const std = @import("std");
const c = @cImport({
    @cInclude("limits.h");
    @cInclude("X11/Xlib.h");
    @cInclude("X11/extensions/Xfixes.h");
});

fn printSelection(display: *c.Display, window: c.Window, bufname: [*c]const u8, fmtname: [*c]const u8, writer: anytype) !bool {
    var ressize: c_ulong = undefined;
    var restail: c_ulong = undefined;
    var resbits: c_int = undefined;
    var bufid = c.XInternAtom(display, bufname, c.False);
    var fmtid = c.XInternAtom(display, fmtname, c.False);
    var propid = c.XInternAtom(display, "XSEL_DATA", c.False);
    var incrid = c.XInternAtom(display, "INCR", c.False);
    var event: c.XEvent = undefined;

    _ = c.XSelectInput(display, window, c.PropertyChangeMask);
    _ = c.XConvertSelection(display, bufid, fmtid, propid, window, c.CurrentTime);
    _ = c.XNextEvent(display, &event);
    while (event.type != c.SelectionNotify or event.xselection.selection != bufid)
        _ = c.XNextEvent(display, &event);

    if (event.xselection.property > 0) {
        var result: [*c]u8 = undefined;
        _ = c.XGetWindowProperty(display, window, propid, 0, c.LONG_MAX / 4, c.True, c.AnyPropertyType, &fmtid, &resbits, &ressize, &restail, &result);
        defer _ = c.XFree(result);
        if (fmtid != incrid)
            try writer.print("{s}", .{result});

        if (fmtid == incrid) {
            ressize = 1;
            while (ressize > 0) {
                _ = c.XNextEvent(display, &event);
                while (event.type != c.PropertyNotify or event.xproperty.atom != propid or event.xproperty.state != c.PropertyNewValue) {
                    _ = c.XNextEvent(display, &event);
                }

                _ = c.XGetWindowProperty(display, window, propid, 0, c.LONG_MAX / 4, c.True, c.AnyPropertyType, &fmtid, &resbits, &ressize, &restail, &result);
                defer _ = c.XFree(result);
                try writer.print("{s}", .{result});
            }
        }
        return true;
    } else // request failed, e.g. owner can't convert to the target format
    return false;
}

fn watch(display: *c.Display, window: c.Window, bufname: [*c]const u8, writer: anytype) !void {
    var event_base: c_int = undefined;
    var error_base: c_int = undefined;
    var event: c.XEvent = undefined;
    var bufid = c.XInternAtom(display, bufname, c.False);

    _ = c.XFixesQueryExtension(display, &event_base, &error_base);
    _ = c.XFixesSelectSelectionInput(display, c.XDefaultRootWindow(display), bufid, c.XFixesSetSelectionOwnerNotifyMask);

    while (true) {
        _ = c.XNextEvent(display, &event);

        // _ = try writer.print("{d} == {d} + {d}. {d} == {d}", .{ event.type, event_base, c.XFixesSelectionNotify, event.xselection.selection, bufid });
        // _ = std.debug.print("{}", .{event.xselection});

        if (event.type == event_base + c.XFixesSelectionNotify and
            event.xselection.property == bufid)
        {
            _ = try writer.print("y", .{});
            if (!try printSelection(display, window, bufname, "UTF8_STRING", writer))
                _ = try printSelection(display, window, bufname, "STRING", writer);
        }
    }
}

pub fn clipboardAction() !void {
    const stdout = std.io.getStdOut().writer();
    var display: *c.Display = c.XOpenDisplay(null).?;
    defer _ = c.XCloseDisplay(display);
    const default_screen = c.XDefaultScreen(display);
    var color = c.XBlackPixel(display, default_screen);
    var window = c.XCreateSimpleWindow(display, c.XDefaultRootWindow(display), 0, 0, 1, 1, 0, color, color);
    defer _ = c.XDestroyWindow(display, window);
    var gpa = std.heap.GeneralPurposeAllocator(.{}){};
    defer _ = gpa.deinit();
    const allocator = &gpa.allocator;
    var args = std.process.args();
    defer args.deinit();
    while (args.next(allocator)) |arg_or_err| {
        const arg = try arg_or_err;
        defer allocator.free(arg);
        if (std.mem.eql(u8, arg, "-w")) {
            try watch(display, window, "CLIPBOARD", stdout);
        }
    }
    var result = (try printSelection(display, window, "CLIPBOARD", "UTF8_STRING", stdout)) or
        (try printSelection(display, window, "CLIPBOARD", "STRING", stdout));
    if (!result) return error.ClipboardActionFailed;
}