T02: settings model, ranges, load and atomic save

src/settings/mod.rs

@@ -0,0 +1,190 @@
+mod store;
+
+use std::ops::RangeInclusive;
+
+use serde::{Deserialize, Serialize};
+
+pub use store::{SettingsStore, load, save};
+
+/// Where a new session starts.
+#[derive(Clone, Copy, Debug, Default, PartialEq, Eq, Serialize, Deserialize)]
+#[serde(rename_all = "snake_case")]
+pub enum StartIn {
+    #[default]
+    Home,
+    Session,
+}
+
+#[derive(Clone, Copy, Debug, Default, PartialEq, Eq, Serialize, Deserialize)]
+#[serde(rename_all = "snake_case")]
+pub enum CursorStyle {
+    #[default]
+    Block,
+    Bar,
+    Underline,
+    Hollow,
+}
+
+/// Which Option keys type Alt on macOS.
+#[derive(Clone, Copy, Debug, Default, PartialEq, Eq, Serialize, Deserialize)]
+#[serde(rename_all = "snake_case")]
+pub enum OptionAsAlt {
+    #[default]
+    Off,
+    Left,
+    Right,
+    Both,
+}
+
+/// What the right panel shows.
+#[derive(Clone, Copy, Debug, Default, PartialEq, Eq, Serialize, Deserialize)]
+#[serde(rename_all = "snake_case")]
+pub enum PanelTab {
+    #[default]
+    Git,
+    Files,
+}
+
+/// Everything the settings window edits. A field the file leaves out takes its default.
+#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
+#[serde(default, deny_unknown_fields)]
+pub struct Settings {
+    /// A program path; empty runs the login shell.
+    pub shell: String,
+    pub start_in: StartIn,
+    pub theme: String,
+    /// The theme while the system is dark; none keeps `theme`.
+    pub dark_theme: Option<String>,
+    pub font_family: String,
+    pub font_size: f32,
+    pub line_height: f32,
+    pub ligatures: bool,
+    pub cursor_style: CursorStyle,
+    pub cursor_blink: bool,
+    pub background_opacity: f32,
+    pub background_blur: bool,
+    pub padding_x: f32,
+    pub padding_y: f32,
+    pub scrollback: u32,
+    pub option_as_alt: OptionAsAlt,
+    pub copy_on_select: bool,
+    pub show_sessions: bool,
+    pub show_panel: bool,
+    pub panel: PanelTab,
+}
+
+impl Default for Settings {
+    fn default() -> Self {
+        Self {
+            shell: String::new(),
+            start_in: StartIn::Home,
+            theme: "catppuccin-mocha".into(),
+            dark_theme: None,
+            font_family: "JetBrains Mono".into(),
+            font_size: 13.0,
+            line_height: 1.2,
+            ligatures: true,
+            cursor_style: CursorStyle::Block,
+            cursor_blink: true,
+            background_opacity: 0.88,
+            background_blur: true,
+            padding_x: 10.0,
+            padding_y: 8.0,
+            scrollback: 10_000,
+            option_as_alt: OptionAsAlt::Off,
+            copy_on_select: false,
+            show_sessions: true,
+            show_panel: true,
+            panel: PanelTab::Git,
+        }
+    }
+}
+
+pub const FONT_SIZE: RangeInclusive<f32> = 6.0..=72.0;
+pub const LINE_HEIGHT: RangeInclusive<f32> = 1.0..=2.0;
+pub const OPACITY: RangeInclusive<f32> = 0.3..=1.0;
+pub const PADDING: RangeInclusive<f32> = 0.0..=64.0;
+pub const SCROLLBACK: RangeInclusive<u32> = 0..=100_000;
+
+impl Settings {
+    /// Every value inside its range, every name filled; the error names the field.
+    pub fn validate(&self) -> anyhow::Result<()> {
+        within("font_size", self.font_size, &FONT_SIZE)?;
+        within("line_height", self.line_height, &LINE_HEIGHT)?;
+        within("background_opacity", self.background_opacity, &OPACITY)?;
+        within("padding_x", self.padding_x, &PADDING)?;
+        within("padding_y", self.padding_y, &PADDING)?;
+        within("scrollback", self.scrollback, &SCROLLBACK)?;
+        anyhow::ensure!(!self.theme.is_empty(), "theme is empty");
+        anyhow::ensure!(
+            self.dark_theme.as_ref().is_none_or(|name| !name.is_empty()),
+            "dark_theme is empty"
+        );
+        anyhow::ensure!(!self.font_family.is_empty(), "font_family is empty");
+        Ok(())
+    }
+}
+
+fn within<T: PartialOrd + std::fmt::Display>(
+    field: &str,
+    value: T,
+    range: &RangeInclusive<T>,
+) -> anyhow::Result<()> {
+    anyhow::ensure!(
+        range.contains(&value),
+        "{field} is {value}, outside {} to {}",
+        range.start(),
+        range.end()
+    );
+    Ok(())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn defaults_are_valid() {
+        Settings::default().validate().expect("defaults pass");
+    }
+
+    #[test]
+    fn a_value_out_of_range_names_its_field() {
+        let settings = Settings {
+            line_height: 2.5,
+            ..Settings::default()
+        };
+        let error = settings.validate().expect_err("2.5 is too tall");
+        assert_eq!(error.to_string(), "line_height is 2.5, outside 1 to 2");
+        let settings = Settings {
+            scrollback: 100_001,
+            ..Settings::default()
+        };
+        let error = settings.validate().expect_err("too many lines");
+        assert_eq!(
+            error.to_string(),
+            "scrollback is 100001, outside 0 to 100000"
+        );
+    }
+
+    #[test]
+    fn a_nan_is_out_of_range() {
+        let settings = Settings {
+            font_size: f32::NAN,
+            ..Settings::default()
+        };
+        assert!(settings.validate().is_err());
+    }
+
+    #[test]
+    fn an_empty_name_fails() {
+        let settings = Settings {
+            dark_theme: Some(String::new()),
+            ..Settings::default()
+        };
+        assert_eq!(
+            settings.validate().expect_err("empty").to_string(),
+            "dark_theme is empty"
+        );
+    }
+}