//! Unit tests for the 9web multiplexer (web/mux.zig): one shared upstream 9P
//! connection fanned out to several downstream sessions. The upstream is an
//! in-process `serve.Runner` over an `fs.Server` backend with a blocking
//! "event" file (its reads park until a write to "data" wakes them). The tests
//! drive the mux with hand-built 9P frames and check fid isolation, a parked
//! read released by a 9P-side write, Tflush forwarding, and reconnection with
//! downstream fids invalidated.
const std = @import("std");
const c9 = @import("cloud9");
const mux = @import("mux");
const wire = c9.wire;
const fs = c9.fs;
const serve = c9.serve;
const transport = c9.transport;
const Io = std.Io;
const testing = std.testing;

const msize = 8192;
const M = mux.Mux(.{ .msize = msize, .upstream_fids = 64, .fids_per_conn = 32, .downstreams = 8 });

// -- the upstream backend: root/{event,data} ---------------------------------

const root_node = 1;
const event_node = 2;
const data_node = 3;

const EventFs = struct {
    pub const Req = fs.Req;
    pub const Reply = fs.Reply;

    mutex: Io.Mutex = .init,
    posted: ?[]const u8 = null,
    store: [256]u8 = undefined,

    fn attrOf(node: u64) fs.Attr {
        return switch (node) {
            root_node => .{ .name = "/", .node = root_node, .dir = true, .mode = 0o500 },
            event_node => .{ .name = "event", .node = event_node, .mode = 0o400 },
            data_node => .{ .name = "data", .node = data_node, .mode = 0o600 },
            else => unreachable,
        };
    }
};

const Runner = serve.Runner(EventFs, .{ .fid_capacity = 32, .slot_capacity = 8 }, .{ .msize = msize, .connections = 2, .listeners = 1 });

fn serveFn(ctx: ?*anyopaque, conn: *Runner.Conn, req: fs.Req) void {
    const st: *EventFs = @ptrCast(@alignCast(ctx.?));
    st.mutex.lockUncancelable(testing.io);
    defer st.mutex.unlock(testing.io);
    const fail: fs.Reply = .fail(req.tag, fs.E.NOENT);
    switch (req.op) {
        .lookup => {
            if (std.mem.eql(u8, req.data, "..")) return conn.reply(&.{ .tag = req.tag, .attr = EventFs.attrOf(root_node) }, "");
            if (std.mem.eql(u8, req.data, "event")) return conn.reply(&.{ .tag = req.tag, .attr = EventFs.attrOf(event_node) }, "");
            if (std.mem.eql(u8, req.data, "data")) return conn.reply(&.{ .tag = req.tag, .attr = EventFs.attrOf(data_node) }, "");
            return conn.reply(&fail, "");
        },
        .getattr, .setattr => conn.reply(&.{ .tag = req.tag, .attr = EventFs.attrOf(req.node) }, ""),
        .open => conn.reply(&.{ .tag = req.tag, .handle = 7 }, ""),
        .release => conn.reply(&.{ .tag = req.tag }, ""),
        .readdir => conn.reply(&.{ .tag = req.tag }, ""),
        .read => {
            if (req.node == event_node) {
                if (st.posted) |bytes| {
                    st.posted = null;
                    return conn.reply(&.{ .tag = req.tag }, bytes);
                }
                return conn.reply(&.{ .tag = req.tag, .status = .again }, "");
            }
            conn.reply(&.{ .tag = req.tag }, ""); // data reads EOF
        },
        .write => {
            const n = @min(req.data.len, st.store.len);
            @memcpy(st.store[0..n], req.data[0..n]);
            st.posted = st.store[0..n];
            conn.reply(&.{ .tag = req.tag, .written = @intCast(n) }, "");
            conn.wake(); // retry the parked event read on this connection
        },
    }
}

// -- a downstream session that captures replies -------------------------------

const Down = struct {
    m: *M,
    conn: M.Conn = undefined,
    mutex: Io.Mutex = .init,
    cond: Io.Condition = .init,
    ring: [8][msize]u8 = undefined,
    len: [8]usize = @splat(0),
    head: usize = 0,
    tail: usize = 0,
    count: usize = 0,

    fn init(d: *Down, m: *M) void {
        d.* = .{ .m = m };
        d.conn = M.Conn.init(m, .{ .ctx = d, .send = sink });
    }
    fn deinit(d: *Down) void {
        d.conn.deinit();
    }
    fn sink(ctx: *anyopaque, frame: []const u8) anyerror!void {
        const d: *Down = @ptrCast(@alignCast(ctx));
        d.mutex.lockUncancelable(testing.io);
        defer d.mutex.unlock(testing.io);
        const i = d.tail;
        const n = @min(frame.len, msize);
        @memcpy(d.ring[i][0..n], frame[0..n]);
        d.len[i] = n;
        d.tail = (i + 1) % d.ring.len;
        d.count += 1;
        d.cond.signal(testing.io);
    }
    fn send(d: *Down, frame: []const u8) void {
        d.m.forward(&d.conn, frame);
    }
    fn recv(d: *Down) !wire.Decoded {
        d.mutex.lockUncancelable(testing.io);
        defer d.mutex.unlock(testing.io);
        var tries: usize = 0;
        while (d.count == 0) : (tries += 1) {
            if (tries > 4000) return error.Timeout;
            d.cond.wait(testing.io, &d.mutex) catch return error.Canceled;
        }
        const i = d.head;
        d.head = (i + 1) % d.ring.len;
        d.count -= 1;
        return wire.decode(d.ring[i][0..d.len[i]]);
    }
};

// -- frame builders -----------------------------------------------------------

var enc_buf: [msize]u8 = undefined;
fn enc(msg: wire.Msg, tag: u16) []const u8 {
    return wire.encode(msg, tag, &enc_buf) catch unreachable;
}

fn handshake(d: *Down) !void {
    d.send(enc(.{ .tversion = .{ .msize = msize, .version = "9P2000" } }, wire.notag));
    const v = try d.recv();
    try testing.expectEqual(wire.Type.rversion, v.msg.msgType());
    d.send(enc(.{ .tattach = .{ .fid = 0, .afid = wire.nofid, .uname = "u", .aname = "" } }, 1));
    const a = try d.recv();
    try testing.expectEqual(wire.Type.rattach, a.msg.msgType());
}

fn walk1(d: *Down, newfid: u32, name: []const u8) !void {
    var wn: [wire.max_welem][]const u8 = @splat("");
    wn[0] = name;
    d.send(enc(.{ .twalk = .{ .fid = 0, .newfid = newfid, .nwname = 1, .wname = wn } }, 2));
    const r = try d.recv();
    try testing.expectEqual(wire.Type.rwalk, r.msg.msgType());
    try testing.expectEqual(@as(u16, 1), r.msg.rwalk.nwqid);
}

// -- the rig ------------------------------------------------------------------

const Rig = struct {
    dir: testing.TmpDir,
    path_buf: [std.fs.max_path_bytes]u8 = undefined,
    sock_buf: [transport.sun_path_len]u8 = undefined,
    sock: [:0]const u8 = undefined,
    fsx: EventFs = .{},
    runner: *Runner = undefined,
    m: *M = undefined,
    reader: Io.Future(void) = undefined,

    fn start(r: *Rig) !void {
        const io = testing.io;
        r.dir = testing.tmpDir(.{});
        const plen = try r.dir.dir.realPath(io, &r.path_buf);
        r.sock = try std.fmt.bufPrintSentinel(&r.sock_buf, "{s}/up", .{r.path_buf[0..plen]}, 0);
        r.runner = try testing.allocator.create(Runner);
        r.runner.init(.{ .io = io, .root = root_node, .handler = .{ .serve = serveFn, .ctx = &r.fsx } });
        _ = try r.runner.listen(.{ .unix = r.sock }, 4);
        r.m = try testing.allocator.create(M);
        r.m.init(io, .{ .network = .{ .unix = r.sock } }, "u", "");
        try r.m.connect();
        r.reader = try io.concurrent(M.readerLoop, .{r.m});
    }

    fn stopUpstream(r: *Rig) void {
        r.runner.stop();
        Io.Dir.cwd().deleteFile(testing.io, r.sock) catch {};
    }

    fn restartUpstream(r: *Rig) !void {
        r.runner.init(.{ .io = testing.io, .root = root_node, .handler = .{ .serve = serveFn, .ctx = &r.fsx } });
        _ = try r.runner.listen(.{ .unix = r.sock }, 4);
    }

    fn end(r: *Rig) void {
        r.m.stop();
        r.reader.cancel(testing.io);
        r.runner.stop();
        testing.allocator.destroy(r.runner);
        testing.allocator.destroy(r.m);
        r.dir.cleanup();
    }
};

test "mux: two downstreams share one upstream with isolated fids" {
    var rig: Rig = .{ .dir = undefined };
    try rig.start();
    defer rig.end();
    var a: Down = undefined;
    a.init(rig.m);
    defer a.deinit();
    var b: Down = undefined;
    b.init(rig.m);
    defer b.deinit();
    try handshake(&a);
    try handshake(&b);
    // Both use downstream fid 1; the mux maps them to distinct upstream fids.
    try walk1(&a, 1, "event");
    try walk1(&b, 1, "data");
    // A opens its event; B opens its data. Independent handles.
    a.send(enc(.{ .topen = .{ .fid = 1, .mode = c9.oread } }, 3));
    try testing.expectEqual(wire.Type.ropen, (try a.recv()).msg.msgType());
    b.send(enc(.{ .topen = .{ .fid = 1, .mode = c9.owrite } }, 3));
    try testing.expectEqual(wire.Type.ropen, (try b.recv()).msg.msgType());
}

test "mux: a parked read is released by another downstream's write" {
    var rig: Rig = .{ .dir = undefined };
    try rig.start();
    defer rig.end();
    var a: Down = undefined;
    a.init(rig.m);
    defer a.deinit();
    var b: Down = undefined;
    b.init(rig.m);
    defer b.deinit();
    try handshake(&a);
    try handshake(&b);
    try walk1(&a, 1, "event");
    try walk1(&b, 1, "data");
    a.send(enc(.{ .topen = .{ .fid = 1, .mode = c9.oread } }, 3));
    _ = try a.recv();
    b.send(enc(.{ .topen = .{ .fid = 1, .mode = c9.owrite } }, 3));
    _ = try b.recv();
    // A's read parks upstream (no reply yet).
    a.send(enc(.{ .tread = .{ .fid = 1, .offset = 0, .count = 128 } }, 4));
    try testing.io.sleep(.fromMilliseconds(30), .awake);
    // B writes "hello", which posts the event and wakes A's parked read.
    b.send(enc(.{ .twrite = .{ .fid = 1, .offset = 0, .data = "hello" } }, 4));
    try testing.expectEqual(wire.Type.rwrite, (try b.recv()).msg.msgType());
    const rr = try a.recv();
    try testing.expectEqual(wire.Type.rread, rr.msg.msgType());
    try testing.expectEqualStrings("hello", rr.msg.rread.data);
}

test "mux: Tflush is forwarded and cancels a parked read" {
    var rig: Rig = .{ .dir = undefined };
    try rig.start();
    defer rig.end();
    var a: Down = undefined;
    a.init(rig.m);
    defer a.deinit();
    try handshake(&a);
    try walk1(&a, 1, "event");
    a.send(enc(.{ .topen = .{ .fid = 1, .mode = c9.oread } }, 3));
    _ = try a.recv();
    a.send(enc(.{ .tread = .{ .fid = 1, .offset = 0, .count = 128 } }, 5));
    try testing.io.sleep(.fromMilliseconds(30), .awake);
    a.send(enc(.{ .tflush = .{ .oldtag = 5 } }, 6));
    // Expect the interrupted read (Rerror) and the Rflush, in either order.
    var saw_err = false;
    var saw_flush = false;
    for (0..2) |_| {
        const got = try a.recv();
        switch (got.msg.msgType()) {
            .rerror => saw_err = true,
            .rflush => saw_flush = true,
            else => return error.Unexpected,
        }
    }
    try testing.expect(saw_err and saw_flush);
}

test "mux: an upstream drop errors downstream, and it reconnects" {
    var rig: Rig = .{ .dir = undefined };
    try rig.start();
    defer rig.end();
    var a: Down = undefined;
    a.init(rig.m);
    defer a.deinit();
    try handshake(&a);
    try walk1(&a, 1, "event");
    // Drop the upstream. An in-flight/next request must error, not hang.
    rig.stopUpstream();
    try testing.io.sleep(.fromMilliseconds(50), .awake);
    a.send(enc(.{ .tstat = .{ .fid = 1 } }, 7));
    const err = try a.recv();
    try testing.expectEqual(wire.Type.rerror, err.msg.msgType());
    // Bring the upstream back; the mux reconnects and a fresh attach works.
    try rig.restartUpstream();
    var tries: usize = 0;
    while (tries < 200) : (tries += 1) {
        try testing.io.sleep(.fromMilliseconds(20), .awake);
        if (std.mem.eql(u8, rig.m.upstreamState(), "connected")) break;
    }
    var b: Down = undefined;
    b.init(rig.m);
    defer b.deinit();
    try handshake(&b); // a new session on the reconnected upstream
    try testing.expect(rig.m.reconnectCount() >= 1);
}