Add HexColorCode Scalar

README.md

@@ -541,3 +541,26 @@ For example, imagine a `phoneNumber` scalar like this :
             .build()
 
 ```
+
+## HexColorCode Scalar
+<table>
+<tr>
+<td>Scalar Definition</td>
+<td>Description</td>
+</tr>
+<tr>
+<td><pre lang="graphql">
+scalar HexColorCode
+  @specifiedBy(url: 
+    "https://tools.ietf.org/html/bcp47"
+  )
+</pre></td>
+<td>The HexColorCode scalar handles <a href="https://en.wikipedia.org/wiki/Web_colors">hex color code</a>. You can handle it via <a href="https://docs.oracle.com/javase/8/docs/api/java/awt/Color.html">java.awt.Color </a>(which was built into JDK)</td>
+</tr>
+</table>
+It Support Following Formats:
+
+- #RRGGBB
+- #RGB
+- #RRGGBBAA
+- #RGBA

src/main/java/graphql/scalars/ExtendedScalars.java

@@ -2,6 +2,7 @@
 
 import graphql.PublicApi;
 import graphql.scalars.alias.AliasedScalar;
+import graphql.scalars.color.hex.HexColorCodeScalar;
 import graphql.scalars.country.code.CountryCodeScalar;
 import graphql.scalars.currency.CurrencyScalar;
 import graphql.scalars.datetime.DateScalar;
@@ -150,6 +151,12 @@ public class ExtendedScalars {
      */
     public static final GraphQLScalarType CountryCode = CountryCodeScalar.INSTANCE;
 
+    /**
+     * A field whose value is a hex color code
+     * See the <a href="https://en.wikipedia.org/wiki/Web_colors">Web colors</a> for more details.
+     */
+    public static final GraphQLScalarType HexColorCode = HexColorCodeScalar.INSTANCE;
+
     /**
      * A UUID scalar that accepts a universally unique identifier and produces {@link
      * java.util.UUID} objects at runtime.

src/main/java/graphql/scalars/color/hex/HexColorCodeScalar.java

@@ -0,0 +1,120 @@
+package graphql.scalars.color.hex;
+
+import graphql.language.StringValue;
+import graphql.language.Value;
+import graphql.schema.*;
+
+import java.awt.*;
+import java.util.function.Function;
+import java.util.regex.Pattern;
+
+import static graphql.scalars.util.Kit.typeName;
+/**
+ * Access this via {@link graphql.scalars.ExtendedScalars#HexColorCode}
+ * See the <a href="https://en.wikipedia.org/wiki/Web_colors">Web colors</a> for more details.
+ * @implNote Supports the following formats: #RGB, #RGBA, #RRGGBB, #RRGGBBAA. Need to be prefixed with '#'
+ */
+public class HexColorCodeScalar {
+
+    public static final GraphQLScalarType INSTANCE;
+
+
+    static {
+        Coercing<Color, String> coercing = new Coercing<Color, String>() {
+
+            private final Pattern HEX_PATTERN = Pattern.compile("^(#([A-Fa-f0-9]{3,4}){1,2})$");
+
+            @Override
+            public String serialize(Object input) throws CoercingSerializeException {
+                Color color = parseColor(input, CoercingSerializeException::new);
+                boolean hasAlpha = color.getAlpha() != 255;
+                if (hasAlpha){
+                    return String.format("#%02x%02x%02x%02x", color.getRed(), color.getGreen(), color.getBlue(), color.getAlpha());
+                } else {
+                    return String.format("#%02x%02x%02x", color.getRed(), color.getGreen(), color.getBlue());
+                }
+            }
+
+            @Override
+            public Color parseValue(Object input) throws CoercingParseValueException {
+                return parseColor(input, CoercingParseValueException::new);
+            }
+
+            @Override
+            public Color parseLiteral(Object input) throws CoercingParseLiteralException {
+                if (!(input instanceof StringValue)) {
+                    throw new CoercingParseLiteralException("Expected type 'StringValue' but was '" + typeName(input) + "'.");
+                }
+                String stringValue = ((StringValue) input).getValue();
+                return parseColor(stringValue, CoercingParseLiteralException::new);
+            }
+
+            @Override
+            public Value<?> valueToLiteral(Object input) {
+                String s = serialize(input);
+                return StringValue.newStringValue(s).build();
+            }
+
+
+            private Color parseColor(Object input, Function<String, RuntimeException> exceptionMaker) {
+                final Color result;
+                if (input instanceof Color) {
+                    result = (Color) input;
+                } else if (input instanceof String) {
+                    try {
+                        String hex = ((String) input);
+
+                        //validation
+                        //regex
+                        if (!HEX_PATTERN.matcher(hex).matches()) {
+                            throw new IllegalArgumentException("Invalid hex color code value : '" + input + "'.");
+                        }
+
+                        int i = Integer.decode(hex);
+                        int inputLength = hex.length();
+
+                        if (inputLength == 4) {
+                            // #RGB
+                            result = new Color(
+                                    (i >> 8 & 0xF) * 0x11,
+                                    (i >> 4 & 0xF) * 0x11,
+                                    (i & 0xF) * 0x11
+                            );
+                        } else if (inputLength == 5) {
+                            // #RGBA
+                            result = new Color(
+                                    (i >> 12 & 0xF) * 0x11,
+                                    (i >> 8 & 0xF) * 0x11,
+                                    (i >> 4 & 0xF) * 0x11,
+                                    (i & 0xF) * 0x11
+                            );
+                        } else if (inputLength == 7) {
+                            // #RRGGBB
+                            result = new Color(i);
+                        } else {
+                            // #RRGGBBAA
+                            result = new Color(
+                                    (i >> 24 & 0xFF),
+                                    (i >> 16 & 0xFF),
+                                    (i >> 8 & 0xFF),
+                                    (i & 0xFF)
+                            );
+                        }
+                    } catch (NullPointerException | IllegalArgumentException ex) {
+                        throw exceptionMaker.apply("Invalid hex color code value : '" + input + "'. because of : '" + ex.getMessage() + "'");
+                    }
+                } else {
+                    throw exceptionMaker.apply("Expected a 'String' or 'Color' but was '" + typeName(input) + "'.");
+                }
+                return result;
+            }
+
+        };
+
+        INSTANCE = GraphQLScalarType.newScalar()
+                .name("HexColorCode")
+                .description("A field whose value is a hexadecimal color code: https://en.wikipedia.org/wiki/Web_colors.")
+                .coercing(coercing).build();
+    }
+
+}

src/test/groovy/graphql/scalars/color/hex/HexColorCodeScalarTest.groovy

@@ -0,0 +1,92 @@
+package graphql.scalars.color.hex
+
+import graphql.language.StringValue
+import graphql.scalars.ExtendedScalars
+import graphql.schema.CoercingParseValueException
+import spock.lang.Specification
+import spock.lang.Unroll
+
+import static graphql.scalars.util.TestKit.mkColor
+
+class HexColorCodeScalarTest extends Specification {
+
+    def coercing = ExtendedScalars.HexColorCode.getCoercing()
+
+    @Unroll
+    def "invoke parseValue for hexCode"() {
+        when:
+        def result = coercing.parseValue(input)
+        then:
+        result.equals(expectedValue)
+        where:
+        input                      | expectedValue
+        "#ff0000"                  | mkColor(0xff, 0, 0)
+        "#123"                     | mkColor(0x11, 0x22, 0x33)
+        "#11223344"                | mkColor(0x11, 0x22, 0x33, 0x44)
+        "#1234"                    | mkColor(0x11, 0x22, 0x33, 0x44)
+    }
+
+    @Unroll
+    def "invoke parseLiteral for hexCode"() {
+        when:
+        def result = coercing.parseLiteral(input)
+        then:
+        result == expectedValue
+        where:
+        input                        | expectedValue
+        new StringValue("#ff0000")   | mkColor(0xff, 0, 0)
+        new StringValue("#123")      | mkColor(0x11, 0x22, 0x33)
+        new StringValue("#11223344") | mkColor(0x11, 0x22, 0x33, 0x44)
+        new StringValue("#1234")     | mkColor(0x11, 0x22, 0x33, 0x44)
+    }
+
+    @Unroll
+    def "invoke serialize with hexCode"() {
+        when:
+        def result = coercing.serialize(input)
+        then:
+        result == expectedValue
+        where:
+        input              | expectedValue
+        "#ff0000"          | "#ff0000"
+        "#123"             | "#112233"
+        "#11223344"        | "#11223344"
+        "#1234"            | "#11223344"
+        mkColor(0x21, 0x23, 0x33) | "#212333"
+        mkColor(0x21, 0x23, 0x33, 0x44) | "#21233344"
+    }
+
+    @Unroll
+    def "invoke valueToLiteral with hexCode"() {
+        when:
+        def result = coercing.valueToLiteral(input)
+        then:
+        result.isEqualTo(expectedValue)
+        where:
+        input              | expectedValue
+        "#ff0000"          | new StringValue("#ff0000")
+        "#123"             | new StringValue("#112233")
+        "#11223344"        | new StringValue("#11223344")
+        "#1234"            | new StringValue("#11223344")
+        mkColor(0x21, 0x23, 0x33) | new StringValue("#212333")
+        mkColor(0x21, 0x23, 0x33, 0x44) | new StringValue("#21233344")
+    }
+
+    @Unroll
+    def "parseValue throws exception for invalid input #value"() {
+        when:
+        def result = coercing.parseValue(input)
+        then:
+        thrown(CoercingParseValueException)
+        where:
+        input              | _
+        "ff000"            | _
+        ""                 | _
+        "not a hex code"   | _
+        "42.3"             | _
+        new Double(42.3)   | _
+        new Float(42.3)    | _
+        new Object()       | _
+    }
+
+}

src/test/groovy/graphql/scalars/util/TestKit.groovy

@@ -5,6 +5,7 @@ import graphql.language.IntValue
 import graphql.language.StringValue
 import graphql.scalars.country.code.CountryCode
 
+import java.awt.Color
 import java.time.LocalDate
 import java.time.LocalDateTime
 import java.time.LocalTime
@@ -97,4 +98,11 @@ class TestKit {
     static CountryCode mkCountryCode(String countryCode) {
         return CountryCode.valueOf(countryCode)
     }
-}
+
+    static Color mkColor(int r, int g, int b, int a) {
+        return new Color(r, g, b, a)
+    }
+    static Color mkColor(int r, int g, int b) {
+        return new Color(r, g, b)
+    }
+}