fix(cortex-cli): add color preview to agent show command

Fixes bounty issue #1380

The agent show command now displays colors with a visual preview block
using ANSI true color escape codes, along with an approximate color name
(e.g., green, blue, red) to make the hex code more understandable.

Author: factorydroid

cortex-cli/src/agent_cmd.rs

@@ -794,6 +794,80 @@ async fn run_list(args: ListArgs) -> Result<()> {
     Ok(())
 }
 
+/// Parse a hex color string (e.g., "#22c55e") into RGB components.
+fn parse_hex_color(hex: &str) -> Option<(u8, u8, u8)> {
+    let hex = hex.trim_start_matches('#');
+    if hex.len() != 6 {
+        return None;
+    }
+    let r = u8::from_str_radix(&hex[0..2], 16).ok()?;
+    let g = u8::from_str_radix(&hex[2..4], 16).ok()?;
+    let b = u8::from_str_radix(&hex[4..6], 16).ok()?;
+    Some((r, g, b))
+}
+
+/// Get a human-readable approximate color name from RGB values.
+fn approximate_color_name(r: u8, g: u8, b: u8) -> &'static str {
+    // Convert to HSL-like heuristics for color naming
+    let max = r.max(g).max(b);
+    let min = r.min(g).min(b);
+    let lightness = (max as u16 + min as u16) / 2;
+
+    // Check for grayscale colors
+    if max - min < 20 {
+        return if lightness < 50 {
+            "black"
+        } else if lightness > 200 {
+            "white"
+        } else {
+            "gray"
+        };
+    }
+
+    // Determine dominant color
+    if r >= g && r >= b {
+        if r > 200 && g < 100 && b < 100 {
+            "red"
+        } else if g > 100 {
+            "orange"
+        } else if b > 100 {
+            "pink"
+        } else {
+            "red"
+        }
+    } else if g >= r && g >= b {
+        if b > 150 {
+            "cyan"
+        } else if r > 150 {
+            "yellow"
+        } else {
+            "green"
+        }
+    } else {
+        // Blue dominant
+        if r > 150 {
+            "purple"
+        } else if g > 150 {
+            "cyan"
+        } else {
+            "blue"
+        }
+    }
+}
+
+/// Format a hex color with a visual preview and approximate color name.
+fn format_color_with_preview(hex: &str) -> String {
+    if let Some((r, g, b)) = parse_hex_color(hex) {
+        let color_name = approximate_color_name(r, g, b);
+        // Use ANSI true color escape codes: \x1b[48;2;R;G;Bm for background
+        // Display a colored block followed by the hex code and color name
+        format!("\x1b[48;2;{r};{g};{b}m  \x1b[0m {hex} ({color_name})")
+    } else {
+        // If parsing fails, just return the hex string
+        hex.to_string()
+    }
+}
+
 /// Show agent details command.
 async fn run_show(args: ShowArgs) -> Result<()> {
     let agents = load_all_agents()?;
@@ -846,7 +920,7 @@ async fn run_show(args: ShowArgs) -> Result<()> {
     }
 
     if let Some(ref color) = agent.color {
-        println!("Color: {color}");
+        println!("Color: {}", format_color_with_preview(color));
     }
 
     if !agent.tags.is_empty() {
@@ -1547,4 +1621,48 @@ This is the system prompt.
         assert!(agents.iter().any(|a| a.name == "plan"));
         assert!(agents.iter().any(|a| a.name == "explore"));
     }
+
+    #[test]
+    fn test_parse_hex_color() {
+        // Valid hex colors
+        assert_eq!(parse_hex_color("#22c55e"), Some((0x22, 0xc5, 0x5e)));
+        assert_eq!(parse_hex_color("#3b82f6"), Some((0x3b, 0x82, 0xf6)));
+        assert_eq!(parse_hex_color("#ffffff"), Some((255, 255, 255)));
+        assert_eq!(parse_hex_color("#000000"), Some((0, 0, 0)));
+        assert_eq!(parse_hex_color("ff0000"), Some((255, 0, 0))); // Without #
+
+        // Invalid hex colors
+        assert_eq!(parse_hex_color("#fff"), None); // Too short
+        assert_eq!(parse_hex_color("#fffffff"), None); // Too long
+        assert_eq!(parse_hex_color(""), None);
+    }
+
+    #[test]
+    fn test_approximate_color_name() {
+        // Green color (#22c55e -> rgb(34, 197, 94))
+        assert_eq!(approximate_color_name(34, 197, 94), "green");
+        // Blue color (#3b82f6 -> rgb(59, 130, 246))
+        assert_eq!(approximate_color_name(59, 130, 246), "blue");
+        // Red color
+        assert_eq!(approximate_color_name(255, 50, 50), "red");
+        // White
+        assert_eq!(approximate_color_name(255, 255, 255), "white");
+        // Black
+        assert_eq!(approximate_color_name(10, 10, 10), "black");
+        // Gray
+        assert_eq!(approximate_color_name(128, 128, 128), "gray");
+    }
+
+    #[test]
+    fn test_format_color_with_preview() {
+        // Test with valid color
+        let result = format_color_with_preview("#22c55e");
+        assert!(result.contains("#22c55e"));
+        assert!(result.contains("green"));
+        assert!(result.contains("\x1b[")); // Contains ANSI escape codes
+
+        // Test with invalid color (should return as-is)
+        let result = format_color_with_preview("invalid");
+        assert_eq!(result, "invalid");
+    }
 }