zits/src/server/main.zig

const std = @import("std");
const Message = @import("./message_parser.zig").Message;
pub const ServerInfo = Message.ServerInfo;

const ClientState = @import("./client.zig").ClientState;
const Server = @This();

info: ServerInfo,
clients: std.AutoHashMapUnmanaged(usize, *ClientState) = .empty,
/// Map of subjects to a map of (client ID => SID)
subscriptions: std.StringHashMapUnmanaged(std.AutoHashMapUnmanaged(usize, []const u8)) = .empty,

var keep_running = std.atomic.Value(bool).init(true);

fn handleSigInt(sig: std.os.linux.SIG) callconv(.c) void {
    _ = sig;
    keep_running.store(false, .monotonic);
}

pub fn main(gpa: std.mem.Allocator, server_config: ServerInfo) !void {
    // Configure the signal action
    // const act = std.posix.Sigaction{
    //     .handler = .{ .handler = handleSigInt },
    //     .mask = std.posix.sigemptyset(),
    //     .flags = 0,
    // };

    // // Register the handler for SIGINT (Ctrl+C)
    // std.posix.sigaction(std.posix.SIG.INT, &act, null);

    var server: Server = .{
        .info = server_config,
    };

    var threaded: std.Io.Threaded = .init(gpa);
    defer threaded.deinit();
    const io = threaded.io();

    var tcp_server = try std.Io.net.IpAddress.listen(try std.Io.net.IpAddress.parse(
        server.info.host,
        server.info.port,
    ), io, .{});
    defer tcp_server.deinit(io);

    var id: usize = 0;
    // Run until SIGINT is handled, then exit gracefully
    while (keep_running.load(.monotonic)) : (id +%= 1) {
        std.debug.print("in server loop\n", .{});
        if (server.clients.contains(id)) continue;
        const stream = try tcp_server.accept(io);
        std.debug.print("accepted connection\n", .{});
        _ = io.concurrent(handleConnection, .{ &server, gpa, io, id, stream }) catch {
            std.debug.print("could not start concurrent handler for {d}\n", .{id});
            stream.close(io);
        };
    }

    std.debug.print("Exiting gracefully\n", .{});
}

fn addClient(server: *Server, allocator: std.mem.Allocator, id: usize, client: *ClientState) !void {
    // server.clients.lockPointers();
    try server.clients.put(allocator, id, client);
    // server.clients.unlockPointers();
}

fn removeClient(server: *Server, allocator: std.mem.Allocator, id: usize) void {
    // TODO: implement
    _ = server;
    _ = allocator;
    _ = id;
}

fn handleConnection(
    server: *Server,
    server_allocator: std.mem.Allocator,
    io: std.Io,
    id: usize,
    stream: std.Io.net.Stream,
) !void {
    var client_allocator: std.heap.DebugAllocator(.{}) = .init;
    client_allocator.backing_allocator = server_allocator;
    defer {
        std.debug.print("deinitializing debug allocator\n", .{});
        _ = client_allocator.deinit();
    }
    const allocator = client_allocator.allocator();
    defer stream.close(io);
    var w_buffer: [1024]u8 = undefined;
    var writer = stream.writer(io, &w_buffer);
    const out = &writer.interface;

    std.debug.print("out pointer in client handler: {*}\n", .{out});

    var r_buffer: [8192]u8 = undefined;
    var reader = stream.reader(io, &r_buffer);
    const in = &reader.interface;

    @import("./client.zig").writeInfo(out, server.info) catch return;
    var connect_arena: std.heap.ArenaAllocator = .init(allocator);
    defer connect_arena.deinit();
    const connect = (Message.next(connect_arena.allocator(), in) catch return).connect;
    var client_state: ClientState = try .init(io, allocator, id, connect, in, out);
    defer client_state.deinit(io, allocator);

    try server.addClient(allocator, id, &client_state);
    defer server.removeClient(allocator, id);

    while (client_state.next(allocator)) |msg| {
        std.debug.print("message from client: {any}\n", .{msg});
        switch (msg) {
            .ping => {
                // Respond to ping with pong.
                for (0..5) |_| {
                    if (try client_state.send(io, .pong)) {
                        break;
                    }
                } else {}
            },
            .@"pub" => |@"pub"| {
                std.debug.print("pub: {any}\n", .{@"pub"});
                try server.publishMessage(io, @"pub");
                if (client_state.connect.connect.verbose) {
                    std.debug.print("server IS sending +ok\n", .{});
                    _ = try client_state.send(io, .@"+ok");
                } else {
                    std.debug.print("server NOT sending +ok\n", .{});
                }
            },
            .sub => |sub| {
                try server.subscribe(allocator, client_state.id, sub);
            },
            .unsub => |unsub| {
                try server.unsubscribe(client_state.id, unsub);
            },
            else => |e| {
                std.debug.panic("Unimplemented message: {any}\n", .{e});
            },
        }

        std.debug.print("processed message from client\n", .{});
        std.debug.print("awaiting next message from client\n", .{});
    } else |err| {
        // This is probably going to be normal on disconnect
        std.debug.print("Ran into error in client process loop: {}\n", .{err});
    }

    // client_state.task.await(io);
}

// // Result is owned by the caller
// fn subscribers(server: *Server, gpa: std.mem.Allocator, subject: []const u8) []ClientState {
//     var acc: std.ArrayList(ClientState) = .empty;

//     return acc.toOwnedSlice();
// }

fn publishMessage(server: *Server, io: std.Io, msg: Message.Pub) !void {
    if (server.subscriptions.get(msg.subject)) |subs| {
        var subs_iter = subs.iterator();
        while (subs_iter.next()) |sub| {
            const client_id = sub.key_ptr.*;
            const sid = sub.value_ptr.*;

            const client = server.clients.getPtr(client_id) orelse {
                std.debug.print("trying to publish to a client that no longer exists: {d}", .{client_id});
                continue;
            };

            _ = try client.*.send(io, .{ .msg = .{
                .subject = msg.subject,
                .sid = sid,
                .reply_to = msg.reply_to,
                .payload = msg.payload,
            } });
        }
    } else {
        std.debug.print("no subs on {s}\n", .{msg.subject});
    }
}

fn subscribe(server: *Server, gpa: std.mem.Allocator, id: usize, msg: Message.Sub) !void {
    std.debug.print("Recieved SUBSCRIBE message: {any}\n\n", .{msg});
    var subs_for_subject: std.AutoHashMapUnmanaged(usize, []const u8) = if (server.subscriptions.fetchRemove(msg.subject)) |s| s.value else .empty;
    try subs_for_subject.put(gpa, id, msg.sid);
    try server.subscriptions.put(gpa, msg.subject, subs_for_subject);
}

fn unsubscribe(server: *Server, id: usize, msg: Message.Unsub) !void {
    // Get the subscription in subscriptions by looping over all the subjects,
    // and getting the SID for that subject for the current client ID.
    // If the SID matches, remove the kv for the client ID from subscriptions for that subject.
    // If the value for that subject is empty, remove the subject.
    var subscriptions_iter = server.subscriptions.iterator();
    while (subscriptions_iter.next()) |*subs_for_sub| {
        if (subs_for_sub.value_ptr.get(id)) |client_sub| {
            if (std.mem.eql(u8, client_sub, msg.sid)) {
                _ = subs_for_sub.value_ptr.*.remove(id);
                if (subs_for_sub.value_ptr.count() == 0) {
                    _ = server.subscriptions.remove(subs_for_sub.key_ptr.*);
                }
                break;
            }
        }
    }
}

pub fn createId() []const u8 {
    return "SERVERID";
}

pub fn createName() []const u8 {
    return "SERVERNAME";
}

// TESTING

// fn initTestServer() Server {
//     return .{
//         .info = .{
//             .server_id = "ABCD",
//             .server_name = "test server",
//             .version = "0.1.2",
//             .max_payload = 1234,
//         },
//     };
// }

// fn initTestClient(
//     io: std.Io,
//     allocator: std.mem.Allocator,
//     id: usize,
//     data_from: []const u8,
// ) !struct {
//     Client,
//     *std.Io.Reader,
//     *std.Io.Writer,
// } {
//     return .init(io, allocator, id, .{}, in, out);
// }

// test {
//     const gpa = std.testing.allocator;
//     const io = std.testing.io;

//     const server = initTestServer();
//     const client: Client = .init(
//         io,
//         gpa,
//         1,
//         .{},
//     );
// }