/*  ALOG: A Logger
 *  Copyright (C) 2022 Aidan Hahn
 *  This program is free software: you can redistribute it and/or modify it
 *  under the terms of the GNU General Public License as published by the Free
 *  Software Foundation, either version 3 of the License, or (at your option)
 *  any later version.
 *
 *  This program is distributed in the hope that it will be useful, but WITHOUT
 *  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 *  FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
 *  more details.
 *
 *  You should have received a copy of the GNU General Public License along with
 *  this program. If not, see https://www.gnu.org/licenses/.
 */

#include "alog.h"
#include <stdlib.h>
// ^^^ TODO: build a memory management library
#include <stdarg.h>
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <time.h>

#define TEST_ALOG_STATE() if (!ALOG_LOGGING_STATE) { _init_alog(); }
#define MAX_TIMESTAMP 30

struct _global_logging_state *ALOG_LOGGING_STATE;
int _alog_num_out_fds;
int *_alog_out_fds;
int _alog_num_err_fds;
int *_alog_err_fds;

void _init_alog() {
  if (!ALOG_LOGGING_STATE) {
    ALOG_LOGGING_STATE = malloc(sizeof(struct _global_logging_state));
    ALOG_LOGGING_STATE->broadcast_to_all_fds = 0;
    ALOG_LOGGING_STATE->log_debug_messages = 0;
  }
  _alog_num_out_fds = 1;
  _alog_out_fds = malloc(sizeof(int) * 1);
  // stdout
  _alog_out_fds[0] = 1;

  _alog_num_err_fds = 1;
  _alog_err_fds = malloc(sizeof(int) * 1);
  // stderr
  _alog_err_fds[0] = 2;
}

void init_alog() {
  TEST_ALOG_STATE();
}

// TODO: should I dont close stdin and stdout?
void deinit_alog() {
  TEST_ALOG_STATE();
  free(ALOG_LOGGING_STATE);
  for (int i = 0; i < _alog_num_out_fds; i++) {
    close(_alog_out_fds[i]);
  }
  for (int i = 0; i < _alog_num_err_fds; i++) {
    close(_alog_err_fds[i]);
  }
  free(_alog_out_fds);
  free(_alog_err_fds);
}

void alog_add_target(int fd, char is_err) {
  TEST_ALOG_STATE();
  int **fd_list = is_err ? &_alog_err_fds : &_alog_out_fds;
  int *size = is_err ? &_alog_num_err_fds : &_alog_num_out_fds;

  int *fds = malloc(sizeof(int) * (*size + 1));
  for (int i = 0; i < *size; i++) {
    fds[i] = (*fd_list)[i];
  }

  fds[*size] = fd;
  free(*fd_list);
  (*fd_list) = fds;
  (*size)++;
}

// inefficient time wise, but avoids extra allocs
// TODO: revisit this and see how to do it less tediously
void alog_remove_target(int fd) {
  TEST_ALOG_STATE();
  int out_fds = 0;
  for (int i = 0; i < _alog_num_out_fds; i++) {
    if (_alog_out_fds[i] != fd) {
      out_fds++;
    }
  }

  if (!out_fds) {
    _alog_num_out_fds = 0;
    free(_alog_out_fds);
    _alog_out_fds = NULL;

  } else {
    int *tmp_outs = malloc(sizeof(int) * out_fds);
    int tmp_iter_idx = 0;
    for (int i = 0; i < _alog_num_out_fds; i++) {
      if (_alog_out_fds[i] != fd) {
        tmp_outs[tmp_iter_idx] = _alog_out_fds[i];
        tmp_iter_idx++;
      }
    }

    free(_alog_out_fds);
    _alog_out_fds = tmp_outs;
    _alog_num_out_fds = out_fds;
  }

  int err_fds = 0;
  for (int i = 0; i < _alog_num_err_fds; i++) {
    if (_alog_err_fds[i] != fd) {
      err_fds++;
    }
  }

  if (!err_fds) {
    _alog_num_err_fds = 0;
    free(_alog_err_fds);
    _alog_err_fds = NULL;

  } else {
    int *tmp_errs = malloc(sizeof(int) * err_fds);
    int tmp_iter_idx = 0;
    for (int i = 0; i < _alog_num_err_fds; i++) {
      if (_alog_err_fds[i] != fd) {
        tmp_errs[tmp_iter_idx] = _alog_err_fds[i];
        tmp_iter_idx++;
      }
    }

    free(_alog_err_fds);
    _alog_err_fds = tmp_errs;
    _alog_num_err_fds = err_fds;
  }
}

// TODO: use preprocessor directives to gate off the posix timestamp stuff
// unless the right variable is passed in at compile time
void alog (
  alog_sev severity,
  const char * message,
  ...
) {
  TEST_ALOG_STATE();
  if (severity == DEBUG &&
      !ALOG_LOGGING_STATE->log_debug_messages) {
    // nop :)
    return;
  }

  va_list fmt_list;
  va_start(fmt_list, message);

  char *buffer;
  int size;
  if (severity != PRINT) {
    // GET TIMESTAMP
    // TODO: try to get this all into 1 call to sprintf
    time_t t = time(NULL);
    struct tm * p = localtime(&t);
    int timestamp_len = strftime(NULL, MAX_TIMESTAMP, "[%c]", p) + 1;
    char *timestamp = calloc(timestamp_len , sizeof(char));
    strftime(timestamp, timestamp_len+1, "[%c]", p);

    size = (timestamp_len + strlen(message) + 1);
    char *msg_and_timestamp = calloc(size, sizeof(char));
    sprintf(msg_and_timestamp, "%s %s\n", timestamp, message);
    free(timestamp);

    // TODO: Why even use msg_and_timestamp if I am going to write it wholesale into buffer?
    size = vsnprintf(NULL, 0, msg_and_timestamp, fmt_list);
    va_start(fmt_list, message);
    va_end(fmt_list);
    buffer = malloc(size + 1);
    vsprintf(buffer, msg_and_timestamp, fmt_list);
    va_end(fmt_list);
    free(msg_and_timestamp);

  // if severity is PRINT we avoid timestamp
  } else {
    size = vsnprintf(NULL, 0, message, fmt_list);
    va_start(fmt_list, message);
    buffer = malloc(size + 1);
    vsprintf(buffer, message, fmt_list);
    va_end(fmt_list);
  }

  for (int i = 0; i < _alog_num_out_fds; i++) {
    if (write(_alog_out_fds[i], buffer, size) < size) {
      // TODO: how to handle? probably cant log another message lmao
      // perhaps it should be yanked from the list? maybe not?
      ;;
    }
    fsync(_alog_out_fds[i]);
  }

  if (severity == ERROR) {
    for (int i = 0; i < _alog_num_err_fds; i++) {
      if (write(_alog_err_fds[i], buffer, size) < size) {
        // TODO: see above
        ;;
      }
      fsync(_alog_err_fds[i]);
    }
  }

  free(buffer);
}

#ifdef ALOG_HIJACK_PRINTF
int printf(const char *format, ...) {
  TEST_ALOG_STATE();
  va_list fmt_list;
  va_start(fmt_list, format);
  /* TODO: this is a duplicate call given the implementation of alog.
   * Lets figure out a better way to handle this */
  int size = snprintf(NULL, 0, format, fmt_list);
  alog(PRINT, NULL, format, fmt_list);
  va_end(fmt_list);
  return size;
  /* potentially accept a mem leak at end of program for alog state.
   * That is, if the program using this is not already using alog correctly
   * or if ALOG has been LD_PRELOAD'ed into a program to override its printf */
}
#endif