name: Build binaries

on:
  push:
    branches: [main]
  pull_request:
    branches: [main]
  workflow_dispatch:

permissions:
  contents: read

env:
  CARGO_TERM_COLOR: always
  # Measure before stripping; package stripped copies separately.
  CARGO_PROFILE_RELEASE_STRIP: none

jobs:
  build:
    name: Build (${{ matrix.target }})
    runs-on: ubuntu-latest
    timeout-minutes: 120
    env:
      TARGET: ${{ matrix.target }}
    defaults:
      run:
        shell: bash
    strategy:
      fail-fast: false
      max-parallel: 2
      matrix:
        target:
          - x86_64-musl
          - i686-musl
          - arm-musleabi
          - arm-musleabihf
          - armv7-musleabi
          - armv7-musleabihf
          - aarch64-musl
          - mips-musl
          - mipsel-musl
          - mips64-muslabi64
          - mips64el-muslabi64
          - riscv64gc-musl

    steps:
      - name: Checkout
        uses: builtin:checkout

      - name: Configure Rust directories
        # Cross remote does not traverse hidden directories under /root.
        run: |
          echo "CARGO_HOME=$RUNNER_TEMP/cargo" >> "$GITHUB_ENV"
          echo "RUSTUP_HOME=$RUNNER_TEMP/rustup" >> "$GITHUB_ENV"
          echo "$RUNNER_TEMP/cargo/bin" >> "$GITHUB_PATH"

      - name: Install standard Rust toolchain
        uses: actions-rust-lang/setup-rust-toolchain@ecabd13d1c56bd1345c230e542e9144811ad706f # v2
        with:
          toolchain: ${{ startsWith(matrix.target, 'mips') && 'nightly' || 'stable' }}
          cache: false
          build-warnings: warn

      - name: Install nightly toolchain and standard library sources
        run: |
          rustup toolchain install nightly \
            --profile minimal \
            --component rust-src

      - name: Install cross and binary tools
        run: |
          sudo apt-get update
          sudo apt-get install -y --no-install-recommends binutils llvm
          cargo install --git https://github.com/cross-rs/cross --locked cross
          echo "RUST_TARGET=${TARGET%-*}-unknown-linux-${TARGET#*-}" >> "$GITHUB_ENV"

      - name: Detect statistics feature
        run: |
          if grep -Eq '^[[:space:]]*stats[[:space:]]*=' crates/irtt-app/Cargo.toml; then
            echo "HAS_STATS_FEATURE=true" >> "$GITHUB_ENV"
          else
            echo "HAS_STATS_FEATURE=false" >> "$GITHUB_ENV"
          fi

      - name: Build, verify, package, and compare
        env:
          # MIPS build-std needs cross GCC's CRT objects.
          RUSTFLAGS: ${{ startsWith(matrix.target, 'mips') && '-C target-feature=+crt-static -C link-self-contained=no' || '-C target-feature=+crt-static' }}
          CROSS_REMOTE: "true"
          CROSS_REMOTE_COPY_FULL_TARGET_DIR: ${{ startsWith(matrix.target, 'mips') && 'true' || 'false' }}
        run: |
          set -euo pipefail

          declare -A raw_size
          declare -A stripped_size
          declare -A compressed_size

          mkdir -p dist

          # MIPS requires nightly build-std via Cross.toml.
          # Every other standard build uses stable.
          standard_toolchain=stable
          if [[ "$TARGET" == mips* ]]; then
            standard_toolchain=nightly
          fi

          build_variant() {
            local variant="$1"
            local toolchain="$2"
            local features="$3"
            shift 3

            local binary="target/${RUST_TARGET}/release/irtt-client"
            local directory="dist/${variant}"
            local artifact="dist/irtt-client-${TARGET}-${variant}.tar.gz"

            echo "::group::Build ${variant} (${toolchain}, ${features})"

            cross "+${toolchain}" build \
              --release \
              --locked \
              --target "$RUST_TARGET" \
              -p irtt-rs \
              --bin irtt-client \
              --no-default-features \
              --features "$features" \
              "$@"

            # Reject dynamically linked executables.
            readelf --program-headers "$binary" > /tmp/program-headers.txt
            readelf --dynamic "$binary" > /tmp/dynamic-section.txt

            if grep -q INTERP /tmp/program-headers.txt ||
               grep -q NEEDED /tmp/dynamic-section.txt; then
              echo "Binary is not statically linked: ${variant}" >&2
              exit 1
            fi

            mkdir -p "$directory"
            cp "$binary" "$directory/irtt-client"

            raw_size[$variant]=$(stat -c %s "$binary")

            llvm-strip --strip-all "$directory/irtt-client"
            stripped_size[$variant]=$(
              stat -c %s "$directory/irtt-client"
            )

            # Each archive contains an executable named irtt-client.
            tar -czf "$artifact" -C "$directory" irtt-client
            compressed_size[$variant]=$(stat -c %s "$artifact")

            echo "::endgroup::"
          }

          human() {
            numfmt --to=iec-i --suffix=B --format='%.1f' "$1"
          }

          # Negative means smaller than the reference binary.
          delta() {
            awk -v base="$1" -v current="$2" 'BEGIN {
              if (base == 0) {
                printf "N/A"
              } else {
                printf "%+.1f%%", 100 * (current - base) / base
              }
            }'
          }

          print_row() {
            local variant="$1"
            local label="$2"
            local baseline="$3"
            local comparison

            if [[ "$variant" == "$baseline" ]]; then
              comparison="Baseline"
            else
              comparison=$(delta \
                "${compressed_size[$baseline]}" \
                "${compressed_size[$variant]}")
            fi

            printf '| %s | %s | %s | %s | %s |\n' \
              "$label" \
              "$(human "${raw_size[$variant]}")" \
              "$(human "${stripped_size[$variant]}")" \
              "$(human "${compressed_size[$variant]}")" \
              "$comparison"
          }

          # ---------------------------------------------------------
          # Standard builds: stable except MIPS.
          # ---------------------------------------------------------

          full_features=client
          if [[ "$HAS_STATS_FEATURE" == "true" ]]; then
            full_features="client,stats"
          fi

          build_variant full "$standard_toolchain" "$full_features"

          standard_baseline=full
          if [[ "$HAS_STATS_FEATURE" == "true" ]]; then
            build_variant minimal "$standard_toolchain" client
            standard_baseline=minimal
          fi

          # ---------------------------------------------------------
          # Nightly baseline: identical compiler for all experiments.
          #
          # MIPS already uses nightly for standard builds, so reuse
          # those binaries rather than compiling them twice.
          # ---------------------------------------------------------

          if [[ "$standard_toolchain" == "nightly" ]]; then
            nightly_full=full
            nightly_baseline="$standard_baseline"
          else
            nightly_full=nightly-full
            build_variant nightly-full nightly "$full_features"

            nightly_baseline=nightly-full
            if [[ "$HAS_STATS_FEATURE" == "true" ]]; then
              build_variant nightly-minimal nightly client
              nightly_baseline=nightly-minimal
            fi
          fi

          # ---------------------------------------------------------
          # Nightly size experiments, always enabled.
          # ---------------------------------------------------------

          # Rebuild std with the ordinary std feature set.
          build_variant rebuilt-std nightly client \
            -Z build-std

          # Rebuild std without backtrace support.
          # Retain normal panic unwinding.
          build_variant no-backtrace nightly client \
            -Z build-std \
            -Z build-std-features=panic-unwind

          # Aggressive option: terminate immediately on panic.
          build_variant immediate-abort nightly client \
            -Z panic-immediate-abort \
            -Z build-std \
            -Z build-std-features= \
            --config 'profile.release.panic="immediate-abort"'

          # ---------------------------------------------------------
          # Job summary.
          # ---------------------------------------------------------

          {
            echo "### irtt-client: ${TARGET}"
            echo

            echo "#### Standard builds"
            echo
            echo "Toolchain: \`${standard_toolchain}\`"
            echo
            echo '| Variant | Unstripped | Stripped | Compressed | Compressed vs baseline |'
            echo '|:--|--:|--:|--:|--:|'

            print_row full "Full" "$standard_baseline"

            if [[ "$HAS_STATS_FEATURE" == "true" ]]; then
              print_row minimal "Minimal" "$standard_baseline"
            fi

            echo
            echo "#### Nightly experiments"
            echo
            echo '| Variant | Unstripped | Stripped | Compressed | Compressed vs baseline |'
            echo '|:--|--:|--:|--:|--:|'

            print_row "$nightly_full" "Nightly full" "$nightly_baseline"

            if [[ "$HAS_STATS_FEATURE" == "true" ]]; then
              print_row "$nightly_baseline" "Nightly minimal" "$nightly_baseline"
            fi

            print_row rebuilt-std "Rebuilt std" "$nightly_baseline"
            print_row no-backtrace "No backtrace" "$nightly_baseline"
            print_row immediate-abort "Immediate abort" "$nightly_baseline"

            if [[ "$standard_toolchain" == "stable" ]]; then
              echo
              echo "Nightly vs stable baseline (compressed): $(delta \
                "${compressed_size[$standard_baseline]}" \
                "${compressed_size[$nightly_baseline]}")"
            else
              echo
              echo "MIPS: standard and nightly baselines are identical."
              echo "Cross.toml already enables build-std for these targets."
            fi

            if [[ "$HAS_STATS_FEATURE" != "true" ]]; then
              echo
              echo "Statistics feature not detected; client includes statistics."
            fi
          } >> "$GITHUB_STEP_SUMMARY"

      - name: Upload binaries
        # Gitea's v3 artifact protocol.
        uses: actions/upload-artifact@cf430e030ddbb5b0abf93d22962f4752f3646cd9 # v7.0.2
        with:
          name: irtt-client-${{ matrix.target }}
          path: dist/irtt-client-${{ matrix.target }}-*.tar.gz
          if-no-files-found: error