/*
 * usb.c
 *
 * (C) 2019 by Sylvain Munaut <tnt@246tNt.com>
 *
 * All Rights Reserved
 *
 * SPDX-License-Identifier: GPL-2.0+
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */

#include <errno.h>
#include <unistd.h>
#include <stdint.h>
#include <string.h>
#include <talloc.h>

#include <osmocom/core/isdnhdlc.h>
#include <osmocom/core/utils.h>
#include <osmocom/usb/libusb.h>

#include <libusb.h>

#include "e1d.h"
#include "log.h"


#define USB_VID		0x1d50
#define USB_PID		0xe1e1

libusb_context *g_usb = NULL;


struct e1_usb_flow;


/* Driver data */

struct e1_usb_line_data {
	/* Interface */
	uint8_t if_num;

	/* End Points */
	uint8_t ep_in;
	uint8_t ep_out;
	uint8_t ep_fb;

	/* Max packet size */
	int pkt_size;

	/* Flow */
	struct e1_usb_flow *flow_in;
	struct e1_usb_flow *flow_out;
	struct e1_usb_flow *flow_fb;

	/* Rate regulation */
	uint32_t r_acc;
	uint32_t r_sw;
};

struct e1_usb_intf_data {
	libusb_device_handle *devh;
};


/* Flow */

struct e1_usb_flow_entry {
	uint8_t *buf;
	struct libusb_transfer *xfr;
};

typedef int (*xfer_cb_t)(struct e1_usb_flow *flow, uint8_t *buf, int size);

struct e1_usb_flow {
	struct e1_line *line;
	xfer_cb_t cb;

	uint8_t ep;

	int count;
	int size;
	int ppx;

	struct e1_usb_flow_entry *entries;
};



// ---------------------------------------------------------------------------
// USB data transfer
// ---------------------------------------------------------------------------

static int
e1_usb_xfer_in(struct e1_usb_flow *flow, uint8_t *buf, int size)
{
	return e1_line_demux_in(flow->line, buf + 4, size - 4);
}

static int
e1_usb_xfer_out(struct e1_usb_flow *flow, uint8_t *buf, int size)
{
	struct e1_line *line = flow->line;
	struct e1_usb_line_data *ld = (struct e1_usb_line_data *) line->drv_data;
	int fts;

	if (size <= 0) {
		LOGPLI(line, DXFR, LOGL_ERROR, "OUT ERROR: %d\n", size);
		return -1;
	}

	/* Flow regulation */
	ld->r_acc += ld->r_sw;

	fts = ld->r_acc >> 10;
	if      (fts <  4) fts = 4;
	else if (fts > 12) fts = 12;

	ld->r_acc -= fts << 10;
	if (ld->r_acc & 0x80000000)
		ld->r_acc = 0;

	memset(buf, 0xff, 4);

	return e1_line_mux_out(line, buf+4, fts);
}

static int
e1_usb_xfer_fb(struct e1_usb_flow *flow, uint8_t *buf, int size)
{
	struct e1_usb_line_data *ld = (struct e1_usb_line_data *) flow->line->drv_data;

	if (size < 0) {
		LOGPLI(flow->line, DE1D, LOGL_ERROR, "Feedback transfer error\n");
		return 0;
	} else if (size != 3) {
		LOGPLI(flow->line, DE1D, LOGL_ERROR, "Feedback packet invalid size (%d)\n", size);
		return 0;
	}

	ld->r_sw = (buf[2] << 16) | (buf[1] << 8) | buf[0];

	return 0;
}


// ---------------------------------------------------------------------------
// USB flow
// ---------------------------------------------------------------------------

static void LIBUSB_CALL
_e1uf_xfr(struct libusb_transfer *xfr)
{
	struct e1_usb_flow *flow = (struct e1_usb_flow *) xfr->user_data;
	struct e1_usb_intf_data *id = (struct e1_usb_intf_data *) flow->line->intf->drv_data;
	int j, rv, len;

	len = 0;

	/* FIXME: Check transfer status ? Error handling ? */

	if (flow->ep & 0x80) {
		for (j=0; j<flow->ppx; j++) {
			flow->cb(flow,
				libusb_get_iso_packet_buffer_simple(xfr, j),
				(xfr->iso_packet_desc[j].status == LIBUSB_TRANSFER_COMPLETED) ?
					xfr->iso_packet_desc[j].actual_length : -1
			);
			len += (xfr->iso_packet_desc[j].length = flow->size);
		}
	} else {
		for (j=0; j<flow->ppx; j++)
			len += (xfr->iso_packet_desc[j].length = flow->cb(flow, &xfr->buffer[len], flow->size));
	}

	libusb_fill_iso_transfer(xfr, id->devh, flow->ep,
		xfr->buffer, len, flow->ppx,
		_e1uf_xfr, flow, 0
	);

	rv = libusb_submit_transfer(xfr);
	if (rv)
		LOGPLI(flow->line, DE1D, LOGL_ERROR, "Failed to resubmit buffer for transfer\n");
}

static struct e1_usb_flow *
e1uf_create(struct e1_line *line, xfer_cb_t cb,
            int ep, int count, int size, int ppx)
{
	void *ctx = line->intf->e1d->ctx;
	struct e1_usb_flow *flow;

	flow = talloc_zero(ctx, struct e1_usb_flow);
	OSMO_ASSERT(flow);

	flow->line  = line;
	flow->cb    = cb;
	flow->ep    = ep;
	flow->count = count;
	flow->size  = size;
	flow->ppx   = ppx;
	flow->entries = talloc_zero_size(ctx, count * sizeof(struct e1_usb_flow_entry));

	for (int i=0; i<count; i++)
		flow->entries[i].buf = talloc_zero_size(ctx, size * ppx);

	return flow;
}

static void __attribute__((unused))
e1uf_destroy(struct e1_usb_flow *flow)
{
	if (!flow)
		return;

	/* FIXME: stop pending transfers */
	for (int i=0; i<flow->count; i++)
		talloc_free(flow->entries[i].buf);

	talloc_free(flow->entries);
	talloc_free(flow);
}

static int
e1uf_start(struct e1_usb_flow *flow)
{
	struct e1_usb_intf_data *id = (struct e1_usb_intf_data *) flow->line->intf->drv_data;
	struct libusb_transfer *xfr;
	int i, j, rv, len;

	for (i=0; i<flow->count; i++)
	{
		xfr = libusb_alloc_transfer(flow->ppx);
		if (!xfr)
			return -ENOMEM;

		len = 0;

		if (flow->ep & 0x80) {
			for (j=0; j<flow->ppx; j++)
				len += (xfr->iso_packet_desc[j].length = flow->size);
		} else {
			for (j=0; j<flow->ppx; j++)
				len += (xfr->iso_packet_desc[j].length = flow->cb(flow, &flow->entries[i].buf[len], flow->size));
		}

		libusb_fill_iso_transfer(xfr, id->devh, flow->ep,
			flow->entries[i].buf, len, flow->ppx,
			_e1uf_xfr, flow, 0
		);

		rv = libusb_submit_transfer(xfr);

		if (rv)
			return rv;

		flow->entries[i].xfr = xfr;
	}

	return 0;
}


// ---------------------------------------------------------------------------
// Init / Probing
// ---------------------------------------------------------------------------

int
_e1_usb_open_device(struct e1_daemon *e1d, struct libusb_device *dev)
{
	struct e1_intf *intf;
	struct e1_line *line;
	struct e1_usb_intf_data *intf_data;
	struct e1_usb_line_data *line_data;
	struct libusb_config_descriptor *cd;
	const struct libusb_interface_descriptor *id;
	libusb_device_handle *devh;
	int i, j, ret;

	ret = libusb_open(dev, &devh);
	if (ret) {
		LOGP(DE1D, LOGL_ERROR, "Failed to open usb device\n");
		return ret;
	}

	intf_data = talloc_zero(e1d->ctx, struct e1_usb_intf_data);
	intf_data->devh = devh;

	intf = e1_intf_new(e1d, intf_data);
	intf->drv = E1_DRIVER_USB;

	ret = libusb_get_active_config_descriptor(dev, &cd);
	if (ret) {
		LOGP(DE1D, LOGL_ERROR, "Failed to talk to usb device\n");
		return ret;
	}

	for (i=0; i<cd->bNumInterfaces; i++) {
		/* Expect 2 altsettings with proper class/subclass/eps */
		if (cd->interface[i].num_altsetting != 2)
			continue;

		id = &cd->interface[i].altsetting[1];
		if ((id->bInterfaceClass != 0xff) || (id->bInterfaceSubClass != 0xe1) || (id->bNumEndpoints != 3))
			continue;

		/* Get interface and set it up */
		ret = libusb_claim_interface(devh, id->bInterfaceNumber);
		if (ret) {
			LOGP(DE1D, LOGL_ERROR, "Failed to claim interface %d\n", id->bInterfaceNumber);
			return ret;
		}

		ret = libusb_set_interface_alt_setting(devh, id->bInterfaceNumber, 1);
		if (ret) {
			LOGP(DE1D, LOGL_ERROR, "Failed to set interface %d altsetting\n", id->bInterfaceNumber);
			return ret;
		}

		/* Setup driver data and find endpoints */
		line_data = talloc_zero(e1d->ctx, struct e1_usb_line_data);

		line_data->if_num = id->bInterfaceNumber;
		line_data->r_acc  = 0;
		line_data->r_sw   = 8192;

		for (j=0; j<id->bNumEndpoints; j++) {
			if (id->endpoint[j].bmAttributes == 0x11) {
				line_data->ep_fb = id->endpoint[j].bEndpointAddress;
			} else if (id->endpoint[j].bmAttributes == 0x05) {
				if (id->endpoint[j].bEndpointAddress & 0x80)
					line_data->ep_in = id->endpoint[j].bEndpointAddress;
				else
					line_data->ep_out = id->endpoint[j].bEndpointAddress;

				if (!line_data->pkt_size)
					line_data->pkt_size = id->endpoint[j].wMaxPacketSize;
				else if (line_data->pkt_size != id->endpoint[j].wMaxPacketSize)
					LOGP(DE1D, LOGL_ERROR, "Inconsistent max packet size %d vs %d\n",
						line_data->pkt_size, (int)id->endpoint[j].wMaxPacketSize);
			} else {
				LOGP(DE1D, LOGL_ERROR, "Invalid EP %02x\n", id->endpoint[j].bEndpointAddress);
			}
		}

		if (!line_data->ep_in || !line_data->ep_out || !line_data->ep_fb || !line_data->pkt_size) {
			LOGP(DE1D, LOGL_ERROR, "Failed to use interface %d\n", id->bInterfaceNumber);
			return -EINVAL;
		}

		line = e1_line_new(intf, line_data);

		line_data->flow_in  = e1uf_create(line, e1_usb_xfer_in,  line_data->ep_in,  2, line_data->pkt_size, 4);
		line_data->flow_out = e1uf_create(line, e1_usb_xfer_out, line_data->ep_out, 2, line_data->pkt_size, 4);
		line_data->flow_fb  = e1uf_create(line, e1_usb_xfer_fb,  line_data->ep_fb,  2, 8, 1);

		e1uf_start(line_data->flow_in);
		e1uf_start(line_data->flow_out);
		e1uf_start(line_data->flow_fb);
	}

	return 0;
}

int
e1_usb_probe(struct e1_daemon *e1d)
{
	struct libusb_device **dev_list;
	ssize_t n_dev;
	int i, ret;

	if (!g_usb) {
		ret = osmo_libusb_init(&g_usb);
		if (ret) {
			LOGP(DE1D, LOGL_ERROR, "Failed to initialize libusb\n");
			return -EIO;
		}
	}

	n_dev = libusb_get_device_list(g_usb, &dev_list);
	if (n_dev < 0) {
		LOGP(DE1D, LOGL_ERROR, "Failed to list devices\n");
		return -EIO;
	}

	for (i=0; i<n_dev; i++) {
		struct libusb_device_descriptor desc;

		ret = libusb_get_device_descriptor(dev_list[i], &desc);
		if (ret)
			continue;

		if ((desc.idVendor != USB_VID) || (desc.idProduct != USB_PID))
			continue;

		_e1_usb_open_device(e1d, dev_list[i]);
	}

	libusb_free_device_list(dev_list, 1);

	return 0;
}