// SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
/* Copyright (c) 2020 Facebook */
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <sys/resource.h>
#include <bpf/libbpf.h>
#include "replica.skel.h"
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <fcntl.h>

#include "replica.h"

typedef enum {
    OFFLINE = 0,
    ONLINE  = 1,
}replica_state_e ;

struct cmd_node {
    __u64 seq;
    __u32 len;
    uint8_t *cmd;
    struct cmd_node *next;
};

struct pending_queue {
    struct cmd_node *head;
    struct cmd_node *tail;
	int count;
};

/* ================= 全局状态 ================= */

static replica_state_e state = OFFLINE;
static int sockfd = -1;

static char peer_ip[MAX_IP_LEN];
static int peer_port;
static __u64 peer_seq;

static struct pending_queue pending = {
    .head = NULL,
    .tail = NULL,
    .count = 0,
};

/* ================= pending 队列操作 ================= */
static void pending_free()
{
    struct pending_queue *q = &pending;
    struct cmd_node *cur = q->head;
    while (cur) {
        struct cmd_node *tmp = cur;
        cur = cur->next;
        free(tmp->cmd);
        free(tmp);
    }
    q->head = q->tail = NULL;
    q->count = 0;
}

static void pending_push(__u64 seq, __u32 len, const uint8_t *cmd)
{
    struct cmd_node *node = malloc(sizeof(*node));
    if (!node)
        return;

    node->cmd = malloc(len);
    if (!node->cmd) {
        free(node);
        return;
    }

    memcpy(node->cmd, cmd, len);
    node->seq  = seq;
    node->len  = len;
    node->next = NULL;

    if (!pending.tail) {
        pending.head = pending.tail = node;
    } else {
        pending.tail->next = node;
        pending.tail = node;
    }

    pending.count++;
}

static void pending_gc(__u64 min_seq)
{
    struct cmd_node *cur = pending.head;

    int n = pending.count;
    while (cur && cur->seq < min_seq) {
        struct cmd_node *tmp = cur;
        cur = cur->next;

        free(tmp->cmd);
        free(tmp);
        pending.count--;
    }

    printf("gc:%d\n", n-pending.count);

    pending.head = cur;
    if (!cur)
        pending.tail = NULL;
}

static void pending_send_one(struct cmd_node *node){
    int rt = send(sockfd, node->cmd, node->len, 0);
    printf("send seq:%lld, rt=%d\n", node->seq, rt);
}

static void pending_send_all(void)
{
    struct cmd_node *cur = pending.head;

    while (cur) {
        pending_send_one(cur);
        cur = cur->next;
    }
}

/* ================= 网络逻辑 ================= */
static void try_connect(void)
{
    if(sockfd > 0){
        close(sockfd);
        sockfd = -1;
    }

    struct sockaddr_in addr = {};
    int i = 0;

    addr.sin_family = AF_INET;
    addr.sin_port = htons(peer_port);
    inet_pton(AF_INET, peer_ip, &addr.sin_addr);

    for(i = 0;i < 10; ++ i){
        sockfd = socket(AF_INET, SOCK_STREAM, 0);
        if (sockfd < 0) {
            perror("socket");
            return;
        }

        printf("connect try %d...\n", i + 1);
        if (connect(sockfd, (struct sockaddr *)&addr, sizeof(addr)) == 0) {
            printf("connect success: %s:%d\n", peer_ip, peer_port);
            state = ONLINE;
            pending_send_all();
            return;
        }

        perror("connect");
        close(sockfd);
        sockfd = -1;

        sleep(1);
    }

    printf("connect failed after 10 retries\n");
}


/* ================= perf buffer 回调 ================= */
static void handle_event(void *ctx, int cpu, void *data, __u32 size)
{
    struct replica_event *evt = data;

    switch (evt->type) {

    case EVENT_SSYNC:
        strncpy(peer_ip, evt->sync.ip, sizeof(peer_ip));
        peer_port = evt->sync.port;
        peer_seq  = evt->sync.seq;
        printf("SSYNC [seq:%lld], [%s:%d]\n", peer_seq, peer_ip, peer_port);

        state = OFFLINE;
        pending_gc(peer_seq);
        break;

    case EVENT_COMPLETED_CMD:
        // printf("CMD [seq:%lld], cmd:\n[\n%s]\n", evt->complete.seq, evt->complete.cmd);
        pending_push(evt->complete.seq,
                     evt->complete.len,
                     evt->complete.cmd);

        if (state == ONLINE && pending.tail) {
            struct cmd_node *n = pending.tail;
            pending_send_one(n);
        }
        break;

    case EVENT_SREADY:
        printf("SREADY \n");
        if (state == OFFLINE)
            try_connect();
        break;
    }
}

/* ================= main ================= */
int main(int argc, char **argv)
{
	struct replica_bpf *skel;
    struct perf_buffer *pb = NULL;
	int err;

	/* Open BPF application */
	skel = replica_bpf__open();
	if (!skel) {
		fprintf(stderr, "Failed to open BPF skeleton\n");
		return 1;
	}

	/* Load & verify BPF programs */
	err = replica_bpf__load(skel);
	if (err) {
		fprintf(stderr, "Failed to load and verify BPF skeleton\n");
		goto cleanup;
	}

	/* Attach tracepoint handler */
	err = replica_bpf__attach(skel);
	if (err) {
		fprintf(stderr, "Failed to attach BPF skeleton\n");
		goto cleanup;
	}

	printf("Successfully started! Please run `sudo cat /sys/kernel/debug/tracing/trace_pipe` "
	       "to see output of the BPF programs.\n");


	pb = perf_buffer__new(bpf_map__fd(skel->maps.events), 8,
                 handle_event, NULL, NULL, NULL);

	if(!pb){
		goto cleanup;
	}

	while (1) {
        perf_buffer__poll(pb, 1000);  // 处理事件
    }

	perf_buffer__free(pb);

cleanup:
	pending_free();
	if (sockfd >= 0) close(sockfd);
	replica_bpf__destroy(skel);
	return -err;
}