✨ Implement demojize function for bidirectional emoji conversion (#16)

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

README.md

@@ -12,7 +12,8 @@
 
 <!-- end badges -->
 
-A Python library for converting Discord emoji names to their Unicode equivalents.
+A Python library for converting Discord emoji names to their Unicode equivalents and
+vice versa.
 
 </div>
 
@@ -31,9 +32,9 @@ A Python library for converting Discord emoji names to their Unicode equivalents
 ## Overview
 
 Dismoji is a lightweight Python library that provides a simple way to convert Discord
-emoji names to their Unicode equivalents. With just a single function call, you can
-transform text containing Discord-style emoji codes (like `:smile:`) into text with
-actual Unicode emoji characters (like "😄").
+emoji names to their Unicode equivalents and vice versa. With just two function calls,
+you can transform text containing Discord-style emoji codes (like `:smile:`) into text
+with actual Unicode emoji characters (like "😄") and back again.
 
 This library uses
 [Paillat-dev/discord-emojis](https://github.com/Paillat-dev/discord-emojis) as the
@@ -56,16 +57,23 @@ import dismoji
 text = "Hello, :wave: I'm excited! :partying_face:"
 converted_text = dismoji.emojize(text)
 print(converted_text)  # Output: "Hello, 👋 I'm excited! 🥳"
+
+# Convert Unicode emojis back to Discord emoji names
+emoji_text = "Hello, 👋 I'm excited! 🥳"
+named_text = dismoji.demojize(emoji_text)
+print(named_text)  # Output: "Hello, :wave: I'm excited! :partying_face:"
 ```
 
 ## Features
 
-- **Simple API**: Just one function to remember - `dismoji.emojize()`
+- **Simple API**: Just two functions to remember - `dismoji.emojize()` and
+  `dismoji.demojize()`
 - **Discord Compatible**: Supports Discord's emoji naming conventions
 - **Comprehensive**: Includes all standard emojis available on Discord
 - **Type Safe**: Fully type-annotated for better IDE integration
 - **Zero Dependencies**: Lightweight with no external dependencies
 - **Fast**: Optimized for quick emoji replacement
+- **Bidirectional**: Convert between emoji names and characters in both directions
 
 ## Getting Help
 

src/dismoji/__init__.py

@@ -14,10 +14,21 @@ with EMOJIS_PATH.open("r", encoding="utf-8") as f:
 
 EMOJI_MAPPING: dict[str, str] = {k: EMOJIS["emojis"][v]["surrogates"] for k, v in EMOJIS["nameToEmoji"].items()}
 
+# Create a reverse mapping for demojizing (emoji to name)
+REVERSE_EMOJI_MAPPING: dict[str, str] = {}
+for emoji_index_str, emoji_index in sorted(EMOJIS["surrogateToEmoji"].items(), key=lambda x: len(x[0]), reverse=True):
+    # Get the first name in the list as the preferred name
+    e = EMOJIS["emojis"][emoji_index]
+    # If it has multiple diversity parents, use the last name because it is the most specific one
+    # e.g. :handshake_light_skin_tone_dark_skin_tone: vs :handshake_tone1_tone5:
+    REVERSE_EMOJI_MAPPING[emoji_index_str] = e["names"][-1 if e.get("hasMultiDiversityParent") else 0]
+
 del EMOJIS  # Clean up to save memory
 
 EMOJI_PATTERN = re.compile(r":([a-zA-Z0-9_-]+):")
 
+EMOJI_CHARS_PATTERN = re.compile("|".join(map(re.escape, REVERSE_EMOJI_MAPPING.keys())))
+
 
 def emojize(s: str) -> str:
     """Convert a string with emoji names to a string with emoji characters.
@@ -37,3 +48,21 @@ def emojize(s: str) -> str:
         return match.group(0)
 
     return EMOJI_PATTERN.sub(replace, s)
+
+
+def demojize(s: str) -> str:
+    """Convert a string with emoji characters to a string with emoji names.
+
+    Args:
+        s (str): The input string containing emoji characters.
+
+    Returns:
+        str: The input string with emoji characters replaced by emoji names.
+
+    """
+
+    def replace(match: re.Match[str]) -> str:
+        emoji = match.group(0)
+        return f":{REVERSE_EMOJI_MAPPING[emoji]}:"
+
+    return EMOJI_CHARS_PATTERN.sub(replace, s)

tests/emoji_test.py

@@ -1,7 +1,7 @@
 # Copyright (c) Paillat-dev
 # SPDX-License-Identifier: MIT
 
-from dismoji import emojize
+from dismoji import REVERSE_EMOJI_MAPPING, demojize, emojize
 
 
 def test_basic() -> None:
@@ -68,3 +68,42 @@ def test_emoji_with_special_characters() -> None:
     ]
     for input_str, expected_output in special_char_tests:
         assert emojize(input_str) == expected_output
+
+
+def test_demojize_basic() -> None:
+    """Test basic functionality of demojize function."""
+    assert demojize("Hello 😄") == "Hello :smile:"
+
+
+def test_demojize_no_match() -> None:
+    """Test demojize function with no matches."""
+    assert demojize("Hello world") == "Hello world"
+
+
+def test_demojize_multiple_emojis() -> None:
+    """Test demojize function with multiple emojis."""
+    assert demojize("😄 👋") == ":smile: :wave:"
+
+
+def test_demojize_complex_sentence() -> None:
+    """Test demojize function with a complex sentence."""
+    assert demojize("Hello 👋, what's up? 😄 ✅ 😄") == "Hello :wave:, what's up? :smile: :white_check_mark: :smile:"
+
+
+def test_demojize_surrogate() -> None:
+    """Test demojize function with surrogate pairs."""
+    surrogate_pairs = [
+        ("🫱🏻‍🫲🏿", ":handshake_light_skin_tone_dark_skin_tone:"),
+        ("🫱🏿‍🫲🏻", ":handshake_dark_skin_tone_light_skin_tone:"),
+        ("🫱🏽‍🫲🏻", ":handshake_medium_skin_tone_light_skin_tone:"),
+        ("🫱🏼‍🫲🏿", ":handshake_medium_light_skin_tone_dark_skin_tone:"),
+        ("🫱🏾‍🫲🏻", ":handshake_medium_dark_skin_tone_light_skin_tone:"),
+    ]
+
+    for surrogate, emoji_name in surrogate_pairs:
+        assert demojize(surrogate) == emoji_name
+
+
+def test_demojize_all() -> None:
+    for emoji, name in REVERSE_EMOJI_MAPPING.items():
+        assert demojize(emoji) == f":{name}:"