#define pr_fmt(fmt) "clock: " fmt

#include <zinnia/clock.h>
#include <zinnia/compiler.h>
#include <zinnia/print.h>
#include <zinnia/spin.h>
#include <arch/cpu.h>
#include <stdint.h>

static struct clock* active_clock = nullptr;
static uint64_t counter_base = 0;
static struct spinlock lock = {};

static uint64_t clock_get_elapsed_ns_locked() {
    if (__unlikely(!active_clock))
        return 0;

    return counter_base + active_clock->get_elapsed_ns(active_clock);
}

bool clock_available() {
    spin_lock(&lock);
    bool available = active_clock != nullptr;
    spin_unlock(&lock);
    return available;
}

uint64_t clock_get_elapsed_ns() {
    spin_lock(&lock);
    uint64_t elapsed = clock_get_elapsed_ns_locked();
    spin_unlock(&lock);
    return elapsed;
}

bool clock_switch(struct clock* clock) {
    spin_lock(&lock);

    if (active_clock) {
        if (clock->priority <= active_clock->priority) {
            spin_unlock(&lock);
            return false;
        }
    }

    uint64_t elapsed = clock_get_elapsed_ns_locked();
    clock->reset(clock);

    counter_base = elapsed;
    active_clock = clock;

    spin_unlock(&lock);

    log("Switching to clock source \"%s\"\n", clock->name);

    return true;
}

void clock_spin_ns(uint64_t ns) {
    if (!clock_available()) {
        log_err("Unable to sleep for %lu ns, no clock available!\n", ns);
        return;
    }

    uint64_t target = clock_get_elapsed_ns() + ns;
    while (clock_get_elapsed_ns() < target) {
        arch_cpu_pause();
    }
}