    if (n >= cap)
      break;
    snprintf(ents[n].id, sizeof(ents[n].id), "%.*s", (int)(len - 6),
             de->name);
    char full[OS_PATH_MAX];
    if (os_path_join(full, sizeof(full), dir, de->name) != 0)
      continue;
    struct stat st;
    ents[n].mtime = (stat(full, &st) == 0) ? st.st_mtime : 0;
    n++;
  }
  os_dir_close(d);
  for (int i = 0; i < n; i++) {
    for (int j = i + 1; j < n; j++) {
      if (ents[j].mtime > ents[i].mtime) {
        ent_t tmp = ents[i];
        ents[i] = ents[j];
        ents[j] = tmp;
      }
    }
  }
  int out_n = n < max_ids ? n : max_ids;
  for (int i = 0; i < out_n; i++)
    snprintf(ids[i], 128, "%s", ents[i].id);
  free(ents);
  return out_n;
}

static int side_path(const char *workspace, const char *id, const char *ext,
                     char *out, size_t out_sz) {
  char dir[OS_PATH_MAX], leaf[192];
  if (!id || !id[0] || strchr(id, '/') || strchr(id, '\\') ||
      cst_agent_store_dir(workspace, dir, sizeof(dir)) != 0)
    return -1;
  snprintf(leaf, sizeof(leaf), "%s%s", id, ext);
  return os_path_join(out, out_sz, dir, leaf);
}

int cst_agent_store_title_set(const char *workspace, const char *id,
                              const char *title) {
  char p[OS_PATH_MAX];
  if (side_path(workspace, id, ".title", p, sizeof(p)) != 0)
    return -1;
  if (!title || !title[0])
    return remove(p) == 0 || errno == ENOENT ? 0 : -1;
  FILE *fp = fopen(p, "wb");
  if (!fp)
    return -1;
  for (const char *c = title; *c; c++)
    fputc(*c == '\n' || *c == '\r' ? ' ' : *c, fp);
  fputc('\n', fp);
  return fclose(fp) == 0 ? 0 : -1;
}

/* Cut to n bytes without splitting a UTF-8 sequence; newlines → spaces. */
static void clip_line(char *dst, size_t n, const char *src) {
  size_t i = 0;
  while (src[i] && i + 1 < n) {
    dst[i] = (src[i] == '\n' || src[i] == '\r' || src[i] == '\t') ? ' '
                                                                 : src[i];
    i++;
  }
  while (i > 0 && src[i] && ((unsigned char)src[i] & 0xC0) == 0x80)
    i--;
  dst[i] = 0;
}

int cst_agent_store_info(const char *workspace, const char *id,
                         cst_session_info_t *info) {
  if (!info)
    return -1;
  memset(info, 0, sizeof(*info));
  snprintf(info->id, sizeof(info->id), "%s", id ? id : "");
  char p[OS_PATH_MAX];
  if (side_path(workspace, id, ".jsonl", p, sizeof(p)) != 0)
    return -1;
  struct stat st;
  if (stat(p, &st) != 0)
    return -1;
  info->mtime = (long long)st.st_mtime;
  char tp[OS_PATH_MAX];
  if (side_path(workspace, id, ".title", tp, sizeof(tp)) == 0) {
    FILE *tf = fopen(tp, "rb");
    if (tf) {
      if (fgets(info->title, sizeof(info->title), tf)) {
        size_t n = strlen(info->title);
        while (n && (info->title[n - 1] == '\n' || info->title[n - 1] == '\r'))
          info->title[--n] = 0;
      }
      fclose(tf);
    }
  }
  FILE *fp = fopen(p, "rb");
  if (!fp)
    return 0;
  size_t cap = 1 << 16;
  char *line = malloc(cap);
  int have_first = 0;
  while (line && fgets(line, (int)cap, fp)) {
    size_t n = strlen(line);
    if (n == cap - 1 && line[n - 1] != '\n') {
      /* very long line: skip the rest, it is not the first user line */
      int ch;
      while ((ch = fgetc(fp)) != EOF && ch != '\n')
        ;
      info->messages++;
      continue;
    }
    if (n <= 1)
      continue;
    info->messages++;
    if (have_first)
      continue;
    cJSON *o = cJSON_Parse(line);
    const cJSON *r = cJSON_GetObjectItemCaseSensitive(o, "role");
    const cJSON *c = cJSON_GetObjectItemCaseSensitive(o, "content");
    if (cJSON_IsString(r) && strcmp(r->valuestring, "user") == 0 &&
        cJSON_IsString(c) && c->valuestring[0]) {
      clip_line(info->first_user, sizeof(info->first_user), c->valuestring);
      have_first = 1;
    }
    cJSON_Delete(o);
  }
  free(line);
  fclose(fp);
  return 0;
}

int cst_agent_store_delete(const char *workspace, const char *id) {
  char p[OS_PATH_MAX];
  if (side_path(workspace, id, ".jsonl", p, sizeof(p)) != 0)
    return -1;
  if (remove(p) != 0)
    return -1;
  if (side_path(workspace, id, ".title", p, sizeof(p)) == 0)
    remove(p);
  /* sub-agent transcripts live in <id>/ */
  if (side_path(workspace, id, "", p, sizeof(p)) == 0) {
    os_dir_t *d = os_dir_open(p);
    if (d) {
      const os_dirent_t *de;
      while ((de = os_dir_next(d)) != NULL) {
        char f[OS_PATH_MAX];
        if (strncmp(de->name, "sub-", 4) == 0 &&
            os_path_join(f, sizeof(f), p, de->name) == 0)
          remove(f);
      }
      os_dir_close(d);
      rmdir(p);
    }
  }
  char cur[128];
  if (cst_agent_store_get_current(workspace, cur, sizeof(cur)) == 0 &&
      strcmp(cur, id) == 0) {
    char dir[OS_PATH_MAX];
    if (cst_agent_store_dir(workspace, dir, sizeof(dir)) == 0 &&
        os_path_join(p, sizeof(p), dir, "CURRENT") == 0)
      remove(p);
  }
  return 0;
}