/*
This adc file will handle:
- packet configuration: bool
- adc ready flag: bool
- adc_read_raw: int_16

Function to read ADC DATA: This function simply retrieves the ADC raw digital
output as 16-bit signed integer.
* The value returned is not yet converted to VOLTAGE.
* adc_data[2]: Buffer with an array of size 2, to store two bytes of ADC data.
*             Since, the ADC output consists of two 8-bit bytes:
*             - adc_data[0] (MSB)
*             - adc_data[1] (LSB)
* Next, we verify if the the I2C bus is busy using the function in the
driverlib: DL_I2C_get ControllerStatus
*       - Prevents collisions by ensuring no two I2C device is using the same
bus before initializing.
* BEGIN I2C READ operation to request 2 bytes from the ADC->
DL_I2C_startControllerTransfer()
* Parameters:
    - I2C_controller_INST: Refererence to the I2C instance bring used.
    - DEF_TARGET_ADDR_ADC: Address of the ADC
    - DL_I2C_CONTROLLER_DIRECTION_RX: Indicates that we want to receive the data
from ADC
    - 2: Specifies that we expect 2 bytes from the ADC
* WAIT for the data to be received: (DL_I2C_getControllerStatus())
    - Waits until the ADC sends the data over I2C.
    - Ensures that the data transfer is complete before proceeding.
* READ the two bytes of ADc Data:
    - adc_data[0] : MSB
    - adc_data[1] : LSB
    - adc_data[2] : config_bytes
    ADC sends its 16-bit value in two parts over 8-bit I2C data frames.
* COMBINE the two bytes into 16-bit Integer:
    - Shifts the MSB(first byte) left by 8 bits to make space for LSB.
    - Performs a bitwise OR operation to combine MSB and LSB into a single
16-bit number.
* PRINT HEXADEC and DECIMAL format for DEBUGGING.
* Output code is in binary and is proportional to the Input Voltage and PGA
settings.
* From the datasheet:
https://ww1.microchip.com/downloads/aemDocuments/documents/OTH/ProductDocuments/DataSheets/22226a.pdf
    - Equation 4.4 is being used to convert the output codes to input voltage

* The ACK bits after conversion is issued by the Master, when the device
receives a READ command, it outputs two data bytes followed by a configuration
register in 16 bit conversion mode the MSB(=sign bit) of the first data type is
D15.
*/


#include "src/interfaces/i2c_controller.h"
#include "src/peripherals/adc/adc_interface.h"
#include "ti_msp_dl_config.h"
#include <stdio.h>
#include "src/battery_data/battery.h"
#include "src/config.h"

/*
* Creating Configuartion Register as mentioned in the datasheet: https://ww1.microchip.com/downloads/aemDocuments/documents/OTH/ProductDocuments/DataSheets/22226a.pdf
* Under section 5.2 Configuration Register
* The function is private to ADC and is can only be called in this file
*/
static uint8_t construct_config_byte(ADC_Params *params) {

    uint8_t config = 0;
    
    config |= ((params->channel) << 5); // Channel Selection (Bits 6-5)
    
    if (params->continuous == 1) {
        config |= (1 << 4); // Continous mode
    } else {
        // One-Shot mode
        // Bit set to zero, BUT the Ready bit needs to be set to start meausrement
        // (read/not write bit)
        config |= (1 << 7);
    }
    
    switch (params->resolution) {
        
        case 12:
            config |= (0b00 << 2);
            break;
        case 14:
            config |= (0b01 << 2);
            break;
        case 16:
            config |= (0b10 << 2);
            break;
        default:
            //printf("ERROR: Invalid Resolution!\n");
            return 0;
    }
    
    switch (params->gain) {
        
        case 1:
            config |= (0b00);
            break;
        case 2:
            config |= (0b01);
            break;
        case 4:
            config |= (0b10);
            break;
        case 8:
            config |= (0b11);
            break;
        default:
            //printf("ERROR: Invalid Gain!\n");
            return 0;
    }

    return config;
}

/* Tansmit Data from MCU to ADC:  Function to SET configuration to ADC over
 * I2C*/

static bool adc_configure(uint8_t slot_id, ADC_Params *params) {
    controllerTxPackage.packet[0] = construct_config_byte(params);

    // Wait for I2C Bus to be Free**
    uint32_t n_cycles = 0;
    while ((DL_I2C_getControllerStatus(I2C_controller_INST) &
            DL_I2C_CONTROLLER_STATUS_BUSY_BUS) && n_cycles++ < MAX_I2C_WAIT_RX)
        ;
    if (n_cycles == MAX_I2C_WAIT_RX) {
        printf("Error in reading from I2C Bus: Bus is not getting ready on config byte\n");
    }
    if(controllerTxPackage.packet[0] == 0xFF){
        // this clause can only happen if the internal memory management is messed up?!
        // the config function should take care that this is never the case
#ifdef DEBUG_ADC
        printf("[ADC] Unable to send config bytes\n");
#endif
        *battery_slots[slot_id].state = SLOT_ERR_CONFIGBYTE;
        return false;
    } 
    // Prepare TX Buffer
    controllerTxPackage.len = 1;
    controllerTxPackage.count = 0;
    controllerTxPackage.complete = false;
    i2c_hal.write(battery_slots[slot_id].adc_addr);
    
    n_cycles = 0;
    while(!controllerTxPackage.complete && n_cycles++ < MAX_I2C_WAIT_RX);
    if (n_cycles == MAX_I2C_WAIT_RX) {
#ifdef DEBUG_ADC
        printf("[ADC] No Response to the config byte!\n");
#endif
        return false;
    }
    return true;
}


/*
READY BIT:
    This bit is the data ready flag. In read mode, this bit indicates if the
output register has been updated with a latest conversion result. In One-Shot
Conversion mode, writing this bit to “1” initiates a new conversion.

    1= Output Register has not been updated
    0= Output Register has been updated

*/

static bool adc_is_ready(uint8_t slot_id, ADC_Params *params) {
    uint8_t adc_address = battery_slots[slot_id].adc_addr;
    controllerRxPackage.len = 3;
    controllerRxPackage.count = 0;
    controllerRxPackage.complete = false;

    i2c_hal.read(adc_address);
    // Ready bit is bit 7
    while(!controllerRxPackage.complete);
    uint8_t config_adc_byte = controllerRxPackage.packet[2];
    bool ready = (config_adc_byte & 0x80) == 1;
    return ready;
}


static int16_t read_adc_raw_data(uint8_t slot_id, ADC_Params *params) {

    // Buffer for ADC data (MSB, LSB, Config Byte)
    uint32_t raw_adc = 0;

    controllerRxPackage.len = 3;
    controllerRxPackage.count = 0;
    controllerRxPackage.complete = false;
    
    i2c_hal.read(battery_slots[slot_id].adc_addr);
    uint32_t n_cycles = 0;
    while(!controllerRxPackage.complete && n_cycles++ < MAX_I2C_WAIT_RX);
    if (n_cycles == MAX_I2C_WAIT_RX) {
        return 0xffff;
    }
    uint8_t msb = controllerRxPackage.packet[0];
    uint8_t lsb = controllerRxPackage.packet[1];
    uint8_t config_adc_byte = controllerRxPackage.packet[2];

    uint32_t max_adc_val = 0;

    switch (params->resolution) {
        case 12: // 12-bit
            raw_adc = ((msb & 0b00001111) << 8) | lsb;
            max_adc_val = 4096;
            break;
        case 14: // 14-bit
            raw_adc = ((msb & 0b00111111) << 8) | lsb;
            max_adc_val = 16384;
            break;
        case 16: // 16-bit
            raw_adc = ((msb & 0b11111111) << 8) | lsb;
            max_adc_val = 65536;
            break;
        default:
            //printf("Error: Unknown ADC Resolution!\n");
            break;
    }
    return raw_adc * params->factor * 2048 / (max_adc_val/2) / params->gain;
}

ADC_Interface adc_hal= {
    .configure= adc_configure,
    .read_voltage = read_adc_raw_data,
    .is_ready= adc_is_ready,
};