Provide a pre-built SourceCode cog based on bot version

2 files changed, 169 insertions, 1 deletions

diff --git a/pydis_core/exts/__init__.py b/pydis_core/exts/__init__.py
index 9d59e8ad..b2d2fa2f 100644
--- a/pydis_core/exts/__init__.py
+++ b/pydis_core/exts/__init__.py
@@ -1,4 +1,6 @@
 """Reusable Discord cogs."""
-__all__ = []
+from .source import SourceCode
+
+__all__ = [SourceCode]
 
 __all__ = [module.__name__ for module in __all__]
diff --git a/pydis_core/exts/source.py b/pydis_core/exts/source.py
new file mode 100644
index 00000000..d17940c3
--- /dev/null
+++ b/pydis_core/exts/source.py
@@ -0,0 +1,166 @@
+import enum
+import inspect
+from pathlib import Path
+from typing import NamedTuple, TYPE_CHECKING
+
+from discord import Embed
+from discord.ext import commands
+from discord.utils import escape_markdown
+
+if TYPE_CHECKING:
+    from pydis_core import BotBase as Bot
+
+
+class TagIdentifierStub(NamedTuple):
+    """A minmally functioning stub representing a tag identifier."""
+
+    group: str | None
+    name: str
+
+    @classmethod
+    def from_string(cls, string: str) -> "TagIdentifierStub":
+        """Create a TagIdentifierStub from a string."""
+        split_string = string.split(" ", maxsplit=2)
+        if len(split_string) == 1:
+            return cls(None, split_string[0])
+        return cls(split_string[0], split_string[1])
+
+
+class SourceType(enum.StrEnum):
+    """The types of source objects recognized by the source command."""
+
+    help_command = enum.auto()
+    command = enum.auto()
+    cog = enum.auto()
+    tag = enum.auto()
+    extension_not_loaded = enum.auto()
+
+
+class SourceCode(commands.Cog, description="Displays information about the bot's source code."):
+    """
+    Pre-built cog to display source code links for commands and cogs (and if applicable, tags).
+
+    To use this cog, instantiate it with the bot instance and the base GitHub repository URL.
+
+    Args:
+        bot (:obj:`pydis_core.BotBase`): The bot instance.
+        github_repo: The base URL to the GitHub repository (e.g. `https://github.com/python-discord/bot`).
+    """
+
+    def __init__(self, bot: "Bot", github_repo: str) -> None:
+        self.bot = bot
+        self.github_repo = github_repo
+
+    @commands.command(name="source", aliases=("src",))
+    async def source_command(
+        self,
+        ctx: commands.Context,
+        *,
+        source_item: str | None = None,
+    ) -> None:
+        """Display information and a GitHub link to the source code of a command, tag, or cog."""
+        if not source_item:
+            embed = Embed(title=f"{self.bot.user.name}'s GitHub Repository")
+            embed.add_field(name="Repository", value=f"[Go to GitHub]({self.github_repo})")
+            embed.set_thumbnail(url="https://avatars1.githubusercontent.com/u/9919")
+            await ctx.send(embed=embed)
+            return
+
+        obj, source_type = await self._get_source_object(ctx, source_item)
+        embed = await self._build_embed(obj, source_type)
+        await ctx.send(embed=embed)
+
+    @staticmethod
+    async def _get_source_object(ctx: commands.Context, argument: str) -> tuple[object, SourceType]:
+        """Convert argument into the source object and source type."""
+        if argument.lower() == "help":
+            return ctx.bot.help_command, SourceType.help_command
+
+        cog = ctx.bot.get_cog(argument)
+        if cog:
+            return cog, SourceType.cog
+
+        cmd = ctx.bot.get_command(argument)
+        if cmd:
+            return cmd, SourceType.command
+
+        tags_cog = ctx.bot.get_cog("Tags")
+        show_tag = True
+
+        if not tags_cog:
+            show_tag = False
+        else:
+            identifier = TagIdentifierStub.from_string(argument.lower())
+            if identifier in tags_cog.tags:
+                return identifier, SourceType.tag
+
+        escaped_arg = escape_markdown(argument)
+
+        raise commands.BadArgument(
+            f"Unable to convert '{escaped_arg}' to valid command{', tag,' if show_tag else ''} or Cog."
+        )
+
+    def _get_source_link(self, source_item: object, source_type: SourceType) -> tuple[str, str, int | None]:
+        """
+        Build GitHub link of source item, return this link, file location and first line number.
+
+        Raise BadArgument if `source_item` is a dynamically-created object (e.g. via internal eval).
+        """
+        if source_type == SourceType.command:
+            source_item = inspect.unwrap(source_item.callback)
+            src = source_item.__code__
+            filename = src.co_filename
+        elif source_type == SourceType.tag:
+            tags_cog = self.bot.get_cog("Tags")
+            filename = tags_cog.tags[source_item].file_path
+        else:
+            src = type(source_item)
+            try:
+                filename = inspect.getsourcefile(src)
+            except TypeError:
+                raise commands.BadArgument("Cannot get source for a dynamically-created object.")
+
+        if source_type != SourceType.tag:
+            try:
+                lines, first_line_no = inspect.getsourcelines(src)
+            except OSError:
+                raise commands.BadArgument("Cannot get source for a dynamically-created object.")
+
+            lines_extension = f"#L{first_line_no}-L{first_line_no+len(lines)-1}"
+        else:
+            first_line_no = None
+            lines_extension = ""
+
+        # Handle tag file location differently than others to avoid errors in some cases
+        if not first_line_no:
+            file_location = Path(filename)
+        else:
+            file_location = Path(filename).relative_to(Path.cwd()).as_posix()
+
+        url = f"{self.github_repo}/blob/main/{file_location}{lines_extension}"
+
+        return url, file_location, first_line_no or None
+
+    async def _build_embed(self, source_object: object, source_type: SourceType) -> Embed | None:
+        """Build embed based on source object."""
+        url, location, first_line = self._get_source_link(source_object, source_type)
+
+        if source_type == SourceType.help_command:
+            title = "Help Command"
+            description = source_object.__doc__.splitlines()[1]
+        elif source_type == SourceType.command:
+            description = source_object.short_doc
+            title = f"Command: {source_object.qualified_name}"
+        elif source_type == SourceType.tag:
+            title = f"Tag: {source_object}"
+            description = ""
+        else:
+            title = f"Cog: {source_object.qualified_name}"
+            description = source_object.description.splitlines()[0]
+
+        embed = Embed(title=title, description=description)
+        embed.add_field(name="Source Code", value=f"[Go to GitHub]({url})")
+        line_text = f":{first_line}" if first_line else ""
+        embed.set_footer(text=f"{location}{line_text}")
+
+        return embed