#include <libk/assert.h>
#include <libk/rbtree.h>
#include <libk/std.h>
#include <libk/string.h>
#include <mm/liballoc.h>
#include <proc/mutex.h>
#include <proc/proc.h>
#include <sync/spin_lock.h>
#include <sys/debug.h>
#include <sys/smp.h>
#include <sys/spin_lock.h>

static void proc_mutex_suspend (struct proc* proc, struct proc_suspension_q* sq,
                                spin_lock_t* resource_lock, spin_lock_ctx_t* ctxrl) {
  spin_lock_ctx_t ctxpr, ctxcpu, ctxsq;
  struct cpu* cpu = proc->cpu;

  struct proc_sq_entry* sq_entry = malloc (sizeof (*sq_entry));
  if (!sq_entry) {
    spin_unlock (resource_lock, ctxrl);
    return;
  }

  sq_entry->proc = proc;
  sq_entry->sq = sq;

  spin_lock (&cpu->lock, &ctxcpu);
  spin_lock (&proc->lock, &ctxpr);
  spin_lock (&sq->lock, &ctxsq);

  spin_unlock (resource_lock, ctxrl);

  atomic_store (&proc->state, PROC_SUSPENDED);

  /* append to sq's list */
  list_append (sq->proc_list, &sq_entry->sq_link);

  /* append to proc's list */
  list_append (proc->sq_entries, &sq_entry->proc_link);

  list_remove (cpu->proc_run_q, &proc->cpu_run_q_link);
  atomic_fetch_sub (&cpu->proc_run_q_count, 1);

  if (cpu->proc_current == proc)
    cpu->proc_current = NULL;

  proc->cpu = NULL;

  spin_unlock (&sq->lock, &ctxsq);
  spin_unlock (&proc->lock, &ctxpr);
  spin_unlock (&cpu->lock, &ctxcpu);

  cpu_request_sched (cpu);
}

static void proc_mutex_resume (struct proc* proc, struct proc_sq_entry* sq_entry) {
  spin_lock_ctx_t ctxsq, ctxpr, ctxcpu;
  struct cpu* cpu = cpu_find_lightest ();
  struct proc_suspension_q* sq = sq_entry->sq;

  spin_lock (&cpu->lock, &ctxcpu);
  spin_lock (&proc->lock, &ctxpr);
  spin_lock (&sq->lock, &ctxsq);

  /* remove from sq's list */
  list_remove (sq->proc_list, &sq_entry->sq_link);

  /* remove from proc's list */
  list_remove (proc->sq_entries, &sq_entry->proc_link);

  proc->cpu = cpu;

  if (proc->sq_entries == NULL)
    atomic_store (&proc->state, PROC_READY);

  list_append (cpu->proc_run_q, &proc->cpu_run_q_link);
  atomic_fetch_add (&cpu->proc_run_q_count, 1);

  spin_unlock (&sq->lock, &ctxsq);
  spin_unlock (&proc->lock, &ctxpr);
  spin_unlock (&cpu->lock, &ctxcpu);

  free (sq_entry);

  cpu_request_sched (cpu);
}

bool proc_create_resource_mutex (struct proc_mutex* mutex) {
  memset (mutex, 0, sizeof (*mutex));

  return true;
}

void proc_cleanup_resource_mutex (struct proc* proc, struct proc_resource* resource) {
  struct proc_mutex* mutex = &resource->u.mutex;
}

void proc_mutex_lock (struct proc* proc, struct proc_mutex* mutex) {
  spin_lock_ctx_t ctxmt;

  for (;;) {
    spin_lock (&mutex->resource->lock, &ctxmt);

    if (!mutex->locked || mutex->owner == proc) {
      mutex->locked = true;
      mutex->owner = proc;
      spin_unlock (&mutex->resource->lock, &ctxmt);
      return;
    }

    proc_mutex_suspend (proc, &mutex->suspension_q, &mutex->resource->lock, &ctxmt);
  }
}

bool proc_mutex_unlock (struct proc* proc, struct proc_mutex* mutex) {
  spin_lock_ctx_t ctxmt, ctxsq;

  spin_lock (&mutex->resource->lock, &ctxmt);

  if (mutex->owner != proc) {
    spin_unlock (&mutex->resource->lock, &ctxmt);
    return false;
  }

  spin_lock (&mutex->suspension_q.lock, &ctxsq);

  struct list_node_link* node = mutex->suspension_q.proc_list;

  if (node) {
    struct proc_sq_entry* sq_entry = list_entry (node, struct proc_sq_entry, sq_link);
    struct proc* resumed_proc = sq_entry->proc;

    mutex->owner = resumed_proc;
    mutex->locked = true;

    spin_unlock (&mutex->suspension_q.lock, &ctxsq);
    spin_unlock (&mutex->resource->lock, &ctxmt);

    proc_mutex_resume (resumed_proc, sq_entry);

    return true;
  }

  mutex->locked = false;
  mutex->owner = NULL;

  spin_unlock (&mutex->suspension_q.lock, &ctxsq);
  spin_unlock (&mutex->resource->lock, &ctxmt);

  return true;
}