1 files changed, 145 insertions, 0 deletions
diff --git a/Meta/label-pull-requests.js b/Meta/label-pull-requests.js
new file mode 100644
index 0000000000..1c203bc515
--- /dev/null
+++ b/Meta/label-pull-requests.js
@@ -0,0 +1,145 @@
+/*
+ * Copyright (c) 2022, Luke Wilde <lukew@serenityos.org>
+ * Copyright (c) 2023, kleines Filmröllchen <filmroellchen@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+const Label = {
+    CommunityApproved: "✅ pr-community-approved",
+    HasConflicts: "⚠️ pr-has-conflicts",
+    IsBlocked: "⛔️ pr-is-blocked",
+    MaintainerApprovedButAwaitingCi: "✅ pr-maintainer-approved-but-awaiting-ci",
+    NeedsReview: "👀 pr-needs-review",
+    Unclear: "🤔 pr-unclear",
+    WaitingForAuthor: "⏳ pr-waiting-for-author",
+};
+
+const subjectiveLabels = [Label.IsBlocked, Label.Unclear];
+
+function removeExistingPrLabels(currentLabels, keepSubjectiveLabels) {
+    return currentLabels.filter(
+        label =>
+            !label.includes("pr-") ||
+            label === Label.HasConflicts ||
+            (keepSubjectiveLabels && subjectiveLabels.includes(label))
+    );
+}
+
+async function labelsForGenericPullRequestChange(currentLabels) {
+    const filteredLabels = removeExistingPrLabels(currentLabels, true);
+    filteredLabels.push(Label.NeedsReview);
+    return filteredLabels;
+}
+
+async function labelsForPullRequestEffectivelyClosed(currentLabels) {
+    return removeExistingPrLabels(currentLabels, false);
+}
+
+function apiErrorHandler(error) {
+    console.log(
+        "::warning::Encountered error during event handling, not updating labels. Error:",
+        error
+    );
+}
+
+module.exports = ({ github, context }) => {
+    async function labelsForPullRequestReviewSubmitted(currentLabels, { pull_request, review }) {
+        let newLabels = currentLabels;
+        const isBlocked = currentLabels.some(label => label === Label.IsBlocked);
+
+        if (review.state.toLowerCase() === "approved") {
+            const maintainers = (
+                await github.rest.teams.listMembersInOrg({
+                    org: "SerenityOS",
+                    team_slug: "maintainers",
+                })
+            ).data;
+
+            const approvedByMaintainer = maintainers.some(
+                maintainerInArray => maintainerInArray.login === review.user.login
+            );
+
+            if (approvedByMaintainer) {
+                newLabels = newLabels.filter(
+                    label => !(label === Label.NeedsReview || label === Label.WaitingForAuthor)
+                );
+
+                if (!newLabels.includes(Label.MaintainerApprovedButAwaitingCi))
+                    newLabels.push(Label.MaintainerApprovedButAwaitingCi);
+            } else {
+                if (!newLabels.includes(Label.CommunityApproved))
+                    newLabels.push(Label.CommunityApproved);
+            }
+        } else if (!isBlocked) {
+            // Remove approval labels.
+            newLabels = newLabels.filter(
+                label =>
+                    !(
+                        label === Label.CommunityApproved ||
+                        label === Label.MaintainerApprovedButAwaitingCi
+                    )
+            );
+
+            if (review.user.login === pull_request.user.login) newLabels.push(Label.NeedsReview);
+            else newLabels.push(Label.WaitingForAuthor);
+        }
+
+        return newLabels;
+    }
+
+    const eventHandlers = {
+        opened: labelsForGenericPullRequestChange,
+        reopened: labelsForGenericPullRequestChange,
+        submitted: labelsForPullRequestReviewSubmitted,
+        dismissed: labelsForGenericPullRequestChange,
+        converted_to_draft: labelsForPullRequestEffectivelyClosed,
+        ready_for_review: labelsForGenericPullRequestChange,
+        synchronize: labelsForGenericPullRequestChange, // synchronize is triggered when the branch is changed
+        edited: labelsForGenericPullRequestChange,
+        review_requested: labelsForGenericPullRequestChange,
+        closed: labelsForPullRequestEffectivelyClosed,
+    };
+
+    const eventName = context.payload.action;
+    const handlerForCurrentEvent = eventHandlers[eventName];
+
+    async function updateLabels(currentLabelsAsObjects) {
+        const currentLabels = [];
+        currentLabelsAsObjects.forEach(labelObject => currentLabels.push(labelObject.name));
+
+        const isEffectivelyClosed =
+            context.payload.pull_request.draft ||
+            context.payload.pull_request.state.toLowerCase() === "closed";
+
+        const newLabels = await (isEffectivelyClosed
+            ? labelsForPullRequestEffectivelyClosed(currentLabels, context.payload)
+            : handlerForCurrentEvent(currentLabels, context.payload));
+
+        console.log(
+            `Received '${eventName}' event for ${
+                isEffectivelyClosed ? "draft/closed" : "open"
+            } pull request, changing labels from '${currentLabels}' to '${newLabels}'`
+        );
+
+        return github.rest.issues.setLabels({
+            issue_number: context.payload.pull_request.number,
+            owner: context.repo.owner,
+            repo: context.repo.repo,
+            labels: newLabels,
+        });
+    }
+
+    if (handlerForCurrentEvent) {
+        github.rest.issues
+            .listLabelsOnIssue({
+                issue_number: context.payload.pull_request.number,
+                owner: context.repo.owner,
+                repo: context.repo.repo,
+            })
+            .then(result => updateLabels(result.data))
+            .catch(apiErrorHandler);
+    } else {
+        console.log(`::warning::No handler for the '${eventName}' event, not updating labels.`);
+    }
+};