#pragma once

#include <cstdint>
#include "Structs.h"

// https://www.pjrc.com/tech/8051/ide/fat32.html
namespace FAT32 {

	template <typename BlockDev> class FS {

		static constexpr const char* NAME = "FAT32";

		BlockDev& dev;
		AbsOffset offset;


		FSDesc desc;
		Precomputed tmp;
		bool valid = false;


	public:

		#include "File.h"
		#include "DirIterator.h"

		/** ctor with the absolute offset addr (in bytes) */
		FS(BlockDev& dev, AbsOffset offset) : dev(dev), offset(offset) {
			init();
		}

		/** is the detected FS valid? */
		bool isValid() const {
			return valid;
		}

		/** get an iterator for the root directory */
		DirIterator getRoot() {
			return DirIterator(*this, desc.rootDirFirstCluster);
		}

		/** open the given file for reading*/
		File open(const DirEntry& de) {
			return File(*this, de.getFirstCluster(), de.size);
		}

	private:

		void init() {

			debugMod3(NAME")
			uint8_t buf[512];
			dev.read(offset, 512, buf);

			desc.bytesPerSector =		getU16(&buf[0x0B]);
			desc.sectorsPerCluster =	getU8(&buf[0x0D]);
			desc.numReservedSectors =	getU16(&buf[0x0E]);
			desc.numberOfFATs = 		getU8(&buf[0x10]);
			desc.sectorsPerFAT = 		getU32(&buf[0x24]);
			desc.rootDirFirstCluster =	getU32(&buf[0x2C]);

			// basic sanity check based on constants
			valid = (desc.bytesPerSector == 512) && (desc.numberOfFATs == 2) && (getU16(&buf[0x1FE]) == 0xAA55);

			tmp.bytesPerCluster =				desc.sectorsPerCluster * desc.bytesPerSector;
			tmp.startOfFAT =					offset + (desc.numReservedSectors * desc.bytesPerSector);
			tmp.startOfFirstDataCluster =		offset + (desc.numReservedSectors * desc.bytesPerSector) + (desc.numberOfFATs * desc.sectorsPerFAT * desc.bytesPerSector);
			tmp.startOfFirstRootDirCluster =	clusterToAbsPos(desc.rootDirFirstCluster);
			tmp.dirEntriesPerSector =			desc.bytesPerSector / sizeof(DirEntry);

			/*
			std::cout << (int)desc.bytesPerSector << std::endl;
			std::cout << (int)desc.sectorsPerCluster << std::endl;
			std::cout << (int)desc.numReservedSectors << std::endl;
			std::cout << (int)desc.numberOfFATs << std::endl;
			std::cout << (int)desc.sectorsPerFAT << std::endl;
			std::cout << (int)desc.rootDirFirstCluster << std::endl;

			std::cout << tmp.startOfFAT << std::endl;
			std::cout << tmp.startOfFirstDataCluster << std::endl;
			std::cout << tmp.startOfFirstRootDirCluster << std::endl;
			*/

		}

		/** determine the ClusterNr following the given ClusterNr */
		ClusterNr getNextCluster(ClusterNr clusterNr) {
			const AbsPos pos = tmp.startOfFAT + ((clusterNr) * sizeof(uint32_t));
			ClusterNr next;
			int read = dev.read(pos, 4, reinterpret_cast<uint8_t*>(&next));
			return next;
		}

		/** convert ClusterNr into an absolute position on disk */
		AbsPos clusterToAbsPos(ClusterNr clusterNr) {
			return tmp.startOfFirstDataCluster + ((clusterNr - 2) * desc.sectorsPerCluster * desc.bytesPerSector);
		}

	};
}