From a85df04fcb2876591ac39d55e920c7cd15411431 Mon Sep 17 00:00:00 2001
From: Valentin Gagarin <valentin.gagarin@tweag.io>
Date: Fri, 26 Aug 2022 23:09:19 +0200
Subject: refactor showOptions

it was quite a pain to manipulate strings just with `builtins`
---
 doc/manual/utils.nix | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

(limited to 'doc/manual/utils.nix')

diff --git a/doc/manual/utils.nix b/doc/manual/utils.nix
index d4b18472f..d0643ef46 100644
--- a/doc/manual/utils.nix
+++ b/doc/manual/utils.nix
@@ -5,6 +5,32 @@ rec {
 
   concatStrings = concatStringsSep "";
 
+  replaceStringsRec = from: to: string:
+    # recursively replace occurrences of `from` with `to` within `string`
+    # example:
+    #     replaceStringRec "--" "-" "hello-----world"
+    #     => "hello-world"
+    let
+      replaced = replaceStrings [ from ] [ to ] string;
+    in
+      if replaced == string then string else replaceStringsRec from to replaced;
+
+  squash = replaceStringsRec "\n\n\n" "\n\n";
+
+  trim = string:
+    # trim trailing spaces and squash non-leading spaces
+    let
+      trimLine = line:
+        let
+          # separate leading spaces from the rest
+          parts = split "(^ *)" line;
+          spaces = head (elemAt parts 1);
+          rest = elemAt parts 2;
+          # drop trailing spaces
+          body = head (split " *$" rest);
+        in spaces + replaceStringsRec "  " " " body;
+    in concatStringsSep "\n" (map trimLine (splitLines string));
+
   # FIXME: O(n^2)
   unique = foldl' (acc: e: if elem e acc then acc else acc ++ [ e ]) [];
 
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