#include "globals.h"
#include "fluxmap.h"
#include "decoders/fluxmapreader.h"
#include "decoders/decoders.h"
#include "sector.h"
#include "micropolis.h"
#include "bytes.h"
#include "fmt/format.h"

/* The sector has a preamble of MFM 0x00s and uses 0xFF as a sync pattern. */
static const FluxPattern SECTOR_SYNC_PATTERN(32, 0xaaaa5555);

AbstractDecoder::RecordType MicropolisDecoder::advanceToNextRecord()
{
	_fmr->seekToIndexMark();
	const FluxMatcher* matcher = nullptr;
	_sector->clock = _fmr->seekToPattern(SECTOR_SYNC_PATTERN, matcher);
	if (matcher == &SECTOR_SYNC_PATTERN) {
		readRawBits(16);
		return SECTOR_RECORD;
	}
	return UNKNOWN_RECORD;
}

/* Adds all bytes, with carry. */
static uint8_t checksum(const Bytes& bytes) {
	ByteReader br(bytes);
	uint16_t sum = 0;
	while (!br.eof()) {
		if (sum > 0xFF) {
			sum -= 0x100 - 1;
		}
		sum += br.read_8();
	}
	/* The last carry is ignored */
	return sum & 0xFF;
}

void MicropolisDecoder::decodeSectorRecord()
{
	auto rawbits = readRawBits(MICROPOLIS_ENCODED_SECTOR_SIZE*16);
	auto bytes = decodeFmMfm(rawbits).slice(0, MICROPOLIS_ENCODED_SECTOR_SIZE);
	ByteReader br(bytes);

	br.read_8();  /* sync */
	_sector->logicalTrack = br.read_8();
	_sector->logicalSide = _sector->physicalSide;
	_sector->logicalSector = br.read_8();
	if (_sector->logicalSector > 15)
		return;
	if (_sector->logicalTrack > 77)
		return;

	br.read(10);  /* OS data or padding */
	_sector->data = br.read(256);
	uint8_t wantChecksum = br.read_8();
	uint8_t gotChecksum = checksum(bytes.slice(1, 2+266));
	br.read(5);  /* 4 byte ECC and ECC-present flag */

	_sector->status = (wantChecksum == gotChecksum) ? Sector::OK : Sector::BAD_CHECKSUM;
}