From 3702aae17decd1a08213b8a0b8be2da841c9c33a Mon Sep 17 00:00:00 2001
From: John Mettraux <jmettraux@gmail.com>
Date: Mon, 5 Dec 2022 11:35:10 +0900
Subject: [PATCH] Bring in Fugit.parse_cronish and .do_parse_cronish

gh-70
---
 CHANGELOG.md       |  2 ++
 README.md          | 17 ++++++++++++++
 lib/fugit/parse.rb | 13 +++++++++++
 spec/parse_spec.rb | 56 ++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 88 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9d5e981..207af05 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,8 @@
 
 ## fugit 1.8.0 not yet released
 
+* Introduce Fugit.parse_cronish and .do_parse_cronish, gh-70
+
 
 ## fugit 1.7.2 released 2022-11-03
 
diff --git a/README.md b/README.md
index d8c39e5..86fde65 100644
--- a/README.md
+++ b/README.md
@@ -89,6 +89,23 @@ Fugit.parse_nat('every day at noon').class  # ==> ::Fugit::Cron
 
 As `Fugit.parse(s)` returns nil when it doesn't grok its input, and `Fugit.do_parse(s)` fails when it doesn't grok, each of the `parse_` methods has its partner `do_parse_` method.
 
+## parse_cronish and do_parse_cronish
+
+Sometimes you know a cron expression or an "every" natural expression will come in and you want to discard the rest.
+
+```
+require 'fugit'
+
+Fugit.parse_cronish('0 0 1 jan *').class             # ==> ::Fugit::Cron
+Fugit.parse_cronish('every saturday at noon').class  # ==> ::Fugit::Cron
+
+Fugit.parse_cronish('12y12M')        # ==> nil
+```
+
+`.parse_cronish(s)` will return a `Fugit::Cron` instance or else nil.
+
+`.do_parse_cronish(s)` will return a `Fugit::Cron` instance or else fail with an `ArgumentError`.
+
 ## `Fugit::Cron`
 
 A class `Fugit::Cron` to parse cron strings and then `#next_time` and `#previous_time` to compute the next or the previous occurrence respectively.
diff --git a/lib/fugit/parse.rb b/lib/fugit/parse.rb
index 8cb1d9f..2304bf8 100644
--- a/lib/fugit/parse.rb
+++ b/lib/fugit/parse.rb
@@ -33,6 +33,19 @@ def do_parse(s, opts={})
       fail(ArgumentError.new("found no time information in #{s.inspect}"))
     end
 
+    def parse_cronish(s, opts={})
+
+      r = parse_cron(s) || parse_nat(s, opts)
+
+      r.is_a?(::Fugit::Cron) ? r : nil
+    end
+
+    def do_parse_cronish(s, opts={})
+
+      parse_cronish(s) ||
+      fail(ArgumentError.new("not cron or 'natural' cron string: #{s.inspect}"))
+    end
+
     def determine_type(s)
 
       case self.parse(s)
diff --git a/spec/parse_spec.rb b/spec/parse_spec.rb
index 2d0cc79..13e7fea 100644
--- a/spec/parse_spec.rb
+++ b/spec/parse_spec.rb
@@ -137,6 +137,62 @@
     end
   end
 
+  CRONISHES = {
+
+    '* * * * *' => '* * * * *',
+    'every day' => '0 0 * * *',
+
+    '2022-12-5 11:32' => ArgumentError,
+    'nada' => ArgumentError,
+    '100 * * * *' => ArgumentError,
+      }
+
+  describe '.parse_cronish' do
+
+    CRONISHES.each do |k, v|
+
+      if v.is_a?(String)
+
+        it "parses #{k.inspect} to #{v.inspect}" do
+
+          r = Fugit.parse_cronish(k)
+
+          expect(r.class).to eq(Fugit::Cron)
+          expect(r.original).to eq(v)
+        end
+      else
+
+        it "returns nil for #{k.inspect}" do
+
+          expect(Fugit.parse_cronish(k)).to eq(nil)
+        end
+      end
+    end
+  end
+
+  describe '.do_parse_cronish' do
+
+    CRONISHES.each do |k, v|
+
+      if v.is_a?(String)
+
+        it "parses #{k.inspect} to #{v.inspect}" do
+
+          r = Fugit.do_parse_cronish(k)
+
+          expect(r.class).to eq(Fugit::Cron)
+          expect(r.original).to eq(v)
+        end
+      else
+
+        it "fails on #{k.inspect}" do
+
+          expect { Fugit.do_parse_cronish(k) }.to raise_error(v)
+        end
+      end
+    end
+  end
+
   describe '.determine_type' do
 
     it 'returns nil if it cannot determine' do