parallelize-tests.yml

name: Parallelize Tests

on:
    workflow_call:
        inputs:
            environments:
                required: true
                type: string
            parallel_jobs:
                required: false
                type: number
                default: 2
            java_version:
                required: true
                type: number
        outputs:
            matrix:
                description: "Generated test matrix"
                value: ${{ jobs.prepare.outputs.matrix }}

jobs:
    prepare:
        name: ""
        runs-on: ubuntu-latest
        outputs:
            matrix: ${{ steps.set-matrix.outputs.matrix }}
        steps:
            - name: Generate matrix
              id: set-matrix
              run: |
                  # Use environment variables
                  N=${{ inputs.parallel_jobs }}
                  JAVA_VERSION=${{ inputs.java_version }}
                  
                  # Convert to array and transform
                  IFS=',' read -ra ENVS <<< "${{ inputs.environments }}"
                  TRANSFORMED=()
                  for env in "${ENVS[@]}"; do
                      TRANSFORMED+=("java${JAVA_VERSION}/paper-${env}")
                  done
                  
                  TOTAL=${#TRANSFORMED[@]}
                  
                  # avoid creating more jobs than needed
                  JOBS=$((TOTAL < N ? TOTAL : N))
                  # environments per job
                  BASE=$((TOTAL / JOBS))
                  EXTRA=$((TOTAL % JOBS))
                  
                  # Build matrix JSON
                  # Format is:
                  # [{"id":1,"envs":"java21/paper-1.20.6,java21/paper-1.21.3","display":"1.20.6, 1.21.3"},...]
                  # Where "envs" is the actual environment strings and "display" is for easier identification
                  MATRIX="["
                  INDEX=0
                  for ((i=0; i<JOBS; i++)); do
                      # Determine count for this job (BASE + 1 if i < EXTRA)
                      COUNT=$BASE
                      if [ $i -lt $EXTRA ]; then
                          COUNT=$((COUNT + 1))
                      fi
                  
                      # Build envs and display strings
                      GROUP=""
                      DISPLAY_GROUP=""
                      for ((j=0; j<COUNT; j++)); do
                          if [ -n "$GROUP" ]; then
                              GROUP="$GROUP,"
                              DISPLAY_GROUP="$DISPLAY_GROUP, "
                          fi
                          GROUP="$GROUP${TRANSFORMED[$INDEX]}"
                          DISPLAY_GROUP="$DISPLAY_GROUP${ENVS[$INDEX]}"
                          INDEX=$((INDEX + 1))
                      done
                  
                      # add to matrix with separating comma if needed
                      if [ $i -gt 0 ]; then
                          MATRIX="$MATRIX,"
                      fi
                      MATRIX="$MATRIX{\"id\":$((i+1)),\"envs\":\"$GROUP\",\"display\":\"$DISPLAY_GROUP\"}"
                  done
                  MATRIX="$MATRIX]"
                  
                  echo "matrix={\"include\":$MATRIX}" >> $GITHUB_OUTPUT
                  echo "Generated matrix: {\"include\":$MATRIX}"