config: add initial-tile-state window rule

toml-config/src/config/parsers/tile_state.rs

@@ -0,0 +1,35 @@
+use {
+    crate::{
+        config::parser::{DataType, ParseResult, Parser, UnexpectedDataType},
+        toml::toml_span::{Span, SpannedExt},
+    },
+    jay_config::window::TileState,
+    thiserror::Error,
+};
+
+#[derive(Debug, Error)]
+pub enum TileStateParserError {
+    #[error(transparent)]
+    Expected(#[from] UnexpectedDataType),
+    #[error("Unknown tile state `{}`", .0)]
+    UnknownTileState(String),
+}
+
+pub struct TileStateParser;
+
+impl Parser for TileStateParser {
+    type Value = TileState;
+    type Error = TileStateParserError;
+    const EXPECTED: &'static [DataType] = &[DataType::String];
+
+    fn parse_string(&mut self, span: Span, string: &str) -> ParseResult<Self> {
+        let ty = match string {
+            "tiled" => TileState::Tiled,
+            "floating" => TileState::Floating,
+            _ => {
+                return Err(TileStateParserError::UnknownTileState(string.to_owned()).spanned(span));
+            }
+        };
+        Ok(ty)
+    }
+}