/***************************************************************************
 *   Copyright (C) 2021 - 2023 by Federico Amedeo Izzo IU2NUO,             *
 *                                Niccolò Izzo IU2KIN                      *
 *                                Frederik Saraci IU2NRO                   *
 *                                Silvano Seva IU2KWO                      *
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 3 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 *   This program is distributed in the hope that it will be useful,       *
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
 *   GNU General Public License for more details.                          *
 *                                                                         *
 *   You should have received a copy of the GNU General Public License     *
 *   along with this program; if not, see <http://www.gnu.org/licenses/>   *
 ***************************************************************************/

#include <interfaces/platform.h>
#include <peripherals/gpio.h>
#include <hwconfig.h>
#include <qdec.h>
#include "chSelector.h"

static uint8_t last_state = 0;  /* State storage */
static int8_t knob_pos    = 0;  /* Knob position */


/* Name of interrupt handler is mangled for C++ compatibility */
void _Z20EXTI15_10_IRQHandlerv()
{
    if(EXTI->PR & (EXTI_PR_PR11 | EXTI_PR_PR14))
    {
        /* Clear interrupt flags */
        EXTI->PR = EXTI_PR_PR11 | EXTI_PR_PR14;

        /* Read curent pin state */
        uint8_t pin_state = (gpio_readPin(CH_SELECTOR_1) << 1)
                          |  gpio_readPin(CH_SELECTOR_0);

        /* Look up next state */
        uint8_t next_state = HALF_STEP_STATE_TRANSITIONS[last_state][pin_state];

        /* update state for next call */
        last_state = next_state & QDECODER_STATE_BITMASK;

        /* Mask out events to switch on */
        uint8_t event = next_state & QDECODER_EVENT_BITMASK;

        /* Update knob_pos variable */
        switch(event)
        {
            case QDECODER_EVENT_CW:
                knob_pos++;
                break;
            case QDECODER_EVENT_CCW:
                knob_pos--;
                break;
            default:
                break;
        }
    }
}


void chSelector_init()
{
    gpio_setMode(CH_SELECTOR_0, INPUT_PULL_UP);
    gpio_setMode(CH_SELECTOR_1, INPUT_PULL_UP);

    /*
     * Configure GPIO interrupts: encoder signal is on PB11 and PE14
     */
    EXTI->IMR  |= EXTI_IMR_MR11  | EXTI_IMR_MR14;
    EXTI->RTSR |= EXTI_RTSR_TR11 | EXTI_RTSR_TR14;
    EXTI->FTSR |= EXTI_FTSR_TR11 | EXTI_FTSR_TR14;

    SYSCFG->EXTICR[2] |= SYSCFG_EXTICR3_EXTI11_PB;
    SYSCFG->EXTICR[3] |= SYSCFG_EXTICR4_EXTI14_PE;

    NVIC_ClearPendingIRQ(EXTI15_10_IRQn);
    NVIC_SetPriority(EXTI15_10_IRQn, 15);
    NVIC_EnableIRQ(EXTI15_10_IRQn);
}

void chSelector_terminate()
{
    EXTI->IMR &= ~(EXTI_IMR_MR1 | EXTI_IMR_MR14);
    NVIC_DisableIRQ(EXTI15_10_IRQn);
}


/*
 * This function is defined in platform.h
 */
int8_t platform_getChSelector()
{
    /*
     * The knob_pos variable is set in the EXTI15_10 interrupt handler
     * this is safe because interrupt nesting is not allowed.
     */
    return knob_pos;
}