feat: add roman command to convert numbers and Roman numerals (#91)

fixit/cli.py

@@ -7,7 +7,7 @@
 from pathlib import Path
 from typing import Optional
 
-from fixit import __version__, convert, jsonfmt, password, textutils, wordcount
+from fixit import __version__, convert, jsonfmt, password, textutils, wordcount, roman
 
 CONVERSIONS = {
     "c2f": convert.celsius_to_fahrenheit,
@@ -75,6 +75,11 @@ def run_top_words(args: argparse.Namespace) -> None:
 def run_slugify(args: argparse.Namespace) -> None:
     print(textutils.slugify(args.text))
 
+def run_roman(args: argparse.Namespace) -> None:
+    if args.value.isdigit():
+        print(roman.to_roman(int(args.value)))
+    else:
+        print(roman.from_roman(args.value))                         
 
 COMMAND_TABLE = {
     "wc": run_wc,
@@ -86,6 +91,7 @@ def run_slugify(args: argparse.Namespace) -> None:
     "reverse": run_reverse,
     "slugify": run_slugify,
     "top-words": run_top_words,
+    "roman" : run_roman,
 }
 
 
@@ -136,6 +142,9 @@ def build_parser() -> argparse.ArgumentParser:
         "--n", type=int, default=3, help="number of words to show (default: 3)"
     )
 
+    rom = sub.add_parser("roman", help="check if value is a roman")
+    rom.add_argument("value")
+
     return parser
 
 

fixit/roman.py

@@ -0,0 +1,33 @@
+ROMAN_VALUES = [
+    (1000, "M"), (900, "CM"), (500, "D"), (400, "CD"),
+    (100, "C"), (90, "XC"), (50, "L"), (40, "XL"),
+    (10, "X"), (9, "IX"), (5, "V"), (4, "IV"), (1, "I"),
+]
+
+def to_roman(number: int) -> str:
+
+    """Convert an integer from 1 to 3999 to a Roman numeral."""
+
+    if number < 1 or number > 3999:
+        raise ValueError("Error: number must be between 0 and 1000")
+
+    result = ""
+    for value, symbol in ROMAN_VALUES:
+        while number >= value:
+            result += symbol
+            number -= value
+    return result
+
+def from_roman(numeral: str) -> int:
+    """Convert a Roman numeral to an integer."""
+
+    text = numeral.upper()
+    total = 0
+    pos = 0
+    for value, symbol in ROMAN_VALUES:
+        while text.startswith(symbol, pos):   
+            total += value                     
+            pos += len(symbol)                  
+    if total == 0 or to_roman(total) != text:   
+        raise ValueError(f"Error: '{numeral}' is not a valid Roman numeral")
+    return total   

tests/test_roman.py

@@ -0,0 +1,57 @@
+import pytest
+
+from fixit.roman import from_roman, to_roman
+
+
+# --- to_roman: normal and edge cases ---
+
+def test_to_roman_1994():
+    assert to_roman(1994) == "MCMXCIV"
+
+
+def test_to_roman_smallest():
+    assert to_roman(1) == "I"            # what is 1 in Roman?
+
+
+def test_to_roman_largest():
+    assert to_roman(3999) == "MMMCMXCIX"         # the biggest Roman numeral (you saw it earlier)
+
+
+def test_to_roman_rejects_zero():
+    with pytest.raises(ValueError):
+        to_roman(0)                    # just below the allowed range
+
+
+def test_to_roman_rejects_4000():
+    with pytest.raises(ValueError):
+        to_roman(4000)                    # just above the allowed range
+
+
+# --- from_roman: normal and edge cases ---
+
+def test_from_roman_1994():
+    assert from_roman("MCMXCIV") == 1994  # the number
+
+
+def test_from_roman_lowercase():
+    assert from_roman("mcmxciv") == 1994       # same numeral, in lowercase letters
+
+
+def test_from_roman_rejects_four_in_a_row():
+    with pytest.raises(ValueError):
+        from_roman("IIII")                  # 4 written the WRONG way (4 of the same letter)
+
+
+def test_from_roman_rejects_bad_pair():
+    with pytest.raises(ValueError):
+        from_roman("IC")
+
+
+def test_from_roman_rejects_empty():
+    with pytest.raises(ValueError):
+        from_roman("")                  # an empty string
+
+
+def test_from_roman_rejects_letters():
+    with pytest.raises(ValueError):
+        from_roman("ABC")