#include "Checksum.h"
#include "InputStreamWrapper.h"
#include <assert.h>
#include <stdio.h>

using namespace saracraft;

unsigned int Checksum::CountChecksumForFile(const char* filename) {
  unsigned int chksum = 0;
  int filesize = 0;
  bool success = CountChecksumForFileImpl(&chksum, &filesize, filename);
  if(success) {
    return chksum;
  } else {
    assert(0);
    return 0;
  }
}

bool Checksum::DoesChecksumAndSizeMatchFile(unsigned int checksum, int filesize, const char* filename) {
  unsigned int chksum = 0;
  int size = 0;
  bool success = CountChecksumForFileImpl(&chksum, &size, filename);
  if(success) {
    if(chksum == checksum && filesize == size)
      return true;
    else
      return false;
  } else {
    return false;
  }
}

bool Checksum::CountChecksumForFileImpl(unsigned int* checksum, int* filesize, const char* filename) {
  assert(filename != NULL);

  filesystem::SC_FILE* f = filesystem::sc_fopen(filename, "rb");
  if(f == NULL) {
    return false;
  }

  int size = filesystem::sc_fsize(f);

  char* buf = new char[size];

  bool success = true;
  int got = filesystem::sc_fread(buf, size, 1, f);
  if(got != 1) {
    success = false;
  } else {
    success = true;
    *filesize = size;
    unsigned int hashCode = 1327341033;
    int hashmult = 0;
    for(int i = 0; i < size; i++) {
      if((i % 73) == 0)
        hashCode += (buf[i] << hashmult);
      else
        hashCode ^= (buf[i] << hashmult);
      hashmult+=4;
      if(hashmult > 23) hashmult -= 23;
    }
    delete [] buf;
    filesystem::sc_fclose(f);
    return success;
  }
}