initial JsonPath support

1 files changed, 70 insertions, 0 deletions

diff --git a/src/main/scala/cc/spray/json/JsonPathParser.scala b/src/main/scala/cc/spray/json/JsonPathParser.scala
new file mode 100644
index 0000000..b216e28
--- /dev/null
+++ b/src/main/scala/cc/spray/json/JsonPathParser.scala
@@ -0,0 +1,70 @@
+package cc.spray.json
+
+import org.parboiled.scala._
+import org.parboiled.errors.{ErrorUtils, ParsingException}
+
+object JsonPathParser extends Parser {
+  def JsonPathExpr = rule { Tree ~ EOI }
+
+  def Tree: Rule1[JsonPath.Expr] = rule { Root ~ OptionalSelection }
+
+  def Root: Rule1[JsonPath.Root.type] = rule { "$" ~ push(JsonPath.Root) }
+
+  /*
+   * To remove the left-recursion I had to factor out Root to here
+   */
+  def OptionalSelection : ReductionRule1[JsonPath.Expr, JsonPath.Expr] = rule {
+    Projection ~~> JsonPath.Selection ~ OptionalSelection |
+    EMPTY ~~> identity
+  }
+
+  def Projection: Rule1[JsonPath.Projection] = rule {
+    "." ~ DotProjection          |
+    "[" ~ BracketProjection ~"]"
+  }
+
+  def DotProjection: Rule1[JsonPath.Projection] = rule {
+    AllElements | ByFieldName
+  }
+  def AllElements = rule { "*" ~ push(JsonPath.AllElements) }
+  def ByFieldName = rule { FieldName ~~> JsonPath.ByField }
+
+  def BracketProjection: Rule1[JsonPath.Projection] = rule {
+    JsonParser.Digits ~> (d => JsonPath.ByIndex(d.toInt)) |
+    SingleQuotedString ~~> JsonPath.ByField
+  }
+
+  def FieldName: Rule1[String] = rule {
+    oneOrMore(!anyOf(".") ~ ANY) ~> identity
+  }
+
+  def SingleQuotedString: Rule1[String] =
+    rule { "'" ~ push(new java.lang.StringBuilder) ~ zeroOrMore(!anyOf("'") ~ ("\\" ~ JsonParser.EscapedChar | JsonParser.NormalChar)) } ~ "'" ~~> (_.toString)
+
+  /**
+   * The main parsing method. Uses a ReportingParseRunner (which only reports the first error) for simplicity.
+   */
+  def apply(path: String): JsonPath.Expr = apply(path.toCharArray)
+
+  /**
+   * The main parsing method. Uses a ReportingParseRunner (which only reports the first error) for simplicity.
+   */
+  def apply(path: Array[Char]): JsonPath.Expr = {
+    val parsingResult = ReportingParseRunner(JsonPathExpr).run(path)
+    parsingResult.result.getOrElse {
+      throw new ParsingException("Invalid JSON source:\n" + ErrorUtils.printParseErrors(parsingResult))
+    }
+  }
+}
+
+object JsonPath {
+  sealed trait Expr
+  case object Root extends Expr
+  case class Selection(previous: Expr, projection: Projection) extends Expr
+
+  sealed trait Projection
+  case object AllElements extends Projection
+  case class ByField(name: String) extends Projection
+  case class ByIndex(idx: Int) extends Projection
+  //case class ByPredicate()
+}
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