1 files changed, 275 insertions, 0 deletions
diff --git a/bot/exts/utilities/issues.py b/bot/exts/utilities/issues.py
new file mode 100644
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+++ b/bot/exts/utilities/issues.py
@@ -0,0 +1,275 @@
+import logging
+import random
+import re
+from dataclasses import dataclass
+from typing import Optional, Union
+
+import discord
+from discord.ext import commands
+
+from bot.bot import Bot
+from bot.constants import (
+    Categories,
+    Channels,
+    Colours,
+    ERROR_REPLIES,
+    Emojis,
+    NEGATIVE_REPLIES,
+    Tokens,
+    WHITELISTED_CHANNELS
+)
+from bot.utils.decorators import whitelist_override
+from bot.utils.extensions import invoke_help_command
+
+log = logging.getLogger(__name__)
+
+BAD_RESPONSE = {
+    404: "Issue/pull request not located! Please enter a valid number!",
+    403: "Rate limit has been hit! Please try again later!"
+}
+REQUEST_HEADERS = {
+    "Accept": "application/vnd.github.v3+json"
+}
+
+REPOSITORY_ENDPOINT = "https://api.github.com/orgs/{org}/repos?per_page=100&type=public"
+ISSUE_ENDPOINT = "https://api.github.com/repos/{user}/{repository}/issues/{number}"
+PR_ENDPOINT = "https://api.github.com/repos/{user}/{repository}/pulls/{number}"
+
+if GITHUB_TOKEN := Tokens.github:
+    REQUEST_HEADERS["Authorization"] = f"token {GITHUB_TOKEN}"
+
+WHITELISTED_CATEGORIES = (
+    Categories.development, Categories.devprojects, Categories.media, Categories.staff
+)
+
+CODE_BLOCK_RE = re.compile(
+    r"^`([^`\n]+)`"  # Inline codeblock
+    r"|```(.+?)```",  # Multiline codeblock
+    re.DOTALL | re.MULTILINE
+)
+
+# Maximum number of issues in one message
+MAXIMUM_ISSUES = 5
+
+# Regex used when looking for automatic linking in messages
+# regex101 of current regex https://regex101.com/r/V2ji8M/6
+AUTOMATIC_REGEX = re.compile(
+    r"((?P<org>[a-zA-Z0-9][a-zA-Z0-9\-]{1,39})\/)?(?P<repo>[\w\-\.]{1,100})#(?P<number>[0-9]+)"
+)
+
+
+@dataclass
+class FoundIssue:
+    """Dataclass representing an issue found by the regex."""
+
+    organisation: Optional[str]
+    repository: str
+    number: str
+
+    def __hash__(self) -> int:
+        return hash((self.organisation, self.repository, self.number))
+
+
+@dataclass
+class FetchError:
+    """Dataclass representing an error while fetching an issue."""
+
+    return_code: int
+    message: str
+
+
+@dataclass
+class IssueState:
+    """Dataclass representing the state of an issue."""
+
+    repository: str
+    number: int
+    url: str
+    title: str
+    emoji: str
+
+
+class Issues(commands.Cog):
+    """Cog that allows users to retrieve issues from GitHub."""
+
+    def __init__(self, bot: Bot):
+        self.bot = bot
+        self.repos = []
+
+    @staticmethod
+    def remove_codeblocks(message: str) -> str:
+        """Remove any codeblock in a message."""
+        return re.sub(CODE_BLOCK_RE, "", message)
+
+    async def fetch_issues(
+            self,
+            number: int,
+            repository: str,
+            user: str
+    ) -> Union[IssueState, FetchError]:
+        """
+        Retrieve an issue from a GitHub repository.
+
+        Returns IssueState on success, FetchError on failure.
+        """
+        url = ISSUE_ENDPOINT.format(user=user, repository=repository, number=number)
+        pulls_url = PR_ENDPOINT.format(user=user, repository=repository, number=number)
+        log.trace(f"Querying GH issues API: {url}")
+
+        async with self.bot.http_session.get(url, headers=REQUEST_HEADERS) as r:
+            json_data = await r.json()
+
+        if r.status == 403:
+            if r.headers.get("X-RateLimit-Remaining") == "0":
+                log.info(f"Ratelimit reached while fetching {url}")
+                return FetchError(403, "Ratelimit reached, please retry in a few minutes.")
+            return FetchError(403, "Cannot access issue.")
+        elif r.status in (404, 410):
+            return FetchError(r.status, "Issue not found.")
+        elif r.status != 200:
+            return FetchError(r.status, "Error while fetching issue.")
+
+        # The initial API request is made to the issues API endpoint, which will return information
+        # if the issue or PR is present. However, the scope of information returned for PRs differs
+        # from issues: if the 'issues' key is present in the response then we can pull the data we
+        # need from the initial API call.
+        if "issues" in json_data["html_url"]:
+            if json_data.get("state") == "open":
+                emoji = Emojis.issue_open
+            else:
+                emoji = Emojis.issue_closed
+
+        # If the 'issues' key is not contained in the API response and there is no error code, then
+        # we know that a PR has been requested and a call to the pulls API endpoint is necessary
+        # to get the desired information for the PR.
+        else:
+            log.trace(f"PR provided, querying GH pulls API for additional information: {pulls_url}")
+            async with self.bot.http_session.get(pulls_url) as p:
+                pull_data = await p.json()
+                if pull_data["draft"]:
+                    emoji = Emojis.pull_request_draft
+                elif pull_data["state"] == "open":
+                    emoji = Emojis.pull_request_open
+                # When 'merged_at' is not None, this means that the state of the PR is merged
+                elif pull_data["merged_at"] is not None:
+                    emoji = Emojis.pull_request_merged
+                else:
+                    emoji = Emojis.pull_request_closed
+
+        issue_url = json_data.get("html_url")
+
+        return IssueState(repository, number, issue_url, json_data.get("title", ""), emoji)
+
+    @staticmethod
+    def format_embed(
+        results: list[Union[IssueState, FetchError]],
+        user: str,
+        repository: Optional[str] = None
+    ) -> discord.Embed:
+        """Take a list of IssueState or FetchError and format a Discord embed for them."""
+        description_list = []
+
+        for result in results:
+            if isinstance(result, IssueState):
+                description_list.append(f"{result.emoji} [{result.title}]({result.url})")
+            elif isinstance(result, FetchError):
+                description_list.append(f":x: [{result.return_code}] {result.message}")
+
+        resp = discord.Embed(
+            colour=Colours.bright_green,
+            description="\n".join(description_list)
+        )
+
+        embed_url = f"https://github.com/{user}/{repository}" if repository else f"https://github.com/{user}"
+        resp.set_author(name="GitHub", url=embed_url)
+        return resp
+
+    @whitelist_override(channels=WHITELISTED_CHANNELS, categories=WHITELISTED_CATEGORIES)
+    @commands.command(aliases=("pr",))
+    async def issue(
+        self,
+        ctx: commands.Context,
+        numbers: commands.Greedy[int],
+        repository: str = "sir-lancebot",
+        user: str = "python-discord"
+    ) -> None:
+        """Command to retrieve issue(s) from a GitHub repository."""
+        # Remove duplicates
+        numbers = set(numbers)
+
+        if len(numbers) > MAXIMUM_ISSUES:
+            embed = discord.Embed(
+                title=random.choice(ERROR_REPLIES),
+                color=Colours.soft_red,
+                description=f"Too many issues/PRs! (maximum of {MAXIMUM_ISSUES})"
+            )
+            await ctx.send(embed=embed)
+            await invoke_help_command(ctx)
+
+        results = [await self.fetch_issues(number, repository, user) for number in numbers]
+        await ctx.send(embed=self.format_embed(results, user, repository))
+
+    @commands.Cog.listener()
+    async def on_message(self, message: discord.Message) -> None:
+        """
+        Automatic issue linking.
+
+        Listener to retrieve issue(s) from a GitHub repository using automatic linking if matching <org>/<repo>#<issue>.
+        """
+        # Ignore bots
+        if message.author.bot:
+            return
+
+        issues = [
+            FoundIssue(*match.group("org", "repo", "number"))
+            for match in AUTOMATIC_REGEX.finditer(self.remove_codeblocks(message.content))
+        ]
+        links = []
+
+        if issues:
+            # Block this from working in DMs
+            if not message.guild:
+                await message.channel.send(
+                    embed=discord.Embed(
+                        title=random.choice(NEGATIVE_REPLIES),
+                        description=(
+                            "You can't retrieve issues from DMs. "
+                            f"Try again in <#{Channels.community_bot_commands}>"
+                        ),
+                        colour=Colours.soft_red
+                    )
+                )
+                return
+
+            log.trace(f"Found {issues = }")
+            # Remove duplicates
+            issues = set(issues)
+
+            if len(issues) > MAXIMUM_ISSUES:
+                embed = discord.Embed(
+                    title=random.choice(ERROR_REPLIES),
+                    color=Colours.soft_red,
+                    description=f"Too many issues/PRs! (maximum of {MAXIMUM_ISSUES})"
+                )
+                await message.channel.send(embed=embed, delete_after=5)
+                return
+
+            for repo_issue in issues:
+                result = await self.fetch_issues(
+                    int(repo_issue.number),
+                    repo_issue.repository,
+                    repo_issue.organisation or "python-discord"
+                )
+                if isinstance(result, IssueState):
+                    links.append(result)
+
+        if not links:
+            return
+
+        resp = self.format_embed(links, "python-discord")
+        await message.channel.send(embed=resp)
+
+
+def setup(bot: Bot) -> None:
+    """Load the Issues cog."""
+    bot.add_cog(Issues(bot))