#include <amd64/apic.h>
#include <amd64/init.h>
#include <amd64/intr_defs.h>
#include <amd64/mm.h>
#include <amd64/msr-index.h>
#include <amd64/msr.h>
#include <libk/std.h>
#include <libk/string.h>
#include <limine/requests.h>
#include <mm/liballoc.h>
#include <proc/proc.h>
#include <sync/spin_lock.h>
#include <sys/debug.h>
#include <sys/sched.h>
#include <sys/smp.h>
#include <sys/syscall.h>

/// Cpu ID counter
static atomic_uint cpu_counter = 0;
/// The CPUs
static struct cpu cpus[CPUS_MAX];

static atomic_int cpu_init_count;

/// Allocate a CPU structure
struct cpu* cpu_make (uint64_t lapic_id) {
  int id = atomic_fetch_add (&cpu_counter, 1);

  struct cpu* cpu = &cpus[id];

  memset (cpu, 0, sizeof (*cpu));
  cpu->lock = SPIN_LOCK_INIT;
  cpu->id = id;
  cpu->lapic_id = lapic_id;

  amd64_wrmsr (MSR_GS_BASE, (uint64_t)cpu);

  return cpu;
}

struct cpu* cpu_get (void) {
  struct cpu* ptr = (struct cpu*)amd64_rdmsr (MSR_GS_BASE);
  return ptr;
}

void cpu_request_sched (struct cpu* cpu) {
  if (cpu == thiscpu) {
    proc_sched ();
    return;
  }

  amd64_lapic_ipi (cpu->lapic_id, CPU_REQUEST_SCHED);
}

struct cpu* cpu_find_lightest (void) {
  struct cpu* cpu = &cpus[0];

  int load = atomic_load (&cpu->proc_run_q_count);

  for (unsigned int i = 1; i < cpu_counter; i++) {
    struct cpu* new_cpu = &cpus[i];
    int new_load = atomic_load (&new_cpu->proc_run_q_count);
    if (new_load < load) {
      load = new_load;
      cpu = new_cpu;
    }
  }

  return cpu;
}

/// Bootstrap code for non-BSP CPUs
static void amd64_smp_bootstrap (struct limine_mp_info* mp_info) {
  amd64_load_kernel_cr3 ();

  struct cpu* cpu = cpu_make (mp_info->lapic_id);

  amd64_init (cpu, true); /* gdt + idt */
  syscall_init ();

  amd64_lapic_init (1000);

  DEBUG ("CPU %u is online!\n", thiscpu->id);

  atomic_fetch_sub (&cpu_init_count, 1);

  struct proc* spin_proc = proc_spawn_rd ("spin.exe");
  proc_register (spin_proc, thiscpu);

  spin_lock_ctx_t ctxcpu;
  spin_lock (&spin_proc->cpu->lock, &ctxcpu);
  do_sched (spin_proc, &spin_proc->cpu->lock, &ctxcpu);
}

/// Initialize SMP subsystem for AMD64. Start AP CPUs
void smp_init (void) {
  amd64_lapic_init (1000);

  struct limine_mp_response* mp = limine_mp_request.response;

  cpu_init_count = mp->cpu_count - 1; /* Don't include BSP */

  for (size_t i = 0; i < mp->cpu_count; i++) {
    if (mp->cpus[i]->lapic_id != thiscpu->lapic_id) {
      DEBUG ("Trying CPU %u\n", mp->cpus[i]->lapic_id);
      mp->cpus[i]->goto_address = &amd64_smp_bootstrap;
    }
  }

  while (atomic_load (&cpu_init_count) > 0)
    ;

  DEBUG ("All CPUs are online\n");
}