name: Update yt-dlp

on:
  schedule:
    - cron: '0 6 * * 1'  # Every Monday at 06:00 UTC
  workflow_dispatch:

jobs:
  update:
    runs-on: ubuntu-latest
    permissions:
      contents: write
      pull-requests: write

    steps:
      - name: Check out repository
        uses: actions/checkout@v4

      - name: Install Nix
        uses: DeterminateSystems/nix-installer-action@main

      - name: Enable Nix cache
        uses: DeterminateSystems/magic-nix-cache-action@main

      - name: Read currently pinned yt-dlp version
        id: current
        run: |
          set -euo pipefail
          current=$(sed -n '/ytDlp = pkgs.stdenv.mkDerivation/,/^          };$/{ s/^ *version = "\([^"]*\)";/\1/p; }' flake.nix | head -1)
          if [ -z "$current" ]; then
            echo "::error::Could not read the pinned yt-dlp version from flake.nix. Did the ytDlp derivation move or get renamed?"
            exit 1
          fi
          echo "Currently pinned yt-dlp: $current"
          echo "version=${current}" >> "$GITHUB_OUTPUT"

      - name: Query latest yt-dlp release
        id: latest
        env:
          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
        run: |
          set -euo pipefail
          latest=$(curl -sSL \
            -H "Authorization: Bearer $GITHUB_TOKEN" \
            -H "Accept: application/vnd.github+json" \
            https://api.github.com/repos/yt-dlp/yt-dlp/releases/latest | jq -r .tag_name)
          if [ -z "$latest" ] || [ "$latest" = "null" ]; then
            echo "::error::Could not determine the latest yt-dlp release tag from the GitHub API."
            exit 1
          fi
          echo "Latest yt-dlp release: $latest"
          echo "version=${latest}" >> "$GITHUB_OUTPUT"

      - name: Decide whether an update is needed
        id: check
        env:
          CURRENT: ${{ steps.current.outputs.version }}
          LATEST: ${{ steps.latest.outputs.version }}
        run: |
          set -euo pipefail
          if [ "$CURRENT" = "$LATEST" ]; then
            echo "Already at $CURRENT"
            echo "changed=false" >> "$GITHUB_OUTPUT"
          else
            echo "Update available: $CURRENT -> $LATEST"
            echo "changed=true" >> "$GITHUB_OUTPUT"
          fi

      - name: Compute SRI hash of the new release
        id: hash
        if: steps.check.outputs.changed == 'true'
        env:
          LATEST: ${{ steps.latest.outputs.version }}
        run: |
          set -euo pipefail
          curl -sSL --fail \
            "https://github.com/yt-dlp/yt-dlp/releases/download/${LATEST}/yt-dlp" \
            -o /tmp/yt-dlp
          hash=$(nix hash file --sri --type sha256 /tmp/yt-dlp)
          case "$hash" in
            sha256-*) ;;
            *)
              echo "::error::Computed hash '${hash}' is not an SRI sha256 hash."
              exit 1
              ;;
          esac
          echo "SRI hash: $hash"
          echo "hash=${hash}" >> "$GITHUB_OUTPUT"

      - name: Rewrite the yt-dlp pin in flake.nix
        if: steps.check.outputs.changed == 'true'
        env:
          CURRENT: ${{ steps.current.outputs.version }}
          LATEST: ${{ steps.latest.outputs.version }}
          HASH: ${{ steps.hash.outputs.hash }}
        run: |
          set -euo pipefail
          sed -i \
            -e "/ytDlp = pkgs.stdenv.mkDerivation/,/^          };\$/{ s|^\( *version = \"\)[^\"]*\(\";\)|\1${LATEST}\2|; }" \
            -e "/ytDlp = pkgs.stdenv.mkDerivation/,/^          };\$/{ s|\(url = \"https://github.com/yt-dlp/yt-dlp/releases/download/\)[^/]*\(/yt-dlp\";\)|\1${LATEST}\2|; }" \
            -e "/ytDlp = pkgs.stdenv.mkDerivation/,/^          };\$/{ s|^\( *hash = \"\)sha256-[^\"]*\(\";\)|\1${HASH}\2|; }" \
            flake.nix

          echo "--- git diff --stat ---"
          git diff --stat flake.nix

          changed_files=$(git diff --name-only)
          if [ "$changed_files" != "flake.nix" ]; then
            echo "::error::Expected only flake.nix to change, got: ${changed_files}"
            exit 1
          fi

          occurrences=$(grep -c "$LATEST" flake.nix || true)
          if [ "$occurrences" -ne 2 ]; then
            echo "::error::Expected the new version ${LATEST} to appear twice in flake.nix (version line + URL), found ${occurrences}."
            exit 1
          fi

          if ! grep -q "$HASH" flake.nix; then
            echo "::error::New SRI hash was not written into flake.nix."
            exit 1
          fi

          echo "Rewrote yt-dlp pin: ${CURRENT} -> ${LATEST}"

      - name: Open pull request
        if: steps.check.outputs.changed == 'true'
        uses: peter-evans/create-pull-request@v6
        with:
          branch: auto/yt-dlp-update
          delete-branch: true
          commit-message: "chore(nix): yt-dlp ${{ steps.current.outputs.version }} → ${{ steps.latest.outputs.version }}"
          title: "chore(nix): yt-dlp ${{ steps.current.outputs.version }} → ${{ steps.latest.outputs.version }}"
          body: |
            Automated bump of the pinned yt-dlp release. Old: `${{ steps.current.outputs.version }}`. New: `${{ steps.latest.outputs.version }}`. SRI hash: `${{ steps.hash.outputs.hash }}`.

            Upstream release: https://github.com/yt-dlp/yt-dlp/releases/tag/${{ steps.latest.outputs.version }}
          labels: dependencies