Backlog/engine/net/src/enet/EnetTransport.zig

pub var TransportInterfaceVTable = net.TransportInterface.Implement(@This());
pub var NeonObjectTable: core.EngineObjectVTable = core.EngineObjectVTable.from(@This(), "net.ENetTransport");

allocator: std.mem.Allocator = undefined,
sessions: std.ArrayListUnmanaged(*net.Session) = .{},
deadSessions: std.ArrayListUnmanaged(*net.Session) = .{},

const MAX_CLIENTS = 128;
const DEFAULT_PORT = 7777;
const ConnectionTimeout = 10000;

const UnreliableChannel = 0;
const ReliableChannel = 1;
const ChannelCount = 1;

// to implement the new links and sessions interface.
//
const QueuedLinkData = struct {
    bytes: []u8,
    reliable: bool,
};

const ENetLinkData = struct {
    peer: [*c]enet.ENetPeer,
    link: *net.Link,

    // todo- split into reliable and unreliable
    // also maybe move to the upper level net.Link instead of LinkData
    queuedMessages: core.RingQueueU(QueuedLinkData),

    testLinkPosition: core.Vectorf = .{},

    pub fn destroy(self: *@This(), allocator: std.mem.Allocator) void {
        self.queuedMessages.deinit();
        allocator.destroy(self);
    }

    pub fn queuePacketData(self: *@This(), bytes: []const u8, reliable: bool) void {
        const allocator = net.netAllocator();
        self.queuedMessages.push(.{
            .bytes = allocator.dupe(u8, bytes) catch unreachable,
            .reliable = reliable,
        }) catch unreachable;
    }

    pub fn readDebugVector(self: *@This(), data: []const u8) void {
        self.testLinkPosition = @as(*const core.Vectorf, @ptrCast(@alignCast(data.ptr))).*;
        //core.engine_log("reading vector position: {d} {d} {d}", self.testLinkPosition);
    }

    pub fn pushDebugLoc(self: *@This()) void {
        // const x = self.testLinkPosition;
        // core.engine_log("sending vector position: {d} {d} {d}", x);

        const allocator = net.netAllocator();
        self.queuedMessages.push(.{
            .bytes = allocator.dupe(u8, &@as([@sizeOf(core.Vectorf)]u8, @bitCast(self.testLinkPosition))) catch unreachable,
            .reliable = true,
        }) catch unreachable;
    }

    pub fn sendPacketChannelDebug(self: *@This(), bytes: []const u8, reliable: bool, channel: u8) void {
        if (enet.enet_packet_create(bytes.ptr, bytes.len, if (reliable) enet.ENET_PACKET_FLAG_RELIABLE else 0)) |packet| {
            _ = enet.enet_peer_send(self.peer, channel, packet);
        }
    }

    // raw access to sendPacket
    pub fn sendPacket(self: *@This(), bytes: []const u8, reliable: bool) void {
        if (enet.enet_packet_create(bytes.ptr, bytes.len, if (reliable) enet.ENET_PACKET_FLAG_RELIABLE else 0)) |packet| {
            _ = enet.enet_peer_send(self.peer, if (reliable) 0 else 1, packet);
        }
    }
};

const ENetTransport = @This();

const ENetSessionData = struct {
    address: enet.ENetAddress,
    host: [*c]enet.ENetHost,
    session: *net.Session,
    messageCount: u32 = 0,

    debugTick: f64 = 0.05,

    pub fn findLinkByPeer(self: *@This(), peer: [*c]enet.ENetPeer) ?*net.Link {
        for (self.session.links.items) |link| {
            if (getLinkData(link).peer == peer) {
                return link;
            }
        }
        return null;
    }

    pub fn tick(self: *@This(), dt: f64) void {
        var event: enet.ENetEvent = undefined;

        // Service the host with a 1000ms timeout
        const result = enet.enet_host_service(self.host, &event, 0);

        if (result > 0) {
            switch (event.type) {
                enet.ENET_EVENT_TYPE_CONNECT => {
                    // core.engine_log("a client connected, creating link", .{});
                    const welcome_msg = "msg: Welcome to ENet test server!";
                    const link = core.get(ENetTransport).createLink(self.session) catch unreachable;
                    const linkData = getLinkData(link);
                    linkData.peer = event.peer;
                    linkData.sendPacket(welcome_msg, true);
                    link.linkType = .server;
                },
                enet.ENET_EVENT_TYPE_RECEIVE => {
                    self.messageCount += 1;
                    const data = @as([*]u8, @ptrCast(event.packet.*.data))[0..event.packet.*.dataLength];
                    // core.engine_log("Received message #{d} channel {d}: '{s}' echoing it back", .{ self.messageCount, event.channelID, data });

                    if (self.findLinkByPeer(event.peer)) |link| {
                        const linkData = getLinkData(link);
                        if (link.linkType == .server) {
                            // linkData.queuePacketData(data, true);
                            if (std.mem.startsWith(u8, data, "cname:")) {
                                const ipAsString = net.ip2String(net.netAllocator(), event.peer.*.address.host) catch unreachable;
                                const id = std.fmt.allocPrint(net.netAllocator(), "{s}@{s}", .{ data[6..data.len], ipAsString }) catch unreachable;
                                link.idString = id;
                            }
                        }
                        if (link.linkType == .client) {
                            if (!std.mem.startsWith(u8, data, "msg:")) {
                                linkData.readDebugVector(data);
                            }
                        }
                    }

                    // Destroy the received packet
                    enet.enet_packet_destroy(event.packet);
                },
                else => {},
            }
        }

        for (self.session.links.items) |link| {
            const linkData = getLinkData(link);

            self.debugTick -= dt;
            if (self.debugTick < 0) {
                self.debugTick = 0.05;
                if (link.linkType == .server) {
                    linkData.pushDebugLoc();
                }
            }

            while (linkData.queuedMessages.pop()) |queuedData| {
                linkData.sendPacket(queuedData.bytes, queuedData.reliable);
                net.netAllocator().free(queuedData.bytes);
            }
        }

        enet.enet_host_flush(self.host);
    }
};

pub fn create(self: *@This(), allocator: std.mem.Allocator, first: bool) !*@This() {
    if (!first)
        return;

    self.* = .{
        .allocator = allocator,
    };

    try enet_mod.initialize();

    return self;
}

fn createSession(self: *@This(), address: ?enet.ENetAddress) !*net.Session {
    const session = try net.netAllocator().create(net.Session);
    session.* = .{
        .transportName = "ENet",
        .transport = .{ .vtable = TransportInterfaceVTable, .ptr = self },
        .allocator = net.netAllocator(),
    };

    const transportData = try net.netAllocator().create(ENetSessionData);
    transportData.session = session;

    if (address != null) {
        transportData.address = address.?;
        transportData.host = enet.enet_host_create(&transportData.address, MAX_CLIENTS, 2, 0, 0) orelse {
            return error.ServerStartFailed;
        };
        net.log("host created on port {d}", .{address.?.port});
    } else {
        transportData.host = enet.enet_host_create(null, 1, 2, 0, 0) orelse {
            return error.ClientStartFailed;
        };
        transportData.address = .{
            .host = 0,
            .port = 0,
        };
        net.log("client session created", .{});
    }

    session.transportData = transportData;
    try self.sessions.append(self.allocator, session);

    return session;
}

pub fn hostSession(self: *@This(), bindInfo: ?[]const []const u8) !*net.Session {
    const port: u16 = try std.fmt.parseInt(u16, bindInfo.?[0], 0);
    const session = try self.createSession(enet.ENetAddress{
        .host = enet.ENET_HOST_ANY,
        .port = port,
    });

    return session;
}

pub fn endSession(self: *@This(), session: *net.Session) void {
    if (session.transportData) |transportData| {
        const td = core.cast(*ENetSessionData, transportData);
        enet.enet_host_destroy(td.host);
    }

    for (self.sessions.items, 0..) |s, i| {
        if (s == session) {
            _ = self.sessions.orderedRemove(i);
            return;
        }
    }
}

pub fn printIp(ip: u32) void {
    core.engine_log("{d}.{d}.{d}.{d}", .{
        (ip >> 0) & 0xFF,
        (ip >> 8) & 0xFF,
        (ip >> 16) & 0xFF,
        (ip >> 24) & 0xFF,
    });
}

pub fn parseConnectTarget(allocator: std.mem.Allocator, in: []const u8) !struct {
    port: u16,
    address: [:0]u8,
} {
    var portStr: ?[]const u8 = null;
    var base: []const u8 = in;

    var j: usize = in.len;
    while (j > 0) : (j -= 1) {
        const i = j - 1;

        if (in[i] == ':') {
            portStr = in[j..in.len];
            base = in[0..i];
            break;
        }
    }

    var p: u16 = DEFAULT_PORT;

    if (portStr) |ps| {
        p = try std.fmt.parseInt(u16, ps, 10);
    }

    return .{ .port = p, .address = try std.fmt.allocPrintSentinel(allocator, "{s}", .{base}, 0) };
}

pub fn createLink(self: *@This(), session: *net.Session) !*net.Link {
    const newLink = try net.netAllocator().create(net.Link);

    newLink.* = .{
        .transport = .{ .vtable = TransportInterfaceVTable, .ptr = self },
        .allocator = net.netAllocator(),
    };
    // errdefer newLink.destroy();

    const linkInfo = try net.netAllocator().create(ENetLinkData);
    errdefer self.allocator.destroy(linkInfo);

    linkInfo.* = .{
        .link = newLink,
        .peer = null,
        .queuedMessages = try core.RingQueueU(QueuedLinkData).init(net.netAllocator(), 4092),
    };

    newLink.transportData = linkInfo;
    newLink.session = session;

    try session.addLink(newLink);

    return newLink;
}

pub fn getSessionData(session: *net.Session) *ENetSessionData {
    return core.cast(*ENetSessionData, session.transportData.?);
}

pub fn getLinkData(link: *net.Link) *ENetLinkData {
    return core.cast(*ENetLinkData, link.transportData.?);
}

// creates a session and a link with that session, to the host
pub fn connect(self: *@This(), target: []const u8) !*net.Link {
    const rv = try parseConnectTarget(self.allocator, target);
    defer self.allocator.free(rv.address);

    // parse address to target
    const session = try self.createSession(null);
    errdefer {
        session.skipEndSession = true;
        session.destroy();
    }

    const newLink = try self.createLink(session);
    newLink.linkType = .client;
    const linkData = core.cast(*ENetLinkData, newLink.transportData.?);

    // Set up server address
    const sessionInfo = getSessionData(session);

    // Resolve server hostname
    if (enet.enet_address_set_host(&sessionInfo.address, rv.address.ptr) != 0) {
        std.debug.print("Failed to resolve server address: {s}\n", .{rv.address});
        return error.AddressResolutionFailed;
    }

    sessionInfo.address.port = rv.port;

    // Connect to server
    linkData.peer = enet.enet_host_connect(sessionInfo.host, &sessionInfo.address, ChannelCount, 0);
    if (linkData.peer == null) {
        std.debug.print("Failed to create connection to server\n", .{});
        return error.ConnectionFailed;
    }

    std.debug.print("connecting to server [{s}] [{d}]\n", .{ rv.address, rv.port });
    var event: enet.ENetEvent = undefined;
    if (enet.enet_host_service(sessionInfo.host.?, &event, ConnectionTimeout) > 0 and event.type == enet.ENET_EVENT_TYPE_CONNECT) {
        std.debug.print("Connected to server successfully!\n", .{});
        newLink.state = .connecting;
        newLink.session = session;
    } else {
        std.debug.print("Failed to connect to server within timeout event.type {d} \n", .{event.type});
        enet.enet_peer_reset(linkData.peer);
        return error.ConnectionTimeout;
    }

    return newLink;
}

pub fn endLink(self: *@This(), link: *net.Link) void {
    const linkData = getLinkData(link);

    enet.enet_peer_reset(linkData.peer);

    net.netAllocator().destroy(linkData);
    self.deadSessions.append(self.allocator, link.session.?) catch {};
}

pub fn sendMessageLink(self: *@This(), link: *net.Link, data: []const u8, reliable: bool) !void {
    _ = self;

    const linkData = getLinkData(link);
    linkData.queuePacketData(data, reliable);
}

pub fn preTick(self: *@This(), dt: f64) !void {
    //switch (self.peerType) {
    // .server => {
    // self.tickServer(dt);
    // },
    // .client => {
    // self.tickClient(dt);
    // },
    //else => {},
    // }

    for (self.sessions.items) |session| {
        const sessionInfo = getSessionData(session);
        sessionInfo.tick(dt);

        // tick messages in here
    }
}

//pub fn tickServer(self: *@This(), dt: f64) void {
// }

pub fn tickClient(self: *@This(), dt: f64) void {
    _ = self;
    _ = dt;
}

pub fn destroy(self: *@This()) void {
    for (self.sessions.items) |session| {
        session.destroy();
    }
    self.sessions.deinit(self.allocator);
    self.deadSessions.deinit(self.allocator);

    enet_mod.deinitialize();
}

const core = @import("core");
const net = @import("../net.zig");
const std = @import("std");
const enet_mod = @import("enet");
const enet = enet_mod.c;