refactor: flatten csi sequence parsing

parse.go

@@ -236,64 +236,36 @@ func parseCsi(b []byte) (int, Msg) {
 	i++
 
 	csi.Params = params[:paramsLen]
-	marker, cmd := csi.Marker(), csi.Command()
-	switch marker {
-	case '?':
-		switch cmd {
-		case 'y':
-			switch intermed {
-			case '$':
-				// Report Mode (DECRPM)
-				if paramsLen != 2 {
-					return i, UnknownMsg(b[:i])
-				}
-				return i, ReportModeMsg{Mode: csi.Param(0), Value: csi.Param(1)}
-			}
-		case 'c':
-			// Primary Device Attributes
-			return i, parsePrimaryDevAttrs(&csi)
-		case 'u':
-			// Kitty keyboard flags
-			if param := csi.Param(0); param != -1 {
-				return i, KittyKeyboardMsg(param)
-			}
-		case 'R':
-			// This report may return a third parameter representing the page
-			// number, but we don't really need it.
-			if paramsLen >= 2 {
-				return i, CursorPositionMsg{Row: csi.Param(0), Column: csi.Param(1)}
-			}
-		}
-		return i, UnknownMsg(b[:i])
-	case '<':
-		switch cmd {
-		case 'm', 'M':
-			// Handle SGR mouse
-			if paramsLen != 3 {
-				return i, UnknownMsg(b[:i])
-			}
+	switch cmd := csi.Cmd; cmd {
+	case 'y' | '?'<<parser.MarkerShift | '$'<<parser.IntermedShift:
+		// Report Mode (DECRPM)
+		if paramsLen == 2 {
+			return i, ReportModeMsg{Mode: csi.Param(0), Value: csi.Param(1)}
+		}
+	case 'c' | '?'<<parser.MarkerShift:
+		// Primary Device Attributes
+		return i, parsePrimaryDevAttrs(&csi)
+	case 'u' | '?'<<parser.MarkerShift:
+		// Kitty keyboard flags
+		if param := csi.Param(0); param != -1 {
+			return i, KittyKeyboardMsg(param)
+		}
+	case 'R' | '?'<<parser.MarkerShift:
+		// This report may return a third parameter representing the page
+		// number, but we don't really need it.
+		if paramsLen >= 2 {
+			return i, CursorPositionMsg{Row: csi.Param(0), Column: csi.Param(1)}
+		}
+	case 'm' | '<'<<parser.MarkerShift, 'M' | '<'<<parser.MarkerShift:
+		// Handle SGR mouse
+		if paramsLen == 3 {
 			return i, parseSGRMouseEvent(&csi)
-		default:
-			return i, UnknownMsg(b[:i])
 		}
-	case '>':
-		switch cmd {
-		case 'm':
-			// XTerm modifyOtherKeys
-			if paramsLen != 2 || csi.Param(0) != 4 {
-				return i, UnknownMsg(b[:i])
-			}
-
+	case 'm' | '>'<<parser.MarkerShift:
+		// XTerm modifyOtherKeys
+		if paramsLen == 2 && csi.Param(0) == 4 {
 			return i, ModifyOtherKeysMsg(csi.Param(1))
-		default:
-			return i, UnknownMsg(b[:i])
 		}
-	case '=':
-		// We don't support any of these yet
-		return i, UnknownMsg(b[:i])
-	}
-
-	switch cmd := csi.Command(); cmd {
 	case 'I':
 		return i, FocusMsg{}
 	case 'O':
@@ -316,7 +288,7 @@ func parseCsi(b []byte) (int, Msg) {
 		}
 
 		if paramsLen != 0 {
-			return i, UnknownMsg(b[:i])
+			break
 		}
 
 		// Unmodified key F3 (CSI R)
@@ -414,13 +386,11 @@ func parseCsi(b []byte) (int, Msg) {
 		}
 
 		switch param {
-		case 1, 2, 3, 4, 5, 6, 7, 8:
-			fallthrough
-		case 11, 12, 13, 14, 15:
-			fallthrough
-		case 17, 18, 19, 20, 21, 23, 24, 25, 26:
-			fallthrough
-		case 28, 29, 31, 32, 33, 34:
+		case 1, 2, 3, 4, 5, 6, 7, 8,
+			11, 12, 13, 14, 15,
+			17, 18, 19, 20, 21,
+			23, 24, 25, 26,
+			28, 29, 31, 32, 33, 34:
 			var k KeyPressMsg
 			switch param {
 			case 1: