/*
  This file is part of Beremiz, a Integrated Development Environment for
  programming IEC 61131-3 automates supporting plcopen standard and CanFestival.

  See COPYING.runtime

  Copyright (C) 2018: Sergey Surkov <surkov.sv@summatechnology.ru>
  Copyright (C) 2018: Andrey Skvortsov <andrej.skvortzov@gmail.com>

*/

#ifndef HAVE_RETAIN
#include <stdio.h>
#include <stdint.h>
#include <unistd.h>
#include "iec_types.h"

int GetRetainSize(void);

/* Retain buffer.  */
FILE *retain_buffer;
const char rb_file[]      = "retain_buffer_file";
const char rb_file_bckp[] = "retain_buffer_file.bak";


/* Retain header struct.  */
struct retain_info_t {
	uint32_t retain_size;
	uint32_t hash_size;
	uint8_t* hash;
	uint32_t header_offset;
	uint32_t header_crc;
};

/* Init retain info structure.  */
struct retain_info_t retain_info;

/* CRC lookup table and initial state.  */
static const uint32_t crc32_table[256] = {
	0x00000000, 0x77073096, 0xEE0E612C, 0x990951BA, 0x076DC419, 0x706AF48F, 0xE963A535, 0x9E6495A3,
	0x0EDB8832, 0x79DCB8A4, 0xE0D5E91E, 0x97D2D988, 0x09B64C2B, 0x7EB17CBD, 0xE7B82D07, 0x90BF1D91,
	0x1DB71064, 0x6AB020F2, 0xF3B97148, 0x84BE41DE, 0x1ADAD47D, 0x6DDDE4EB, 0xF4D4B551, 0x83D385C7,
	0x136C9856, 0x646BA8C0, 0xFD62F97A, 0x8A65C9EC, 0x14015C4F, 0x63066CD9, 0xFA0F3D63, 0x8D080DF5,
	0x3B6E20C8, 0x4C69105E, 0xD56041E4, 0xA2677172, 0x3C03E4D1, 0x4B04D447, 0xD20D85FD, 0xA50AB56B,
	0x35B5A8FA, 0x42B2986C, 0xDBBBC9D6, 0xACBCF940, 0x32D86CE3, 0x45DF5C75, 0xDCD60DCF, 0xABD13D59,
	0x26D930AC, 0x51DE003A, 0xC8D75180, 0xBFD06116, 0x21B4F4B5, 0x56B3C423, 0xCFBA9599, 0xB8BDA50F,
	0x2802B89E, 0x5F058808, 0xC60CD9B2, 0xB10BE924, 0x2F6F7C87, 0x58684C11, 0xC1611DAB, 0xB6662D3D,
	0x76DC4190, 0x01DB7106, 0x98D220BC, 0xEFD5102A, 0x71B18589, 0x06B6B51F, 0x9FBFE4A5, 0xE8B8D433,
	0x7807C9A2, 0x0F00F934, 0x9609A88E, 0xE10E9818, 0x7F6A0DBB, 0x086D3D2D, 0x91646C97, 0xE6635C01,
	0x6B6B51F4, 0x1C6C6162, 0x856530D8, 0xF262004E, 0x6C0695ED, 0x1B01A57B, 0x8208F4C1, 0xF50FC457,
	0x65B0D9C6, 0x12B7E950, 0x8BBEB8EA, 0xFCB9887C, 0x62DD1DDF, 0x15DA2D49, 0x8CD37CF3, 0xFBD44C65,
	0x4DB26158, 0x3AB551CE, 0xA3BC0074, 0xD4BB30E2, 0x4ADFA541, 0x3DD895D7, 0xA4D1C46D, 0xD3D6F4FB,
	0x4369E96A, 0x346ED9FC, 0xAD678846, 0xDA60B8D0, 0x44042D73, 0x33031DE5, 0xAA0A4C5F, 0xDD0D7CC9,
	0x5005713C, 0x270241AA, 0xBE0B1010, 0xC90C2086, 0x5768B525, 0x206F85B3, 0xB966D409, 0xCE61E49F,
	0x5EDEF90E, 0x29D9C998, 0xB0D09822, 0xC7D7A8B4, 0x59B33D17, 0x2EB40D81, 0xB7BD5C3B, 0xC0BA6CAD,
	0xEDB88320, 0x9ABFB3B6, 0x03B6E20C, 0x74B1D29A, 0xEAD54739, 0x9DD277AF, 0x04DB2615, 0x73DC1683,
	0xE3630B12, 0x94643B84, 0x0D6D6A3E, 0x7A6A5AA8, 0xE40ECF0B, 0x9309FF9D, 0x0A00AE27, 0x7D079EB1,
	0xF00F9344, 0x8708A3D2, 0x1E01F268, 0x6906C2FE, 0xF762575D, 0x806567CB, 0x196C3671, 0x6E6B06E7,
	0xFED41B76, 0x89D32BE0, 0x10DA7A5A, 0x67DD4ACC, 0xF9B9DF6F, 0x8EBEEFF9, 0x17B7BE43, 0x60B08ED5,
	0xD6D6A3E8, 0xA1D1937E, 0x38D8C2C4, 0x4FDFF252, 0xD1BB67F1, 0xA6BC5767, 0x3FB506DD, 0x48B2364B,
	0xD80D2BDA, 0xAF0A1B4C, 0x36034AF6, 0x41047A60, 0xDF60EFC3, 0xA867DF55, 0x316E8EEF, 0x4669BE79,
	0xCB61B38C, 0xBC66831A, 0x256FD2A0, 0x5268E236, 0xCC0C7795, 0xBB0B4703, 0x220216B9, 0x5505262F,
	0xC5BA3BBE, 0xB2BD0B28, 0x2BB45A92, 0x5CB36A04, 0xC2D7FFA7, 0xB5D0CF31, 0x2CD99E8B, 0x5BDEAE1D,
	0x9B64C2B0, 0xEC63F226, 0x756AA39C, 0x026D930A, 0x9C0906A9, 0xEB0E363F, 0x72076785, 0x05005713,
	0x95BF4A82, 0xE2B87A14, 0x7BB12BAE, 0x0CB61B38, 0x92D28E9B, 0xE5D5BE0D, 0x7CDCEFB7, 0x0BDBDF21,
	0x86D3D2D4, 0xF1D4E242, 0x68DDB3F8, 0x1FDA836E, 0x81BE16CD, 0xF6B9265B, 0x6FB077E1, 0x18B74777,
	0x88085AE6, 0xFF0F6A70, 0x66063BCA, 0x11010B5C, 0x8F659EFF, 0xF862AE69, 0x616BFFD3, 0x166CCF45,
	0xA00AE278, 0xD70DD2EE, 0x4E048354, 0x3903B3C2, 0xA7672661, 0xD06016F7, 0x4969474D, 0x3E6E77DB,
	0xAED16A4A, 0xD9D65ADC, 0x40DF0B66, 0x37D83BF0, 0xA9BCAE53, 0xDEBB9EC5, 0x47B2CF7F, 0x30B5FFE9,
	0xBDBDF21C, 0xCABAC28A, 0x53B39330, 0x24B4A3A6, 0xBAD03605, 0xCDD70693, 0x54DE5729, 0x23D967BF,
	0xB3667A2E, 0xC4614AB8, 0x5D681B02, 0x2A6F2B94, 0xB40BBE37, 0xC30C8EA1, 0x5A05DF1B, 0x2D02EF8D,
};
uint32_t retain_crc;


/* Calculate CRC32 for len bytes from pointer buf with init starting value.  */
uint32_t GenerateCRC32Sum(const void* buf, unsigned int len, uint32_t init)
{
	uint32_t crc = ~init;
	unsigned char* current = (unsigned char*) buf;
	while (len--)
		crc = crc32_table[(crc ^ *current++) & 0xFF] ^ (crc >> 8);
	return ~crc;
}

/* Calc CRC32 for retain file byte by byte.  */
int CheckFileCRC(FILE* file_buffer)
{
	/* Set the magic constant for one-pass CRC calc according to ZIP CRC32.  */
	const uint32_t magic_number = 0x2144df1c;

	/* CRC initial state.  */
	uint32_t calc_crc32 = 0;
	char data_block = 0;

	while(!feof(file_buffer)){
		if (fread(&data_block, sizeof(data_block), 1, file_buffer))
			calc_crc32 = GenerateCRC32Sum(&data_block, sizeof(char), calc_crc32);
	}

	/* Compare crc result with a magic number.  */
	return (calc_crc32 == magic_number) ? 1 : 0;
}

/* Compare current hash with hash from file byte by byte.  */
int CheckFilehash(void)
{
	int k,ret;
	int offset = sizeof(retain_info.retain_size);

	rewind(retain_buffer);
	fseek(retain_buffer, offset , SEEK_SET);

	uint32_t size;
	ret = fread(&size, sizeof(size), 1, retain_buffer);
	if (size != retain_info.hash_size)
		return 0;

	for(k = 0; k < retain_info.hash_size; k++){
		uint8_t file_digit;
		ret = fread(&file_digit, sizeof(char), 1, retain_buffer);
		if (file_digit != *(retain_info.hash+k))
			return 0;
	}

	return 1;
}

void InitRetain(void)
{
	int i;

	/* Get retain size in bytes */
	retain_info.retain_size = GetRetainSize();

	/* Hash stored in retain file as array of char in hex digits
	   (that's why we divide strlen in two).  */
	retain_info.hash_size = PLC_ID ? strlen(PLC_ID)/2 : 0;
	//retain_info.hash_size = 0;
	retain_info.hash = malloc(retain_info.hash_size);

	/* Transform hash string into byte sequence.  */
	for (i = 0; i < retain_info.hash_size; i++) {
		int byte = 0;
		sscanf((PLC_ID + i*2), "%02X", &byte);
		retain_info.hash[i] = byte;
	}

	/* Calc header offset.  */
	retain_info.header_offset = sizeof(retain_info.retain_size) + \
		sizeof(retain_info.hash_size) + \
		retain_info.hash_size;

	/*  Set header CRC initial state.  */
	retain_info.header_crc = 0;

	/* Calc crc for header.  */
	retain_info.header_crc = GenerateCRC32Sum(
		&retain_info.retain_size,
		sizeof(retain_info.retain_size),
		retain_info.header_crc);

	retain_info.header_crc = GenerateCRC32Sum(
		&retain_info.hash_size,
		sizeof(retain_info.hash_size),
		retain_info.header_crc);

	retain_info.header_crc = GenerateCRC32Sum(
		retain_info.hash,
		retain_info.hash_size,
		retain_info.header_crc);
}

void CleanupRetain(void)
{
	/* Free hash memory.  */
	free(retain_info.hash);
}

int CheckRetainFile(const char * file)
{
	retain_buffer = fopen(file, "rb");
	if (retain_buffer) {
		/* Check CRC32 and hash.  */
		if (CheckFileCRC(retain_buffer))
			if (CheckFilehash())
				return 1;
		fclose(retain_buffer);
		retain_buffer = NULL;
	}
	return 0;
}

int CheckRetainBuffer(void)
{
	retain_buffer = NULL;
	if (!retain_info.retain_size)
		return 1;

	/* Check latest retain file.  */
	if (CheckRetainFile(rb_file))
		return 1;

	/* Check if we have backup.  */
	if (CheckRetainFile(rb_file_bckp))
		return 1;

	/* We don't have any valid retain buffer - nothing to remind.  */
	return 0;
}

#ifndef FILE_RETAIN_SAVE_PERIOD_S
#define FILE_RETAIN_SAVE_PERIOD_S 1.0
#endif

static double CalcDiffSeconds(IEC_TIME* t1, IEC_TIME *t2)
{
	IEC_TIME dt ={
		t1->tv_sec  - t2->tv_sec,
		t1->tv_nsec - t2->tv_nsec
	};

	if ((dt.tv_nsec < -1000000000) || ((dt.tv_sec > 0) && (dt.tv_nsec < 0))){
		dt.tv_sec--;
		dt.tv_nsec += 1000000000;
	}
	if ((dt.tv_nsec > +1000000000) || ((dt.tv_sec < 0) && (dt.tv_nsec > 0))){
		dt.tv_sec++;
		dt.tv_nsec -= 1000000000;
	}
	return dt.tv_sec + 1e-9*dt.tv_nsec;
}


int RetainSaveNeeded(void)
{
	int ret = 0;
	static IEC_TIME last_save;
	IEC_TIME now;
	double diff_s;

	/* no retain */
	if (!retain_info.retain_size)
		return 0;

	/* periodic retain flush to avoid high I/O load */
	PLC_GetTime(&now);

	diff_s = CalcDiffSeconds(&now, &last_save);

	if ((diff_s > FILE_RETAIN_SAVE_PERIOD_S) || ForceSaveRetainReq()) {
		ret = 1;
		last_save = now;
	}
	return ret;
}

void ValidateRetainBuffer(void)
{
	if (!retain_buffer)
		return;

	/* Add retain data CRC to the end of buffer file.  */
	fseek(retain_buffer, 0, SEEK_END);
	fwrite(&retain_crc, sizeof(uint32_t), 1, retain_buffer);

	/* Sync file buffer and close file.  */
#ifdef __WIN32
	fflush(retain_buffer);
#else
	fsync(fileno(retain_buffer));
#endif

	fclose(retain_buffer);
	retain_buffer = NULL;
}

void InValidateRetainBuffer(void)
{
	if (!RetainSaveNeeded())
		return;

	/* Rename old retain file into *.bak if it exists.  */
	rename(rb_file, rb_file_bckp);

	/* Set file CRC initial value.  */
	retain_crc = retain_info.header_crc;

	/* Create new retain file.  */
	retain_buffer = fopen(rb_file, "wb+");
	if (!retain_buffer) {
		fprintf(stderr, "Failed to create retain file : %s\n", rb_file);
		return;
	}

	/* Write header to the new file.  */
	fwrite(&retain_info.retain_size,
		sizeof(retain_info.retain_size), 1, retain_buffer);
	fwrite(&retain_info.hash_size,
		sizeof(retain_info.hash_size),   1, retain_buffer);
	fwrite(retain_info.hash ,
		sizeof(char), retain_info.hash_size, retain_buffer);
}

void Retain(unsigned int offset, unsigned int count, void *p)
{
	if (!retain_buffer)
		return;

	/* Generate CRC 32 for each data block.  */
	retain_crc = GenerateCRC32Sum(p, count, retain_crc);

	/* Save current var in file.  */
	fseek(retain_buffer, retain_info.header_offset+offset, SEEK_SET);
	fwrite(p, count, 1, retain_buffer);
}

void Remind(unsigned int offset, unsigned int count, void *p)
{
    int ret;
	/* Remind variable from file.  */
	fseek(retain_buffer, retain_info.header_offset+offset, SEEK_SET);
	ret = fread((void *)p, count, 1, retain_buffer);
}
#endif // !HAVE_RETAIN