#define _FILE_OFFSET_BITS 64
#define _LARGEFILE64_SOURCE

#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <zlib.h>
#include <bzlib.h>

#include "sanitizer.h"
#include "input.h"

struct Input {
  char *name;
  enum { plainFile, gzipFile, bzip2File } type;
  void *fileHandle;
  // needed by bzip2 when decompressing from multiple streams. other
  // decompressors must ignore it.
  FILE *systemHandle; 
  int eof;
  char buf[4096];
  int buf_ptr, buf_fill;
};

// tries to re-open the bz stream at the next stream start.
// returns 0 on success, -1 on failure.
int bzReOpen(struct Input *ctx, int *error) {
  // for copying out the last unused part of the block which
  // has an EOS token in it. needed for re-initialising the
  // next stream.
  unsigned char unused[BZ_MAX_UNUSED];
  void *unused_tmp_ptr = NULL;
  int nUnused, i;

  BZ2_bzReadGetUnused(error, (BZFILE *)(ctx->fileHandle), &unused_tmp_ptr, &nUnused);
  if (*error != BZ_OK) return -1;
	      
  // when bzReadClose is called the unused buffer is deallocated, 
  // so it needs to be copied somewhere safe first.
  for (i = 0; i < nUnused; ++i)
    unused[i] = ((unsigned char *)unused_tmp_ptr)[i];
  
  BZ2_bzReadClose(error, (BZFILE *)(ctx->fileHandle));
  if (*error != BZ_OK) return -1;

  // reassign the file handle
  ctx->fileHandle = BZ2_bzReadOpen(error, ctx->systemHandle, 0, 0, unused, nUnused);
  if (ctx->fileHandle == NULL || *error != BZ_OK) return -1;

  return 0;
}

int readFile(void *context, char * buffer, int len)
{
    struct Input *ctx = context;
    void *f = ctx->fileHandle;
    int l = 0, error = 0;

    if (ctx->eof || (len == 0))
        return 0;
 
    switch(ctx->type) {
        case plainFile:
            l = read(*(int *)f, buffer, len);
	    if (l <= 0) ctx->eof = 1;
            break;
        case gzipFile:
            l = gzread((gzFile)f, buffer, len);
	    if (l <= 0) ctx->eof = 1;
            break;
        case bzip2File:
	  l = BZ2_bzRead(&error, (BZFILE *)f, buffer, len);

	  // error codes BZ_OK and BZ_STREAM_END are both "OK", but the stream 
	  // end means the reader needs to be reset from the original handle.
	  if (error != BZ_OK) {
	    // for stream errors, try re-opening the stream before admitting defeat.
	    if (error != BZ_STREAM_END || bzReOpen(ctx, &error) != 0) {
	      l = 0;
	      ctx->eof = 1;
	    }
	  }
	  break;
        default:
            fprintf(stderr, "Bad file type\n");
            break;
    }

    if (l < 0) {
      fprintf(stderr, "File reader received error %d (%d)\n", l, error);
        l = 0;
    }

    return l;
}

char inputGetChar(void *context)
{
    struct Input *ctx = context;

    if (ctx->buf_ptr == ctx->buf_fill) {
        ctx->buf_fill = readFile(context, &ctx->buf[0], sizeof(ctx->buf));
        ctx->buf_ptr = 0;
        if (ctx->buf_fill == 0)
            return 0;
        if (ctx->buf_fill < 0) {
            perror("Error while reading file");
            exit(1);
        }
    }
    //readFile(context, &c, 1);
    return ctx->buf[ctx->buf_ptr++];
}

int inputEof(void *context)
{
    return ((struct Input *)context)->eof;
}


void *inputOpen(const char *name)
{
    const char *ext = strrchr(name, '.');
    struct Input *ctx = malloc (sizeof(*ctx));

    if (!ctx)
        return NULL;

    memset(ctx, 0, sizeof(*ctx));

    ctx->name = strdup(name);

    if (ext && !strcmp(ext, ".gz")) {
        ctx->fileHandle = (void *)gzopen(name, "rb");
        ctx->type = gzipFile;
    } else if (ext && !strcmp(ext, ".bz2")) {
      int error = 0;
      ctx->systemHandle = fopen(name, "rb");
      if (!ctx->systemHandle) {
        fprintf(stderr, "error while opening file %s\n", name);
        exit(10);
      }

      ctx->fileHandle = (void *)BZ2_bzReadOpen(&error, ctx->systemHandle, 0, 0, NULL, 0);
      ctx->type = bzip2File;
      
    } else {
        int *pfd = malloc(sizeof(pfd));
        if (pfd) {
            if (!strcmp(name, "-")) {
                *pfd = STDIN_FILENO;
            } else {
                int flags = O_RDONLY;
#ifdef O_LARGEFILE
                flags |= O_LARGEFILE;
#endif
                *pfd = open(name, flags);
                if (*pfd < 0) {
                    free(pfd);
                    pfd = NULL;
                }
            }
        }
        ctx->fileHandle = (void *)pfd;
        ctx->type = plainFile;
    }
    if (!ctx->fileHandle) {
        fprintf(stderr, "error while opening file %s\n", name);
        exit(10);
    }
    ctx->buf_ptr = 0;
    ctx->buf_fill = 0;
    return (void *)ctx;
}

int inputClose(void *context)
{
    struct Input *ctx = context;
    void *f = ctx->fileHandle;

    switch(ctx->type) {
        case plainFile:
            close(*(int *)f);
            free(f);
            break;
        case gzipFile:
            gzclose((gzFile)f);
            break;
        case bzip2File:
            BZ2_bzclose((BZFILE *)f);
            break;
        default:
            fprintf(stderr, "Bad file type\n");
            break;
    }

    free(ctx->name);
    free(ctx);
    return 0;
}

xmlTextReaderPtr inputUTF8(const char *name)
{
    void *ctx = inputOpen(name);

    if (!ctx) {
        fprintf(stderr, "Input reader create failed for: %s\n", name);
        return NULL;
    }

    return xmlReaderForIO(readFile, inputClose, (void *)ctx, NULL, NULL, 0);
}