#include <stdint.h>
#include <stdbool.h>
#include "inc/tm4c1294ncpdt.h"
#include "driverlib/adc.h"
#include "driverlib/pin_map.h"
#include "driverlib/gpio.h"
#include "driverlib/sysctl.h"
#include "driverlib/interrupt.h"
#include "driverlib/timer.h"
#include "sysctl_pll.h"
#include "inc/hw_types.h"
#include "inc/hw_memmap.h"
#include <math.h>
#include "buttons.h"
#include "sampling.h"

extern uint32_t gSystemClock;   // [Hz] system clock frequency

// latest sample index
void ADC_ISR(void)
{
    // clear ADC1 sequence0 interrupt flag in the ADCISC register
    //HWREGBITW(ADC1_ISC_R, 1) = 1;
    ADC1_ISC_R |= 1;

    // check for ADC FIFO overflow
    if(ADC1_OSTAT_R & ADC_OSTAT_OV0) {
    gADCErrors++; // count errors
    ADC1_OSTAT_R = ADC_OSTAT_OV0; // clear overflow condition
    }
    gADCBufferIndex = ADC_BUFFER_WRAP(gADCBufferIndex + 1);
    // read sample from the ADC1 sequence 0 FIFO
    gADCBuffer[gADCBufferIndex] = (ADC1_SSFIFO0_R & ADC_SSFIFO0_DATA_M);
}


void start_sampler() {
    gADCBufferIndex = ADC_BUFFER_SIZE - 1;
    gADCErrors = 0;

    SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOE);
    GPIOPinTypeADC(GPIO_PORTE_BASE,
                    GPIO_PIN_0); // GPIO setup for analog input AIN3
    // initialize ADC peripherals
    SysCtlPeripheralEnable(SYSCTL_PERIPH_ADC0);
    SysCtlPeripheralEnable(SYSCTL_PERIPH_ADC1);

    // timer for low-speed
    SysCtlPeripheralEnable(SYSCTL_PERIPH_TIMER2);
    // ADC clock
    uint32_t pll_frequency = SysCtlFrequencyGet(CRYSTAL_FREQUENCY);
    uint32_t pll_divisor =
        (pll_frequency - 1) / (16 * ADC_SAMPLING_RATE) + 1; // round up
    ADCClockConfigSet(ADC0_BASE, ADC_CLOCK_SRC_PLL | ADC_CLOCK_RATE_FULL,
                    pll_divisor);
    ADCClockConfigSet(ADC1_BASE, ADC_CLOCK_SRC_PLL | ADC_CLOCK_RATE_FULL,
                    pll_divisor);
    // choose ADC1 sequence 0; disable before configuring
    ADCSequenceDisable(ADC1_BASE, 0);
    ADCSequenceConfigure(ADC1_BASE, 0, ADC_TRIGGER_ALWAYS,
                        0); // specify the "Always" trigger
    // in the 0th step, sample channel 3 (AIN3)
    // enable interrupt, and make it the end of sequence
    ADCSequenceStepConfigure(ADC1_BASE, 0, 0, ADC_CTL_CH3 | ADC_CTL_END | ADC_CTL_IE);
    // enable the sequence. it is now sampling
    ADCSequenceEnable(ADC1_BASE, 0);
    // enable sequence 0 interrupt in the ADC1 peripheral
    ADCIntEnable(ADC1_BASE, 0); // INT_ADC1SS0
}

void set_frequency(uint64_t microseconds) {
    if (microseconds == 1) {
        ADCSequenceDisable(ADC1_BASE, 0);
        // don't use a timer for high speed
        ADCSequenceConfigure(ADC1_BASE, 0, ADC_TRIGGER_ALWAYS, 0);
        ADCSequenceEnable(ADC1_BASE, 0);
        return;
    }

    // initialize timer 2 in periodic mode
    TimerDisable(TIMER2_BASE, TIMER_BOTH);
    TimerConfigure(TIMER2_BASE, TIMER_CFG_PERIODIC);
    #define MICROSECONDS_PER_SECOND 1000000
    TimerLoadSet(TIMER2_BASE, TIMER_A, (uint32_t) ((uint64_t) gSystemClock * microseconds / MICROSECONDS_PER_SECOND) - 1);
    TimerControlTrigger(TIMER2_BASE, TIMER_A, true);
    TimerEnable(TIMER2_BASE, TIMER_A);

    ADCSequenceDisable(ADC1_BASE, 0);
    ADCSequenceConfigure(ADC1_BASE, 0, ADC_TRIGGER_TIMER, 0);
    ADCSequenceEnable(ADC1_BASE, 0);
}