1 files changed, 165 insertions, 0 deletions
diff --git a/src/attributes/color.rs b/src/attributes/color.rs
new file mode 100644
index 0000000..92a26eb
--- /dev/null
+++ b/src/attributes/color.rs
@@ -0,0 +1,165 @@
+use crate::dot::DotString;
+use std::borrow::Cow;
+
+#[derive(Copy, Clone, PartialEq, Debug)]
+pub enum Color<'a> {
+    RGB {
+        red: u8,
+        green: u8,
+        blue: u8,
+    },
+    RGBA {
+        red: u8,
+        green: u8,
+        blue: u8,
+        alpha: u8,
+    },
+    // TODO: constrain?
+    // Hue-Saturation-Value (HSV) 0.0 <= H,S,V <= 1.0
+    HSV {
+        hue: f32,
+        saturation: f32,
+        value: f32,
+    },
+    Named(&'a str),
+}
+
+impl<'a> DotString<'a> for Color<'a> {
+    fn dot_string(&self) -> Cow<'a, str> {
+        match self {
+            Color::RGB { red, green, blue } => {
+                format!("#{:02x?}{:02x?}{:02x?}", red, green, blue).into()
+            }
+            Color::RGBA {
+                red,
+                green,
+                blue,
+                alpha,
+            } => {
+                format!("#{:02x?}{:02x?}{:02x?}{:02x?}", red, green, blue, alpha).into()
+            }
+            Color::HSV {
+                hue,
+                saturation,
+                value,
+            } => format!("{} {} {}", hue, saturation, value).into(),
+            Color::Named(color) => (*color).into(),
+        }
+    }
+}
+
+// The sum of the optional weightings must sum to at most 1.
+pub struct WeightedColor<'a> {
+    pub color: Color<'a>,
+
+    // TODO: constrain
+    /// Must be in range 0 <= W <= 1.
+    pub weight: Option<f32>,
+}
+
+impl<'a> DotString<'a> for WeightedColor<'a> {
+    fn dot_string(&self) -> Cow<'a, str> {
+        let mut dot_string = self.color.dot_string().to_string();
+        if let Some(weight) = &self.weight {
+            dot_string.push_str(format!(";{}", weight).as_str());
+        }
+        dot_string.into()
+    }
+}
+
+pub struct ColorList<'a> {
+    pub colors: Vec<WeightedColor<'a>>,
+}
+
+impl<'a> DotString<'a> for ColorList<'a> {
+    /// A colon-separated list of weighted color values: WC(:WC)* where each WC has the form C(;F)?
+    /// Ex: fillcolor=yellow;0.3:blue
+    fn dot_string(&self) -> Cow<'a, str> {
+        let mut dot_string = String::new();
+        let mut iter = self.colors.iter();
+        let first = iter.next();
+        if first.is_none() {
+            return dot_string.into();
+        }
+        dot_string.push_str(&first.unwrap().dot_string());
+        for weighted_color in iter {
+            dot_string.push_str(":");
+            dot_string.push_str(&weighted_color.dot_string())
+        }
+
+        dot_string.into()
+    }
+}
+
+/// Convert an element like `(i, j)` into a WeightedColor
+pub trait IntoWeightedColor<'a> {
+    fn into_weighted_color(self) -> WeightedColor<'a>;
+}
+
+impl<'a> IntoWeightedColor<'a> for &(Color<'a>, Option<f32>) {
+    fn into_weighted_color(self) -> WeightedColor<'a> {
+        let (s, t) = *self;
+        WeightedColor {
+            color: s,
+            weight: t,
+        }
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use crate::attributes::{Color, ColorList, WeightedColor};
+    use crate::DotString;
+
+    #[test]
+    fn colorlist_dot_string() {
+        let yellow = WeightedColor {
+            color: Color::Named("yellow"),
+            weight: Some(0.3),
+        };
+
+        let blue = WeightedColor {
+            color: Color::Named("blue"),
+            weight: None,
+        };
+
+        let color_list = ColorList {
+            colors: vec![yellow, blue],
+        };
+
+        let dot_string = color_list.dot_string();
+
+        assert_eq!("yellow;0.3:blue", dot_string);
+    }
+
+    #[test]
+    fn color_rbg_dot_string() {
+        let color = Color::RGB {
+            red: 160,
+            green: 82,
+            blue: 45,
+        };
+        assert_eq!("#a0522d", color.dot_string());
+    }
+
+    #[test]
+    fn color_rbga_dot_string() {
+        let color = Color::RGBA {
+            red: 160,
+            green: 82,
+            blue: 45,
+            alpha: 10,
+        };
+        assert_eq!("#a0522d0a", color.dot_string());
+    }
+
+    #[test]
+    fn color_hsv_dot_string() {
+        let color = Color::HSV {
+            hue: 0.051,
+            saturation: 0.718,
+            value: 0.627,
+        };
+        assert_eq!("0.051 0.718 0.627", color.dot_string());
+    }
+}