//
// Created by epagris on 2022.12.09..
//

#include <stdlib.h>
#include "dhcp.h"
#include "../../dynmem.h"
#include "../../utils.h"
#include "../../connection_block.h"
#include "../conn_blocks/udp_connblock.h"

static struct {
   DhcpState state;
   void * buf;
   ConnBlock connb;
   uint32_t tranId;
} s;

static const uint8_t DHCP_MAGIC_COOKIE[] = { 99, 130, 83, 99 };

#define SNAME_LEN (64)
#define FILE_LEN (128)

// (Exact copy of the standard.)
typedef enum {
    DHCPDISCOVER = 1,
    DHCPOFFER = 2,
    DHCPREQUEST = 3,
    DHCPDECLINE = 4,
    DHCPACK = 5,
    DHCPNAK = 6,
    DHCPRELEASE = 7
} DhcpMsgType;

static void dhcp_option_insert_msg_type(uint8_t ** bufPtr, int msgType) {
    (*bufPtr)[0] = 0x35;
    (*bufPtr)[1] = 1;
    (*bufPtr)[2] = msgType;
    (*bufPtr) += 3;
}

static void dhcp_option_insert_max_msg_size(uint8_t ** bufPtr, uint16_t maxSize) {
    (*bufPtr)[0] = 0x39;
    (*bufPtr)[1] = 2;
    (*bufPtr)[2] = (maxSize >> 8) & 0xFF;
    (*bufPtr)[3] = maxSize & 0xFF;
    (*bufPtr) += 4;
}

static void dhcp_option_insert_end(uint8_t ** bufPtr) {
    (*bufPtr)[0] = 0xFF;
    (*bufPtr) += 1;
}

static void dhcp_send(EthInterface * intf, DhcpOps * ops) {
    // construct message
    uint8_t * buf = (uint8_t *)s.buf;
    memset(buf, 0, DHCP_MIN_PACKET_SIZE);
    FILL_BYTE_ADVANCE(buf, &(ops->op));
    FILL_BYTE_ADVANCE(buf, &(ops->htype));
    FILL_BYTE_ADVANCE(buf, &(ops->hlen));
    FILL_BYTE_ADVANCE(buf, &(ops->hops));
    FILL_DWORD_H2N_ADVANCE(buf, ops->xid);
    FILL_WORD_H2N_ADVANCE(buf, ops->secs);
    FILL_WORD_H2N_ADVANCE(buf, ops->flags);
    FILL_DWORD_H2N_ADVANCE(buf, ops->ciaddr);
    FILL_DWORD_H2N_ADVANCE(buf, ops->yiaddr);
    FILL_DWORD_H2N_ADVANCE(buf, ops->siaddr);
    FILL_DWORD_H2N_ADVANCE(buf, ops->giaddr);
    FILL_ADVANCE(buf, ops->chaddr, 16);
    buf += SNAME_LEN + FILE_LEN;
    FILL_ADVANCE(buf, DHCP_MAGIC_COOKIE, 4); // DHCP magic cookie

    // insert options
    dhcp_option_insert_msg_type(&buf, DHCPDISCOVER);
    dhcp_option_insert_max_msg_size(&buf, 1500);
    dhcp_option_insert_end(&buf);

    udp_sendto(&s.connb, s.buf, DHCP_MIN_PACKET_SIZE, IPv4_ANY_ADDR, DHCP_SERVER_PORT);
}

static void dhcp_discover(EthInterface * intf) {
    s.tranId = rand();
    DhcpOps ops = { 0 };

    ops.op = DHCP_BOOTREQUEST;
    ops.htype = 1;
    ops.hlen = 6;
    ops.hops = 0;
    ops.xid = s.tranId;
    ops.secs = 0;
    ops.flags = 0;
    ops.ciaddr = 0;
    ops.yiaddr = 0;
    ops.siaddr = 0;
    ops.giaddr = 0;

    memcpy(ops.chaddr, intf->mac, ETH_HW_ADDR_LEN);

    dhcp_send(intf, &ops);
}

static int dhcp_resp_cb(const Pckt * pckt) {
    return 0;
}

void dhcp_initiate(EthInterface *intf) {
    s.state = DHCP_INIT_REBOOT;
    s.buf = dynmem_alloc(DHCP_MIN_PACKET_SIZE);
    s.connb = udp_new_connblock(intf, IPv4_ANY_ADDR, DHCP_CLIENT_PORT, dhcp_resp_cb);

    dhcp_discover(intf);
}