/*
 * Copyright © 2020 Red Hat, Inc.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice (including the next
 * paragraph) shall be included in all copies or substantial portions of the
 * Software.
 *
 * 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 OR COPYRIGHT HOLDERS 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.
 */

#include "config.h"

#include <errno.h>
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>

#include "util-bits.h"
#include "util-io.h"
#include "util-logger.h"
#include "util-macros.h"
#include "util-mem.h"
#include "util-sources.h"
#include "util-strings.h"

#include "libeis-private.h"

#include "proto/ei.pb-c.h"

/* The message type for the wire format */
enum message_type {
	MESSAGE_CONNECT,
	MESSAGE_DISCONNECT,
	MESSAGE_ADD_DEVICE,
	MESSAGE_REMOVE_DEVICE,
	MESSAGE_POINTER_REL,
};

struct message {
	enum message_type type;
	union {
		struct message_connect {
			char *name;
		} connect;
		struct message_disconnect {
			uint8_t pad; /* no data */
		} disconnect;
		struct message_add_device {
			uint32_t deviceid;
			uint32_t capabilities;
		} add_device;
		struct message_remove_device {
			uint32_t deviceid;
		} remove_device;
		struct message_pointer_rel {
			uint32_t deviceid;
			int32_t x;
			int32_t y;
		} pointer_rel;
	};
};

static void
message_free(struct message *msg)
{
	switch (msg->type) {
	case MESSAGE_CONNECT:
		free(msg->connect.name);
		break;
	default:
		break;
	}
	free(msg);
}

DEFINE_TRIVIAL_CLEANUP_FUNC(struct message*, message_free);

static void
eis_client_destroy(struct eis_client *client)
{
	free(client->name);
	source_unref(client->source);
	list_remove(&client->link);
}
OBJECT_DECLARE_CREATE(eis_client);
static
OBJECT_DECLARE_PARENT(eis_client, eis);

_public_
OBJECT_DECLARE_REF(eis_client);

_public_
OBJECT_DECLARE_UNREF(eis_client);

_public_
OBJECT_DECLARE_GETTER(eis_client, name, const char*);

_public_ struct eis*
eis_client_get_context(struct eis_client *client)
{
	return eis_client_parent(client);
}

static int
client_send_msg(struct eis_client *client, const ServerMessage *msg)
{
	size_t sz = server_message__get_packed_size(msg);
	uint8_t buf[sz];
	size_t len = server_message__pack(msg, buf);
	return min(0, xsend(source_get_fd(client->source), buf, len));
}

static int
client_send_hello(struct eis_client *client)
{
	ServerMessage msg = SERVER_MESSAGE__INIT;
	Hello hello = HELLO__INIT;

	msg.hello = &hello;
	msg.msg_case = SERVER_MESSAGE__MSG_HELLO;

	return client_send_msg(client, &msg);
}

static int
client_send_disconnect(struct eis_client *client)
{
	ServerMessage msg = SERVER_MESSAGE__INIT;
	Disconnected disconnected = DISCONNECTED__INIT;

	msg.disconnected = &disconnected;
	msg.msg_case = SERVER_MESSAGE__MSG_DISCONNECTED;

	return client_send_msg(client, &msg);
}

static int
client_send_connect(struct eis_client *client)
{
	ServerMessage msg = SERVER_MESSAGE__INIT;
	Connected connected = CONNECTED__INIT;

	msg.connected = &connected;
	msg.msg_case = SERVER_MESSAGE__MSG_CONNECTED;

	return client_send_msg(client, &msg);
}

static int
client_send_accepted(struct eis_client *client, struct eis_device *device)
{
	ServerMessage msg = SERVER_MESSAGE__INIT;
	Accepted accepted = ACCEPTED__INIT;

	accepted.deviceid = device->id;

	msg.accepted = &accepted;
	msg.msg_case = SERVER_MESSAGE__MSG_ACCEPTED;

	return client_send_msg(client, &msg);
}

static int
client_send_removed(struct eis_client *client, struct eis_device *device)
{
	ServerMessage msg = SERVER_MESSAGE__INIT;
	Removed removed = REMOVED__INIT;

	msg.removed = &removed;
	msg.msg_case = SERVER_MESSAGE__MSG_REMOVED;

	return client_send_msg(client, &msg);
}

_public_ void
eis_client_connect(struct eis_client *client)
{
	switch(client->state) {
	case EIS_CLIENT_STATE_CONNECTING:
		break;
	default:
		return;
	}

	int rc = client_send_connect(client);
	if (rc) {
		eis_client_disconnect(client);
	} else {
		client->state = EIS_CLIENT_STATE_CONNECTED;
	}
}

_public_ void
eis_client_disconnect(struct eis_client *client)
{
	switch(client->state) {
	case EIS_CLIENT_STATE_DISCONNECTED:
		/* Client already disconnected? don't bother sending an
		 * event */
		return;
	case EIS_CLIENT_STATE_CONNECTING:
	case EIS_CLIENT_STATE_CONNECTED:
		{
			struct eis_device *d, *tmp;
			list_for_each_safe(d, tmp, &client->devices, link)
				eis_device_disconnect(d);
		}
		eis_queue_disconnect_event(client);
		/* fallthrough */
	case EIS_CLIENT_STATE_HELLO:
		client_send_disconnect(client);
		client->state = EIS_CLIENT_STATE_DISCONNECTED;
		source_remove(client->source);
		break;
	}
}

static int
client_new_device(struct eis_client *client,
		  uint32_t id, uint32_t capabilities)
{
	/* Check for duplicate IDs */
	struct eis_device *d;
	list_for_each(d, &client->devices, link) {
		if (d->id == id)
			return -EINVAL;
	}

	if (capabilities == 0 ||
	    capabilities & ~(bit(EIS_DEVICE_CAP_POINTER) |
			     bit(EIS_DEVICE_CAP_POINTER_ABSOLUTE) |
			     bit(EIS_DEVICE_CAP_KEYBOARD) |
			     bit(EIS_DEVICE_CAP_TOUCH)))
		return -EINVAL;

	struct eis_device *device = eis_device_new(client, id, capabilities);
	list_append(&client->devices, &device->link);

	log_debug(eis_client_parent(client), "New device %d caps: %#x\n",
		  id, capabilities);

	eis_queue_added_event(device);

	return 0;
}

static int
client_pointer_rel(struct eis_client *client, uint32_t deviceid,
		   int32_t x, int32_t y)
{
	struct eis_device *device;

	list_for_each(device, &client->devices, link) {
		if (device->id == deviceid) {
			return eis_device_pointer_rel(device, x, y);
		}
	}
	return -EINVAL;
}

static int
client_hello_handle_msg(struct eis_client *client, struct message *msg)
{
	int rc = 0;

	switch (msg->type) {
	case MESSAGE_CONNECT:
		eis_queue_connect_event(client);
		client->name = steal(&msg->connect.name);
		client->state = EIS_CLIENT_STATE_CONNECTING;
		break;
	case MESSAGE_DISCONNECT:
		rc = -ECANCELED;
		break;
	case MESSAGE_ADD_DEVICE:
	case MESSAGE_REMOVE_DEVICE:
	case MESSAGE_POINTER_REL:
		rc = -EPROTO;
		break;
	}

	return rc;
}

static int
client_connecting_handle_msg(struct eis_client *client, const struct message *msg)
{
	int rc = 0;

	switch (msg->type) {
	case MESSAGE_CONNECT:
		rc = -EPROTO;
		break;
	case MESSAGE_DISCONNECT:
		rc = -ECANCELED;
		break;
	case MESSAGE_ADD_DEVICE:
	case MESSAGE_REMOVE_DEVICE:
	case MESSAGE_POINTER_REL:
		rc = -EPROTO;
		break;
	}

	return rc;
}

static int
client_connected_handle_msg(struct eis_client *client,
			    const struct message *msg)
{
	int rc = 0;

	switch (msg->type) {
	case MESSAGE_CONNECT:
		rc = -EPROTO;
		break;
	case MESSAGE_DISCONNECT:
		client->state = EIS_CLIENT_STATE_DISCONNECTED;
		rc = -ECANCELED;
		break;
	case MESSAGE_ADD_DEVICE:
		rc = client_new_device(client, msg->add_device.deviceid,
				       msg->add_device.capabilities);
		break;
	case MESSAGE_REMOVE_DEVICE:
		/* FIXME: remove device */
		break;
	case MESSAGE_POINTER_REL:
		rc = client_pointer_rel(client, msg->pointer_rel.deviceid,
					msg->pointer_rel.x, msg->pointer_rel.y);
		break;
	}
	return rc;
}

static struct message *
client_parse_message(const char *data_in, size_t *len)
{
	_cleanup_(message_freep) struct message *msg = xalloc(sizeof(*msg));
	ClientMessage *proto = client_message__unpack(NULL, *len,
						      (const unsigned char*)data_in);

	if (!proto)
		return NULL;

	switch (proto->msg_case) {
	case CLIENT_MESSAGE__MSG_CONNECT:
		{
			Connect *c = proto->connect;
			*msg = (struct message) {
				.type = MESSAGE_CONNECT,
				.connect.name = xstrdup(c->name),
			};
		}
		break;
	case CLIENT_MESSAGE__MSG_DISCONNECT:
		*msg = (struct message) {
			.type = MESSAGE_DISCONNECT,
		};
		break;
	case CLIENT_MESSAGE__MSG_ADD:
		{
			AddDevice *a = proto->add;
			*msg = (struct message) {
				.type = MESSAGE_ADD_DEVICE,
				.add_device.deviceid = a->deviceid,
				.add_device.capabilities = a->capabilities,
			};
		}
		break;
	case CLIENT_MESSAGE__MSG_REMOVE:
		{
			RemoveDevice *r = proto->remove;
			*msg = (struct message) {
				.type = MESSAGE_REMOVE_DEVICE,
				.remove_device.deviceid = r->deviceid,
			};
		}
		break;
	case CLIENT_MESSAGE__MSG_REL:
		{
			PointerRelative *r = proto->rel;
			*msg = (struct message) {
				.type = MESSAGE_POINTER_REL,
				.pointer_rel.deviceid = r->deviceid,
				.pointer_rel.x = r->x,
				.pointer_rel.y = r->y,
			};
		}
		break;
	default:
		client_message__free_unpacked(proto, NULL);
		return NULL;
	}

	*len = client_message__get_packed_size(proto);

	client_message__free_unpacked(proto, NULL);

	return steal(&msg);
}

static void
client_dispatch(struct source *source, void *userdata)
{
	struct eis_client *client = userdata;
	enum eis_client_state old_state = client->state;
	_cleanup_(message_freep) struct message *msg = NULL;

	_cleanup_iobuf_ struct iobuf *buf = iobuf_new(64);
	int rc = iobuf_append_from_fd(buf, source_get_fd(source));
	if (rc == -EAGAIN) {
		return;
	} else if (rc == 0) {
		rc = -ECANCELED;
		goto error;
	} else if (rc < 0) {
		goto error;
	}

	size_t idx = 0;
	while (true) {
		const char *data = iobuf_data(buf) + idx;
		size_t len = iobuf_len(buf) - idx;

		if (len == 0)
			break;

		msg = client_parse_message(data, &len);
		if (!msg) {
			rc = -EBADMSG;
			goto error;
		}

		idx += len;

		switch (client->state) {
			case EIS_CLIENT_STATE_HELLO:
				rc = client_hello_handle_msg(client, msg);
				break;
			case EIS_CLIENT_STATE_CONNECTING:
				/* Client is waiting for us, shouldn't send anything
				 * but disconnect */
				rc = client_connecting_handle_msg(client, msg);
				break;
			case EIS_CLIENT_STATE_CONNECTED:
				rc = client_connected_handle_msg(client, msg);
				break;
			case EIS_CLIENT_STATE_DISCONNECTED:
				abort();
		}
	}

error:
	if (rc < 0)
		eis_client_disconnect(client);

	static const char *client_states[] = {
		"HELLO",
		"CONNECTING",
		"CONNECTED",
		"DISCONNECTED",
	};
	if (rc)
		log_warn(eis_client_parent(client), "Client error: %s\n",
			 strerror(-rc));
	if (old_state != client->state) {
		log_debug(eis_client_parent(client), "Client dispatch: %s -> %s\n",
			  client_states[old_state],
			  client_states[client->state]);
	}

}

struct eis_client *
eis_client_new(struct eis *eis, int fd)
{
	static uint32_t client_id;
	struct eis_client *client = eis_client_create(&eis->object);

	client->id = ++client_id;
	list_init(&client->devices);

	list_append(&eis->clients, &client->link);
	client->source = source_add_autoclose(eis->sink, fd,
					      client_dispatch, client);

	client->state = EIS_CLIENT_STATE_HELLO;
	int rc = client_send_hello(client);
	if (rc != 0)
		client = eis_client_unref(client);

	return client;
}

void
eis_client_connect_device(struct eis_client *client, struct eis_device *device)
{
	client_send_accepted(client, device);
}

void
eis_client_disconnect_device(struct eis_client *client, struct eis_device *device)
{
	client_send_removed(client, device);
	eis_queue_removed_event(device);
	list_remove(&device->link);
	eis_device_unref(device);
}