/* subscribers.c - Subscriber pool implementation */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <strings.h>
#include <errno.h>
#include <ctype.h>
#include <unistd.h>

#include <ilib/subscribers.h>

/* Case-insensitive string comparison for email addresses */
static long subscriber_cmp(const void *a, const void *b)
{
  const char *s1 = (const char *)a;
  const char *s2 = (const char *)b;
  return strcasecmp(s1, s2);
}

/* Helper to trim leading/trailing whitespace and newlines */
static char *trim_whitespace(char *str)
{
  char *end;
  while (isspace((unsigned char)*str)) str++;
  if (*str == 0) return str;

  end = str + strlen(str) - 1;
  while (end > str && isspace((unsigned char)*end)) end--;
  end[1] = '\0';

  return str;
}

int subscriber_pool_init(subscriber_pool_t *pool, const char *filepath)
{
  if (!pool || !filepath) return -EINVAL;

  memset(pool, 0, sizeof(subscriber_pool_t));
  pool->filepath = strdup(filepath);
  if (!pool->filepath) return -ENOMEM;

  return splay_init(&pool->tree, subscriber_cmp);
}

int subscriber_add(subscriber_pool_t *pool, const char *email)
{
  if (!pool || !email || strlen(email) == 0) return -EINVAL;

  /* Allocate container entry */
  subscriber_entry_t *entry = calloc(1, sizeof(subscriber_entry_t));
  if (!entry) return -ENOMEM;

  entry->email = strdup(email);
  if (!entry->email) {
    free(entry);
    return -ENOMEM;
  }

  /* Insert into splay tree using normalized email as key */
  int rc = splay_insert(&pool->tree, &entry->node, entry->email);
  if (rc != 0) {
    /* Entry already exists or insertion error */
    free(entry->email);
    free(entry);
    return rc;
  }

  return 0;
}

int subscriber_remove(subscriber_pool_t *pool, const char *email)
{
  if (!pool || !email) return -EINVAL;

  splay_node_t *node = splay_lookup(&pool->tree, email);
  if (!node) return -ENOENT;

  splay_delete(&pool->tree, node);

  /* Retrieve wrapping entry struct and release memory */
  subscriber_entry_t *entry = (subscriber_entry_t *)node;
  free(entry->email);
  free(entry);

  return 0;
}

int subscriber_exists(subscriber_pool_t *pool, const char *email)
{
  if (!pool || !email) return 0;
  return (splay_lookup(&pool->tree, email) != NULL);
}

int subscriber_load_file(subscriber_pool_t *pool)
{
  if (!pool || !pool->filepath) return -EINVAL;

  FILE *fp = fopen(pool->filepath, "r");
  if (!fp) {
    /* If file doesn't exist yet, it will be created on first save */
    if (errno == ENOENT) return 0;
    return -errno;
  }

  char line[512];
  while (fgets(line, sizeof(line), fp)) {
    char *email = trim_whitespace(line);
    /* Ignore empty lines and comment lines starting with '#' */
    if (*email == '\0' || *email == '#') continue;

    subscriber_add(pool, email);
  }

  fclose(fp);
  return 0;
}

/* Atomic save using temporary file + rename to prevent corruption */
int subscriber_save_file(subscriber_pool_t *pool)
{
  if (!pool || !pool->filepath) return -EINVAL;

  char tmp_path[1024];
  snprintf(tmp_path, sizeof(tmp_path), "%s.tmp.%d", pool->filepath, getpid());

  FILE *fp = fopen(tmp_path, "w");
  if (!fp) return -errno;

  /* Write plain-text header */
  fprintf(fp, "# Subrelay Subscribers List\n");
  fprintf(fp, "# Do not edit manually while subrelayd is running\n\n");

  /* In-order traversal across splay tree nodes */
  splay_node_t *curr = splay_first(&pool->tree);
  while (curr != NULL) {
    subscriber_entry_t *entry = (subscriber_entry_t *)curr;
    fprintf(fp, "%s\n", entry->email);
    curr = splay_next(&pool->tree, curr);
  }

  fflush(fp);
  fclose(fp);

  /* Atomic swap */
  if (rename(tmp_path, pool->filepath) != 0) {
    unlink(tmp_path);
    return -errno;
  }

  return 0;
}

void subscriber_pool_destroy(subscriber_pool_t *pool)
{
  if (!pool) return;

  /* Traverse tree and free all allocated nodes */
  splay_node_t *curr = splay_first(&pool->tree);
  while (curr != NULL) {
    splay_node_t *next = splay_next(&pool->tree, curr);
    splay_delete(&pool->tree, curr);

    subscriber_entry_t *entry = (subscriber_entry_t *)curr;
    free(entry->email);
    free(entry);

    curr = next;
  }

  if (pool->filepath) free(pool->filepath);
  memset(pool, 0, sizeof(subscriber_pool_t));

  return;
}