From df0c3657b46ef1f40ca9aecad09ebde27cd7987d Mon Sep 17 00:00:00 2001
From: Asmir A <asmir.abdulahovic@gmail.com>
Date: Sun, 3 Sep 2023 12:46:08 +0200
Subject: [PATCH] intercept: implement intercept functionality with libevdev

---
 src/main.zig | 89 ++++++++++++++++++++++++++++++++++++++--------------
 1 file changed, 65 insertions(+), 24 deletions(-)

diff --git a/src/main.zig b/src/main.zig
index 87c3a27..e13e770 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -1,26 +1,29 @@
 const std = @import("std");
-const print = std.debug.print;
-const input = @cImport(@cInclude("linux/input.h"));
+const c = @cImport({
+    @cInclude("linux/input.h");
+    @cInclude("libevdev-1.0/libevdev/libevdev.h");
+    @cInclude("errno.h");
+});
 
-const CapsLockDown = input.input_event{ .type = input.EV_KEY, .code = input.KEY_CAPSLOCK, .value = 1, .time = undefined };
-const CapsLockUp = input.input_event{ .type = input.EV_KEY, .code = input.KEY_CAPSLOCK, .value = 0, .time = undefined };
-const EscDown = input.input_event{ .type = input.EV_KEY, .code = input.KEY_ESC, .value = 1, .time = undefined };
-const EscUp = input.input_event{ .type = input.EV_KEY, .code = input.KEY_ESC, .value = 0, .time = undefined };
-const LShiftDown = input.input_event{ .type = input.EV_KEY, .code = input.KEY_LEFTSHIFT, .value = 1, .time = undefined };
-const LShiftUp = input.input_event{ .type = input.EV_KEY, .code = input.KEY_LEFTSHIFT, .value = 0, .time = undefined };
-const RShiftDown = input.input_event{ .type = input.EV_KEY, .code = input.KEY_RIGHTSHIFT, .value = 1, .time = undefined };
-const RShiftUp = input.input_event{ .type = input.EV_KEY, .code = input.KEY_RIGHTSHIFT, .value = 0, .time = undefined };
-const Syn = input.input_event{ .type = input.EV_SYN, .code = input.SYN_REPORT, .value = 0, .time = undefined };
+const CapsLockDown = c.input_event{ .type = c.EV_KEY, .code = c.KEY_CAPSLOCK, .value = 1, .time = undefined };
+const CapsLockUp = c.input_event{ .type = c.EV_KEY, .code = c.KEY_CAPSLOCK, .value = 0, .time = undefined };
+const EscDown = c.input_event{ .type = c.EV_KEY, .code = c.KEY_ESC, .value = 1, .time = undefined };
+const EscUp = c.input_event{ .type = c.EV_KEY, .code = c.KEY_ESC, .value = 0, .time = undefined };
+const LShiftDown = c.input_event{ .type = c.EV_KEY, .code = c.KEY_LEFTSHIFT, .value = 1, .time = undefined };
+const LShiftUp = c.input_event{ .type = c.EV_KEY, .code = c.KEY_LEFTSHIFT, .value = 0, .time = undefined };
+const RShiftDown = c.input_event{ .type = c.EV_KEY, .code = c.KEY_RIGHTSHIFT, .value = 1, .time = undefined };
+const RShiftUp = c.input_event{ .type = c.EV_KEY, .code = c.KEY_RIGHTSHIFT, .value = 0, .time = undefined };
+const Syn = c.input_event{ .type = c.EV_SYN, .code = c.SYN_REPORT, .value = 0, .time = undefined };
 
-fn event_equal(e1: *const input.input_event, e2: *const input.input_event) bool {
+fn event_equal(e1: *const c.input_event, e2: *const c.input_event) bool {
     return (e1.*.type == e2.*.type) and (e1.*.code == e2.*.code) and (e1.*.value == e2.*.value);
 }
 
-fn event_read(event: *input.input_event) !void {
-    event.* = try std.io.getStdIn().reader().readStruct(@TypeOf(event.*));
-}
+//fn event_read(event: *c.input_event) !void {
+//    event.* = try std.io.getStdIn().reader().readStruct(@TypeOf(event.*));
+//}
 
-fn event_write(event: *const input.input_event) !void {
+fn event_write(event: *const c.input_event) !void {
     try std.io.getStdOut().writer().writeStruct(event.*);
 }
 
@@ -32,22 +35,60 @@ fn write_esc() !void {
     try event_write(&EscUp);
 }
 
+fn device_open() !void {}
+
 pub fn main() !void {
-    var event: input.input_event = undefined;
+    var gpa = std.heap.GeneralPurposeAllocator(.{}){};
+    const allocator = gpa.allocator();
+    defer _ = gpa.deinit();
+
+    const args = try std.process.argsAlloc(allocator);
+
+    if (args.len != 2) {
+        std.debug.print("error: expected one argument", .{});
+        std.os.exit(1);
+    }
+    const dev_name = args[1];
+    var dev_fd = try std.fs.openFileAbsolute(dev_name, .{});
+
+    const dev = c.libevdev_new();
+    if (c.libevdev_set_fd(dev, dev_fd.handle) < 0) {
+        std.debug.print("evdev: failed creating device from descriptor", .{});
+        std.os.exit(1);
+    }
+    if (c.libevdev_grab(dev, c.LIBEVDEV_GRAB) < 0) {
+        std.debug.print("evdev: failed grabbing device", .{});
+        std.os.exit(1);
+    }
+
     var write_esc_lshift: bool = undefined;
     var write_esc_rshift: bool = undefined;
     var is_lshift_down: bool = false;
     var is_rshift_down: bool = false;
 
-    while (true) {
-        try event_read(&event);
-        if (event.type == input.EV_MSC and event.type == input.MSC_SCAN) {
-            continue;
+    outer: while (true) {
+        var event: c.input_event = undefined;
+        var rc = c.libevdev_next_event(dev, c.LIBEVDEV_READ_FLAG_NORMAL | c.LIBEVDEV_READ_FLAG_BLOCKING, @ptrCast(&event));
+
+        while (rc == c.LIBEVDEV_READ_STATUS_SYNC) {
+            rc = c.libevdev_next_event(dev, c.LIBEVDEV_READ_FLAG_SYNC, @ptrCast(&event));
         }
 
-        if (event.type != input.EV_KEY) {
+        if (rc == -c.EAGAIN) {
+            continue :outer;
+        }
+
+        if (rc != c.LIBEVDEV_READ_STATUS_SUCCESS) {
+            break :outer;
+        }
+
+        if (event.type == c.EV_MSC and event.type == c.MSC_SCAN) {
+            continue :outer;
+        }
+
+        if (event.type != c.EV_KEY) {
             try event_write(&event);
-            continue;
+            continue :outer;
         }
 
         write_esc_lshift = event_equal(&event, &LShiftUp) and is_lshift_down;
@@ -56,7 +97,7 @@ pub fn main() !void {
         is_rshift_down = event_equal(&event, &RShiftDown);
 
         if (event_equal(&event, &CapsLockUp) or event_equal(&event, &CapsLockDown)) {
-            event.code = input.KEY_LEFTMETA;
+            event.code = c.KEY_LEFTMETA;
         }
 
         try event_write(&event);