//! PS/2 Mouse Driver
//!
//! Spawned by the ps2-bus driver once the controller is initialized and the port
//! has passed its interface test and device reset. The bus driver hands us our
//! device HID as argv[1].
//!
//! Like the keyboard, this driver never touches the hardware: the 8042's ports
//! and both port IRQs are owned by the ps2-bus driver (the auxiliary port's
//! IRQ12 lives on the PNP0F13 node, which the bus claims alongside the
//! controller). The driver **attaches** to the bus and receives every byte the
//! mouse sends as a forwarded asynchronous message. The bytes assemble into
//! three-byte packets, and each packet becomes input-protocol events:
//!
//!   packet -> button transitions -> button_down / button_up
//!          -> movement            -> motion (dx/dy, screen convention)

const std = @import("std");
const runtime = @import("runtime");
const ps2 = @import("ps2-library.zig");
const mouse_packet = @import("mouse-packet.zig");
const device = runtime.device;
const ipc = runtime.ipc;
const protocol = runtime.input_protocol;

fn writeLine(comptime fmt: []const u8, arguments: anytype) void {
    var line: [128]u8 = undefined;
    _ = runtime.system.write(std.fmt.bufPrint(&line, fmt, arguments) catch return);
}

/// Look up the ps2-bus service, retrying while the bus (which spawned us before
/// registering) is still coming up.
fn lookupBus() ?ipc.Handle {
    var attempts: usize = 0;
    while (attempts < 100) : (attempts += 1) {
        if (ipc.lookup(.ps2_bus)) |handle| return handle;
        runtime.system.sleep(50);
    }
    return null;
}

/// The protocol's pressed-button bitmask for a packet.
fn buttonMask(packet: mouse_packet.Packet) u32 {
    var mask: u32 = 0;
    if (packet.left) mask |= protocol.mouse_button_left;
    if (packet.right) mask |= protocol.mouse_button_right;
    if (packet.middle) mask |= protocol.mouse_button_middle;
    return mask;
}

pub fn main(init: runtime.process.Init) void {
    const hid = init.arguments.get(1).?;

    if (hid.len == 0) {
        _ = runtime.system.write("/system/drivers/ps2-bus/mouse: no HID argument\n");
        return;
    }
    writeLine("/system/drivers/ps2-bus/mouse: starting for hid {s}\n", .{hid});

    const buffer = runtime.allocator().alloc(device.DeviceDescriptor, 64) catch {
        _ = runtime.system.write("/system/drivers/ps2-bus/mouse: out of memory\n");
        return;
    };
    if (device.findDeviceDescriptorByHid(buffer, hid) == null) {
        writeLine("/system/drivers/ps2-bus/mouse: no device for hid {s}\n", .{hid});
        return;
    }

    // Attach to the bus: hand it our endpoint, and it forwards every byte the
    // mouse sends (it owns the controller; we own the decoding).
    const bus = lookupBus() orelse {
        _ = runtime.system.write("/system/drivers/ps2-bus/mouse: ps2-bus service unavailable\n");
        return;
    };
    const endpoint = ipc.createIpcEndpoint() orelse {
        _ = runtime.system.write("/system/drivers/ps2-bus/mouse: no endpoint\n");
        return;
    };
    var attach = ps2.AttachRequest{ .device_type = @intFromEnum(ps2.DeviceType.mouse) };
    var attach_reply: [@sizeOf(ps2.AttachReply)]u8 = undefined;
    const attached = ipc.callCap(bus, std.mem.asBytes(&attach), &attach_reply, endpoint) catch {
        _ = runtime.system.write("/system/drivers/ps2-bus/mouse: attach call failed\n");
        return;
    };
    if (attached.len < @sizeOf(ps2.AttachReply) or
        std.mem.bytesToValue(ps2.AttachReply, attach_reply[0..@sizeOf(ps2.AttachReply)]).status != @intFromEnum(ps2.AttachStatus.ok))
    {
        _ = runtime.system.write("/system/drivers/ps2-bus/mouse: attach refused\n");
        return;
    }

    // Broadcast mouse events through the input service so programs can listen
    // for them (docs/input.md).
    var source = runtime.input.connectSource() orelse {
        _ = runtime.system.write("/system/drivers/ps2-bus/mouse: input service unavailable\n");
        return;
    };
    _ = runtime.system.write("/system/drivers/ps2-bus/mouse: ok\n");

    var assembler = mouse_packet.Assembler{};
    var buttons: u32 = 0;
    var receive: [@sizeOf(ps2.ForwardedByte)]u8 = undefined;
    while (true) {
        const got = ipc.replyWait(endpoint, &.{}, &receive, null);
        if (!got.isMessage() or got.len < @sizeOf(ps2.ForwardedByte)) continue;
        const forwarded = std.mem.bytesToValue(ps2.ForwardedByte, receive[0..@sizeOf(ps2.ForwardedByte)]);

        const packet = assembler.feed(@intCast(forwarded.byte & 0xFF)) orelse continue;
        const new_buttons = buttonMask(packet);

        // A button transition per changed button, carrying the new whole mask.
        const changed = buttons ^ new_buttons;
        for ([_]u32{ protocol.mouse_button_left, protocol.mouse_button_right, protocol.mouse_button_middle }) |button| {
            if (changed & button == 0) continue;
            const kind: protocol.MouseEventKind = if (new_buttons & button != 0) .button_down else .button_up;
            _ = source.publishMouseEvent(.{
                .kind = @intFromEnum(kind),
                .button = button,
                .dx = 0,
                .dy = 0,
                .scroll_x = 0,
                .scroll_y = 0,
                .buttons = new_buttons,
            });
        }
        buttons = new_buttons;

        if (packet.dx != 0 or packet.dy != 0) {
            _ = source.publishMouseEvent(.{
                .kind = @intFromEnum(protocol.MouseEventKind.motion),
                .button = 0,
                .dx = packet.dx,
                .dy = packet.dy,
                .scroll_x = 0,
                .scroll_y = 0,
                .buttons = new_buttons,
            });
        }
    }
}