#include "hash.h"

#include <cstring>
#include <fcntl.h>
#include <iomanip>
#include <sstream>
#include <sys/mman.h>
#include <unistd.h>

#include <openssl/sha.h>

#include <Log.h>

const static size_t HASHSIZE = 32; // the size of the SHA256 Hashsum in bytes

Hash::Hash() {}

Hash::~Hash() {
	if(data) {
		delete data;
		data = nullptr;
	}
}


bool Hash::create(Hash& h, const std::string& file) {
	int fd = ::open(file.c_str(), O_RDONLY);

	bool result = Hash::create(h, fd);

	::close(fd);

	return result;
}

bool Hash::create(Hash& h, int fd) {
	if(fd < 0 || h.data) {
		return false;
	}

	SHA256_CTX hashctx;
	if(SHA256_Init(&hashctx) != 1) {
		Log::error << "Can not create SHA256 CTX";
		return false;
	}

	//determine filesize
	loff_t fs = lseek64(fd, 0, SEEK_END);
	lseek64(fd, 0, SEEK_SET);

	void* mapping = ::mmap(NULL, fs, PROT_READ, MAP_SHARED | MAP_POPULATE, fd, 0);
	if(mapping == MAP_FAILED) {
		return false;
	}

	::madvise(mapping, fs, MADV_DONTDUMP);
	::madvise(mapping, fs, MADV_DONTFORK);
	::madvise(mapping, fs, MADV_SEQUENTIAL);
	::madvise(mapping, fs, MADV_WILLNEED);

	if(SHA256_Update(&hashctx, mapping, fs) != 1) {
		Log::error << "Can not update hash";
		return false;
	}

	::munmap(mapping, fs);

	unsigned char* md = new unsigned char[HASHSIZE];
	if(SHA256_Final(md, &hashctx) != 1) {
		Log::error << "Can not finalize hash";
		return false;
	}

	h.data = md;

	return true;
}


Hash::operator bool() const {
	return data;
}

Hash::operator std::string() const {
	std::stringstream str;
	str << *this;
	return str.str();
}


bool Hash::operator==(const Hash& rhs) const {
	// same data ptr
	if(data == rhs.data) return true;

	// both no data
	if(static_cast<bool>(data) == static_cast<bool>(rhs) && data == nullptr) return true;

	return std::memcmp(data, rhs.data, HASHSIZE) == 0;
}

bool Hash::operator!=(const Hash& rhs) const {
	return !(*this == rhs);
}


std::ostream& operator<<(std::ostream& str, const Hash& rhs) {
	str << std::hex << std::setfill('0');

	for(size_t i = 0; i < HASHSIZE; ++i) {
		str << std::setw(2) << (int) rhs.data[i];
	}

	return str;
}