feat: add users and sessions discovery

- also add clangd multi-file intellisense

src/users.c

@@ -0,0 +1,61 @@
+#include <pwd.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/types.h>
+
+#include <users.h>
+#include <util.h>
+
+static struct user __new_user(struct passwd *p) {
+  struct user __user;
+  strcln(&__user.username, p->pw_name);
+  if (p->pw_gecos[0] == '\0')
+    __user.display_name = __user.username;
+  else
+    strcln(&__user.display_name, p->pw_gecos);
+
+  return __user;
+}
+
+static const u_int8_t bs = 16;
+static const u_int8_t unit_size = sizeof(struct user);
+
+static u_int16_t alloc_size = bs;
+static u_int16_t used_size = 0;
+
+static struct user *users = NULL;
+static struct users_list *__users_list = NULL;
+
+struct users_list __list;
+// This code is designed to be run purely sinlge threaded
+struct users_list *get_human_users() {
+  if (users != NULL)
+    return __users_list;
+  else
+    users = malloc(alloc_size * unit_size);
+
+  struct passwd *pwd;
+  while ((pwd = getpwent()) != NULL) {
+    // practically impossible to reach this (== 0xffff)
+    // but will prevent break
+    if (used_size == 0xffff ||
+        !(pwd->pw_dir && strncmp(pwd->pw_dir, "/home/", 6) == 0))
+      continue;
+
+    if (used_size >= alloc_size) {
+      alloc_size += bs;
+      users = realloc(users, alloc_size * unit_size);
+    }
+
+    users[used_size] = __new_user(pwd);
+    used_size++;
+  }
+
+  users = realloc(users, used_size * unit_size);
+
+  __list.length = used_size;
+  __list.users = users;
+  return __users_list = &__list;
+}