/*
   * Copyright (C) 2013 Freie Universität Berlin
   *
   * This file is subject to the terms and conditions of the GNU Lesser
   * General Public License v2.1. See the file LICENSE in the top level
   * directory for more details.
   */
  
  /**
   * @defgroup pthread POSIX threads
   * POSIX conforming multi-threading features.
   * @ingroup posix
   * @{
   * @file
   * @brief   Thread creation features.
   * @see     [The Open Group Base Specifications Issue 7: pthread.h - threads](http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/pthread.h.html)
   * @author  Christian Mehlis <mehlis@inf.fu-berlin.de>
   * @author  René Kijewski <kijewski@inf.fu-berlin.de>
   * @}
   */
  
  #include <malloc.h>
  #include <stdbool.h>
  #include <stddef.h>
  #include <string.h>
  
  #include "cpu_conf.h"
  #include "irq.h"
  #include "msg.h"
  #include "mutex.h"
  #include "priority_queue.h"
  #include "thread.h"
  #include "sched.h"
  
  #include "pthread.h"
  
  #define ENABLE_DEBUG (0)
  
  #if ENABLE_DEBUG
  #   define PTHREAD_REAPER_STACKSIZE THREAD_STACKSIZE_MAIN
  #   define PTHREAD_STACKSIZE THREAD_STACKSIZE_MAIN
  #else
  #   define PTHREAD_REAPER_STACKSIZE THREAD_STACKSIZE_DEFAULT
  #   define PTHREAD_STACKSIZE THREAD_STACKSIZE_DEFAULT
  #endif
  
  #include "debug.h"
  
  typedef enum {
      PTS_RUNNING,
      PTS_DETACHED,
      PTS_ZOMBIE,
  } pthread_thread_status_t;
  
  typedef struct {
      kernel_pid_t thread_pid;
  
      pthread_thread_status_t status;
      kernel_pid_t joining_thread;
      void *returnval;
      bool should_cancel;
  
      void *(*start_routine)(void *);
      void *arg;
  
      char *stack;
  
      struct __pthread_tls_datum *tls_head;
  
      __pthread_cleanup_datum_t *cleanup_top;
  } pthread_thread_t;
  
  static pthread_thread_t *volatile pthread_sched_threads[MAXTHREADS];
  static mutex_t pthread_mutex;
  
  static volatile kernel_pid_t pthread_reaper_pid = KERNEL_PID_UNDEF;
  
  static char pthread_reaper_stack[PTHREAD_REAPER_STACKSIZE];
  
  static void *pthread_start_routine(void *pt_)
  {
      pthread_thread_t *pt = pt_;
      void *retval = pt->start_routine(pt->arg);
      pthread_exit(retval);
  }
  
  static int insert(pthread_thread_t *pt)
  {
      int result = -1;
      mutex_lock(&pthread_mutex);
  
      for (int i = 0; i < MAXTHREADS; i++){
          if (!pthread_sched_threads[i]) {
              pthread_sched_threads[i] = pt;
              result = i+1;
              break;
          }
      }
  
      mutex_unlock(&pthread_mutex);
      return result;
  }
  
  static void *pthread_reaper(void *arg)
  {
      (void) arg;
  
      while (1) {
          msg_t m;
          msg_receive(&m);
          DEBUG("pthread_reaper(): free(%p)\n", m.content.ptr);
          free(m.content.ptr);
      }
  
      return NULL;
  }
  
  int pthread_create(pthread_t *newthread, const pthread_attr_t *attr, void *(*start_routine)(void *), void *arg)
  {
      pthread_thread_t *pt = calloc(1, sizeof(pthread_thread_t));
  
      kernel_pid_t pthread_pid = insert(pt);
      if (pthread_pid == KERNEL_PID_UNDEF) {
          free(pt);
          return -1;
      }
      *newthread = pthread_pid;
  
      pt->status = attr && attr->detached ? PTS_DETACHED : PTS_RUNNING;
      pt->start_routine = start_routine;
      pt->arg = arg;
  
      bool autofree = attr == NULL || attr->ss_sp == NULL || attr->ss_size == 0;
      size_t stack_size = attr && attr->ss_size > 0 ? attr->ss_size : PTHREAD_STACKSIZE;
      void *stack = autofree ? malloc(stack_size) : attr->ss_sp;
      pt->stack = autofree ? stack : NULL;
  
      if (autofree && pthread_reaper_pid != KERNEL_PID_UNDEF) {
          mutex_lock(&pthread_mutex);
          if (pthread_reaper_pid != KERNEL_PID_UNDEF) {
              /* volatile pid to overcome problems with double checking */
              volatile kernel_pid_t pid = thread_create(pthread_reaper_stack,
                                               PTHREAD_REAPER_STACKSIZE,
                                               0,
                                               THREAD_CREATE_STACKTEST,
                                               pthread_reaper,
                                               NULL,
                                               "pthread-reaper");
              pthread_reaper_pid = pid;
          }
          mutex_unlock(&pthread_mutex);
      }
  
      pt->thread_pid = thread_create(stack,
                                     stack_size,
                                     THREAD_PRIORITY_MAIN,
                                     THREAD_CREATE_WOUT_YIELD |
                                     THREAD_CREATE_STACKTEST,
                                     pthread_start_routine,
                                     pt,
                                     "pthread");
      if (pt->thread_pid == KERNEL_PID_UNDEF) {
          free(pt->stack);
          free(pt);
          pthread_sched_threads[pthread_pid-1] = NULL;
          return -1;
      }
  
      sched_switch(THREAD_PRIORITY_MAIN);
  
      return 0;
  }
  
  void pthread_exit(void *retval)
  {
      pthread_t self_id = pthread_self();
  
      if (self_id == 0) {
          DEBUG("ERROR called pthread_self() returned 0 in \"%s\"!\n", __func__);
      }
      else {
          pthread_thread_t *self = pthread_sched_threads[self_id - 1];
  
          while (self->cleanup_top) {
              __pthread_cleanup_datum_t *ct = self->cleanup_top;
              self->cleanup_top = ct->__next;
  
              ct->__routine(ct->__arg);
          }
  
          /* Prevent linking in pthread_tls.o if no TSS functions were used. */
          extern void __pthread_keys_exit(int self_id) __attribute__((weak));
          if (__pthread_keys_exit) {
              __pthread_keys_exit(self_id);
          }
  
          self->thread_pid = KERNEL_PID_UNDEF;
          DEBUG("pthread_exit(%p), self == %p\n", retval, (void *) self);
          if (self->status != PTS_DETACHED) {
              self->returnval = retval;
              self->status = PTS_ZOMBIE;
  
              if (self->joining_thread) {
                  /* our thread got an other thread waiting for us */
                  thread_wakeup(self->joining_thread);
              }
          }
  
          irq_disable();
          if (self->stack) {
              msg_t m;
              m.content.ptr = self->stack;
              msg_send_int(&m, pthread_reaper_pid);
          }
      }
  
      sched_task_exit();
  }
  
  int pthread_join(pthread_t th, void **thread_return)
  {
      if (th < 1 || th > MAXTHREADS) {
          DEBUG("passed pthread_t th (%d) exceeds bounds of pthread_sched_threads[] in \"%s\"!\n", th, __func__);
          return -3;
      }
  
      pthread_thread_t *other = pthread_sched_threads[th-1];
      if (!other) {
          return -1;
      }
  
      switch (other->status) {
          case (PTS_RUNNING):
              other->joining_thread = sched_active_pid;
              /* go blocked, I'm waking up if other thread exits */
              thread_sleep();
              /* no break */
          case (PTS_ZOMBIE):
              if (thread_return) {
                  *thread_return = other->returnval;
              }
              free(other);
              /* we only need to free the pthread layer struct,
              native thread stack is freed by other */
              pthread_sched_threads[th-1] = NULL;
              return 0;
          case (PTS_DETACHED):
              return -1;
      }
  
      return -2;
  }
  
  int pthread_detach(pthread_t th)
  {
      if (th < 1 || th > MAXTHREADS) {
          DEBUG("passed pthread_t th (%d) exceeds bounds of pthread_sched_threads[] in \"%s\"!\n", th, __func__);
          return -2;
      }
  
      pthread_thread_t *other = pthread_sched_threads[th-1];
      if (!other) {
          return -1;
      }
  
      if (other->status == PTS_ZOMBIE) {
          free(other);
          /* we only need to free the pthread layer struct,
          native thread stack is freed by other */
          pthread_sched_threads[th-1] = NULL;
      } else {
          other->status = PTS_DETACHED;
      }
  
      return 0;
  }
  
  pthread_t pthread_self(void)
  {
      pthread_t result = 0;
      mutex_lock(&pthread_mutex);
      kernel_pid_t pid = sched_active_pid; /* sched_active_pid is volatile */
      for (int i = 0; i < MAXTHREADS; i++) {
          if (pthread_sched_threads[i] && pthread_sched_threads[i]->thread_pid == pid) {
              result = i+1;
              break;
          }
      }
      mutex_unlock(&pthread_mutex);
      return result;
  }
  
  int pthread_cancel(pthread_t th)
  {
      pthread_thread_t *other = pthread_sched_threads[th-1];
      if (!other) {
          return -1;
      }
  
      other->should_cancel = 1;
  
      return 0;
  }
  
  int pthread_setcancelstate(int state, int *oldstate)
  {
      (void) state;
      (void) oldstate;
      return -1;
  }
  
  int pthread_setcanceltype(int type, int *oldtype)
  {
      (void) type;
      (void) oldtype;
      return -1;
  }
  
  void pthread_testcancel(void)
  {
      pthread_t self = pthread_self();
  
      if (self == 0) {
          DEBUG("ERROR called pthread_self() returned 0 in \"%s\"!\n", __func__);
          return;
      }
  
      if (pthread_sched_threads[self-1]->should_cancel) {
          pthread_exit(PTHREAD_CANCELED);
      }
  }
  
  void __pthread_cleanup_push(__pthread_cleanup_datum_t *datum)
  {
      pthread_t self_id = pthread_self();
  
      if (self_id == 0) {
          DEBUG("ERROR called pthread_self() returned 0 in \"%s\"!\n", __func__);
          return;
      }
  
      pthread_thread_t *self = pthread_sched_threads[self_id-1];
      datum->__next = self->cleanup_top;
      self->cleanup_top = datum;
  }
  
  void __pthread_cleanup_pop(__pthread_cleanup_datum_t *datum, int execute)
  {
      pthread_t self_id = pthread_self();
  
      if (self_id == 0) {
          DEBUG("ERROR called pthread_self() returned 0 in \"%s\"!\n", __func__);
          return;
      }
  
      pthread_thread_t *self = pthread_sched_threads[self_id-1];
      self->cleanup_top = datum->__next;
  
      if (execute != 0) {
          /* "The pthread_cleanup_pop() function shall remove the routine at the
           *  top of the calling thread's cancellation cleanup stack and optionally
           *  invoke it (if execute is non-zero)." */
          datum->__routine(datum->__arg);
      }
  }
  
  struct __pthread_tls_datum **__pthread_get_tls_head(int self_id)
  {
      pthread_thread_t *self = pthread_sched_threads[self_id-1];
      return self ? &self->tls_head : NULL;
  }