/*
* Copyright (c) 2017 rxi
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to
* deal in the Software without restriction, including without limitation the
* rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
* sell copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
* IN THE SOFTWARE.
*/

#include "stdafx.h"
#include <stdio.h>
#include <stdlib.h>
#include <stddef.h>
#include <string.h>
#include <fstream>
#include <iostream>
#include <vector>
#include "microtar.h"
#include "utils.h"

#pragma warning(disable : 4996)

typedef struct {
	char name[100];
	char mode[8];
	char owner[8];
	char group[8];
	char size[12];
	char mtime[12];
	char checksum[8];
	char type;
	char linkname[100];
	char _padding[255];
} mtar_raw_header_t;


static unsigned round_up(unsigned n, unsigned incr) {
	return n + (incr - n % incr) % incr;
}


static unsigned checksum(const mtar_raw_header_t* rh) {
	unsigned i;
	unsigned char *p = (unsigned char*)rh;
	unsigned res = 256;
	for (i = 0; i < offsetof(mtar_raw_header_t, checksum); i++) {
		res += p[i];
	}
	for (i = offsetof(mtar_raw_header_t, type); i < sizeof(*rh); i++) {
		res += p[i];
	}
	return res;
}


static int tread(mtar_t *tar, void *data, unsigned size) {
	int err = tar->read(tar, data, size);
	tar->pos += size;
	return err;
}


static int twrite(mtar_t *tar, const void *data, unsigned size) {
	int err = tar->write(tar, data, size);
	tar->pos += size;
	return err;
}


static int write_null_bytes(mtar_t *tar, int n) {
	int i, err;
	char nul = '\0';
	for (i = 0; i < n; i++) {
		err = twrite(tar, &nul, 1);
		if (err) {
			return err;
		}
	}
	return MTAR_ESUCCESS;
}


static int raw_to_header(mtar_header_t *h, const mtar_raw_header_t *rh) {
	unsigned chksum1, chksum2;

	/* If the checksum starts with a null byte we assume the record is NULL */
	if (*rh->checksum == '\0') {
		return MTAR_ENULLRECORD;
	}

	/* Build and compare checksum */
	chksum1 = checksum(rh);
	sscanf(rh->checksum, "%o", &chksum2);
	if (chksum1 != chksum2) {
		return MTAR_EBADCHKSUM;
	}

	/* Load raw header into header */
	sscanf(rh->mode, "%o", &h->mode);
	sscanf(rh->owner, "%o", &h->owner);
	sscanf(rh->size, "%o", &h->size);
	sscanf(rh->mtime, "%o", &h->mtime);
	h->type = rh->type;
	strcpy(h->name, rh->name);
	strcpy(h->linkname, rh->linkname);

	return MTAR_ESUCCESS;
}


static int header_to_raw(mtar_raw_header_t *rh, const mtar_header_t *h) {
	unsigned chksum;

	/* Load header into raw header */
	memset(rh, 0, sizeof(*rh));
	sprintf(rh->mode, "%o", h->mode);
	sprintf(rh->owner, "%o", h->owner);
	sprintf(rh->size, "%o", h->size);
	sprintf(rh->mtime, "%o", h->mtime);
	rh->type = h->type ? h->type : MTAR_TREG;
	strcpy(rh->name, h->name);
	strcpy(rh->linkname, h->linkname);

	/* Calculate and write checksum */
	chksum = checksum(rh);
	sprintf(rh->checksum, "%06o", chksum);
	rh->checksum[7] = ' ';

	return MTAR_ESUCCESS;
}


const char* mtar_strerror(int err) {
	switch (err) {
	case MTAR_ESUCCESS: return "success";
	case MTAR_EFAILURE: return "failure";
	case MTAR_EOPENFAIL: return "could not open";
	case MTAR_EREADFAIL: return "could not read";
	case MTAR_EWRITEFAIL: return "could not write";
	case MTAR_ESEEKFAIL: return "could not seek";
	case MTAR_EBADCHKSUM: return "bad checksum";
	case MTAR_ENULLRECORD: return "null record";
	case MTAR_ENOTFOUND: return "file not found";
	}
	return "unknown error";
}


static int file_write(mtar_t *tar, const void *data, unsigned size) {
	unsigned res = fwrite(data, 1, size, (FILE *) tar->stream);
	return (res == size) ? MTAR_ESUCCESS : MTAR_EWRITEFAIL;
}

static int file_read(mtar_t *tar, void *data, unsigned size) {
	unsigned res = fread(data, 1, size, (FILE *)tar->stream);
	return (res == size) ? MTAR_ESUCCESS : MTAR_EREADFAIL;
}

static int file_seek(mtar_t *tar, unsigned offset) {
	int res = fseek((FILE *)tar->stream, offset, SEEK_SET);
	return (res == 0) ? MTAR_ESUCCESS : MTAR_ESEEKFAIL;
}


static int file_close(mtar_t *tar) {
	fclose((FILE *)tar->stream);
	return MTAR_ESUCCESS;
}


int mtar_open(mtar_t *tar, const char *filename, const char *mode) {
	int err;
	mtar_header_t h;

	/* Init tar struct and functions */
	memset(tar, 0, sizeof(*tar));
	tar->write = file_write;
	tar->read = file_read;
	tar->seek = file_seek;
	tar->close = file_close;

	/* Assure mode is always binary */
	if (strchr(mode, 'r')) mode = "rb";
	if (strchr(mode, 'w')) mode = "wb";
	if (strchr(mode, 'a')) mode = "ab";
	/* Open file */
	tar->stream = fopen(filename, mode);
	if (!tar->stream) {
		return MTAR_EOPENFAIL;
	}
	/* Read first header to check it is valid if mode is `r` */
	if (*mode == 'r') {
		err = mtar_read_header(tar, &h);
		if (err != MTAR_ESUCCESS) {
			mtar_close(tar);
			return err;
		}
	}

	/* Return ok */
	return MTAR_ESUCCESS;
}


int mtar_close(mtar_t *tar) {
	return tar->close(tar);
}


int mtar_seek(mtar_t *tar, unsigned pos) {
	int err = tar->seek(tar, pos);
	tar->pos = pos;
	return err;
}


int mtar_rewind(mtar_t *tar) {
	tar->remaining_data = 0;
	tar->last_header = 0;
	return mtar_seek(tar, 0);
}


int mtar_next(mtar_t *tar) {
	int err, n;
	mtar_header_t h;
	/* Load header */
	err = mtar_read_header(tar, &h);
	if (err) {
		return err;
	}
	/* Seek to next record */
	n = round_up(h.size, 512) + sizeof(mtar_raw_header_t);
	return mtar_seek(tar, tar->pos + n);
}


int mtar_find(mtar_t *tar, const char *name, mtar_header_t *h) {
	int err;
	mtar_header_t header;
	/* Start at beginning */
	err = mtar_rewind(tar);
	if (err) {
		return err;
	}
	/* Iterate all files until we hit an error or find the file */
	while ((err = mtar_read_header(tar, &header)) == MTAR_ESUCCESS) {
		if (!strcmp(header.name, name)) {
			if (h) {
				*h = header;
			}
			return MTAR_ESUCCESS;
		}
		mtar_next(tar);
	}
	/* Return error */
	if (err == MTAR_ENULLRECORD) {
		err = MTAR_ENOTFOUND;
	}
	return err;
}


int mtar_read_header(mtar_t *tar, mtar_header_t *h) {
	int err;
	mtar_raw_header_t rh;
	/* Save header position */
	tar->last_header = tar->pos;
	/* Read raw header */
	err = tread(tar, &rh, sizeof(rh));
	if (err) {
		return err;
	}
	/* Seek back to start of header */
	err = mtar_seek(tar, tar->last_header);
	if (err) {
		return err;
	}
	/* Load raw header into header struct and return */
	return raw_to_header(h, &rh);
}


int mtar_read_data(mtar_t *tar, void *ptr, unsigned size) {
	int err;
	/* If we have no remaining data then this is the first read, we get the size,
	* set the remaining data and seek to the beginning of the data */
	if (tar->remaining_data == 0) {
		mtar_header_t h;
		/* Read header */
		err = mtar_read_header(tar, &h);
		if (err) {
			return err;
		}
		/* Seek past header and init remaining data */
		err = mtar_seek(tar, tar->pos + sizeof(mtar_raw_header_t));
		if (err) {
			return err;
		}
		tar->remaining_data = h.size;
	}
	/* Read data */
	err = tread(tar, ptr, size);
	if (err) {
		return err;
	}
	tar->remaining_data -= size;
	/* If there is no remaining data we've finished reading and seek back to the
	* header */
	if (tar->remaining_data == 0) {
		return mtar_seek(tar, tar->last_header);
	}
	return MTAR_ESUCCESS;
}


int mtar_write_header(mtar_t *tar, const mtar_header_t *h) {
	mtar_raw_header_t rh;
	/* Build raw header and write */
	header_to_raw(&rh, h);
	tar->remaining_data = h->size;
	return twrite(tar, &rh, sizeof(rh));
}


int mtar_write_file_header(mtar_t *tar, std::string  name, unsigned size) {
	mtar_header_t h;
	/* Build header */
	memset(&h, 0, sizeof(h));
	strcpy(h.name, name.c_str());
	h.size = size;
	h.type = MTAR_TREG;
	h.mode = 0664;
	/* Write header */
	return mtar_write_header(tar, &h);
}


int mtar_write_dir_header(mtar_t *tar, std::string  name) {
	mtar_header_t h;
	/* Build header */
	memset(&h, 0, sizeof(h));
	strcpy(h.name, name.c_str());
	h.type = MTAR_TDIR;
	h.mode = 0775;
	/* Write header */
	return mtar_write_header(tar, &h);
}


int mtar_write_data(mtar_t *tar, const void *data, unsigned size) {
	int err;
	/* Write data */
	err = twrite(tar, data, size);
	if (err) {
		return err;
	}
	tar->remaining_data -= size;
	/* Write padding if we've written all the data for this file */
	if (tar->remaining_data == 0) {
		return write_null_bytes(tar, round_up(tar->pos, 512) - tar->pos);
	}
	return MTAR_ESUCCESS;
}
 
int mtar_write_file(mtar_t *tar, std::string name, std::string path) {
	char buf[1024];
	FILE *fp;
	size_t nread;
	size_t size = tp::filesize(path);
	if (size > 0) {
		fp = fopen(path.c_str(), "rb");
		if (fp) {
			mtar_write_file_header(tar, name, size);
			while (size > 0 && (nread = fread(buf, 1, sizeof buf, fp)) > 0) {
				mtar_write_data(tar, buf, nread);
			}
			return MTAR_ESUCCESS;
		}
		return MTAR_EREADFAIL;
	}
	return MTAR_ENOTFOUND;
}

int mtar_write_file(mtar_t *tar, std::string path, size_t size) {
	int err;
	unsigned write_size = 0;
	std::ifstream fin(path, std::ifstream::binary);
	std::vector<char> buffer(1024, 0); 
	while (write_size < size && !fin.eof()) {
		fin.read(buffer.data(), buffer.size()); 
		std::streamsize s = fin.gcount();
		write_size += s;
		if ( write_size > size) {
			//file size has increased, write upto this point only.
			std::cout << "file size has increased, s = " << s << " end would have been " << write_size<<  std::endl;
			s = write_size - size;
		}
		err = twrite(tar, buffer.data(), s);
		if (err) {
			return err;
		}
		tar->remaining_data -= s;
		std::cout << "Wrote " << write_size << "bytes, remaining " << tar->remaining_data << ", Expected : " << size  << std::endl;
	}
	/* Write padding if we've written all the data for this file */
	if (tar->remaining_data == 0) {
		return write_null_bytes(tar, round_up(tar->pos, 512) - tar->pos);
	}
	return MTAR_ESUCCESS;
}


int mtar_finalize(mtar_t *tar) {
	/* Write two NULL records */
	return write_null_bytes(tar, sizeof(mtar_raw_header_t) * 2);
}