/*
 * SPDX-License-Identifier: AGPL-3.0-only
 * Copyright (c) Camden Dixie O'Brien
 */

#include "protocol_interface.h"

#include "esp_log.h"
#include "lwip/sockets.h"
#include <string.h>

#define TAG "Protocol interface"

#define PORT 3498

static CommandHandler handlers[COMMAND_INSTRUCTION_COUNT];

static Message command;
static Message response;

static char string_buffer[CONFIG_MESSAGE_STRING_BUFFER_SIZE];
static char *string_buffer_free_ptr;

static bool receive(int socket, unsigned n, char *p)
{
	int len;
	do {
		len = recv(socket, p, n, 0);
		if (len < 0) {
			ESP_LOGE(TAG, "Error reading from socket: %d", errno);
			return false;
		} else if (len == 0) {
			ESP_LOGI(TAG, "Connection closed");
			return false;
		} else {
			n -= len;
			p += len;
		}
	} while (n > 0);
	return true;
}

static bool receive_param(int socket, unsigned i)
{
	MessageParam *param = &command.params[i];

	uint8_t type_buf;
	if (!receive(socket, 1, &type_buf))
		return false;
	// TODO handle invalid param type
	param->type = (MessageParamType)type_buf;

	uint8_t len, alarm_buf[3];
	switch (param->type) {
	case MESSAGE_PARAM_TYPE_U8:
		if (!receive(socket, 1, (char *)&param->u8))
			return false;
		break;
	case MESSAGE_PARAM_TYPE_U16:
		if (!receive(socket, 2, (char *)&param->u16))
			return false;
		param->u16 = ntohs(param->u16);
		break;
	case MESSAGE_PARAM_TYPE_U32:
		if (!receive(socket, 4, (char *)&param->u32))
			return false;
		param->u32 = ntohl(param->u32);
		break;
	case MESSAGE_PARAM_TYPE_U64:
		if (!receive(socket, 8, (char *)&param->u64))
			return false;
		param->u64 = ntohll(param->u64);
		break;

	case MESSAGE_PARAM_TYPE_STRING:
		if (!receive(socket, 1, &len))
			return false;
		char *buf = alloc_message_string(len);
		// TODO handle out-of-memory
		if (!receive(socket, len, buf))
			return false;
		param->string = buf;
		break;

	case MESSAGE_PARAM_TYPE_ALARM:
		if (!receive(socket, 3, alarm_buf))
			return false;
		param->alarm.time.hour = alarm_buf[0];
		param->alarm.time.minute = alarm_buf[1];
		for (unsigned i = 0; i < WEEK_DAY_COUNT; ++i)
			param->alarm.days[i] = (alarm_buf[2] >> i) & 1;
		break;
	}
}

static bool receive_command(int socket)
{
	char header_buf[2];
	if (!receive(socket, 2, header_buf))
		return false;
	// TODO handle invalid instruction
	command.instruction = (CommandInstruction)header_buf[0];
	command.param_count = (uint8_t)header_buf[1];

	for (unsigned i = 0; i < command.param_count; ++i) {
		if (!receive_param(socket, i))
			return false;
	}

	return true;
}

static void send_response(int socket)
{
}

static void drop_message_strings(void)
{
	string_buffer_free_ptr = string_buffer;
}

static void handle_command(void)
{
	const CommandHandler handler = handlers[command.instruction];
	if (handler == NULL) {
		ESP_LOGW(
		    TAG, "Unhandled command, instruction: %u", command.instruction);
		return;
	}

	const ResponseStatus status = handler(&command, &response);
	if (status != RESPONSE_STATUS_OK) {
		response.status = status;
		response.param_count = 0;
	}

	send_response();
	drop_message_strings();
}

void server_task(void *arg)
{
	int status;

	// Create listening socket
	const int listen_socket = socket(AF_INET6, SOCK_STREAM, IPPROTO_IPV6);
	if (listen_socket < 0) {
		ESP_LOGE(TAG, "Error creating socket: %d", errno);
		goto error_no_cleanup;
	}

	// Configure listening socket
	int opt = 1;
	setsockopt(listen_socket, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt));

	// Bind socket to port (any address)
	struct sockaddr_storage server_addr;
	struct sockaddr_in6 *server_addr_ip6
	    = (struct sockaddr_in6 *)&server_addr;
	memset(
	    &server_addr_ip6->sin6_addr.un, 0,
	    sizeof(server_addr_ip6->sin6_addr.un));
	server_addr_ip6->sin6_family = AF_INET6;
	server_addr_ip6->sin6_port = htons(PORT);
	status = bind(
	    listen_socket, (struct sockaddr *)&server_addr, sizeof(server_addr));
	if (status != 0) {
		ESP_LOGE(TAG, "Error binding socket: %d", errno);
		goto error_cleanup_socket;
	}

	// Listen on socket
	status = listen(listen_socket, 1);
	if (status != 0) {
		ESP_LOGE(TAG, "Error listening on socket: %d", errno);
		goto error_cleanup_socket;
	}

	while (1) {
		struct sockaddr_storage client_addr;
		socklen_t addr_len = sizeof(client_addr);

		// Accept incoming connection
		int socket = accept(
		    listen_socket, (struct sockaddr *)&client_addr, &addr_len);
		if (socket < 0) {
			ESP_LOGE(TAG, "Error accepting connection: %d", errno);
			continue;
		}

		// Log client address, run command-response loop until
		// connection closed.
		const char *addr_str
		    = ((struct sockaddr_in6 *)&client_addr)->sin6_addr;
		ESP_LOGI(TAG, "Accepted connection from %s", addr_str);
		while (1) {
			if (!receive_command())
				break;
			handle_command();
		}

		// Cleanup connection
		shutdown(socket, 0);
		close(socket);
	}

error_cleanup_socket:
	close(listen_socket);
error_no_cleanup:
	vTaskDelete(NULL);
}

void protocol_interface_init(void)
{
	memset(handlers, 0, sizeof(handlers));
	string_buffer_free = string_buffer;
	memset(command, 0, sizeof(command));
	memset(response, 0, sizeof(response));
}

void set_command_handler(
    CommandInstruction instruction, CommandHandler handler)
{
	if (instruction < COMMAND_INSTRUCTION_COUNT) {
		if (handlers[instruction] != NULL)
			ESP_LOGW(TAG, "Handler #%u overwritten", instruction);
		handlers[instruction] = handler;
	} else {
		ESP_LOGE(TAG, "Invalid instruction passed to %s()", __func__);
	}
}

char *alloc_message_string(unsigned length)
{
	if (string_buffer_free_ptr + length + 1
	    < string_buffer + CONFIG_MESSAGE_STRING_BUFFER_SIZE) {
		char *s = string_buffer_free_ptr;
		string_buffer_free_ptr += length + 1;
		s[length] = '\0';
		return s;
	} else {
		return NULL;
	}
}