/*
 * 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-io.h"
#include "util-logger.h"
#include "util-macros.h"
#include "util-object.h"
#include "util-sources.h"
#include "util-strings.h"

#include "libei.h"
#include "libei-private.h"

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

/* The message type for the wire format */
enum message_type {
	MESSAGE_HELLO,
	MESSAGE_CONNECTED,
	MESSAGE_DISCONNECTED,
	MESSAGE_ACCEPTED,
	MESSAGE_REMOVED,
};

struct message {
	enum message_type type;
	union {
		struct message_hello {
			uint8_t pad; /* no data */
		} hello;
		struct message_connected {
			uint8_t pad; /* no data */
		} connected;
		struct message_disconnected {
			uint8_t pad; /* no data */
		} disconnected;
		struct message_accepted {
			uint32_t deviceid;
		} accepted;
		struct message_removed {
			uint32_t deviceid;
		} removed;
	};
};

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

DEFINE_TRIVIAL_CLEANUP_FUNC(struct message*, message_free);

static void
ei_event_destroy(struct ei_event *event)
{
	switch (event->type) {
	case EI_EVENT_CONNECT:
	case EI_EVENT_DISCONNECT:
	case EI_EVENT_DEVICE_ADDED:
	case EI_EVENT_DEVICE_REMOVED:
		break;
	default:
		abort(); /* not yet implemented */
	}
	ei_device_unref(event->device);
}

static
OBJECT_IMPLEMENT_INIT(ei_event);
static
OBJECT_IMPLEMENT_REF(ei_event);
_public_
OBJECT_IMPLEMENT_UNREF(ei_event);
_public_
OBJECT_IMPLEMENT_GETTER(ei_event, type, enum ei_event_type);
_public_
OBJECT_IMPLEMENT_GETTER(ei_event, device, struct ei_device*);

static void
ei_disconnect(struct ei *ei);

static void
ei_destroy(struct ei *ei)
{
	ei_disconnect(ei);

	struct ei_event *e;
	while ((e = ei_get_event(ei)) != NULL)
		ei_event_unref(e);

	ei->logger = logger_unref(ei->logger);
	if (ei->backend_interface.destroy)
		ei->backend_interface.destroy(ei, ei->backend);
	ei->backend = NULL;
	sink_unref(ei->sink);
	free(ei->name);
}

OBJECT_IMPLEMENT_CREATE(ei);
_public_
OBJECT_IMPLEMENT_REF(ei);
_public_
OBJECT_IMPLEMENT_UNREF(ei);
#define _cleanup_ei_ _cleanup_(ei_cleanup)
_public_
OBJECT_IMPLEMENT_SETTER(ei, user_data, void *);
OBJECT_IMPLEMENT_GETTER(ei, user_data, void *);

_public_ struct ei *
ei_new(void *user_data)
{
	_cleanup_ei_ struct ei *ei = ei_create(NULL);

	ei->state = EI_STATE_NEW;
	list_init(&ei->event_queue);
	list_init(&ei->devices);

	ei->logger = logger_new(ei);
	logger_set_priority(ei->logger, LOGGER_DEBUG);
	ei->sink = sink_new();
	if (!ei->sink)
		return NULL;

	ei->user_data = user_data;
	ei->backend = NULL;

	return steal(&ei);
}

_public_ int
ei_get_fd(struct ei *ei)
{
	return sink_get_fd(ei->sink);
}

_public_ void
ei_dispatch(struct ei *ei)
{
	sink_dispatch(ei->sink);
}

static void
ei_queue_event(struct ei *ei, struct ei_event *event)
{
	list_append(&ei->event_queue, &event->link);
}

static void
ei_queue_connect_event(struct ei *ei)
{
	struct ei_event_client *e = xalloc(sizeof(*e));
	ei_event_init_object(&e->base, &ei->object);
	e->base.type = EI_EVENT_CONNECT;

	ei_queue_event(ei, &e->base);
}

static void
ei_queue_disconnect_event(struct ei *ei)
{
	struct ei_event_client *e = xalloc(sizeof(*e));
	ei_event_init_object(&e->base, &ei->object);
	e->base.type = EI_EVENT_DISCONNECT;

	ei_queue_event(ei, &e->base);
}

static void
ei_queue_added_event(struct ei_device *device)
{
	struct ei *ei= ei_device_get_context(device);

	struct ei_event_client *e = xalloc(sizeof(*e));
	ei_event_init_object(&e->base, &ei->object);
	e->base.type = EI_EVENT_DEVICE_ADDED;
	e->base.device = ei_device_ref(device);

	ei_queue_event(ei, &e->base);
}

static void
ei_queue_removed_event(struct ei_device *device)
{
	struct ei *ei= ei_device_get_context(device);

	struct ei_event_client *e = xalloc(sizeof(*e));
	ei_event_init_object(&e->base, &ei->object);
	e->base.type = EI_EVENT_DEVICE_REMOVED;
	e->base.device = ei_device_ref(device);

	ei_queue_event(ei, &e->base);
}

static int
connection_send_msg(struct ei *ei, const ClientMessage *msg)
{
	size_t msglen = client_message__get_packed_size(msg);
	Frame frame = FRAME__INIT;
	frame.length = msglen;
	size_t framelen = frame__get_packed_size(&frame);

	uint8_t buf[framelen + msglen];
	frame__pack(&frame, buf);
	client_message__pack(msg, buf + framelen);
	return min(0, xsend(source_get_fd(ei->source), buf, sizeof(buf)));
}

static int
connection_send_connect(struct ei *ei)
{
	if (ei->state == EI_STATE_NEW ||
	    ei->state == EI_STATE_DISCONNECTED)
		return 0;

	ClientMessage msg = CLIENT_MESSAGE__INIT;
	Connect connect = CONNECT__INIT;

	msg.connect = &connect;
	msg.msg_case = CLIENT_MESSAGE__MSG_CONNECT;

	return connection_send_msg(ei, &msg);
}

static int
connection_send_disconnect(struct ei *ei)
{
	if (ei->state == EI_STATE_NEW ||
	    ei->state == EI_STATE_DISCONNECTED)
		return 0;

	ClientMessage msg = CLIENT_MESSAGE__INIT;
	Disconnect disconnect = DISCONNECT__INIT;

	msg.disconnect = &disconnect;
	msg.msg_case = CLIENT_MESSAGE__MSG_DISCONNECT;

	return connection_send_msg(ei, &msg);
}

static int
connection_send_add(struct ei *ei, struct ei_device *device)
{
	if (ei->state == EI_STATE_NEW ||
	    ei->state == EI_STATE_DISCONNECTED)
		return 0;

	ClientMessage msg = CLIENT_MESSAGE__INIT;
	AddDevice add = ADD_DEVICE__INIT;

	add.deviceid = device->id;
	add.capabilities = device->capabilities;

	msg.add = &add;
	msg.msg_case = CLIENT_MESSAGE__MSG_ADD;

	return connection_send_msg(ei, &msg);
}

static int
connection_send_remove(struct ei *ei, struct ei_device *device)
{
	if (ei->state == EI_STATE_NEW ||
	    ei->state == EI_STATE_DISCONNECTED)
		return 0;

	ClientMessage msg = CLIENT_MESSAGE__INIT;
	RemoveDevice remove = REMOVE_DEVICE__INIT;

	remove.deviceid = device->id;

	msg.remove = &remove;
	msg.msg_case = CLIENT_MESSAGE__MSG_REMOVE;

	return connection_send_msg(ei, &msg);
}

static int
connection_send_rel(struct ei *ei, struct ei_device *device, int32_t x, int32_t y)
{
	if (ei->state == EI_STATE_NEW ||
	    ei->state == EI_STATE_DISCONNECTED)
		return 0;

	ClientMessage msg = CLIENT_MESSAGE__INIT;
	PointerRelative rel = POINTER_RELATIVE__INIT;

	rel.deviceid = device->id;
	rel.x = x;
	rel.y = y;

	msg.rel = &rel;
	msg.msg_case = CLIENT_MESSAGE__MSG_REL;

	return connection_send_msg(ei, &msg);
}

static int
connection_send_button(struct ei *ei, struct ei_device *device,
		       uint32_t b, bool is_press)
{
	if (ei->state == EI_STATE_NEW ||
	    ei->state == EI_STATE_DISCONNECTED)
		return 0;

	ClientMessage msg = CLIENT_MESSAGE__INIT;
	PointerButton button = POINTER_BUTTON__INIT;

	button.deviceid = device->id;
	button.button = b;
	button.state = is_press;

	msg.button = &button;
	msg.msg_case = CLIENT_MESSAGE__MSG_BUTTON;

	return connection_send_msg(ei, &msg);
}

static int
connection_send_key(struct ei *ei, struct ei_device *device,
		    uint32_t k, bool is_press)
{
	if (ei->state == EI_STATE_NEW ||
	    ei->state == EI_STATE_DISCONNECTED)
		return 0;

	ClientMessage msg = CLIENT_MESSAGE__INIT;
	KeyboardKey key = KEYBOARD_KEY__INIT;

	key.deviceid = device->id;
	key.key = k;
	key.state = is_press;

	msg.key = &key;
	msg.msg_case = CLIENT_MESSAGE__MSG_KEY;

	return connection_send_msg(ei, &msg);
}

static void
ei_disconnect(struct ei *ei)
{
	if (ei->state == EI_STATE_DISCONNECTED ||
	    ei->state == EI_STATE_DISCONNECTING)
		return;

	enum ei_state state = ei->state;

	/* We need the disconnecting state to be re-entrant
	   ei_device_remove() may call ei_disconnect() on a socket error */
	ei->state = EI_STATE_DISCONNECTING;

	struct ei_device *d, *tmp;
	list_for_each_safe(d, tmp, &ei->devices, link) {
		ei_device_remove(d);
	}

	if (state != EI_STATE_NEW) {
		connection_send_disconnect(ei);
		ei_queue_disconnect_event(ei);
	}
	ei->state = EI_STATE_DISCONNECTED;
	if (ei->source)
		source_remove(ei->source);
	ei->source = source_unref(ei->source);
}

int
ei_add_device(struct ei_device *device)
{
	struct ei *ei = ei_device_get_context(device);
	int rc = connection_send_add(ei, device);
	if (rc) {
		ei_disconnect(ei);
		return rc;
	}

	ei_device_ref(device);
	list_append(&ei->devices, &device->link);

	return 0;
}

int
ei_remove_device(struct ei_device *device)
{
	struct ei *ei = ei_device_get_context(device);
	int rc = connection_send_remove(ei, device);

	list_remove(&device->link);
	ei_device_unref(device);

	if (rc)
		ei_disconnect(ei);
	return rc;
}

static int
ei_accepted(struct ei *ei, uint32_t deviceid)
{
	struct ei_device *d;

	list_for_each(d, &ei->devices, link) {
		if (d->id == deviceid) {
			ei_device_accepted(d);
			ei_queue_added_event(d);
			return 0;
		}
	}

	/* FIXME: could be a device since removed by the client */
	return -EBADMSG;
}

static int
ei_removed(struct ei *ei, uint32_t deviceid)
{
	struct ei_device *d;

	list_for_each(d, &ei->devices, link) {
		if (d->id == deviceid) {
			ei_queue_removed_event(d);
			list_remove(&d->link);
			ei_device_unref(d);
			break;
		}
	}

	return -0;
}


int
ei_pointer_rel(struct ei_device *device, int32_t x, int32_t y)
{
	struct ei *ei = ei_device_get_context(device);
	int rc = connection_send_rel(ei, device, x, y);
	if (rc)
		ei_disconnect(ei);
	return rc;
}

int
ei_pointer_button(struct ei_device *device, uint32_t button, bool is_press)
{
	struct ei *ei = ei_device_get_context(device);
	int rc = connection_send_button(ei, device, button, is_press);
	if (rc)
		ei_disconnect(ei);
	return rc;
}

int
ei_keyboard_key(struct ei_device *device, uint32_t key, bool is_press)
{
	struct ei *ei = ei_device_get_context(device);
	int rc = connection_send_key(ei, device, key, is_press);
	if (rc)
		ei_disconnect(ei);
	return rc;
}

_public_ struct ei_event*
ei_get_event(struct ei *ei)
{
	if (list_empty(&ei->event_queue))
		return NULL;

	struct ei_event *e = list_first_entry(&ei->event_queue, e, link);
	list_remove(&e->link);

	return e;
}

_public_ struct ei_event*
ei_peek_event(struct ei *ei)
{
	if (list_empty(&ei->event_queue))
		return NULL;

	struct ei_event *e = list_first_entry(&ei->event_queue, e, link);
	return ei_event_ref(e);
}

_public_ enum ei_event_type
ei_next_event_type(struct ei *ei)
{
	if (list_empty(&ei->event_queue))
		return EI_EVENT_NONE;

	struct ei_event *e = list_first_entry(&ei->event_queue, e, link);
	return e->type;
}

static struct message *
connection_parse_message(const char *data, size_t *len)
{
	/* Every message is prefixed by a fixed-length Frame message which
	 * contains the length of the next message. Parse that one first,
	 * then the real message */
	static size_t framelen = 0;
	if (framelen == 0) {
		Frame f = FRAME__INIT;
		f.length = 0xffff;
		framelen = frame__get_packed_size(&f);
		assert(framelen >= 5);
	}

	_cleanup_(message_freep) struct message *msg = xalloc(sizeof(*msg));

	Frame *frame = frame__unpack(NULL, framelen, (const unsigned char *)data);
	if (!frame)
		return NULL;

	size_t msglen = frame->length;
	frame__free_unpacked(frame, NULL);

	const unsigned char *msgdata = (const unsigned char *)data + framelen;

	ServerMessage *proto = server_message__unpack(NULL, msglen, msgdata);
	if (!proto)
		return NULL;

	bool success = true;
	switch (proto->msg_case) {
	case SERVER_MESSAGE__MSG_HELLO:
		*msg = (struct message) {
			.type = MESSAGE_HELLO,
		};
		break;
	case SERVER_MESSAGE__MSG_CONNECTED:
		*msg = (struct message) {
			.type = MESSAGE_CONNECTED,
		};
		break;
	case SERVER_MESSAGE__MSG_DISCONNECTED:
		*msg = (struct message) {
			.type = MESSAGE_DISCONNECTED,
		};
		break;
	case SERVER_MESSAGE__MSG_ACCEPTED:
		{
			Accepted *a = proto->accepted;
			*msg = (struct message) {
				.type = MESSAGE_ACCEPTED,
				.accepted.deviceid = a->deviceid,
			};
		}
		break;
	case SERVER_MESSAGE__MSG_REMOVED:
		{
			Removed *r = proto->removed;
			*msg = (struct message) {
				.type = MESSAGE_REMOVED,
				.removed.deviceid = r->deviceid,
			};
		}
		break;
	default:
		success = false;
		break;
	}

	server_message__free_unpacked(proto, NULL);

	return success ? steal(&msg) : NULL;
}

static int
connection_new_handle_msg(struct ei *ei, struct message *msg)
{
	int rc = 0;

	switch (msg->type) {
	case MESSAGE_HELLO:
		ei->state = EI_STATE_CONNECTING;
		rc = connection_send_connect(ei);
		break;
	case MESSAGE_CONNECTED:
	case MESSAGE_DISCONNECTED:
	case MESSAGE_ACCEPTED:
	case MESSAGE_REMOVED:
		rc = -EPROTO;
		break;
	}

	return rc;
}

static int
connection_connecting_handle_msg(struct ei *ei, struct message *msg)
{
	int rc = 0;

	switch (msg->type) {
	case MESSAGE_HELLO:
		rc = -EPROTO;
		break;
	case MESSAGE_CONNECTED:
		ei->state = EI_STATE_CONNECTED;
		ei_queue_connect_event(ei);
		break;
	case MESSAGE_DISCONNECTED:
		rc = -ECANCELED;
		break;
	case MESSAGE_ACCEPTED:
	case MESSAGE_REMOVED:
		rc = -EPROTO;
		break;
	}

	return rc;
}

static int
connection_connected_handle_msg(struct ei *ei, struct message *msg)
{
	int rc = 0;

	switch (msg->type) {
	case MESSAGE_HELLO:
	case MESSAGE_CONNECTED:
		rc = -EPROTO;
		break;
	case MESSAGE_DISCONNECTED:
		rc = -ECANCELED;
		break;
	case MESSAGE_ACCEPTED:
		rc = ei_accepted(ei, msg->accepted.deviceid);
		break;
	case MESSAGE_REMOVED:
		rc = ei_removed(ei, msg->removed.deviceid);
		break;
	}

	return rc;
}

static void
connection_dispatch(struct source *source, void *userdata)
{
	struct ei *ei = userdata;
	enum ei_state old_state = ei->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 = connection_parse_message(data, &len);
		if (!msg) {
			rc = -EBADMSG;
			goto error;
		}

		idx += len;

		switch (ei->state) {
			case EI_STATE_NEW:
				abort();
			case EI_STATE_BACKEND:
				rc = connection_new_handle_msg(ei, msg);
				break;
			case EI_STATE_CONNECTING:
				rc = connection_connecting_handle_msg(ei, msg);
				break;
			case EI_STATE_CONNECTED:
				rc = connection_connected_handle_msg(ei, msg);
				break;
			case EI_STATE_DISCONNECTING:
			case EI_STATE_DISCONNECTED:
				abort();
		}
	}

error:
	if (rc < 0)
		ei_disconnect(ei);

	static const char *states[] = {
		"NEW",
		"BACKEND",
		"CONNECTING",
		"CONNECTED",
		"DISCONNECTED",
		"DISCONNECTING",
	};
	if (rc)
		log_warn(ei, "Connnection error: %s\n", strerror(-rc));
	log_debug(ei, "Connnection dispatch: %s -> %s\n",
		  states[old_state],
		  states[ei->state]);
}

int
ei_set_connection(struct ei *ei, int fd)
{
	struct source *source = source_add_autoclose(ei->sink, fd, connection_dispatch, ei);
	if (!source)
		return -ENOMEM;

	ei->source = source_ref(source);
	ei->state = EI_STATE_BACKEND;

	return 0;
}

_public_ void
ei_configure_name(struct ei *ei, const char *name)
{
	if (ei->state != EI_STATE_NEW)
		return;

	if (strlen(name) > 1024)
		return;

	free(ei->name);
	ei->name = xstrdup(name);
}

#ifdef _enable_tests_
#include <munit.h>

static MunitResult
test_init_unref(const MunitParameter params[], void *user_data)
{
	struct ei *ei = ei_new(NULL);

	munit_assert_int(ei->state, ==, EI_STATE_NEW);
	munit_assert(list_empty(&ei->event_queue));
	munit_assert(list_empty(&ei->devices));

	munit_assert_not_null(ei->sink);
	munit_assert_not_null(ei->logger);

	struct ei *refd = ei_ref(ei);
	munit_assert_ptr_equal(ei, refd);
	munit_assert_int(ei->object.refcount, ==, 2);

	struct ei *unrefd = ei_unref(ei);
	munit_assert_null(unrefd);

	unrefd = ei_unref(ei);
	munit_assert_null(unrefd);

	return MUNIT_OK;
}

static MunitResult
test_configure_name(const MunitParameter params[], void *user_data)
{
	struct ei *ei = ei_new(NULL);

	ei_configure_name(ei, "foo");
	munit_assert_string_equal(ei->name, "foo");
	ei_configure_name(ei, "bar");
	munit_assert_string_equal(ei->name, "bar");

	/* ignore names that are too long */
	char buf[1200] = {0};
	memset(buf, 'a', sizeof(buf) - 1);
	ei_configure_name(ei, buf);
	munit_assert_string_equal(ei->name, "bar");

	/* ignore names in all other states */
	for (enum ei_state state = EI_STATE_NEW + 1;
	     state <= EI_STATE_DISCONNECTED;
	     state++) {
		ei->state = state;
		ei_configure_name(ei, "expect ignored");
		munit_assert_string_equal(ei->name, "bar");
	}

	ei_unref(ei);

	return MUNIT_OK;
}

static MunitTest ei_tests[] = {
	{ "/init_unref", test_init_unref, NULL, NULL, MUNIT_TEST_OPTION_NONE, NULL},
	{ "/name", test_configure_name, NULL, NULL, MUNIT_TEST_OPTION_NONE, NULL},
	{ NULL },
};

static const MunitSuite libei_suite
__attribute__((used))
__attribute__((section("test_section"))) = {
	"",
	ei_tests,
	NULL,
	1,
	MUNIT_SUITE_OPTION_NONE,
};
#endif