/*
 * This file is part of fwm-sysdaemon
 *  backlight.c
 *
 * Copyright (c) 2019, 2022 firk (firk@cantconnect.ru)
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The origin of this software must not be misrepresented; you must
 *    not claim that you wrote the original software.
 * 4. Altered versions in any form must be plainly marked as such, and
 *    must not be misinterpreted as being the original software.
 *
 * This software is provided by the author and contributors `as is'
 * without any express or implied warranty.
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <dirent.h>
#include <unistd.h>
#include <fcntl.h>
#include <math.h>
#include "config.h"
#include "util.h"
#include "backlight.h"

typedef struct {
  int valid;
  char path[256];
  int min;
  int range;
  int values[101];
} bl_dev;

static bl_dev bl;

static char const *bl_find(void) {
  static char name[200];
  DIR *dp;
  struct dirent *de;
  int found;
  size_t len;
  
  found = 0;
  dp = opendir("/sys/class/backlight");
  while(de=readdir(dp)) {
    if(de->d_name[0]=='.') continue;
    if((len = strlen(de->d_name))>100) continue;
    if(!found) {
      found = 1;
      bcopy(de->d_name, name, len);
      name[len] = 0;
    } else if(found==1) {
      found = 2;
      printlog("multiple backlight devices found, you may select needed one manually if you want");
      printlog("backlight device: %S", name);
      printlog("backlight device: %S", de->d_name);
    } else {
      printlog("backlight device: %S", de->d_name);
    }
  }
  closedir(dp);
  return (found?name:NULL);
}

extern int bl_init(char const *name, int raw_max, int max, int linear) {
  char path[256];
  int fd, i, raw_cur, raw_new, rem;
  
  if(!name && !(name = bl_find()) || !*name) { printlog("can't find backlight device, you may try to specify one manually"); return -1; }
  if(strlen(name)>100) { printlog("backlight device %\"S name too long", name); return -1; }
  snprintf(bl.path, sizeof(bl.path), "/sys/class/backlight/%s/brightness", name);
  if(raw_max<=0) {
    snprintf(path, sizeof(path), "/sys/class/backlight/%s/max_brightness", name);
    if((fd = open(path,O_RDONLY))<0) { printlog("can't open %\"S", path); return -1; }
    raw_max = fd_get_int_S(fd);
    close(fd);
    if(raw_max<=0) { printlog("can't read %\"S or it is malformed", path); return -1; }
  }
  if(max<=0 || max>100) max = 100;
  
  printlog("using backlight device %\"S raw values 0..%d for 0..%d", name, raw_max, max);
  bl.min = 0;
  bl.range = max+1;
  bl.values[0] = raw_cur = 1;
  for(i=1; i<=max; i++) {
    if(i==max) raw_cur = raw_max;
    else {
      rem = max-i;
      raw_new = (int)(pow(((double)raw_cur)/raw_max, ((double)rem)/(rem+1))*raw_max);
      if(raw_new>raw_cur && raw_new<=raw_max) raw_cur = raw_new;
      else raw_cur++;
    }
    bl.values[i] = raw_cur;
  }
  bl.valid = 1;
  return 0;
}

extern int bl_set(int v) {
  int fd;
  if(!bl.valid) return -1;
  if(v<bl.min) v = 0;
  else if((v-=bl.min)>bl.range) v = bl.range;
  v = bl.values[v];
  if((fd = open(bl.path,O_WRONLY))<0) return -1;
  if(fd_set_int_S(fd, v)<0) { close(fd); return -1; }
  close(fd); return 0;
}

extern int bl_get(void) {
  int fd, v, j;
  if(!bl.valid) return -1;
  if((fd = open(bl.path,O_RDONLY))<0) return -1;
  if((v=fd_get_int_S(fd))<0) { close(fd); return -1; }
  close(fd);
  j = bl.range-1;
  while(j && v<(bl.values[j-1] + (bl.values[j] - bl.values[j-1] + 1)/2)) j--;
  return j+bl.min;
}