/**
 * CS 521 Project 1 - System Report
 *
 * @author your_name_here
 */

#ifndef SYSREPORT_H
#define SYSREPORT_H

struct loadavg {
    double one;
    double five;
    double fifteen;
};

struct mem_info {
    unsigned long total;
    unsigned long avail;
};

struct cpuinfo {
    unsigned long idle_time;
    unsigned long total_time;
};

/**
 * Retrieves the host name of this machine from procfs.
 *
 * @param proc_fd file descriptor of the proc directory (from openat)
 * @param name buffer to store the hostname
 *
 * @return 0 on success, -1 on failure
 */
int host_name(int proc_fd, char name[64]);

/**
 * Retrieves the kernel version of this machine from procfs.
 *
 * @param proc_fd file descriptor of the proc directory (from openat)
 * @param version buffer to store the version string
 *
 * @return 0 on success, -1 on failure
 */
int kernel_version(int proc_fd, char version[32]);

/**
 * Retrieves the number of CPUs available on this machine.
 *
 * @param proc_fd file descriptor of the proc directory (from openat)
 *
 * @return number of CPUs, or -1 on error
 */
int num_cpus(int proc_fd);

/**
 * Retrieves the amount of main memory (RAM) available.
 *
 * @param proc_fd file descriptor of the proc directory (from openat)
 *
 * @return available memory, or 0 on failure
 */
unsigned long total_memory(int proc_fd);

/**
 * Retrieves the total system uptime (time running since boot) as a human
 * readable string in the format:
 *
 *  X days, HH:MM:SS
 *
 * @param proc_fd file descriptor of the proc directory (from openat)
 * @param buf buffer to store the formatted string
 * @buf_sz size of the buffer
 *
 * @return 0 on success, -1 on failure
 */
int uptime(int proc_fd, char *buf, size_t buf_sz);

/**
 * Retrieves the system load average over the last minute, five minutes, and
 * fifteen minutes.
 *
 * @param proc_fd file descriptor of the proc directory (from openat)
 *
 * @return loadavg struct with load average information, or a zeroed out struct
 * on failure.
 */
struct loadavg load_average(int proc_fd);

/**
 * Retrieves memory usage information.
 *
 * @param proc_fd file descriptor of the proc directory (from openat)
 *
 * @return mem_info struct with total and available memory, or a zeroed out
 * struct on failure.
 */
struct mem_info memory_usage(int proc_fd);

/**
 * Retrieves CPU usage information.
 *
 * @param proc_fd file descriptor of the proc directory (from openat)
 *
 * @return cpuinfo struct with idle time and total time spent by the CPU during
 * the last sampling period.
 */
struct cpuinfo cpu_usage(int proc_fd);

/**
 * Converts a number of bytes into human-friendly units (such as MiB, GiB, etc)
 * expressed as a string.
 *
 * @param num_bytes the raw amount of bytes to convert
 * @param decimal_places number of decimal places to show after the '.' in the * output
 * @param buf buffer to place the formatted string
 * @param buf_sz size of the output buffer
 */
void human_readable_sz(
        unsigned long num_bytes, unsigned short decimal_places,
        char *buf, size_t buf_sz);

#endif