WIP - An alternative approach to #31 (see also #33)

src/main/scala/io/circe/yaml/parser/NodeAlg.scala

@@ -0,0 +1,160 @@
+package io.circe.yaml.parser
+
+import cats.data.ValidatedNel
+import cats.instances.either._
+import cats.instances.list._
+import cats.syntax.either._
+import cats.syntax.traverse._
+import io.circe.{Json, JsonNumber, JsonObject, ParsingFailure}
+import org.yaml.snakeyaml.constructor.SafeConstructor
+import org.yaml.snakeyaml.nodes._
+import scala.collection.JavaConverters._
+import scala.collection.immutable.Queue
+
+abstract class NodeAlg[T] {
+  def int(node: ScalarNode): T
+  def float(node: ScalarNode): T
+  def timestamp(node: ScalarNode): T
+  def bool(node: ScalarNode): T
+  def yNull(node: ScalarNode): T
+  def string(node: ScalarNode): T
+  def otherScalar(node: ScalarNode): T
+
+  def sequence(node: SequenceNode): T = fromValues {
+    node.getValue.asScala.foldLeft(Queue.empty[T]) {
+      (accum, next) => accum enqueue any(next)
+    }
+  }
+
+  def mapping(node: MappingNode): T = fromFields {
+    node.getValue.asScala.map {
+      nodeTuple => nodeTuple.getKeyNode match {
+        case keyNode: ScalarNode => keyNode.getValue -> any(nodeTuple.getValueNode)
+        case _ => throw ParsingFailure("Only string keys can be represented in JSON", null)
+      }
+    }
+  }
+
+  def fromValues(ts: Iterable[T]): T
+  def fromFields(ts: Iterable[(String, T)]): T
+
+  final def any(node: Node): T = node match {
+    case node: ScalarNode => node.getTag match {
+      case Tag.INT       => int(node)
+      case Tag.FLOAT     => float(node)
+      case Tag.TIMESTAMP => timestamp(node)
+      case Tag.BOOL      => bool(node)
+      case Tag.NULL      => yNull(node)
+      case Tag.STR       => string(node)
+      case _             => otherScalar(node)
+    }
+    case node: SequenceNode => sequence(node)
+    case node: MappingNode  => mapping(node)
+  }
+}
+
+final class LiftedAlg[A](lifted: NodeAlg[A]) extends NodeAlg[Either[ParsingFailure, A]] {
+  private def wrap(what: String)(err: Throwable) = ParsingFailure(s"Failed to parse $what", err)
+  def int(node: ScalarNode): Either[ParsingFailure, A] =
+    Either.catchNonFatal(lifted.int(node)).leftMap(wrap("integer value"))
+
+  def float(node: ScalarNode): Either[ParsingFailure, A] =
+    Either.catchNonFatal(lifted.float(node)).leftMap(wrap("float value"))
+
+  def timestamp(node: ScalarNode): Either[ParsingFailure, A] =
+    Either.catchNonFatal(lifted.timestamp(node)).leftMap(wrap("timestamp value"))
+
+  def bool(node: ScalarNode): Either[ParsingFailure, A] =
+    Either.catchNonFatal(lifted.bool(node)).leftMap(wrap("boolean value"))
+
+  def yNull(node: ScalarNode): Either[ParsingFailure, A] =
+    Either.catchNonFatal(lifted.yNull(node)).leftMap(wrap("null value"))
+
+  def string(node: ScalarNode): Either[ParsingFailure, A] =
+    Either.catchNonFatal(lifted.string(node)).leftMap(wrap("string value"))
+
+  def otherScalar(node: ScalarNode): Either[ParsingFailure, A] =
+    Either.catchNonFatal(lifted.otherScalar(node)).leftMap(wrap("scalar value"))
+
+  override def sequence(node: SequenceNode): Either[ParsingFailure, A] =
+    Either.catchNonFatal(lifted.sequence(node)).leftMap(wrap("sequence"))
+
+  override def mapping(node: MappingNode): Either[ParsingFailure, A] =
+    Either.catchNonFatal(lifted.mapping(node)).leftMap(wrap("mapping"))
+
+  def fromValues(ts: Iterable[Either[ParsingFailure, A]]): Either[ParsingFailure, A] = try {
+    Either.right {
+      lifted.fromValues {
+        ts.map(_.valueOr(throw _))
+      }
+    }
+  } catch {
+    case f @ ParsingFailure(_, _) => Either.left(f)
+  }
+
+  def fromFields(ts: Iterable[(String, Either[ParsingFailure, A])]): Either[ParsingFailure, A] = try {
+    Either.right {
+      lifted.fromFields {
+        ts.map {
+          case (key, value) => key -> value.valueOr(throw _)
+        }
+      }
+    }
+  } catch {
+    case f @ ParsingFailure(_, _) => Either.left(f)
+  }
+}
+
+final class AccumlatingAlg[A](base: NodeAlg[A]) extends NodeAlg[ValidatedNel[ParsingFailure, A]] {
+  private val lifted = new LiftedAlg(base)
+  def int(node: ScalarNode): ValidatedNel[ParsingFailure, A] = lifted.int(node).toValidatedNel
+  def float(node: ScalarNode): ValidatedNel[ParsingFailure, A] = lifted.float(node).toValidatedNel
+  def timestamp(node: ScalarNode): ValidatedNel[ParsingFailure, A] = lifted.timestamp(node).toValidatedNel
+  def bool(node: ScalarNode): ValidatedNel[ParsingFailure, A] = lifted.bool(node).toValidatedNel
+  def yNull(node: ScalarNode): ValidatedNel[ParsingFailure, A] = lifted.yNull(node).toValidatedNel
+  def string(node: ScalarNode): ValidatedNel[ParsingFailure, A] = lifted.string(node).toValidatedNel
+  def otherScalar(node: ScalarNode): ValidatedNel[ParsingFailure, A] = lifted.otherScalar(node).toValidatedNel
+
+  def fromFields(ts: Iterable[(String, ValidatedNel[ParsingFailure, A])]): ValidatedNel[ParsingFailure, A] =
+    ts.toList.traverseU {
+      case (key, value) => value.map(key -> _)
+    }.map(base.fromFields)
+
+  def fromValues(ts: Iterable[ValidatedNel[ParsingFailure, A]]): ValidatedNel[ParsingFailure, A] =
+    ts.toList.sequenceU.map(base.fromValues)
+}
+
+class DefaultAlg extends NodeAlg[Json] {
+  protected object Constructor extends SafeConstructor {
+    def flatten(node: MappingNode): Unit = flattenMapping(node)
+  }
+
+  final protected def number(str: String): Json = JsonNumber.fromString(str).map(Json.fromJsonNumber).getOrElse {
+    throw new NumberFormatException(s"Invalid numeric string $str")
+  }
+
+  def int(node: ScalarNode): Json = number(node.getValue)
+  def float(node: ScalarNode): Json = number(node.getValue)
+  def timestamp(node: ScalarNode): Json = Json.fromString(node.getValue)
+  def bool(node: ScalarNode): Json = Json.fromBoolean(node.getValue.toBoolean)
+  def yNull(node: ScalarNode): Json = Json.Null
+  def string(node: ScalarNode): Json = Json.fromString(node.getValue)
+  def otherScalar(node: ScalarNode): Json = if (!node.getTag.startsWith(Tag.PREFIX)) {
+    Json.fromJsonObject(JsonObject.singleton(node.getTag.getValue.stripPrefix("!"), Json.fromString(node.getValue)))
+  } else Json.fromString(node.getValue)
+
+  def fromValues(ts: Iterable[Json]): Json = Json.fromValues(ts)
+  def fromFields(ts: Iterable[(String, Json)]): Json = Json.fromFields(ts)
+}
+
+case class ConfiguredAlg(
+  numericTimestamps: Boolean
+) extends DefaultAlg {
+  final override def timestamp(node: ScalarNode): Json = if (!numericTimestamps) {
+    super.timestamp(node)
+  } else {
+    val constructor = new SafeConstructor.ConstructYamlTimestamp()
+    constructor.construct(node)
+    Json.fromLong(constructor.getCalendar.getTimeInMillis)
+  }
+}

src/main/scala/io/circe/yaml/parser/Parser.scala

@@ -0,0 +1,91 @@
+package io.circe.yaml.parser
+
+
+import cats.data.ValidatedNel
+import cats.syntax.either._
+import io.circe._
+import java.io.{Reader, StringReader}
+import org.yaml.snakeyaml.Yaml
+import scala.collection.JavaConverters._
+
+class Parser(algebra: NodeAlg[Json] = new DefaultAlg) {
+
+  /**
+    * Configure the parser
+    * @param numericTimestamps if true, timestamps will be returned as epoch millisecond [[Long]]s
+    * @return A configured parser
+    */
+  def configured(
+    numericTimestamps: Boolean = false
+  ): Parser = new Parser(ConfiguredAlg(
+    numericTimestamps = numericTimestamps
+  ))
+
+
+  /**
+    * Parse YAML from the given [[Reader]], returning either [[ParsingFailure]] or [[Json]]
+    */
+  def parse(yaml: Reader): Either[ParsingFailure, Json] = for {
+    parsed <- parseSingle(yaml)
+    json   <- Either.catchNonFatal(algebra.any(parsed)).leftMap {
+      case p @ ParsingFailure(_, _) => p
+      case err => ParsingFailure(err.getMessage, err)
+    }
+  } yield json
+
+  /**
+    * Parse YAML from the given [[Reader]], accumulating errors and returning either a list of [[ParsingFailure]]s
+    * or a [[Json]]
+    */
+  def parseAccumulating(yaml: Reader): ValidatedNel[ParsingFailure, Json] = for {
+    parsed <- parseSingle(yaml)
+    json   <- new AccumlatingAlg(algebra).any(parsed)
+  } yield json
+
+  /**
+    * Parse YAML from the given string, returning either [[ParsingFailure]] or [[Json]]
+    */
+  def parse(yaml: String): Either[ParsingFailure, Json] = parse(new StringReader(yaml))
+
+  /**
+    * Parse YAML from the given string, accumulating errors and returning either a list of [[ParsingFailure]]s
+    * or a [[Json]]
+    */
+  def parseAccumulating(yaml: String): ValidatedNel[ParsingFailure, Json] = parseAccumulating(new StringReader(yaml))
+
+  /**
+    * Parse a succession of documents from the given [[Reader]], returning the result as a [[Stream]] of [[Either]]
+    */
+  def parseDocuments(yaml: Reader): Stream[Either[ParsingFailure, Json]] = {
+    val alg = new LiftedAlg(algebra)
+    parseStream(yaml).map(alg.any)
+  }
+
+  /**
+    * Parse a succession of documents from the given [[Reader]], accumulating errors within each document and
+    * returning the result as a [[Stream]] of [[ValidatedNel]]
+    */
+  def parseDocumentsAccumulating(yaml: Reader): Stream[ValidatedNel[ParsingFailure, Json]] = {
+    val alg = new AccumlatingAlg(algebra)
+    parseStream(yaml).map(alg.any)
+  }
+
+  /**
+    * Parse a succession of documents from the given string, returning the result as a [[Stream]] of [[Either]]
+    */
+  def parseDocuments(yaml: String): Stream[Either[ParsingFailure, Json]] = parseDocuments(new StringReader(yaml))
+
+  /**
+    * Parse a succession of documents from the given string, accumulating errors within each document and
+    * returning the result as a [[Stream]] of [[ValidatedNel]]
+    */
+  def parseDocumentsAccumulating(yaml: String): Stream[ValidatedNel[ParsingFailure, Json]] =
+    parseDocumentsAccumulating(new StringReader(yaml))
+
+  private[this] def parseSingle(reader: Reader) =
+    Either.catchNonFatal(new Yaml().compose(reader)).leftMap(err => ParsingFailure(err.getMessage, err))
+
+  private[this] def parseStream(reader: Reader) =
+    new Yaml().composeAll(reader).asScala.toStream
+
+}

src/main/scala/io/circe/yaml/parser/package.scala

@@ -1,94 +1,3 @@
 package io.circe.yaml
 
-import cats.syntax.either._
-import io.circe._
-import java.io.{Reader, StringReader}
-import org.yaml.snakeyaml.Yaml
-import org.yaml.snakeyaml.constructor.SafeConstructor
-import org.yaml.snakeyaml.nodes._
-import scala.collection.JavaConverters._
-
-package object parser {
-
-
-  /**
-    * Parse YAML from the given [[Reader]], returning either [[ParsingFailure]] or [[Json]]
-    * @param yaml
-    * @return
-    */
-  def parse(yaml: Reader): Either[ParsingFailure, Json] = for {
-    parsed <- parseSingle(yaml)
-    json   <- yamlToJson(parsed)
-  } yield json
-
-  def parse(yaml: String): Either[ParsingFailure, Json] = parse(new StringReader(yaml))
-
-  def parseDocuments(yaml: Reader): Stream[Either[ParsingFailure, Json]] = parseStream(yaml).map(yamlToJson)
-  def parseDocuments(yaml: String): Stream[Either[ParsingFailure, Json]] = parseDocuments(new StringReader(yaml))
-
-  private[this] def parseSingle(reader: Reader) =
-    Either.catchNonFatal(new Yaml().compose(reader)).leftMap(err => ParsingFailure(err.getMessage, err))
-
-  private[this] def parseStream(reader: Reader) =
-    new Yaml().composeAll(reader).asScala.toStream
-
-  private[this] object CustomTag {
-    def unapply(tag: Tag): Option[String] = if (!tag.startsWith(Tag.PREFIX))
-      Some(tag.getValue)
-    else
-      None
-  }
-
-  private[this] class FlatteningConstructor extends SafeConstructor {
-    def flatten(node: MappingNode): MappingNode = {
-      flattenMapping(node)
-      node
-    }
-  }
-
-  private[this] val flattener: FlatteningConstructor = new FlatteningConstructor
-
-  private[this] def yamlToJson(node: Node): Either[ParsingFailure, Json] = {
-
-    def convertScalarNode(node: ScalarNode) = Either.catchNonFatal(node.getTag match {
-      case Tag.INT | Tag.FLOAT => JsonNumber.fromString(node.getValue).map(Json.fromJsonNumber).getOrElse {
-        throw new NumberFormatException(s"Invalid numeric string ${node.getValue}")
-      }
-      case Tag.BOOL => Json.fromBoolean(node.getValue.toBoolean)
-      case Tag.NULL => Json.Null
-      case CustomTag(other) =>
-        Json.fromJsonObject(JsonObject.singleton(other.stripPrefix("!"), Json.fromString(node.getValue)))
-      case other => Json.fromString(node.getValue)
-    }).leftMap {
-      err =>
-        ParsingFailure(err.getMessage, err)
-    }
-
-    def convertKeyNode(node: Node) = node match {
-      case scalar: ScalarNode => Right(scalar.getValue)
-      case _ => Left(ParsingFailure("Only string keys can be represented in JSON", null))
-    }
-
-    node match {
-      case mapping: MappingNode =>
-        flattener.flatten(mapping).getValue.asScala.foldLeft(
-          Either.right[ParsingFailure, JsonObject](JsonObject.empty)
-        ) {
-          (objEither, tup) => for {
-            obj <- objEither
-            key <- convertKeyNode(tup.getKeyNode)
-            value <- yamlToJson(tup.getValueNode)
-          } yield obj.add(key, value)
-        }.map(Json.fromJsonObject)
-      case sequence: SequenceNode =>
-        sequence.getValue.asScala.foldLeft(Either.right[ParsingFailure, List[Json]](List.empty[Json])) {
-          (arrEither, node) => for {
-            arr <- arrEither
-            value <- yamlToJson(node)
-          } yield value :: arr
-        }.map(arr => Json.fromValues(arr.reverse))
-      case scalar: ScalarNode => convertScalarNode(scalar)
-    }
-  }
-
-}
+package object parser extends Parser