/* SPDX-License-Identifier: Unlicense */

#include "debug.h"
#include "proto.h"
#include "proto_io.h"

#include "timespec/timespec.h"
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wunused-function"
#define OPTPARSE_IMPLEMENTATION
#define OPTPARSE_API static
#include "optparse/optparse.h"
#pragma GCC diagnostic pop

#include <assert.h>
#include <errno.h>
#include <fcntl.h>
#include <inttypes.h>
#include <netinet/in.h>
#include <poll.h>
#include <signal.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <time.h>
#include <unistd.h>

struct connection {
    int fd;
    uint16_t port;
    uint32_t addr;
    bool connected;
    uint32_t connection_id;
    struct timespec last_syn;
    uint32_t server_roundtrip_prev;
    uint32_t client_roundtrip_prev;
};

static volatile bool g_should_exit = false;
struct connection g_conn = { .fd = -1, };

static inline bool IsDigit(char c) { return c >= '0' && c <= '9'; }

static void HandleFrame(
        struct connection *self,
        struct frame const *frame,
        struct timespec now)
{
    if (frame->type == FT_HANDSHAKE_RESP) {
        self->connection_id = frame->connection_id;
        self->connected = true;
    } else if (frame->type == FT_SYN && self->connected) {
        if (g_log_level >= LOG_LEVEL_DEBUG) {
            fprintf(stderr, "client_rt %5" PRIu32 "\n", self->client_roundtrip_prev);
        }
        struct frame outgoing = *frame;
        outgoing.type = FT_SYNACK,
        outgoing.syn = (struct frame_data_syn){
            .tick = frame->syn.tick,
            .roundtrip_prev = self->client_roundtrip_prev,
            .prev_is_lost = false,
        };
        SendFrame(self->fd, &outgoing);
        self->last_syn = now;
        self->server_roundtrip_prev = frame->syn.roundtrip_prev;
    } else if (frame->type == FT_ACK && self->connected) {
        long const ms = timespec_to_ms(timespec_sub(now, self->last_syn));
        assert(ms >= 0);
        self->client_roundtrip_prev = ms;
    } else if (frame->type == FT_RST) {
        // TODO
    }
}

static uint32_t ParseAddress(char const *str, FILE *log_stream)
{
    uint32_t addr = 0;
    unsigned byte_counter = 0, byte = 0, digits_counter = 0;
    for (size_t i = 0;; i++) {
        char const c = str[i];
        if (c == '\0') {
            if (byte_counter != 3) {
                fprintf(log_stream, "Invalid address specified: %u bytes of 4 expected are specified\n", byte_counter + 1);
                return INADDR_NONE;
            }
            if (digits_counter == 0) {
                fprintf(log_stream, "Invalid address specified: no digits on byte %u\n", byte_counter + 1);
                return INADDR_NONE;
            }
            addr |= byte << (8 * (3 - byte_counter));
            break;
        } else if (IsDigit(c)) {
            digits_counter++;
            if (digits_counter > 3) {
                fprintf(log_stream, "Invalid address specified: too many digits for byte %u\n", byte_counter + 1);
                return INADDR_NONE;
            }
            byte = byte * 10 + (c - '0');
            if (byte > UINT8_MAX) {
                fprintf(log_stream, "Invalid address specified: too big number for byte %u\n", byte_counter + 1);
                return INADDR_NONE;
            }
        } else if (c == '.') {
            if (digits_counter == 0) {
                fprintf(log_stream, "Invalid address specified: no digits on byte %u\n", byte_counter + 1);
                return INADDR_NONE;
            }
            digits_counter = 0;
            addr |= byte << (8 * (3 - byte_counter));
            byte = 0;
            byte_counter++;
            if (byte_counter > 3) {
                fprintf(log_stream, "Invalid address specified: unexpected dot after 4th byte\n");
                return INADDR_NONE;
            }
        } else {
            fprintf(log_stream, "Invalid address specified: char '%c' (0x%02x) is not allowed\n", c, c);
            return INADDR_NONE;
        }
    }
    if (addr == INADDR_NONE) {
        fprintf(log_stream, "Invalid address specified\n");
    }
    return addr;
}

static void sigintHandler(int a)
{
    (void) a;
}

static void PrintUsage(FILE *s, const char *argv0)
{
    // Please, keep all lines in 80 columns range when printed.
    fprintf(s,
    "Usage: %s [options] <address> <port>\n"
    "Options:\n"
    "  -h, --help,           Show this message.\n"
    "  -d, --debug-level=<level>,\n"
    "                        Set id of debug log level: 0 means no logs, \n"
    "                        1 means info, 2 means some debug,\n"
    "                        3 is for maximum trace\n"
    , argv0);
}

int main(int argc, char *argv[])
{
    (void) argc;
    struct optparse_long longopts[] = {
        {"help", 'h', OPTPARSE_NONE},
        {"debug-level", 'd', OPTPARSE_REQUIRED},
        {0},
    };
    struct optparse options;
    optparse_init(&options, argv);
    // Parse opts
    int option;
    while ((option = optparse_long(&options, longopts, NULL)) != -1) {
        switch (option) {
        case 'h':
            PrintUsage(stdout, argv[0]);
            return EXIT_SUCCESS;
            break;
        case 'd':
            g_log_level = atoi(options.optarg);
            break;
        case '?':
            fprintf(stderr, "main: optparse_long: Error: \"%s\"\n", options.errmsg);
            return EXIT_FAILURE;
        }
    }
    char const *const addr_arg = optparse_arg(&options);
    char const *const port_arg = optparse_arg(&options);
    if (addr_arg == NULL || port_arg == NULL) {
        PrintUsage(stdout, argv[0]);
        return EXIT_SUCCESS;
    }
    unsigned const addr = ParseAddress(addr_arg, stderr);
    if (addr == INADDR_NONE) {
        return 1;
    }
    int const port = atoi(port_arg);
    if (port <= 0 || port > UINT16_MAX) {
        fprintf(stderr, "Invalid port specified\n");
        return 1;
    }
    int const fd = socket(AF_INET, SOCK_DGRAM, 0);
    if (fd < 0) {
        perror("socket failed");
        return 1;
    }
    fcntl(fd, F_SETFL, fcntl(fd, F_GETFL, 0) | O_NONBLOCK);
    g_conn.addr = addr;
    g_conn.port = port;
    g_conn.fd = fd;
    struct frame const handshake = {
        .addr = addr,
        .port = port,
        .type = FT_HANDSHAKE,
        .handshake = {
            .tick_period = 200,
        },
    };
    SendFrame(fd, &handshake);
    struct sigaction sa = { .sa_handler = sigintHandler, };
    sigaction(SIGINT, &sa, NULL);
    struct pollfd fds[1] = { { .fd = fd, .events = POLLIN, }, };
    while (!g_should_exit) {
        int const pollret = poll(fds, sizeof(fds)/sizeof(*fds), -1);
        int const poll_err = errno;
        struct timespec start;
        if (-1 == clock_gettime(CLOCK_MONOTONIC, &start)) {
            int const err = errno;
            fprintf(stderr,
                    "clock_gettime(CLOCK_MONOTONIC, &start) failed (%d): \"%s\"",
                    err, strerror(err));
        }
        if (pollret > 0) {
            if (fds[0].revents & POLLIN) {
                while (1) {
                    struct frame frame = { .type = FT_NONE, };
                    int const ret = ReceiveFrame(fds[0].fd, &frame);
                    if (ret) {
                        break;
                    }
                    HandleFrame(&g_conn, &frame, start);
                }
            }
            if (fds[0].revents & POLLRDNORM) {
                fprintf(stderr, "POLLRDNORM, ignoring...\n");
            }
            if (fds[0].revents & POLLRDBAND) {
                fprintf(stderr, "POLLRDBAND, ignoring...\n");
            }
            if (fds[0].revents & POLLPRI) {
                fprintf(stderr, "POLLPRI, ignoring...\n");
            }
            if (fds[0].revents & POLLPRI) {
                fprintf(stderr, "POLLPRI, ignoring...\n");
            }
            if (fds[0].revents & POLLHUP) {
                fprintf(stderr, "POLLHUP, ignoring...\n");
            }
            if (fds[0].revents & POLLERR) {
                fprintf(stderr, "POLLERR, ignoring...\n");
            }
            if (fds[0].revents & POLLNVAL) {
                fprintf(stderr, "POLLNVAL, exiting...\n");
                return 1;
            }
        } else if (pollret < 0) {
            if (poll_err == EINTR) {
                fprintf(stderr, "SIGINT received\n");
                if (g_conn.connected) {
                    struct frame const rst = {
                        .addr = g_conn.addr,
                        .port = g_conn.port,
                        .type = FT_RST,
                    };
                    SendFrame(g_conn.fd, &rst);
                }
                break;
            }
            fprintf(stderr,
                    "poll() failed (%d): \"%s\"",
                    poll_err, strerror(poll_err));
        }
    }
    close(fd);
}