/****************************************************************************
 * fs/procfs/fs_procfscpuload.c
 *
 * SPDX-License-Identifier: Apache-2.0
 *
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.  The
 * ASF licenses this file to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance with the
 * License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
 * License for the specific language governing permissions and limitations
 * under the License.
 *
 ****************************************************************************/

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <nuttx/config.h>

#include <sys/types.h>
#include <sys/stat.h>

#include <stdint.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <inttypes.h>
#include <time.h>
#include <string.h>
#include <fcntl.h>
#include <assert.h>
#include <errno.h>
#include <debug.h>

#include <nuttx/clock.h>
#include <nuttx/kmalloc.h>
#include <nuttx/fs/fs.h>
#include <nuttx/fs/procfs.h>

#include "fs_heap.h"

#if !defined(CONFIG_DISABLE_MOUNTPOINT) && defined(CONFIG_FS_PROCFS)
#if !defined(CONFIG_SCHED_CPULOAD_NONE) && \
    !defined(CONFIG_FS_PROCFS_EXCLUDE_CPULOAD)

/****************************************************************************
 * Pre-processor Definitions
 ****************************************************************************/

/* Determines the size of an intermediate buffer that must be large enough
 * to handle the longest line generated by this logic.
 */

#define CPULOAD_LINELEN 16

/****************************************************************************
 * Private Types
 ****************************************************************************/

/* This structure describes one open "file" */

struct cpuload_file_s
{
  struct procfs_file_s  base;   /* Base open file structure */
  unsigned int linesize;        /* Number of valid characters in line[] */
  char line[CPULOAD_LINELEN];   /* Pre-allocated buffer for formatted lines */
};

/****************************************************************************
 * Private Function Prototypes
 ****************************************************************************/

/* File system methods */

static int     cpuload_open(FAR struct file *filep, FAR const char *relpath,
                 int oflags, mode_t mode);
static int     cpuload_close(FAR struct file *filep);
static ssize_t cpuload_read(FAR struct file *filep, FAR char *buffer,
                 size_t buflen);

/****************************************************************************
 * Public Data
 ****************************************************************************/

/* See fs_mount.c -- this structure is explicitly externed there.
 * We use the old-fashioned kind of initializers so that this will compile
 * with any compiler.
 */

const struct procfs_operations g_cpuload_operations =
{
  cpuload_open,       /* open */
  cpuload_close,      /* close */
  cpuload_read,       /* read */
};

/****************************************************************************
 * Private Functions
 ****************************************************************************/

/****************************************************************************
 * Name: cpuload_open
 ****************************************************************************/

static int cpuload_open(FAR struct file *filep, FAR const char *relpath,
                      int oflags, mode_t mode)
{
  FAR struct cpuload_file_s *attr;

  finfo("Open '%s'\n", relpath);

  /* PROCFS is read-only.  Any attempt to open with any kind of write
   * access is not permitted.
   *
   * REVISIT:  Write-able proc files could be quite useful.
   */

  if ((oflags & O_WRONLY) != 0 || (oflags & O_RDONLY) == 0)
    {
      ferr("ERROR: Only O_RDONLY supported\n");
      return -EACCES;
    }

  /* Allocate a container to hold the file attributes */

  attr = fs_heap_zalloc(sizeof(struct cpuload_file_s));
  if (!attr)
    {
      ferr("ERROR: Failed to allocate file attributes\n");
      return -ENOMEM;
    }

  /* Save the attributes as the open-specific state in filep->f_priv */

  filep->f_priv = (FAR void *)attr;
  return OK;
}

/****************************************************************************
 * Name: cpuload_close
 ****************************************************************************/

static int cpuload_close(FAR struct file *filep)
{
  FAR struct cpuload_file_s *attr;

  /* Recover our private data from the struct file instance */

  attr = (FAR struct cpuload_file_s *)filep->f_priv;
  DEBUGASSERT(attr);

  /* Release the file attributes structure */

  fs_heap_free(attr);
  filep->f_priv = NULL;
  return OK;
}

/****************************************************************************
 * Name: cpuload_read
 ****************************************************************************/

static ssize_t cpuload_read(FAR struct file *filep, FAR char *buffer,
                           size_t buflen)
{
  FAR struct cpuload_file_s *attr;
  size_t linesize;
  off_t offset;
  ssize_t ret;

  finfo("buffer=%p buflen=%d\n", buffer, (int)buflen);

  /* Recover our private data from the struct file instance */

  attr = (FAR struct cpuload_file_s *)filep->f_priv;
  DEBUGASSERT(attr);

  /* If f_pos is zero, then sample the system time.  Otherwise, use
   * the cached system time from the previous read().  It is necessary
   * save the cached value in case, for example, the user is reading
   * the time one byte at a time.  In that case, the time must remain
   * stable throughout the reads.
   */

  if (filep->f_pos == 0)
    {
      clock_t total = 0;
      clock_t active = 0;
      uint32_t intpart;
      uint32_t fracpart;

      /* Sample the counts for the IDLE thread.  clock_cpuload should only
       * fail if the PID is not valid.  This, however, should never happen
       * for the IDLE thread.
       */
#ifdef CONFIG_SMP
      struct cpuload_s cpuloads[CONFIG_SMP_NCPUS];
      uint32_t i;

      for (i = 0; i < CONFIG_SMP_NCPUS; i++)
        {
          DEBUGVERIFY(clock_cpuload(i, &cpuloads[i]));
          active += cpuloads[i].active;
        }

      total = cpuloads[0].total;
#else
      struct cpuload_s cpuload;

      DEBUGVERIFY(clock_cpuload(0, &cpuload));
      active = cpuload.active;
      total = cpuload.total;
#endif

      if (active > total)
        {
          active = total;
        }

      /* On the simulator, you may hit cpuload.total == 0, but probably never
       * on real hardware.
       */

      if (total > 0)
        {
          uint32_t tmp;

          tmp      = 1000 - (1000 * active) / total;
          intpart  = tmp / 10;
          fracpart = tmp - 10 * intpart;
        }
      else
        {
          intpart  = 0;
          fracpart = 0;
        }

      linesize = procfs_snprintf(attr->line, CPULOAD_LINELEN,
                                 "%3" PRId32 ".%01" PRId32 "%%\n",
                                 intpart, fracpart);

      /* Save the linesize in case we are re-entered with f_pos > 0 */

      attr->linesize = linesize;
    }

  /* Transfer the system up time to user receive buffer */

  offset = filep->f_pos;
  ret = procfs_memcpy(attr->line, attr->linesize, buffer, buflen, &offset);

  /* Update the file offset */

  if (ret > 0)
    {
      filep->f_pos += ret;
    }

  return ret;
}

#endif /* CONFIG_FS_PROCFS_EXCLUDE_CPULOAD */
#endif /* !CONFIG_DISABLE_MOUNTPOINT && CONFIG_FS_PROCFS */