phone-number 1.2.0.3: enforce area/exchange not starting with 1

1.0.1 and 1.0.2: description clarifications
exercism/problem-specifications#719
exercism/problem-specifications#724

1.1.0: enforce area/exchange not starting with 1
exercism/problem-specifications#745

1.2.0: 1a2b3c4d5e6f7g8h9i0j removed
exercism/problem-specifications#772

Closes #518

exercises/phone-number/examples/success-standard/src/Phone.hs

@@ -1,9 +1,18 @@
 module Phone (number) where
-import Data.Char (isDigit, isLetter)
+import Data.Char (isDigit)
 
 number :: String -> Maybe String
-number input
-  | any isLetter input = Nothing
+number input = clean input >>= check
+
+check :: String -> Maybe String
+check ('0':_) = Nothing
+check ('1':_) = Nothing
+check (_:_:_:'0':_) = Nothing
+check (_:_:_:'1':_) = Nothing
+check s = Just s
+
+clean :: String -> Maybe String
+clean input
   | len == 10 = Just digits
   | len == 11 && head digits == '1' = Just $ tail digits
   | otherwise = Nothing

exercises/phone-number/package.yaml

@@ -1,5 +1,5 @@
 name: phone-number
-version: 1.0.0.2
+version: 1.2.0.3
 
 dependencies:
   - base

exercises/phone-number/test/Tests.hs

@@ -23,30 +23,34 @@ data Case = Case { description ::       String
 cases :: [Case]
 cases =
     [ Case { description = "cleans the number"
-           , input       = "(123) 456-7890"
-           , expected    = Just "1234567890"
+           , input       = "(223) 456-7890"
+           , expected    = Just "2234567890"
            }
-    , Case { description = "cleans number with dots"
-           , input       = "123.456.7890"
-           , expected    = Just "1234567890"
+    , Case { description = "cleans numbers with dots"
+           , input       = "223.456.7890"
+           , expected    = Just "2234567890"
            }
     , Case { description = "cleans numbers with multiple spaces"
-           , input       = "123 456   7890   "
-           , expected    = Just "1234567890"
+           , input       = "223 456   7890   "
+           , expected    = Just "2234567890"
            }
     , Case { description = "invalid when 9 digits"
            , input       = "123456789"
            , expected    = Nothing
            }
-    , Case { description = "invalid when 11 digits"
-           , input       = "21234567890"
+    , Case { description = "invalid when 11 digits does not start with a 1"
+           , input       = "22234567890"
            , expected    = Nothing
            }
-    , Case { description = "valid when 11 digits and first is 1"
-           , input       = "11234567890"
-           , expected    = Just "1234567890"
+    , Case { description = "valid when 11 digits and starting with 1"
+           , input       = "12234567890"
+           , expected    = Just "2234567890"
+           }
+    , Case { description = "valid when 11 digits and starting with 1 even with punctuation"
+           , input       = "+1 (223) 456-7890"
+           , expected    = Just "2234567890"
            }
-    , Case { description = "invalid when 12 digits"
+    , Case { description = "invalid when more than 11 digits"
            , input       = "321234567890"
            , expected    = Nothing
            }
@@ -58,8 +62,12 @@ cases =
            , input       = "123-@:!-7890"
            , expected    = Nothing
            }
-    , Case { description = "invalid with right number of digits but letters mixed in"
-           , input       = "1a2b3c4d5e6f7g8h9i0j"
+    , Case { description = "invalid if area code does not start with 2-9"
+           , input       = "(123) 456-7890"
+           , expected    = Nothing
+           }
+    , Case { description = "invalid if exchange code does not start with 2-9"
+           , input       = "(223) 056-7890"
            , expected    = Nothing
            }
     ]