API improvements and better examples

1 files changed, 65 insertions, 0 deletions

diff --git a/examples/src/main/scala/decode.scala b/examples/src/main/scala/decode.scala
new file mode 100644
index 0000000..1cc8a12
--- /dev/null
+++ b/examples/src/main/scala/decode.scala
@@ -0,0 +1,65 @@
+package magnolia.examples
+
+import scala.language.existentials
+import scala.language.higherKinds
+
+import magnolia._
+import scala.language.experimental.macros
+
+trait Decoder[T] { def decode(str: String): T }
+
+object Decoder {
+  
+  implicit val string: Decoder[String] = new Decoder[String] { def decode(str: String): String = str }
+  implicit val int: Decoder[Int] = new Decoder[Int] { def decode(str: String): Int = str.toInt }
+  implicit def generic[T]: Decoder[T] = macro Magnolia.generic[T]
+
+  type Typeclass[T] = Decoder[T]
+  
+  def join[T](ctx: JoinContext[Decoder, T]): Decoder[T] = new Decoder[T] {
+    def decode(value: String) = {
+      val (name, values) = parse(value)
+      ctx.construct { param => param.typeclass.decode(values(param.label)) }
+    }
+  }
+
+  def dispatch[T](ctx: DispatchContext[Decoder, T]): Decoder[T] = new Decoder[T] {
+    def decode(param: String) = {
+      val (name, values) = parse(param)
+      val subtype = ctx.subtypes.find(_.label == name).get
+      subtype.typeclass.decode(param)
+    }
+  }
+
+  private def parse(value: String): (String, Map[String, String]) = {
+    val end = value.indexOf('(')
+    val name = value.substring(0, end)
+    
+    def parts(value: String, idx: Int = 0, depth: Int = 0, collected: List[String] = List("")): List[String] = {
+      def plus(char: Char): List[String] = collected.head+char :: collected.tail
+      
+      if(idx == value.length) collected
+      else value(idx) match {
+        case '(' =>
+          parts(value, idx + 1, depth + 1, plus('('))
+        case ')' =>
+          if(depth == 1) plus(')')
+          else parts(value, idx + 1, depth - 1, plus(')'))
+        case ',' =>
+          if(depth == 0) parts(value, idx + 1, depth, "" :: collected)
+          else parts(value, idx + 1, depth, plus(','))
+        case char =>
+          parts(value, idx + 1, depth, plus(char))
+      }
+    }
+    
+    def keyValue(str: String): (String, String) = {
+      val List(label, value) = str.split("=", 2).to[List]
+      (label, value)
+    }
+
+    (name, parts(value.substring(end + 1, value.length - 1)).map(keyValue).toMap)
+  }
+
+}
+