name: Select Go module proxy
description: Select the fastest reachable Go module proxy for Docker builds
inputs:
  go_mirrors:
    description: Newline-separated Go module proxies
    required: false
    default: |
      https://go.devneeds.ir/
      https://package-mirror.liara.ir/repository/go/
      https://go.reg.darano.ir/
      https://proxy.golang.org/
outputs:
  go_proxy:
    description: Selected Go module proxy
    value: ${{ steps.select.outputs.go_proxy }}
runs:
  using: composite
  steps:
    - name: Select fastest reachable proxy
      id: select
      shell: bash
      env:
        GO_MIRRORS: ${{ inputs.go_mirrors }}
      run: |
        set -euo pipefail
        scores="$(mktemp)"
        fallback=""

        while IFS= read -r mirror; do
          mirror="$(printf '%s' "$mirror" | sed -e 's/^[[:space:]]*//' -e 's/[[:space:]]*$//')"
          [[ -z "$mirror" || "$mirror" == \#* ]] && continue
          [[ -z "$fallback" ]] && fallback="$mirror"
          result="$(curl --location --silent --output /dev/null \
            --connect-timeout 3 --max-time 10 \
            --write-out '%{http_code} %{time_total}' "$mirror" 2>/dev/null || true)"
          read -r status duration <<< "$result"
          if [[ "$status" =~ ^(2|3)[0-9]{2}$ ]] && [[ "$duration" =~ ^[0-9]+([.][0-9]+)?$ ]]; then
            printf '%s\t%s\n' "$duration" "$mirror" >> "$scores"
          fi
        done <<< "$GO_MIRRORS"

        if [[ -s "$scores" ]]; then
          go_proxy="$(sort -n -k1,1 "$scores" | head -n 1 | cut -f2-)"
        else
          go_proxy="$fallback"
        fi
        rm -f "$scores"

        test -n "$go_proxy"
        echo "GOPROXY=$go_proxy" >> "$GITHUB_ENV"
        echo "go_proxy=$go_proxy" >> "$GITHUB_OUTPUT"
        echo "Selected Go proxy: $go_proxy"