lib: add color function collection

outputs/lib/color/check.nix

@@ -0,0 +1,65 @@
+{lib, ...}: let
+  inherit (lib) toInt all min max;
+  inherit (builtins) isInt isFloat match getAttr hasAttr;
+
+  # basic checks
+  range = a: b: v: (v <= max a b) && (v >= min a b);
+  number = v: isInt v || isFloat v;
+  unary = range 0.0 1.0;
+  hue = range 0.0 360.0;
+
+  # type checking
+  hex = {
+    string = color: let
+      hexPatternWithHash = match "#[[:xdigit:]]{6}" color;
+      hexPatternNoHash = match "[[:xdigit:]]{6}" color;
+      isValid = hexPatternWithHash != null || hexPatternNoHash != null;
+    in
+      assert isValid || throw "Invalid hex color format: ${color}";
+        hexPatternWithHash != null || hexPatternNoHash != null;
+    set = color: let
+      hasAttributes = all (k: hasAttr k color) ["r" "g" "b"];
+      validPattern = all (k: let
+        v = getAttr k color;
+      in
+        match "[[:xdigit:]]{2}" v != null) ["r" "g" "b"];
+    in
+      hasAttributes && validPattern;
+  };
+
+  rgb = {
+    string = color: let
+      rgbPattern = match "([0-9]{1,3}),([0-9]{1,3}),([0-9]{1,3})" color;
+      toNum = str: let
+        num = toInt str;
+      in
+        num != null && range 0 255 num;
+      isValid = rgbPattern != null && all toNum rgbPattern;
+    in
+      isValid;
+    set = color: let
+      hasAttributes = all (k: hasAttr k color) ["r" "g" "b"];
+      validRanges = all (
+        k: let
+          v = getAttr k color;
+        in
+          number v && range 0 255 v
+      ) ["r" "g" "b"];
+    in
+      hasAttributes && validRanges;
+  };
+
+  hsl = {
+    # TODO: add range checks
+    string = color: let
+      hslPattern = match "([0-9]{1,3}),[ ]*([0-9]{1,3})%,[ ]*([0-9]{1,3})%" color;
+    in
+      hslPattern != null;
+
+    set = color: let
+      hasAttributes = all (k: hasAttr k color) ["h" "s" "l"];
+      validRanges = hue color.h && all (k: unary (getAttr k color)) ["s" "l"];
+    in
+      hasAttributes && validRanges;
+  };
+in {inherit range number unary hue hex rgb hsl;}