// Copyright (c) 2026 Storm Dragon
// SPDX-License-Identifier: GPL-3.0-or-later

#include "hardware_native.h"
#include <dlfcn.h>
#include <errno.h>
#include <fcntl.h>
#include <stdint.h>
#include <stdlib.h>
#include <sys/file.h>
#include <sys/types.h>
#include <termios.h>
#include <unistd.h>

struct SpeechSerial {
    int fd;
    struct termios original;
};

SpeechSerial *speech_serial_open(const char *path, int baud, int xon, int *status) {
    SpeechSerial *port = calloc(1, sizeof(*port));
    *status = -ENOMEM;
    if (!port) return NULL;
    port->fd = open(path, O_RDWR | O_NOCTTY | O_NONBLOCK | O_CLOEXEC);
    if (port->fd < 0) goto failed;
    // A short-lived candidate must never configure another reader's device.
    if (flock(port->fd, LOCK_EX | LOCK_NB) < 0) goto failed;
    if (tcgetattr(port->fd, &port->original) < 0) goto failed;
    struct termios options = port->original;
    cfmakeraw(&options);
    options.c_cflag |= CLOCAL | CREAD;
    options.c_cflag &= ~(CRTSCTS | CSTOPB);
    options.c_iflag &= ~(IXON | IXOFF | IXANY);
    if (xon) options.c_iflag |= IXON;
    options.c_cc[VSTART] = 0x11;
    options.c_cc[VSTOP] = 0x13;
    speed_t speed;
    switch (baud) {
    case 1200: speed = B1200; break;
    case 2400: speed = B2400; break;
    case 4800: speed = B4800; break;
    case 9600: speed = B9600; break;
    case 19200: speed = B19200; break;
    case 38400: speed = B38400; break;
    case 57600: speed = B57600; break;
    case 115200: speed = B115200; break;
    default: errno = EINVAL; goto failed;
    }
    cfsetispeed(&options, speed);
    cfsetospeed(&options, speed);
    options.c_cc[VMIN] = 0;
    options.c_cc[VTIME] = 0;
    if (tcsetattr(port->fd, TCSANOW, &options) < 0) goto failed;
    *status = 0;
    return port;
failed:
    *status = -errno;
    if (port->fd >= 0) close(port->fd);
    free(port);
    return NULL;
}

int speech_serial_write(SpeechSerial *port, const void *data, size_t length) {
    ssize_t result = write(port->fd, data, length);
    return result < 0 ? -errno : (int)result;
}

int speech_serial_cancel(SpeechSerial *port, unsigned char command) {
    if (tcflush(port->fd, TCOFLUSH) < 0) return -errno;
    if (tcflow(port->fd, TCOON) < 0) return -errno;
    // TCOON clears an explicit tcflow stop, but not a received XOFF in Linux's
    // N_TTY discipline. Temporarily clearing IXON restarts that output path.
    // Restore software flow control immediately after submitting the cancel.
    struct termios options;
    if (tcgetattr(port->fd, &options) < 0) return -errno;
    int xon = (options.c_iflag & IXON) != 0;
    if (xon) {
        struct termios resumed = options;
        resumed.c_iflag &= ~IXON;
        if (tcsetattr(port->fd, TCSANOW, &resumed) < 0) return -errno;
    }
    int result = speech_serial_write(port, &command, 1);
    if (xon && tcsetattr(port->fd, TCSANOW, &options) < 0) return -errno;
    return result;
}

void speech_serial_close(SpeechSerial *port) {
    tcsetattr(port->fd, TCSANOW, &port->original);
    close(port->fd);
    free(port);
}

// Optional libusb 1.0 ABI, resolved at runtime like Enchant. Neither headers
// nor a link-time libusb dependency are required for other speech drivers.
typedef struct libusb_context USBContext;
typedef struct libusb_device USBDevice;
typedef struct libusb_device_handle USBHandle;
struct USBDescriptor {
    uint8_t length, type;
    uint16_t usb;
    uint8_t device_class, subclass, protocol, packet_size;
    uint16_t vendor, product, device;
    uint8_t manufacturer, product_name, serial, configurations;
};

struct SpeechUSB {
    void *library;
    USBContext *context;
    USBHandle *handle;
    int claimed;
    int (*init)(USBContext **);
    void (*exit)(USBContext *);
    ssize_t (*get_device_list)(USBContext *, USBDevice ***);
    void (*free_device_list)(USBDevice **, int);
    int (*get_device_descriptor)(USBDevice *, struct USBDescriptor *);
    int (*open)(USBDevice *, USBHandle **);
    void (*close)(USBHandle *);
    int (*get_configuration)(USBHandle *, int *);
    int (*set_configuration)(USBHandle *, int);
    int (*claim_interface)(USBHandle *, int);
    int (*release_interface)(USBHandle *, int);
    int (*bulk_transfer)(USBHandle *, unsigned char, unsigned char *, int, int *, unsigned int);
};

void speech_usb_close(SpeechUSB *port) {
    if (!port) return;
    if (port->claimed) port->release_interface(port->handle, 0);
    if (port->handle) port->close(port->handle);
    if (port->context) port->exit(port->context);
    if (port->library) dlclose(port->library);
    free(port);
}

static SpeechUSB *load_usb(void) {
    SpeechUSB *port = calloc(1, sizeof(*port));
    if (!port) return NULL;
    port->library = dlopen("libusb-1.0.so.0", RTLD_NOW | RTLD_LOCAL);
    if (!port->library) goto failed;
#define LOAD(field) port->field = dlsym(port->library, "libusb_" #field); if (!port->field) goto failed
    LOAD(init); LOAD(exit); LOAD(get_device_list); LOAD(free_device_list);
    LOAD(get_device_descriptor); LOAD(open); LOAD(close);
    LOAD(get_configuration); LOAD(set_configuration);
    LOAD(claim_interface); LOAD(release_interface); LOAD(bulk_transfer);
#undef LOAD
    return port;
failed:
    speech_usb_close(port);
    return NULL;
}

int speech_usb_available(void) {
    SpeechUSB *port = load_usb();
    if (!port) return 0;
    speech_usb_close(port);
    return 1;
}

SpeechUSB *speech_usb_open(int *status) {
    *status = -100;
    SpeechUSB *port = load_usb();
    if (!port) return NULL;
    *status = port->init(&port->context);
    if (*status < 0) goto failed;
    USBDevice **devices = NULL;
    ssize_t count = port->get_device_list(port->context, &devices);
    if (count < 0) { *status = (int)count; goto failed; }
    USBDevice *selected = NULL;
    int matches = 0;
    for (ssize_t index = 0; index < count; index++) {
        struct USBDescriptor descriptor;
        if (port->get_device_descriptor(devices[index], &descriptor) == 0 &&
            descriptor.vendor == 0x0dd0 && descriptor.product == 0x2001) {
            selected = devices[index];
            matches++;
        }
    }
    *status = matches == 0 ? -4 : -101;
    if (matches == 1) *status = port->open(selected, &port->handle);
    port->free_device_list(devices, 1);
    if (*status < 0) goto failed;
    int configuration = 0;
    *status = port->get_configuration(port->handle, &configuration);
    if (*status < 0) goto failed;
    if (configuration == 0) {
        *status = port->set_configuration(port->handle, 1);
        if (*status < 0) goto failed;
    }
    *status = port->claim_interface(port->handle, 0);
    if (*status < 0) goto failed;
    port->claimed = 1;
    return port;
failed:
    speech_usb_close(port);
    return NULL;
}

int speech_usb_write(SpeechUSB *port, unsigned char endpoint, void *data, int length) {
    int transferred = 0;
    int result = port->bulk_transfer(port->handle, endpoint, data, length, &transferred, 1000);
    // Never replay a partial failed transfer: it may already be on the wire.
    if (result < 0) return result;
    return transferred == length ? 0 : -102;
}