/*
 * This is free and unencumbered software released into the public domain.
 *
 * Anyone is free to copy, modify, publish, use, compile, sell, or
 * distribute this software, either in source code form or as a compiled
 * binary, for any purpose, commercial or non-commercial, and by any
 * means.
 *
 * In jurisdictions that recognize copyright laws, the author or authors
 * of this software dedicate any and all copyright interest in the
 * software to the public domain. We make this dedication for the benefit
 * of the public at large and to the detriment of our heirs and
 * successors. We intend this dedication to be an overt act of
 * relinquishment in perpetuity of all present and future rights to this
 * software under copyright law.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
 * IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 * OTHER DEALINGS IN THE SOFTWARE.
 *
 * For more information, please refer to <http://unlicense.org/>
 */

#define _BSD_SOURCE /* for endian.h */

#include <endian.h>
#include <errno.h>
#include <fcntl.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ioctl.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/poll.h>
#include <unistd.h>
#include <stdbool.h>
#include <sys/eventfd.h>

#include "libaio.h"
#define IOCB_FLAG_RESFD         (1 << 0)

#include <linux/usb/functionfs.h>

#define BUF_LEN         8192
#define BUFS_MAX        128
#define AIO_MAX         (BUFS_MAX*2)

/******************** Descriptors and Strings *******************************/

static const struct {
        struct usb_functionfs_descs_head_v2 header;
        __le32 fs_count;
        __le32 hs_count;
        struct {
                struct usb_interface_descriptor intf;
                struct usb_endpoint_descriptor_no_audio bulk_sink;
                struct usb_endpoint_descriptor_no_audio bulk_source;
        } __attribute__ ((__packed__)) fs_descs, hs_descs;
} __attribute__ ((__packed__)) descriptors = {
        .header = {
                .magic = htole32(FUNCTIONFS_DESCRIPTORS_MAGIC_V2),
                .flags = htole32(FUNCTIONFS_HAS_FS_DESC |
                                     FUNCTIONFS_HAS_HS_DESC),
                .length = htole32(sizeof(descriptors)),
        },
        .fs_count = htole32(3),
        .fs_descs = {
                .intf = {
                        .bLength = sizeof(descriptors.fs_descs.intf),
                        .bDescriptorType = USB_DT_INTERFACE,
                        .bNumEndpoints = 2,
                        .bInterfaceClass = USB_CLASS_VENDOR_SPEC,
                        .iInterface = 1,
                },
                .bulk_sink = {
                        .bLength = sizeof(descriptors.fs_descs.bulk_sink),
                        .bDescriptorType = USB_DT_ENDPOINT,
                        .bEndpointAddress = 1 | USB_DIR_IN,
                        .bmAttributes = USB_ENDPOINT_XFER_BULK,
                },
                .bulk_source = {
                        .bLength = sizeof(descriptors.fs_descs.bulk_source),
                        .bDescriptorType = USB_DT_ENDPOINT,
                        .bEndpointAddress = 2 | USB_DIR_OUT,
                        .bmAttributes = USB_ENDPOINT_XFER_BULK,
                },
        },
        .hs_count = htole32(3),
        .hs_descs = {
                .intf = {
                        .bLength = sizeof(descriptors.hs_descs.intf),
                        .bDescriptorType = USB_DT_INTERFACE,
                        .bNumEndpoints = 2,
                        .bInterfaceClass = USB_CLASS_VENDOR_SPEC,
                        .iInterface = 1,
                },
                .bulk_sink = {
                        .bLength = sizeof(descriptors.hs_descs.bulk_sink),
                        .bDescriptorType = USB_DT_ENDPOINT,
                        .bEndpointAddress = 1 | USB_DIR_IN,
                        .bmAttributes = USB_ENDPOINT_XFER_BULK,
                        .wMaxPacketSize = htole16(512),
                },
                .bulk_source = {
                        .bLength = sizeof(descriptors.hs_descs.bulk_source),
                        .bDescriptorType = USB_DT_ENDPOINT,
                        .bEndpointAddress = 2 | USB_DIR_OUT,
                        .bmAttributes = USB_ENDPOINT_XFER_BULK,
                        .wMaxPacketSize = htole16(512),
                },
        },
};

#define STR_INTERFACE "AIO Test"

static const struct {
        struct usb_functionfs_strings_head header;
        struct {
                __le16 code;
                const char str1[sizeof(STR_INTERFACE)];
        } __attribute__ ((__packed__)) lang0;
} __attribute__ ((__packed__)) strings = {
        .header = {
                .magic = htole32(FUNCTIONFS_STRINGS_MAGIC),
                .length = htole32(sizeof(strings)),
                .str_count = htole32(1),
                .lang_count = htole32(1),
        },
        .lang0 = {
                htole16(0x0409), /* en-us */
                STR_INTERFACE,
        },
};

/********************** Buffer structure *******************************/

struct io_buffer {
        struct iocb **iocb;
        unsigned char **buf;
        unsigned cnt;
        unsigned len;
        unsigned requested;
};

/******************** Endpoints handling *******************************/

static void display_event(struct usb_functionfs_event *event)
{
        static const char *const names[] = {
                [FUNCTIONFS_BIND] = "BIND",
                [FUNCTIONFS_UNBIND] = "UNBIND",
                [FUNCTIONFS_ENABLE] = "ENABLE",
                [FUNCTIONFS_DISABLE] = "DISABLE",
                [FUNCTIONFS_SETUP] = "SETUP",
                [FUNCTIONFS_SUSPEND] = "SUSPEND",
                [FUNCTIONFS_RESUME] = "RESUME",
        };
        switch (event->type) {
        case FUNCTIONFS_BIND:
        case FUNCTIONFS_UNBIND:
        case FUNCTIONFS_ENABLE:
        case FUNCTIONFS_DISABLE:
        case FUNCTIONFS_SETUP:
        case FUNCTIONFS_SUSPEND:
        case FUNCTIONFS_RESUME:
                printf("Event %s\n", names[event->type]);
        }
}

static void handle_ep0(int ep0, bool *ready)
{
        int ret;
        struct usb_functionfs_event event;

        ret = read(ep0, &event, sizeof(event));
        if (!ret) {
                perror("unable to read event from ep0");
                return;
        }
        display_event(&event);
        switch (event.type) {
        case FUNCTIONFS_SETUP:
                if (event.u.setup.bRequestType & USB_DIR_IN)
                        write(ep0, NULL, 0);
                else
                        read(ep0, NULL, 0);
                break;

        case FUNCTIONFS_ENABLE:
                *ready = true;
                break;

        case FUNCTIONFS_DISABLE:
                *ready = false;
                break;

        default:
                break;
        }
}

void init_bufs(struct io_buffer *iobuf, unsigned n, unsigned len)
{
        unsigned i;
        iobuf->buf = malloc(n*sizeof(*iobuf->buf));
        iobuf->iocb = malloc(n*sizeof(*iobuf->iocb));
        iobuf->cnt = n;
        iobuf->len = len;
        iobuf->requested = 0;
        for (i = 0; i < n; ++i) {
                iobuf->buf[i] = malloc(len*sizeof(**iobuf->buf));
                iobuf->iocb[i] = malloc(sizeof(**iobuf->iocb));
        }
        iobuf->cnt = n;
}

void delete_bufs(struct io_buffer *iobuf)
{
        unsigned i;
        for (i = 0; i < iobuf->cnt; ++i) {
                free(iobuf->buf[i]);
                free(iobuf->iocb[i]);
        }
        free(iobuf->buf);
        free(iobuf->iocb);
}

int main(int argc, char *argv[])
{
        int ret;
        unsigned i, j;
        char *ep_path;

        int ep0, ep1;

        io_context_t ctx;

        int evfd;
        fd_set rfds;

        struct io_buffer iobuf[2];
        int actual = 0;
        bool ready;

        if (argc != 2) {
                printf("ffs directory not specified!\n");
                return 1;
        }

        ep_path = malloc(strlen(argv[1]) + 4 /* "/ep#" */ + 1 /* '\0' */);
        if (!ep_path) {
                perror("malloc");
                return 1;
        }

        /* open endpoint files */
        sprintf(ep_path, "%s/ep0", argv[1]);
        ep0 = open(ep_path, O_RDWR);
        if (ep0 < 0) {
                perror("unable to open ep0");
                return 1;
        }
        if (write(ep0, &descriptors, sizeof(descriptors)) < 0) {
                perror("unable do write descriptors");
                return 1;
        }
        if (write(ep0, &strings, sizeof(strings)) < 0) {
                perror("unable to write strings");
                return 1;
        }
        sprintf(ep_path, "%s/ep1", argv[1]);
        ep1 = open(ep_path, O_RDWR);
        if (ep1 < 0) {
                perror("unable to open ep1");
                return 1;
        }

        free(ep_path);

        memset(&ctx, 0, sizeof(ctx));
        /* setup aio context to handle up to AIO_MAX requests */
        if (io_setup(AIO_MAX, &ctx) < 0) {
                perror("unable to setup aio");
                return 1;
        }

        evfd = eventfd(0, 0);
        if (evfd < 0) {
                perror("unable to open eventfd");
                return 1;
        }

        for (i = 0; i < sizeof(iobuf)/sizeof(*iobuf); ++i)
                init_bufs(&iobuf[i], BUFS_MAX, BUF_LEN);

        while (1) {
                FD_ZERO(&rfds);
                FD_SET(ep0, &rfds);
                FD_SET(evfd, &rfds);

                ret = select(((ep0 > evfd) ? ep0 : evfd)+1,
                             &rfds, NULL, NULL, NULL);
                if (ret < 0) {
                        if (errno == EINTR)
                                continue;
                        perror("select");
                        break;
                }

                if (FD_ISSET(ep0, &rfds))
                        handle_ep0(ep0, &ready);

                /* we are waiting for function ENABLE */
                if (!ready)
                        continue;

                /*
                 * when we're preparing new data to submit,
                 * second buffer being transmitted
                 */
                for (i = 0; i < sizeof(iobuf)/sizeof(*iobuf); ++i) {
                        if (iobuf[i].requested)
                                continue;
                        /* prepare requests */
                        for (j = 0; j < iobuf[i].cnt; ++j) {
                                io_prep_pwrite(iobuf[i].iocb[j], ep1,
                                               iobuf[i].buf[j],
                                               iobuf[i].len, 0);
                                /* enable eventfd notification */
                                iobuf[i].iocb[j]->u.c.flags |= IOCB_FLAG_RESFD;
                                iobuf[i].iocb[j]->u.c.resfd = evfd;
                        }
                        /* submit table of requests */
                        ret = io_submit(ctx, iobuf[i].cnt, iobuf[i].iocb);
                        if (ret >= 0) {
                                iobuf[i].requested = ret;
                                printf("submit: %d requests buf: %d\n", ret, i);
                        } else
                                perror("unable to submit requests");
                }

                /* if event is ready to read */
                if (!FD_ISSET(evfd, &rfds))
                        continue;

                uint64_t ev_cnt;
                ret = read(evfd, &ev_cnt, sizeof(ev_cnt));
                if (ret < 0) {
                        perror("unable to read eventfd");
                        break;
                }

                struct io_event e[BUFS_MAX];
                /* we read aio events */
                ret = io_getevents(ctx, 1, BUFS_MAX, e, NULL);
                if (ret > 0) /* if we got events */
                        iobuf[actual].requested -= ret;

                /* if all req's from iocb completed */
                if (!iobuf[actual].requested)
                        actual = (actual + 1)%(sizeof(iobuf)/sizeof(*iobuf));
        }

        /* free resources */

        for (i = 0; i < sizeof(iobuf)/sizeof(*iobuf); ++i)
                delete_bufs(&iobuf[i]);
        io_destroy(ctx);

        close(ep1);
        close(ep0);

        return 0;
}