/**
 ******************************************************************************
 * @file    cdc.c
 * @copyright András Wiesner, 2024-\showdate "%Y"
 * @brief   CDC ACM implementation module for the flatUSB project.
 ******************************************************************************
 */

#include "acm.h"

#include <memory.h>
#include <string.h>

#include "../usb.h"
#include "../usb_device_types.h"

#include <blocking_io/blocking_fifo.h>

// -------------------------

static Usb_AcmState acms = {0};                 ///< ACM module state
static uint8_t tx_buffer[USB_ACM_PCKT_BUFSIZE]; ///< Transmit buffer
static uint8_t fifo_mem[USB_ACM_FIFO_MEM_SIZE]; ///< Memory assigned to the TX BFifo
static BFifo fifo;                              ///< TX Blocking FIFO

// -------------------------

void usb_acm_read_callback(const uint8_t *data, uint32_t size);

void usb_acm_init(const Usb_Acm_EpAssignments *as) {
    // clear the structure
    memset(&acms, 0, sizeof(Usb_AcmState));

    // set Control Line State to something invalid
    acms.control_line_state.D = USB_ACM_INVALID_CONTROL_LINE_STATE;

    // fill-in assigments
    acms.ep_assignments = *as;

    // initialize buffer
    bfifo_create(&fifo, fifo_mem, USB_ACM_FIFO_MEM_SIZE);

    // initialize an all-0 interrupt
    acms.interrupt_data = 0;
    acms.interrupt_pending = true;

    // communication parameters have not been set
    acms.commInit = false;

    // from now on CDC module is considered initialized
    acms.moduleInit = true;
}

static void usb_cdc_review_comm_init() {
    // check if line coding was initialized
    Usb_Acm_LineCodingStruct *lc = &acms.line_coding;
    bool lcOk = (lc->dwDTERate != 0) && (lc->bDataBits != 0);

    // check if control line state was initialized
    bool clsOk = acms.control_line_state.D != USB_ACM_INVALID_CONTROL_LINE_STATE;

    // combine the above criteria
    acms.commInit = lcOk && clsOk;
}

int usb_acm_process_and_return(Usb_CallbackEvent *cbevt) {
    int ret = -1;
    switch (cbevt->type) {
    case USB_CBEVT_UNKNOWN_REQ: {
        // initialize reply
        cbevt->reply_data = NULL;
        cbevt->reply_size = 0;
        cbevt->reply_valid = true;

        switch (cbevt->setup_request->bRequest) {
        case USB_ACM_SET_LINE_CODING: // set line coding
            memcpy(&acms.line_coding, cbevt->data, sizeof(Usb_Acm_LineCodingStruct));
            usb_cdc_review_comm_init(); // review the communcation initialization state
            ret = 0;
            break;
        case USB_ACM_GET_LINE_CODING:                               // get line coding
            cbevt->reply_data = (const uint8_t *)&acms.line_coding; // expert move: pass the pointer, no copying
            cbevt->reply_size = sizeof(Usb_Acm_LineCodingStruct);
            ret = 0;
            break;
        case USB_ACM_SEND_BREAK: // send break
            // do nothing
            ret = 0;
            break;
        case USB_ACM_SET_CONTROL_LINE_STATE:                          // set control line state
            acms.control_line_state.D = cbevt->setup_request->wValue; // control line state is carried in wValue of the SETUP request
            usb_cdc_review_comm_init();                               // review the communcation initialization state
            ret = 0;
            break;
        default:
            cbevt->reply_valid = false; // this event is not processed by or not related to the CDC ACM module
            break;
        }
        break;
    }

    case USB_CBEVT_OUT: {
        if (cbevt->ep == acms.ep_assignments.data_ep) {
            ret = 0;
            usb_acm_read_callback(cbevt->data, cbevt->size);
        }
        break;
    }

    case USB_CBEVT_IN: {
        if (cbevt->ep == acms.ep_assignments.control_ep) { // if notification feeding is requested
            if (acms.interrupt_pending) {
                usbcore_schedule_transmission(acms.ep_assignments.control_ep, (const uint8_t *)&(acms.interrupt_data), sizeof(uint16_t)); // send ZLP
                acms.interrupt_pending = false;
            }
            ret = 0;
        } else if (cbevt->ep == acms.ep_assignments.data_ep) { // if data are requested
            ret = 0;

            // read from the fifo
            if (acms.commInit) {
                uint32_t readSize = bfifo_read(&fifo, tx_buffer, USB_ACM_PCKT_BUFSIZE);
                if (readSize > 0) {
                    uint32_t writeSize = usbcore_schedule_transmission(acms.ep_assignments.data_ep, tx_buffer, readSize); // write data acquired from the buffer
                    bfifo_pop(&fifo, writeSize, 0);                                                                       // pop with no blocking
                }
            }
        }
    }

    default:
        break;
    }

    return ret;
}

void usb_acm_write(const uint8_t *data, uint32_t size) {
    if (acms.moduleInit) {
        bfifo_push_all(&fifo, data, size);
        usbcore_wake_up_endpoint(acms.ep_assignments.data_ep, USB_IN);
    }
}


/**
 * @fn void usb_acm_read_callback(const uint8_t *data, uint32_t size)
 * Callback function prototype for data reception. This function is
 * expected to be overridden by the application.
 * 
 * @param data ingress data
 * @param size length of the data
 */
__attribute__((weak)) void usb_acm_read_callback(const uint8_t *data, uint32_t size) {
    (void)data;
    (void)size;
    return;
}