From 46695146e95a14bfd3c98a2bf84e259b63550795 Mon Sep 17 00:00:00 2001
From: sksamuel <sam@sksamuel.com>
Date: Sat, 30 Dec 2023 15:15:13 -0600
Subject: [PATCH] Added lengthOrNull variant

---
 .../kotlin/com/sksamuel/tribune/core/nulls.kt |  2 +-
 .../sksamuel/tribune/core/strings/lengths.kt  | 23 ++++++++++++++++++-
 2 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/tribune-core/src/main/kotlin/com/sksamuel/tribune/core/nulls.kt b/tribune-core/src/main/kotlin/com/sksamuel/tribune/core/nulls.kt
index ffc53f3..f69cfcf 100644
--- a/tribune-core/src/main/kotlin/com/sksamuel/tribune/core/nulls.kt
+++ b/tribune-core/src/main/kotlin/com/sksamuel/tribune/core/nulls.kt
@@ -42,7 +42,7 @@ fun <I, A, E> Parser<I, A?, E>.notNull(ifNull: () -> E): Parser<I, A, E> =
    Parser { input: I -> this@notNull.parse(input).flatMap { it?.right() ?: ifNull().leftNel() } }
 
 /**
- * Maps a [Parser] to never fail, by replacing any failing values with null.
+ * Transforms a [Parser] to never fail, by replacing any failing values with null.
  */
 fun <I, A, E> Parser<I, A, E>.failAsNull(): Parser<I, A?, Nothing> =
    Parser { input: I -> this@failAsNull.parse(input).fold({ Either.Right(null) }, { it.right() }) }
diff --git a/tribune-core/src/main/kotlin/com/sksamuel/tribune/core/strings/lengths.kt b/tribune-core/src/main/kotlin/com/sksamuel/tribune/core/strings/lengths.kt
index 98eb7b6..237b983 100644
--- a/tribune-core/src/main/kotlin/com/sksamuel/tribune/core/strings/lengths.kt
+++ b/tribune-core/src/main/kotlin/com/sksamuel/tribune/core/strings/lengths.kt
@@ -9,7 +9,7 @@ import com.sksamuel.tribune.core.flatMap
 /**
  * Narrows an existing String -> String [Parser] by enforcing an exact length on the input string.
  *
- * For strings which have length that differs than the given [len] arguments, an invalid is
+ * For strings which have length that differs than the given [len] arguments, a failure is
  * returned with the error message generated by [ifError].
  *
  * @param len the max length, inclusive
@@ -25,6 +25,27 @@ fun <I, E> Parser<I, String, E>.length(len: Int, ifError: (String) -> E): Parser
       }
    }
 
+/**
+ * Narrows an existing String -> String [Parser] by enforcing an exact length on the input string.
+ *
+ * For strings which have length that differs than the given [len] arguments, a failure is
+ * returned with the error message generated by [ifError].
+ *
+ * @param len the max length, inclusive
+ * @param ifError the error generating function
+ *
+ * @return valid if the input string is less than or equal to [len] or an invalid otherwise.
+ */
+@JvmName("lengthOrNull")
+fun <I, E> Parser<I, String?, E>.length(len: Int, ifError: (String) -> E): Parser<I, String?, E> =
+   flatMap {
+      when {
+         it == null -> Either.Right(null)
+         it.length == len -> it.right()
+         else -> ifError(it).leftNel()
+      }
+   }
+
 /**
  * Maps a string producing [Parser] by enforcing a length on the string.
  *