/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "prio.h"
#include "prprf.h"
#include "prinit.h"
#include "prthread.h"
#include "prinrval.h"

#include "plerror.h"
#include "plgetopt.h"

#include <stdlib.h>

#define BUFFER_SIZE 500

static PRFileDesc *out = NULL, *err = NULL;

static void Help(void) {
  PR_fprintf(err, "Usage: tail [-n <n>] [-f] [-h] <filename>\n");
  PR_fprintf(err, "\t-t <n>	Dally time in milliseconds\n");
  PR_fprintf(err, "\t-n <n>	Number of bytes before <eof>\n");
  PR_fprintf(err, "\t-f   	Follow the <eof>\n");
  PR_fprintf(err, "\t-h   	This message and nothing else\n");
} /* Help */

PRIntn main(PRIntn argc, char** argv) {
  PRIntn rv = 0;
  PLOptStatus os;
  PRStatus status;
  PRFileDesc* file;
  PRFileInfo fileInfo;
  PRIntervalTime dally;
  char buffer[BUFFER_SIZE];
  PRBool follow = PR_FALSE;
  const char* filename = NULL;
  PRUint32 position = 0, seek = 0, time = 0;
  PLOptState* opt = PL_CreateOptState(argc, argv, "hfn:");

  out = PR_GetSpecialFD(PR_StandardOutput);
  err = PR_GetSpecialFD(PR_StandardError);

  while (PL_OPT_EOL != (os = PL_GetNextOpt(opt))) {
    if (PL_OPT_BAD == os) {
      continue;
    }
    switch (opt->option) {
      case 0: /* it's the filename */
        filename = opt->value;
        break;
      case 'n': /* bytes before end of file */
        seek = atoi(opt->value);
        break;
      case 't': /* dally time */
        time = atoi(opt->value);
        break;
      case 'f': /* follow the end of file */
        follow = PR_TRUE;
        break;
      case 'h':   /* user wants some guidance */
        Help();   /* so give him an earful */
        return 2; /* but not a lot else */
        break;
      default:
        break;
    }
  }
  PL_DestroyOptState(opt);

  if (0 == time) {
    time = 1000;
  }
  dally = PR_MillisecondsToInterval(time);

  if (NULL == filename) {
    (void)PR_fprintf(out, "Input file not specified\n");
    rv = 1;
    goto done;
  }
  file = PR_Open(filename, PR_RDONLY, 0);
  if (NULL == file) {
    PL_FPrintError(err, "File cannot be opened for reading");
    return 1;
  }

  status = PR_GetOpenFileInfo(file, &fileInfo);
  if (PR_FAILURE == status) {
    PL_FPrintError(err, "Cannot acquire status of file");
    rv = 1;
    goto done;
  }
  if (seek > 0) {
    if (seek > fileInfo.size) {
      seek = 0;
    }
    position = PR_Seek(file, (fileInfo.size - seek), PR_SEEK_SET);
    if (-1 == (PRInt32)position) {
      PL_FPrintError(err, "Cannot seek to starting position");
    }
  }

  do {
    while (position < fileInfo.size) {
      PRInt32 read, bytes = fileInfo.size - position;
      if (bytes > sizeof(buffer)) {
        bytes = sizeof(buffer);
      }
      read = PR_Read(file, buffer, bytes);
      if (read != bytes) {
        PL_FPrintError(err, "Cannot read to eof");
      }
      position += read;
      PR_Write(out, buffer, read);
    }

    if (follow) {
      PR_Sleep(dally);
      status = PR_GetOpenFileInfo(file, &fileInfo);
      if (PR_FAILURE == status) {
        PL_FPrintError(err, "Cannot acquire status of file");
        rv = 1;
        goto done;
      }
    }
  } while (follow);

done:
  PR_Close(file);

  return rv;
} /* main */

/* tail.c */