Add scheduled link checker workflow

.github/workflows/link-check.yml

@@ -1,18 +1,86 @@
-name: Link check
+name: Link Check
 
 on:
+  schedule:
+    - cron: "0 3 * * 0" # Every Sunday at 3 AM UTC
   pull_request:
+    paths:
+      - "**.md"
   workflow_dispatch:
-  schedule:
-    - cron: "0 17 1 * *"
+
+permissions:
+  contents: read
+  issues: write
 
 jobs:
-  links:
+  link-check:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
-      - uses: actions/setup-python@v5
+
+      - name: Restore lychee cache
+        uses: actions/cache@v4
+        with:
+          path: .lycheecache
+          key: cache-lychee-${{ github.sha }}
+          restore-keys: cache-lychee-
+
+      # On PRs, only check changed markdown files to avoid failing on
+      # pre-existing broken links unrelated to this PR.
+      - name: Get changed markdown files
+        id: changed
+        if: github.event_name == 'pull_request'
+        run: |
+          files=$(gh pr diff ${{ github.event.pull_request.number }} --name-only | grep '\.md$' || true)
+          echo "md_files<<EOF" >> "$GITHUB_OUTPUT"
+          echo "$files" >> "$GITHUB_OUTPUT"
+          echo "EOF" >> "$GITHUB_OUTPUT"
+          if [ -z "$files" ]; then
+            echo "has_md=false" >> "$GITHUB_OUTPUT"
+          else
+            echo "has_md=true" >> "$GITHUB_OUTPUT"
+          fi
+        env:
+          GH_TOKEN: ${{ github.token }}
+
+      - name: Check links (all files)
+        id: lychee-all
+        if: github.event_name != 'pull_request'
+        uses: lycheeverse/lychee-action@v2
+        with:
+          args: >-
+            --verbose
+            --no-progress
+            --timeout 10
+            --max-retries 3
+            --max-concurrency 8
+            --cache
+            --max-cache-age 1d
+            '**/*.md'
+          fail: false
+          output: /tmp/lychee/out.md
+
+      - name: Check links (changed files only)
+        id: lychee-pr
+        if: github.event_name == 'pull_request' && steps.changed.outputs.has_md == 'true'
+        uses: lycheeverse/lychee-action@v2
+        with:
+          args: >-
+            --verbose
+            --no-progress
+            --timeout 10
+            --max-retries 3
+            --max-concurrency 8
+            --cache
+            --max-cache-age 1d
+            ${{ steps.changed.outputs.md_files }}
+          fail: true
+          output: /tmp/lychee/out.md
+
+      - name: Open issue on broken links (scheduled runs only)
+        if: github.event_name == 'schedule' && steps.lychee-all.outputs.exit_code != 0
+        uses: peter-evans/create-issue-from-file@v5
         with:
-          python-version: "3.x"
-      - name: Check links
-        run: python scripts/check_links.py --online --include-resources
+          title: "🔗 Broken links found"
+          content-filepath: /tmp/lychee/out.md
+          labels: maintenance

.lycheeignore

@@ -0,0 +1,16 @@
+# Known flaky or rate-limited URLs
+# Add URLs (one per line) that should be excluded from link checking.
+# Supports regex patterns.
+
+# Twitter/X often rate-limits or blocks automated checks
+https?://(www\.)?twitter\.com(/.*)?
+https?://(www\.)?x\.com(/.*)?
+
+# LinkedIn blocks automated requests
+https?://(www\.)?linkedin\.com(/.*)?
+
+# Facebook blocks automated requests
+https?://(www\.)?facebook\.com(/.*)?
+
+# Archive.org can be slow or intermittently unavailable
+https?://web\.archive\.org(/.*)?

README.md

@@ -1,5 +1,7 @@
 # Learn to Code
 
+[![Link Check](https://github.com/ashleymcnamara/learn_to_code/actions/workflows/link-check.yml/badge.svg)](https://github.com/ashleymcnamara/learn_to_code/actions/workflows/link-check.yml)
+
 A free-first, beginner-friendly guide to learning programming, computer science,
 AI, and the practical tools developers use every day.