/// @file permanent_storage.h
#pragma once
#include "../hal/eeprom.h"

namespace modules {

/// @brief The permanent_storage namespace provides all necessary facilities related to permanently storing data (into EEPROM) on the MMU unit.
///
/// It uses some clever logic/wear levelling/data structure on top of the raw EEPROM API.
/// The code was originally written by Marek Bel for the previous MMU firmware.
namespace permanent_storage {

/// Initialization of the permanent storage hive
void Init();

/// Erase the whole EEPROM
void EraseAll();

/// @brief Read manipulate and store bowden length
///
/// Value is stored independently for each filament.
/// Active filament is deduced from active_extruder global variable.
class BowdenLength {
public:
    static uint16_t get();
    static const uint8_t stepSize = 10u; ///< increase()/decrease() bowden length step size
    BowdenLength();
    bool increase();
    bool decrease();
    ~BowdenLength();

private:
    uint8_t filament; ///< Selected filament
    uint16_t length; ///< Selected filament bowden length
};

/// @brief Read and store last filament loaded to nozzle
///
/// 800(data) + 3(status) EEPROM cells are used to store 4 bit value frequently
/// to spread wear between more cells to increase durability.
///
/// Expected worst case durability scenario:
/// @n Print has 240mm height, layer height is 0.1mm, print takes 10 hours,
///    filament is changed 5 times each layer, EEPROM endures 100 000 cycles
/// @n Cell written per print: 240/0.1*5/800 = 15
/// @n Cell written per hour : 15/10 = 1.5
/// @n Fist cell failure expected: 100 000 / 1.5 = 66 666 hours = 7.6 years
///
/// Algorithm can handle one cell failure in status and one cell in data.
/// Status use 2 of 3 majority vote.
/// If bad data cell is detected, status is switched to next key.
/// Key alternates between begin to end and end to begin write order.
/// Two keys are needed for each start point and direction.
/// If two data cells fails, area between them is unavailable to write.
/// If this is first and last cell, whole storage is disabled.
/// This vulnerability can be avoided by adding additional keys
/// and start point in the middle of the EEPROM.
///
/// It would be possible to implement twice as efficient algorithm, if
/// separate EEPROM erase and EEPROM write commands would be available and
/// if write command would allow to be invoked twice between erases to update
/// just one nibble. Such commands are not available in AVR Libc, and possibility
/// to use write command twice is not documented in atmega32U4 datasheet.
///
class FilamentLoaded {
public:
    static bool get(uint8_t &filament);
    static bool set(uint8_t filament);

private:
    enum Key {
        KeyFront1,
        KeyReverse1,
        KeyFront2,
        KeyReverse2,
        BehindLastKey,
    };
    static_assert(BehindLastKey - 1 <= 0xf, "Key doesn't fit into a nibble.");
    static uint8_t getStatus();
    static bool setStatus(uint8_t status);
    static int16_t getIndex();
    static void getNext(uint8_t &status, int16_t &index);
    static void getNext(uint8_t &status);
};

/// @brief Read and increment drive errors
///
/// (Motor power rail voltage loss)
class DriveError {
public:
    static uint16_t get();
    static void increment();

private:
    static uint8_t getL();
    static void setL(uint8_t lowByte);
    static uint8_t getH();
    static void setH(uint8_t highByte);
};

} // namespace permanent_storage
} // namespace modules

namespace mps = modules::permanent_storage;