name: Compute Preview Slug
description: Derive a URL-safe slug and deterministic port from a branch name

inputs:
  branch:
    required: true
    description: Branch name to slugify

outputs:
   slug:
     description: URL-safe branch slug
     value: ${{ steps.compute.outputs.slug }}
   port:
     description: Deterministic port derived from the slug
     value: ${{ steps.compute.outputs.port }}

runs:
  using: composite
  steps:
    - name: Compute slug and port
      id: compute
      shell: bash
      run: |
        SLUG=$(echo "${{ inputs.branch }}" | tr '/' '-' | tr '_' '-' | tr '[:upper:]' '[:lower:]' | sed 's/[^a-z0-9-]//g' | cut -c1-40)
        echo "slug=$SLUG" >> "$GITHUB_OUTPUT"
        PORT=$(( 20000 + ( $(echo -n "$SLUG" | cksum | awk '{print $1}') % 10000 ) ))
        echo "port=$PORT" >> "$GITHUB_OUTPUT"