#include <arpa/inet.h>
#include <atomic>
#include <cstring>
#include <iomanip>
#include <iostream>
#include <netinet/in.h>
#include <pthread.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#include <vector>

#ifdef __SWITCH__
#include <server.hpp>
#include <switch.h>
#include <main.hpp>
#endif

#include <protocol.hpp>
#include <TransferState.hpp>
#include <net/Socket.hpp>

static TransferState    g_server_state;
static std::atomic<int> g_server_client_sock{-1};
static std::atomic<int> g_server_listen_sock{-1};
static std::atomic<int> g_broadcast_sock{-1};
static std::atomic<bool> g_accept_thread_active{false};
static std::atomic<bool> g_broadcast_thread_active{false};
static pthread_t         g_broadcast_thread{};

bool isServerTransferDone()       { return g_server_state.done.load(); }
bool isServerTransferCancelled()  { return g_server_state.cancelled.load(); }
bool isServerWorkersIdle()        { return !g_accept_thread_active.load() && !g_broadcast_thread_active.load(); }
double getServerProgress()        { return g_server_state.progress(); }
std::string getServerStatusText() { return g_server_state.getStatus(); }

void cancelServerTransfer() {
    g_server_state.cancelled.store(true);
    int sock = g_server_client_sock.exchange(-1);
    if (sock >= 0) {
        shutdown(sock, SHUT_RDWR);
        close(sock);
    }
    int lsock = g_server_listen_sock.exchange(-1);
    if (lsock >= 0) {
        shutdown(lsock, SHUT_RDWR);
        close(lsock);
    }
    int bsock = g_broadcast_sock.exchange(-1);
    if (bsock >= 0) {
        shutdown(bsock, SHUT_RDWR);
        close(bsock);
    }
    if (g_broadcast_thread_active.load()) {
        pthread_cancel(g_broadcast_thread);
    }
}

#ifdef __SWITCH__
static std::string replaceUsername(const std::string& path) {
    std::string username = StringUtils::removeNotAscii(
        StringUtils::removeAccents(Account::username(g_currentUId)));
    size_t lastSlash = path.rfind('/');
    if (lastSlash == std::string::npos) return path;
    size_t prevSlash = path.rfind('/', lastSlash - 1);
    if (prevSlash == std::string::npos)
        return username + path.substr(lastSlash);
    return path.substr(0, prevSlash + 1) + username + path.substr(lastSlash);
}
#endif

static bool recv_all(int sock, void* buf, size_t len) {
    size_t received = 0;
    while (received < len) {
        ssize_t n = read(sock, static_cast<char*>(buf) + received, len - received);
        if (n <= 0) return false;
        received += n;
    }
    return true;
}

static void mkdirs(const std::string& path) {
    for (size_t i = 1; i < path.size(); i++) {
        if (path[i] == '/') {
            std::string component = path.substr(0, i);
            mkdir(component.c_str(), 0777);
        }
    }
    mkdir(path.c_str(), 0777);
}

static void receive_file(int sock, const std::string& relative_path, uint64_t file_size) {
    std::cout << "Receiving: " << relative_path << " (" << file_size << " bytes)" << std::endl;

    size_t last_slash = relative_path.rfind('/');
    if (last_slash != std::string::npos) {
        std::string dir = relative_path.substr(0, last_slash);
        if (!dir.empty()) mkdirs(dir);
    }

    FILE* outfile = fopen(relative_path.c_str(), "wb");
    if (!outfile) {
        std::cerr << "Failed to open for writing: " << relative_path
                  << " errno=" << errno << std::endl;
        // Drain so sender doesn't hang
        std::vector<char> drain(proto::BUF_SIZE);
        uint64_t remaining = file_size;
        while (remaining > 0) {
            size_t to_read = (size_t)std::min(remaining, (uint64_t)proto::BUF_SIZE);
            ssize_t n = read(sock, drain.data(), to_read);
            if (n <= 0) break;
            remaining -= (uint64_t)n;
        }
        return;
    }

    g_server_state.bytes_total.store(file_size);
    g_server_state.bytes_done.store(0);

    std::vector<char> buffer(proto::BUF_SIZE);
    uint64_t total_received = 0;
    while (total_received < file_size) {
        size_t to_read = (size_t)std::min(file_size - total_received, (uint64_t)proto::BUF_SIZE);
        ssize_t n = read(sock, buffer.data(), to_read);
        if (n <= 0) {
            std::cerr << "Read error receiving: " << relative_path << std::endl;
            break;
        }
        fwrite(buffer.data(), 1, (size_t)n, outfile);
        total_received += (uint64_t)n;
        g_server_state.bytes_done.store(total_received);
    }

    fclose(outfile);
    std::cout << "Received: " << relative_path << std::endl;
}

static void* handle_client(void* socket_desc) {
    int client_socket = *(int*)socket_desc;
    delete static_cast<int*>(socket_desc);

    while (true) {
        uint32_t filename_len = 0;
        if (!recv_all(client_socket, &filename_len, sizeof(filename_len)))
            break;

        if (filename_len == proto::EOF_SENTINEL) {
            std::cout << "End of transfer." << std::endl;
            break;
        }

        if (filename_len > proto::MAX_FILENAME) {
            std::cerr << "filename_len=" << filename_len << " exceeds MAX_FILENAME, aborting." << std::endl;
            break;
        }

        std::vector<char> filename(filename_len + 1, '\0');
        if (!recv_all(client_socket, filename.data(), filename_len)) {
            std::cerr << "Short read on filename, aborting." << std::endl;
            break;
        }
        std::string filename_str(filename.data(), filename_len);

#ifdef __SWITCH__
        filename_str = replaceUsername(filename_str);
#endif

        {
            size_t sl = filename_str.rfind('/');
            g_server_state.setStatus(
                sl != std::string::npos ? filename_str.substr(sl + 1) : filename_str);
        }

        uint64_t file_size = 0;
        if (!recv_all(client_socket, &file_size, sizeof(file_size))) {
            std::cerr << "Short read on file_size, aborting." << std::endl;
            break;
        }

        receive_file(client_socket, filename_str, file_size);
    }

    int owned_client = g_server_client_sock.exchange(-1);
    if (owned_client == client_socket) {
        close(client_socket);
    }
    return nullptr;
}

struct AcceptArgs { int server_fd; };

static void* accept_and_handle(void* arg) {
    g_accept_thread_active.store(true);
    int server_fd = static_cast<AcceptArgs*>(arg)->server_fd;
    delete static_cast<AcceptArgs*>(arg);

    g_server_listen_sock.store(server_fd);
    sockaddr_in client_addr{};
    socklen_t   client_len = sizeof(client_addr);
    int client_socket = accept(server_fd, (sockaddr*)&client_addr, &client_len);
    int owned_listen = g_server_listen_sock.exchange(-1);
    if (owned_listen == server_fd) {
        close(server_fd);
    }

    if (client_socket >= 0) {
        g_server_client_sock.store(client_socket);
        int* pclient = new (std::nothrow) int(client_socket);
        if (pclient) {
            handle_client(pclient);
        } else {
            close(client_socket);
        }
    }

    g_server_state.done.store(true);
    g_accept_thread_active.store(false);
    return nullptr;
}

static void* broadcast_listener(void* arg) {
    g_broadcast_thread_active.store(true);
    pthread_setcancelstate(PTHREAD_CANCEL_ENABLE, nullptr);
    pthread_setcanceltype(PTHREAD_CANCEL_DEFERRED, nullptr);
    int udp = socket(AF_INET, SOCK_DGRAM, 0);
    if (udp < 0) {
        perror("broadcast_listener: socket");
        g_broadcast_thread_active.store(false);
        return nullptr;
    }

    g_broadcast_sock.store(udp);

    struct timeval tv{0, 20000};  // 20ms poll so cancel/exit wins race with socketExit
    setsockopt(udp, SOL_SOCKET, SO_RCVTIMEO, &tv, sizeof(tv));

    sockaddr_in addr{};
    addr.sin_family      = AF_INET;
    addr.sin_addr.s_addr = htonl(INADDR_ANY);
    addr.sin_port        = htons(proto::MULTICAST_PORT);

    if (bind(udp, (sockaddr*)&addr, sizeof(addr)) < 0) {
        perror("broadcast_listener: bind");
        int owned = g_broadcast_sock.exchange(-1);
        if (owned == udp) close(udp);
        g_broadcast_thread_active.store(false);
        return nullptr;
    }

    ip_mreq group{};
    group.imr_multiaddr.s_addr = inet_addr(proto::MULTICAST_GROUP);
    group.imr_interface.s_addr = htonl(INADDR_ANY);
    if (setsockopt(udp, IPPROTO_IP, IP_ADD_MEMBERSHIP, &group, sizeof(group)) < 0) {
        perror("broadcast_listener: setsockopt");
        int owned = g_broadcast_sock.exchange(-1);
        if (owned == udp) close(udp);
        g_broadcast_thread_active.store(false);
        return nullptr;
    }

    std::cout << "Broadcast listener started" << std::endl;
    char buf[256];
    sockaddr_in from{};
    socklen_t   fromlen = sizeof(from);

    while (true) {
        ssize_t n = recvfrom(udp, buf, sizeof(buf) - 1, 0, (sockaddr*)&from, &fromlen);
        if (n < 0) {
            if (g_server_state.cancelled.load()) break;
            continue;
        }
        buf[n] = '\0';
        if (strcmp(buf, "DISCOVER_SERVER") == 0) {
            const char* reply = "SERVER_HERE";
            sendto(udp, reply, strlen(reply), 0, (sockaddr*)&from, fromlen);
            std::cout << "Discovery replied." << std::endl;
            break;
        }
    }

    int owned = g_broadcast_sock.exchange(-1);
    if (owned == udp) close(udp);
    g_broadcast_thread_active.store(false);
    return nullptr;
}

int startSendingThread() {
    g_server_state.reset();
    g_server_state.setStatus("Waiting for connection...");

    pthread_t broadcast_thread;
    if (pthread_create(&broadcast_thread, nullptr, broadcast_listener, nullptr) != 0) {
        perror("startSendingThread: broadcast thread");
        return 1;
    }
    g_broadcast_thread = broadcast_thread;
    pthread_detach(broadcast_thread);

    Socket server(socket(AF_INET, SOCK_STREAM, 0));
    if (!server.valid()) {
        perror("startSendingThread: socket");
        cancelServerTransfer();
        return 1;
    }

    int yes = 1;
    setsockopt(server, SOL_SOCKET, SO_REUSEADDR, &yes, sizeof(yes));

    sockaddr_in addr{};
    addr.sin_family      = AF_INET;
    addr.sin_addr.s_addr = INADDR_ANY;
    addr.sin_port        = htons(proto::TCP_PORT);

    if (bind(server, (sockaddr*)&addr, sizeof(addr)) < 0) {
        perror("startSendingThread: bind");
        cancelServerTransfer();
        return 1;
    }
    if (listen(server, 3) < 0) {
        perror("startSendingThread: listen");
        cancelServerTransfer();
        return 1;
    }

    AcceptArgs* acc_args = new AcceptArgs{server.fd};
    pthread_t   accept_thread;
    if (pthread_create(&accept_thread, nullptr, accept_and_handle, acc_args) != 0) {
        delete acc_args;
        cancelServerTransfer();
        return 1;
    }
    pthread_detach(accept_thread);
    server.release();  // accepted by accept_and_handle
    return 0;
}

#ifndef __SWITCH__
int main() {
    if (startSendingThread() != 0) return 1;
    while (!isServerTransferDone()) usleep(16000);
    return 0;
}
#endif