FIX: Work undone

We are not going to follow this path, but I will leave this commit as
part of the git history

base/src/user_model/border_utils.rs

@@ -0,0 +1,143 @@
+use crate::types::BorderItem;
+
+fn parse_color(s: &str) -> Option<(u8, u8, u8)> {
+    let s = s.trim_start_matches('#');
+    match s.len() {
+        6 => {
+            let r = u8::from_str_radix(&s[0..2], 16).ok()?;
+            let g = u8::from_str_radix(&s[2..4], 16).ok()?;
+            let b = u8::from_str_radix(&s[4..6], 16).ok()?;
+            Some((r, g, b))
+        }
+        3 => {
+            let r = u8::from_str_radix(&s[0..1], 16).ok()?;
+            let g = u8::from_str_radix(&s[1..2], 16).ok()?;
+            let b = u8::from_str_radix(&s[2..3], 16).ok()?;
+            // Expand single hex digits to full bytes
+            Some((r * 17, g * 17, b * 17))
+        }
+        _ => None,
+    }
+}
+
+fn compute_luminance(r: u8, g: u8, b: u8) -> f64 {
+    // Normalize RGB values to [0, 1]
+    let r = r as f64 / 255.0;
+    let g = g as f64 / 255.0;
+    let b = b as f64 / 255.0;
+    // Calculate luminance using the Rec. 601 formula
+    0.299 * r + 0.587 * g + 0.114 * b
+}
+
+fn is_max_color(a: &str, b: &str) -> bool {
+    let (ar, ag, ab) = match parse_color(a) {
+        Some(rgb) => rgb,
+        None => return false, // Invalid color format for 'a'
+    };
+
+    let (br, bg, bb) = match parse_color(b) {
+        Some(rgb) => rgb,
+        None => return false, // Invalid color format for 'b'
+    };
+
+    let luminance_a = compute_luminance(ar, ag, ab);
+    let luminance_b = compute_luminance(br, bg, bb);
+
+    // 'b' is heavier if its luminance is less than 'a's luminance
+    luminance_b < luminance_a
+}
+
+pub(crate) fn is_max_border(a: &Option<BorderItem>, b: &Option<BorderItem>) -> bool {
+    match (a, b) {
+        (_, None) => false,
+        (None, Some(_)) => true,
+        (Some(item_a), Some(item_b)) => {
+            if item_a.style < item_b.style {
+                return true;
+            } else if item_a.style > item_b.style {
+                return false;
+            }
+            match (&item_a.color, &item_b.color) {
+                (_, None) => false,
+                (None, Some(_)) => true,
+                (Some(color_a), Some(color_b)) => is_max_color(color_a, color_b),
+            }
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_basic_colors() {
+        // Black vs White
+        assert!(is_max_color("#FFFFFF", "#000000"));
+        assert!(!is_max_color("#000000", "#FFFFFF"));
+
+        // Red vs Dark Red
+        assert!(is_max_color("#FF0000", "#800000"));
+        assert!(!is_max_color("#800000", "#FF0000"));
+
+        // Green vs Dark Green
+        assert!(is_max_color("#00FF00", "#008000"));
+        assert!(!is_max_color("#008000", "#00FF00"));
+
+        // Blue vs Dark Blue
+        assert!(is_max_color("#0000FF", "#000080"));
+        assert!(!is_max_color("#000080", "#0000FF"));
+    }
+
+    #[test]
+    fn test_same_color() {
+        // Comparing the same color should return false
+        assert!(!is_max_color("#123456", "#123456"));
+    }
+
+    #[test]
+    fn test_shorthand_colors() {
+        // Shorthand notation (#RGB)
+        assert!(is_max_color("#FFF", "#000"));
+        assert!(is_max_color("#F00", "#800"));
+        assert!(is_max_color("#0F0", "#080"));
+        assert!(is_max_color("#00F", "#008"));
+        assert!(!is_max_color("#ABC", "#123"));
+    }
+
+    #[test]
+    fn test_invalid_colors() {
+        // Invalid color formats
+        assert!(!is_max_color("#GGGGGG", "#000000"));
+        assert!(!is_max_color("#12345", "#000000"));
+        assert!(!is_max_color("#1234567", "#000000"));
+        assert!(!is_max_color("123456", "#000000"));
+        assert!(!is_max_color("#123456", "#XYZ"));
+        assert!(!is_max_color("#", "#000000"));
+    }
+
+    #[test]
+    fn test_edge_cases() {
+        // Colors with minimal luminance difference
+        assert!(!is_max_color("#000000", "#010101"));
+        assert!(!is_max_color("#FEFEFE", "#FFFFFF"));
+        assert!(!is_max_color("#7F7F7F", "#808080"));
+    }
+
+    #[test]
+    fn test_luminance_ordering() {
+        // Colors with known luminance differences
+        assert!(is_max_color("#CCCCCC", "#333333")); // Light gray vs Day
+        assert!(is_max_color("#FFFF00", "#808000")); // Yellow ve
+        assert!(is_max_color("#FF00FF", "#800080")); // Magenta vle
+    }
+
+    #[test]
+    fn test_borderline_cases() {
+        // Testing colors with equal luminance
+        assert!(!is_max_color("#777777", "#777777"));
+
+        // Testing black against near-black
+        assert!(!is_max_color("#000000", "#010000"));
+    }
+}