name: flutter-setup (slim)
description: >-
  Flutter for gating jobs (analyze, test, web build) from a slim cached SDK:
  a depth-1 clone of the release tag plus host and web artifacts only.
  subosito/flutter-action caches the full 1.6 GB SDK, whose restore alone
  costs ~38 s per job even on a hit; this cache is 393 MB.
  Release (APK) builds keep subosito: they need the Android artifacts.

inputs:
  flutter-version:
    description: Exact Flutter release tag, e.g. 3.47.6 (never a channel).
    required: true
  working-directory:
    description: The Flutter project, for keying and restoring its pub cache.
    default: "."

runs:
  using: composite
  steps:
    - name: Restore the slim Flutter SDK
      id: sdk
      uses: actions/cache/restore@v4
      with:
        path: ~/sdk/flutter-slim
        key: flutter-slim-${{ inputs.flutter-version }}-${{ runner.os }}-${{ runner.arch }}-v1

    # Miss path only: build the SDK once per version, then save it. A depth-1
    # clone keeps .git at ~40 MB (the tool refuses to run without one).
    # precache pulls the Android engines even with --no-android; nothing a
    # gating job runs (test, analyze, build web) touches them, so they go,
    # along with the desktop profile/release engines. Measured: 393 MB
    # zstd'd, against 1642 MB for subosito's cache.
    - name: Build the slim SDK (cache miss)
      if: steps.sdk.outputs.cache-hit != 'true'
      shell: bash
      env:
        FLUTTER_VERSION: ${{ inputs.flutter-version }}
      run: |
        set -euo pipefail
        git clone --quiet --depth 1 --branch "$FLUTTER_VERSION" \
          https://github.com/flutter/flutter.git ~/sdk/flutter-slim
        ~/sdk/flutter-slim/bin/flutter --disable-analytics >/dev/null
        ~/sdk/flutter-slim/bin/flutter precache --web --no-android --no-ios
        engine=~/sdk/flutter-slim/bin/cache/artifacts/engine
        rm -rf "$engine"/android-* "$engine"/linux-x64-profile "$engine"/linux-x64-release
        ~/sdk/flutter-slim/bin/flutter --version

    - name: Save the slim SDK
      if: steps.sdk.outputs.cache-hit != 'true'
      uses: actions/cache/save@v4
      with:
        path: ~/sdk/flutter-slim
        key: ${{ steps.sdk.outputs.cache-primary-key }}

    - name: Put flutter on PATH
      shell: bash
      run: |
        echo "$HOME/sdk/flutter-slim/bin" >> "$GITHUB_PATH"
        echo "PUB_CACHE=$HOME/.pub-cache" >> "$GITHUB_ENV"

    # Exact key only, no prefix restore-keys: an older lockfile's pub cache,
    # restored after a git-dependency bump, made `flutter pub get` fail with
    # "package_graph.json: dependencies for <pkg> missing" (daily-limits,
    # 2026-10-10), and a failed job never saves the new key, so every rerun
    # failed the same way. A lockfile change now pays one cold `pub get`.
    - name: Restore the pub cache
      uses: actions/cache@v4
      with:
        path: ~/.pub-cache
        key: pub-${{ inputs.flutter-version }}-${{ runner.os }}-${{ hashFiles(format('{0}/pubspec.lock', inputs.working-directory)) }}