From 9ef9cae60fe45ad0aff3f4b294d7f4e89266d4d9 Mon Sep 17 00:00:00 2001
From: Doug Coleman <doug.coleman@gmail.com>
Date: Sat, 16 Sep 2017 17:21:31 -0500
Subject: [PATCH] escape-strings: Add a way to find minmal escapes for a
 lua/magic string.

---
 basis/escape-strings/authors.txt              |  2 ++
 .../escape-strings-tests.factor               | 12 ++++++++++
 basis/escape-strings/escape-strings.factor    | 22 +++++++++++++++++++
 3 files changed, 36 insertions(+)
 create mode 100644 basis/escape-strings/authors.txt
 create mode 100644 basis/escape-strings/escape-strings-tests.factor
 create mode 100644 basis/escape-strings/escape-strings.factor

diff --git a/basis/escape-strings/authors.txt b/basis/escape-strings/authors.txt
new file mode 100644
index 0000000000..dbe8e57c80
--- /dev/null
+++ b/basis/escape-strings/authors.txt
@@ -0,0 +1,2 @@
+John Benediktsson
+Doug Coleman
diff --git a/basis/escape-strings/escape-strings-tests.factor b/basis/escape-strings/escape-strings-tests.factor
new file mode 100644
index 0000000000..4aa82f8242
--- /dev/null
+++ b/basis/escape-strings/escape-strings-tests.factor
@@ -0,0 +1,12 @@
+! Copyright (C) 2017 John Benediktsson, Doug Coleman.
+! See http://factorcode.org/license.txt for BSD license.
+USING: tools.test escape-strings ;
+IN: escape-strings.tests
+
+{ "[[asdf]]" } [ "asdf" escape-string ] unit-test
+{ "[[[[]]" } [ "[[" escape-string ] unit-test
+{ "[=[]]]=]" } [ "]]" escape-string ] unit-test
+
+{ "[===[]]]==][=[=]=]]===]" } [ "]]]==][=[=]=]" escape-string ] unit-test
+{ "[[[=[=]=]]]" } [ "[=[=]=]" escape-string ] unit-test
+{ "[[[a[]]" } [ "[a[" escape-string ] unit-test
diff --git a/basis/escape-strings/escape-strings.factor b/basis/escape-strings/escape-strings.factor
new file mode 100644
index 0000000000..1140100dbf
--- /dev/null
+++ b/basis/escape-strings/escape-strings.factor
@@ -0,0 +1,22 @@
+! Copyright (C) 2017 John Benediktsson, Doug Coleman.
+! See http://factorcode.org/license.txt for BSD license.
+USING: combinators kernel math math.order sequences ;
+IN: escape-strings
+
+! TODO: Move the "]]" subseq? check into the each loop logic
+: #escapes ( str -- n/f )
+    [ f f f ] dip [
+        {
+            { char: = [ [ dup [ 1 + ] when ] bi@ ] }
+            { char: ] [ [ [ 0 or ] 2dip [ max ] curry dip ] when* 0 ] }
+            [ 2drop f ]
+        } case
+    ] each 2drop ;
+
+: escape-string ( str -- str' )
+    "]]" over subseq? [
+        dup #escapes ?1+ char: = <repetition>
+        [ "[" dup surround ] [ "]" dup surround ] bi surround
+    ] [
+        "[[" "]]" surround
+    ] if ;
\ No newline at end of file