//
// SPDX-FileCopyrightText: Hadad <hadad@linuxmail.org>
// SPDX-License-Identifier: Apache-2.0
//

#include "ipc_handler.hpp"
#include <cstring>
#include <sys/socket.h>
#include <sys/un.h>
#include <unistd.h>

namespace pocket_tts_accelerator {

IpcHandler::IpcHandler(const std::string& socket_path)
    : socket_file_path(socket_path)
    , server_socket_fd(-1)
    , is_server_running(false) {
}

IpcHandler::~IpcHandler() {
    stop_server();
}

bool IpcHandler::start_server() {
    if (is_server_running.load()) {
        return true;
    }
    
    unlink(socket_file_path.c_str());
    
    server_socket_fd = socket(AF_UNIX, SOCK_STREAM, 0);
    
    if (server_socket_fd < 0) {
        return false;
    }
    
    struct sockaddr_un server_address;
    std::memset(&server_address, 0, sizeof(server_address));
    server_address.sun_family = AF_UNIX;
    std::strncpy(server_address.sun_path, socket_file_path.c_str(), sizeof(server_address.sun_path) - 1);
    
    if (bind(server_socket_fd, reinterpret_cast<struct sockaddr*>(&server_address), sizeof(server_address)) < 0) {
        close(server_socket_fd);
        server_socket_fd = -1;
        return false;
    }
    
    if (listen(server_socket_fd, CONNECTION_BACKLOG) < 0) {
        close(server_socket_fd);
        server_socket_fd = -1;
        return false;
    }
    
    is_server_running.store(true);
    accept_thread = std::thread(&IpcHandler::accept_connections_loop, this);
    
    return true;
}

void IpcHandler::stop_server() {
    if (!is_server_running.load()) {
        return;
    }
    
    is_server_running.store(false);
    
    if (server_socket_fd >= 0) {
        shutdown(server_socket_fd, SHUT_RDWR);
        close(server_socket_fd);
        server_socket_fd = -1;
    }
    
    if (accept_thread.joinable()) {
        accept_thread.join();
    }
    
    unlink(socket_file_path.c_str());
}

bool IpcHandler::is_running() const {
    return is_server_running.load();
}

void IpcHandler::register_command_handler(CommandType command_type, CommandHandlerFunction handler) {
    std::unique_lock<std::mutex> lock(handlers_mutex);
    command_handlers[command_type] = std::move(handler);
}

void IpcHandler::set_shutdown_callback(std::function<void()> callback) {
    shutdown_callback = std::move(callback);
}

void IpcHandler::accept_connections_loop() {
    while (is_server_running.load()) {
        struct sockaddr_un client_address;
        socklen_t client_address_length = sizeof(client_address);
        
        int client_socket_fd = accept(
            server_socket_fd,
            reinterpret_cast<struct sockaddr*>(&client_address),
            &client_address_length
        );
        
        if (client_socket_fd < 0) {
            if (!is_server_running.load()) {
                break;
            }
            continue;
        }
        
        handle_client_connection(client_socket_fd);
        close(client_socket_fd);
    }
}

void IpcHandler::handle_client_connection(int client_socket_fd) {
    RequestHeader request_header;
    std::vector<std::uint8_t> request_payload;
    
    if (!receive_request(client_socket_fd, request_header, request_payload)) {
        return;
    }
    
    if (request_header.magic_number != PROTOCOL_MAGIC_NUMBER) {
        ResponseHeader error_response;
        error_response.magic_number = PROTOCOL_MAGIC_NUMBER;
        error_response.status_code = static_cast<std::uint32_t>(ResponseStatus::ERROR_INVALID_COMMAND);
        error_response.payload_size = 0;
        error_response.request_id = request_header.request_id;
        send_response(client_socket_fd, error_response, {});
        return;
    }
    
    CommandType command_type = static_cast<CommandType>(request_header.command_type);
    
    if (command_type == CommandType::SHUTDOWN) {
        ResponseHeader shutdown_response;
        shutdown_response.magic_number = PROTOCOL_MAGIC_NUMBER;
        shutdown_response.status_code = static_cast<std::uint32_t>(ResponseStatus::SUCCESS);
        shutdown_response.payload_size = 0;
        shutdown_response.request_id = request_header.request_id;
        send_response(client_socket_fd, shutdown_response, {});
        
        if (shutdown_callback) {
            shutdown_callback();
        }
        return;
    }
    
    std::vector<std::uint8_t> response_payload;
    ResponseStatus status = ResponseStatus::SUCCESS;
    
    {
        std::unique_lock<std::mutex> lock(handlers_mutex);
        auto handler_iterator = command_handlers.find(command_type);
        
        if (handler_iterator != command_handlers.end()) {
            try {
                response_payload = handler_iterator->second(request_payload);
            } catch (...) {
                status = ResponseStatus::ERROR_INTERNAL;
            }
        } else {
            status = ResponseStatus::ERROR_INVALID_COMMAND;
        }
    }
    
    ResponseHeader response_header;
    response_header.magic_number = PROTOCOL_MAGIC_NUMBER;
    response_header.status_code = static_cast<std::uint32_t>(status);
    response_header.payload_size = static_cast<std::uint32_t>(response_payload.size());
    response_header.request_id = request_header.request_id;
    
    send_response(client_socket_fd, response_header, response_payload);
}

bool IpcHandler::send_response(
    int socket_fd,
    const ResponseHeader& header,
    const std::vector<std::uint8_t>& payload
) {
    ssize_t bytes_written = write(socket_fd, &header, sizeof(ResponseHeader));
    
    if (bytes_written != sizeof(ResponseHeader)) {
        return false;
    }
    
    if (!payload.empty()) {
        bytes_written = write(socket_fd, payload.data(), payload.size());
        
        if (bytes_written != static_cast<ssize_t>(payload.size())) {
            return false;
        }
    }
    
    return true;
}

bool IpcHandler::receive_request(
    int socket_fd,
    RequestHeader& header,
    std::vector<std::uint8_t>& payload
) {
    ssize_t bytes_read = read(socket_fd, &header, sizeof(RequestHeader));
    
    if (bytes_read != sizeof(RequestHeader)) {
        return false;
    }
    
    if (header.payload_size > MAXIMUM_PAYLOAD_SIZE) {
        return false;
    }
    
    if (header.payload_size > 0) {
        payload.resize(header.payload_size);
        bytes_read = read(socket_fd, payload.data(), header.payload_size);
        
        if (bytes_read != static_cast<ssize_t>(header.payload_size)) {
            return false;
        }
    }
    
    return true;
}

}