two line demo

data/one-line.txt

@@ -0,0 +1 @@
+one line

data/two-lines.txt

@@ -0,0 +1,2 @@
+foo
+bar

firepower-demo/src/main/scala/com/htmlism/firepower/demo/Line.scala

@@ -0,0 +1,10 @@
+package com.htmlism.firepower.demo
+
+case class Line(s: String)
+
+object Line:
+  def mkString(xs: List[Line]): String =
+    xs
+      .iterator
+      .map(_.s)
+      .mkString("\n")

firepower-demo/src/main/scala/com/htmlism/firepower/demo/PrintPrograms.scala

@@ -7,12 +7,21 @@ import java.io.IOException
 import com.htmlism.rufio.withzio._
 
 object PrintPrograms extends ZIOAppDefault:
-  def run: ZIO[Any, Throwable, Unit] =
-    for {
-      _ <- File("data/out.txt")
-        .writeLine("out")
+  private def writeLine(file: String)(s: String) =
+    File(s"data/$file.txt")
+      .writeLine(s)
 
-      _ <- File("data/example.txt")
-        .contents
-        .map(Console.printLine(_))
+  private val programs =
+    List[(String, String)](
+      "one-line.txt"  -> "one line",
+      "two-lines.txt" -> (Line.mkString _)
+        .apply(List("foo", "bar").map(Line(_)))
+    )
+
+  def run: Task[Unit] =
+    for {
+      // just a traverse in slow motion...
+      _ <- programs
+             .map { case (f, s) => File(s"data/$f").writeLine(s) }
+             .foldLeft[Task[Unit]](ZIO.unit)((acc, z) => acc *> z)
     } yield ()