add tests, tweak functionality

build.sbt

@@ -1,4 +1,2 @@
 name := "strings"
-version := "1.0.0"
-libraryDependencies ++= Seq(
-)
+version := "1.0.0-SNAPSHOT"

src/main/scala/org/hammerlab/csv/ProductToCSVRow.scala

@@ -1,6 +1,7 @@
-package org.hammerlab.pageant.utils
+package org.hammerlab.csv
 
 class ProductToCSVRow(val prod: Product) extends AnyVal {
+  // cf. http://stackoverflow.com/questions/30271823/converting-a-case-class-to-csv-in-scala
   def toCSV = prod.productIterator.map {
     case Some(value) => value
     case None => ""

src/main/scala/org/hammerlab/csv/ProductsToCSV.scala

@@ -1,24 +1,37 @@
-package org.hammerlab.pageant.utils
+package org.hammerlab.csv
 
-import ProductToCSVRow._
+import org.hammerlab.csv.ProductToCSVRow._
 
-class ProductsToCSV[T <: Product](products: BufferedIterator[T]) {
+import scala.reflect.ClassTag
+
+class ProductsToCSV[T <: Product: ClassTag](products: Iterator[T]) {
   def toCSV(includeHeaderLine: Boolean = true): Iterator[String] =
     if (includeHeaderLine) {
-      val clazz =
-        if (products.hasNext)
-          products.head.getClass
-        else
-          classOf[T]
+      val (clazz, firstOpt) =
+        if (products.hasNext) {
+          val first = products.next()
+          (first.getClass, Some(first))
+        } else {
+          val ctag = implicitly[reflect.ClassTag[T]]
+          (ctag.runtimeClass.asInstanceOf[Class[T]], None)
+        }
 
-      val headerLine = clazz.getDeclaredFields.map(_.getName).mkString(",")
+      val headerLine =
+        clazz
+          .getDeclaredFields
+          .map(_.getName)
+          .filterNot(_ == "$outer")  // Field added on case classes nested inside another class.
+          .mkString(",")
 
-      Iterator(headerLine) ++ toCSV(includeHeaderLine = false)
+      Iterator(headerLine) ++
+        firstOpt.map(_.toCSV).iterator ++
+        toCSV(includeHeaderLine = false)
     } else
       products.map(_.toCSV)
 }
 
 object ProductsToCSV {
-  implicit def apply[T <: Product](products: Iterable[T]): ProductsToCSV[T] = new ProductsToCSV(products.iterator.buffered)
-  implicit def apply[T <: Product](products: Array[T]): ProductsToCSV[T] = new ProductsToCSV(products.iterator.buffered)
+  implicit def apply[T <: Product: ClassTag](products: Iterator[T]): ProductsToCSV[T] = new ProductsToCSV(products)
+  implicit def apply[T <: Product: ClassTag](products: Iterable[T]): ProductsToCSV[T] = new ProductsToCSV(products.iterator)
+  implicit def apply[T <: Product: ClassTag](products: Array[T]): ProductsToCSV[T] = new ProductsToCSV(products.iterator)
 }

src/main/scala/org/hammerlab/strings/TruncatedToString.scala

@@ -1,38 +1,50 @@
 package org.hammerlab.strings
 
 trait TruncatedToString {
-  override def toString: String = truncatedString(Int.MaxValue)
-
-  /** String representation, truncated to maxLength characters. */
-  def truncatedString(maxLength: Int = 500): String =
-    TruncatedToString(stringPieces, maxLength)
+  override def toString: String = toString(Int.MaxValue)
 
-  /**
-   * Iterator over string representations of data comprising this object.
-   */
-  def stringPieces: Iterator[String]
-}
-
-object TruncatedToString {
   /**
    * Like Scala's List.mkString method, but supports truncation.
    *
    * Return the concatenation of an iterator over strings, separated by separator, truncated to at most maxLength
    * characters. If truncation occurs, the string is terminated with ellipses.
    */
-  def apply(pieces: Iterator[String],
-            maxLength: Int,
-            separator: String = ",",
-            ellipses: String = " [...]"): String = {
+  def toString(maxLength: Int,
+               separator: String = ",",
+               ellipses: String = "…"): String = {
+
     val builder = StringBuilder.newBuilder
     var remaining: Int = maxLength
-    while (pieces.hasNext && remaining > ellipses.length) {
-      val string = pieces.next()
-      builder.append(string)
-      if (pieces.hasNext) builder.append(separator)
-      remaining -= string.length + separator.length
+
+    val separatedPieces =
+      stringPieces
+        .flatMap(piece ⇒ Iterator(separator, piece))
+        .drop(1)
+        .buffered
+
+    while (separatedPieces.hasNext && remaining >= 0) {
+      val piece = separatedPieces.head.toString
+      val len = piece.length
+
+      if (len <= remaining) {
+        builder.append(piece)
+        separatedPieces.next()
+        remaining -= len
+      } else {
+        remaining = -1
+      }
     }
-    if (pieces.hasNext) builder.append(ellipses)
-    builder.result
+
+    val result = builder.result
+
+    if (separatedPieces.hasNext)
+      result.substring(0, maxLength - ellipses.length) + ellipses
+    else
+      result
   }
+
+  /**
+   * Iterator over string representations of data comprising this object.
+   */
+  def stringPieces: Iterator[String]
 }

src/test/scala/org/hammerlab/csv/ProductsToCSVTest.scala

@@ -0,0 +1,35 @@
+package org.hammerlab.csv
+
+import org.scalatest.{ FunSuite, Matchers }
+
+import ProductsToCSV._
+
+class ProductsToCSVTest
+  extends FunSuite
+    with Matchers {
+
+  // cf. http://stackoverflow.com/questions/30271823/converting-a-case-class-to-csv-in-scala
+  case class Person(name: String, age: Int, address: Option[String])
+
+  test("people") {
+    val ppl =
+      Seq(
+        Person("alice", 123, None),
+        Person("bob", 456, Some("foo"))
+      )
+
+    ppl.toCSV().mkString("\n") should be(
+      """name,age,address
+        |alice,123,
+        |bob,456,foo""".stripMargin
+    )
+  }
+
+  test("no people") {
+    Seq[Person]().toCSV().mkString("\n") should be("name,age,address")
+  }
+
+  test("no people, no header") {
+    Seq[Person]().toCSV(includeHeaderLine = false).mkString("\n") should be("")
+  }
+}

src/test/scala/org/hammerlab/strings/TruncatedToStringTest.scala

@@ -0,0 +1,34 @@
+package org.hammerlab.strings
+
+import org.scalatest.{ FunSuite, Matchers }
+
+class TruncatedToStringTest
+  extends FunSuite
+    with Matchers {
+
+  test("numbers") {
+    val o = new TruncatedToString {
+      override def stringPieces = (1 to 10).iterator.map(_.toString)
+    }
+
+    o.toString(10) should be("1,2,3,4,5…")
+    o.toString(17) should be("1,2,3,4,5,6,7,8,…")
+    o.toString(18) should be("1,2,3,4,5,6,7,8,9…")
+    o.toString(19) should be("1,2,3,4,5,6,7,8,9,…")
+    o.toString(20) should be("1,2,3,4,5,6,7,8,9,10")
+    o.toString(100) should be("1,2,3,4,5,6,7,8,9,10")
+    o.toString() should be("1,2,3,4,5,6,7,8,9,10")
+  }
+
+  test("empties") {
+    val o = new TruncatedToString {
+      override def stringPieces = Array.fill(5)("").iterator
+    }
+
+    o.toString(5) should be(",,,,")
+    o.toString(4) should be(",,,,")
+    o.toString(3) should be(",,…")
+    o.toString(2) should be(",…")
+    o.toString(1) should be("…")
+  }
+}