#include <cstring>
#include <fcntl.h>
#include <unistd.h>
#include <sys/epoll.h>
#include <system_error>

#include "log.h"
#include "misc.h"
#include "logcat_thread.h"

#define EPOLL_MAX_EVENTS 10

static void mark_nonblock(int fd) {
    int flags = fcntl(fd, F_GETFL);
    if (flags < 0) {
        throw_system_error("fcntl(fd, F_GETFL)");
    }
    if (!(flags & O_NONBLOCK) && fcntl(fd, F_SETFL, flags | O_NONBLOCK) == -1) {
        throw_system_error("fcntl(fd, F_SETFL)");
    }
}

static inline void look_for_newlines(char buf[NEWLINE_BUF_SIZE], size_t* used, size_t previous_used,
        void(LogcatThread::*handle_line)(char*, size_t, bool), LogcatThread* logcat_thread, bool is_stdout) {
    size_t search_offset = previous_used;
    size_t real_offset = 0;

    while (*used > search_offset) {
        char* newline_ptr = static_cast<char*>(memchr(&buf[search_offset], '\n', (*used - search_offset) * sizeof(char)));
        if (!newline_ptr) {
            break;
        }

        size_t newline_length = (reinterpret_cast<size_t>(newline_ptr) - reinterpret_cast<size_t>(&buf[real_offset])) / sizeof(char);
        (logcat_thread->*handle_line)(&buf[real_offset], newline_length, is_stdout);

        search_offset += newline_length + 1;
        real_offset = search_offset;
    }

    if (real_offset) {
        if (*used > search_offset) {
            memcpy(buf, &buf[real_offset], (*used - real_offset) * sizeof(char));
            *used -= real_offset;
        } else {
            *used = 0;
        }
    }
}

static inline void handle_fd(int fd, char* buf, size_t* used,
        void(LogcatThread::*handle_line)(char*, size_t, bool), LogcatThread* logcat_thread, bool is_stdout) {
    while (true) {
        ssize_t read_size_u = read(fd, &buf[*used], (NEWLINE_BUF_SIZE - *used) * sizeof(char));
        if (read_size_u == 0) {
            return;
        } else if (read_size_u < 0 && (errno == EAGAIN || errno == EWOULDBLOCK)) {
            return;
        } else if (read_size_u < 0) {
            throw_system_error("read()");
        }
        size_t read_size = static_cast<size_t>(read_size_u) / sizeof(char);
        if (*used + read_size > NEWLINE_BUF_SIZE) {
            throw std::runtime_error("Received line longer than 512k");
        }
        size_t previous_used = *used;
        *used += read_size;

        look_for_newlines(buf, used, previous_used, handle_line, logcat_thread, is_stdout);
    }
}


LogcatThread::LogcatThread() {
    int fds[2];
    struct epoll_event event = {.events = EPOLLIN | EPOLLET};

    if (pipe(fds)) {
        int errsv = errno;
        this->~LogcatThread();
        throw_system_error(errsv, "pipe() for stdout");
    }
    this->_stdout_read_fd = fds[0];
    this->_stdout_write_fd = fds[1];
    try {
        mark_nonblock(this->_stdout_read_fd);
    } catch (const std::exception& e) {
        this->~LogcatThread();
        throw;
    }

    if (pipe(fds)) {
        int errsv = errno;
        this->~LogcatThread();
        throw_system_error(errsv, "pipe() for stderr");
    }
    this->_stderr_read_fd = fds[0];
    this->_stderr_write_fd = fds[1];
    try {
        mark_nonblock(this->_stderr_read_fd);
    } catch (const std::exception& e) {
        this->~LogcatThread();
        throw;
    }

    this->_epoll_fd = epoll_create1(EPOLL_CLOEXEC);
    if (this->_epoll_fd == -1) {
        int errsv = errno;
        this->~LogcatThread();
        throw_system_error(errsv, "epoll_create1()");
    }
    event.data.fd = this->_stdout_read_fd;
    if (epoll_ctl(this->_epoll_fd, EPOLL_CTL_ADD, this->_stdout_read_fd, &event)) {
        int errsv = errno;
        this->~LogcatThread();
        throw_system_error(errsv, "epoll_ctl() for stdout");
    }
    event.data.fd = this->_stderr_read_fd;
    if (epoll_ctl(this->_epoll_fd, EPOLL_CTL_ADD, this->_stderr_read_fd, &event)) {
        int errsv = errno;
        this->~LogcatThread();
        throw_system_error(errsv, "epoll_ctl() for stderr");
    }

    this->_thread = std::thread(&LogcatThread::_run, this, this->_stop_source.get_token());
}

LogcatThread::~LogcatThread() {
    if (this->_epoll_fd != -1 && close(this->_epoll_fd)) {
        log(std::string("Failed to close epoll file descriptor: close(): ") + strerror(errno));
    }
    if (this->_stdout_read_fd != -1 && close(this->_stdout_read_fd)) {
        log(std::string("Failed to close stdout read pipe: close(): ") + strerror(errno));
    }
    if (this->_stdout_write_fd != -1 && close(this->_stdout_write_fd)) {
        log(std::string("Failed to close stdout write pipe: close(): ") + strerror(errno));
    }
    if (this->_stderr_read_fd != -1 && close(this->_stderr_read_fd)) {
        log(std::string("Failed to close stderr read pipe: close(): ") + strerror(errno));
    }
    if (this->_stderr_write_fd != -1 && close(this->_stderr_write_fd)) {
        log(std::string("Failed to close stderr write pipe: close(): ") + strerror(errno));
    }
}

void LogcatThread::request_stop() {
    this->_stop_source.request_stop();
}

void LogcatThread::join() {
    this->_thread.join();
}

void LogcatThread::_handle_line(char* buf, size_t used, bool is_stdout) {
    if (!is_stdout) {
        std::string log_entry = format_log(std::string("logcat stderr: ") + std::string(buf, used));
        printf("%s\n", log_entry.c_str());
        this->atomic_ring_buffer.put_and_increment_write(std::move(log_entry));
        return;
    }

    // TODO actually parse
    std::string log_entry = format_log(std::string("logcat stdout: ") + std::string(buf, used));
    printf("%s\n", log_entry.c_str());
    this->atomic_ring_buffer.put_and_increment_write(std::move(log_entry));
}

void LogcatThread::_run(std::stop_token stoken) {
    struct epoll_event events[EPOLL_MAX_EVENTS];

    while (!stoken.stop_requested()) {
#ifndef NDEBUG
        if (this->debug_log_request.test()) {
            this->atomic_ring_buffer.put_and_increment_write(format_log("A log entry from the logcat thread :D"));
            this->debug_log_request.clear();
        }
#endif

        int ready_fds = epoll_wait(this->_epoll_fd, events, EPOLL_MAX_EVENTS, 1000);
        if (ready_fds == -1) {
            std::string log_entry = format_log(std::string("epoll_wait(): ") + strerror(errno));
            printf("%s\n", log_entry.c_str());
            this->atomic_ring_buffer.put_and_increment_write(std::move(log_entry));
            break;
        }

        for (int i=0; i < ready_fds; i++) {
            const bool is_stdout = events[i].data.fd == this->_stdout_read_fd;
            char* buf = is_stdout ? this->_stdout_buf : this->_stderr_buf;
            size_t* used = is_stdout ? &this->_stdout_buf_used : &this->_stderr_buf_used;

            try {
                handle_fd(events[i].data.fd, buf, used, &LogcatThread::_handle_line, this, is_stdout);
            } catch (const std::exception& e) {
                std::string log_entry = "Failed to handle std";
                log_entry += is_stdout ? "out: " : "err: ";
                log_entry += e.what();
                log_entry = format_log(std::move(log_entry));
                printf("%s\n", log_entry.c_str());
                this->atomic_ring_buffer.put_and_increment_write(std::move(log_entry));
            }
        }
    }
}