#!/usr/bin/env bash

set -euo pipefail

ROOT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
DIST_DIR="${DIST_DIR:-$ROOT_DIR/dist}"
MAIN_PKG="./cmd/sing-box"
GO_BIN="${GO_BIN:-go}"
CGO_ENABLED_VALUE="${CGO_ENABLED_VALUE:-0}"
BUILD_JOBS="${GO_BUILD_JOBS:-}"

DEFAULT_TARGETS=(
  "linux-amd64"
  "linux-arm64"
  "linux-armv7"
  "windows-amd64"
  "windows-arm64"
  "darwin-amd64"
  "darwin-arm64"
)

usage() {
  cat <<'EOF'
Usage:
  ./build.sh                Build common targets
  ./build.sh all            Build common targets
  ./build.sh linux-amd64    Build a single target
  ./build.sh linux-amd64 windows-amd64
  ./build.sh current        Build current host platform

Environment variables:
  GO_BIN              Go binary path, default: go
  DIST_DIR            Output directory, default: ./dist
  CGO_ENABLED_VALUE   CGO_ENABLED value, default: 0
  GO_BUILD_JOBS       Go build parallel jobs, default: detected CPU core count
  VERSION             Embedded version string, default: git describe --tags --always
  BUILD_TAGS_OTHERS   Override tags for non-Windows builds
  BUILD_TAGS_WINDOWS  Override tags for Windows builds
EOF
}

require_file() {
  local file="$1"
  if [[ ! -f "$file" ]]; then
    echo "Missing required file: $file" >&2
    exit 1
  fi
}

trim_file() {
  local file="$1"
  awk 'BEGIN{ORS=""} {gsub(/\r/, ""); print}' "$file"
}

resolve_version() {
  if [[ -n "${VERSION:-}" ]]; then
    printf '%s' "$VERSION"
    return
  fi
  if git -C "$ROOT_DIR" rev-parse --is-inside-work-tree >/dev/null 2>&1; then
    git -C "$ROOT_DIR" describe --tags --always 2>/dev/null || git -C "$ROOT_DIR" rev-parse --short HEAD
    return
  fi
  printf '%s' "custom"
}

resolve_build_jobs() {
  if [[ -n "$BUILD_JOBS" ]]; then
    printf '%s' "$BUILD_JOBS"
    return
  fi
  if command -v nproc >/dev/null 2>&1; then
    nproc
    return
  fi
  if command -v getconf >/dev/null 2>&1; then
    getconf _NPROCESSORS_ONLN
    return
  fi
  printf '%s' "1"
}

build_target() {
  local target="$1"
  local goos goarch goarm="" output tags

  case "$target" in
    linux-amd64)
      goos="linux"
      goarch="amd64"
      output="$DIST_DIR/sing-box-linux-amd64"
      tags="$BUILD_TAGS_OTHERS"
      ;;
    linux-arm64)
      goos="linux"
      goarch="arm64"
      output="$DIST_DIR/sing-box-linux-arm64"
      tags="$BUILD_TAGS_OTHERS"
      ;;
    linux-armv7)
      goos="linux"
      goarch="arm"
      goarm="7"
      output="$DIST_DIR/sing-box-linux-armv7"
      tags="$BUILD_TAGS_OTHERS"
      ;;
    windows-amd64)
      goos="windows"
      goarch="amd64"
      output="$DIST_DIR/sing-box-windows-amd64.exe"
      tags="$BUILD_TAGS_WINDOWS"
      ;;
    windows-arm64)
      goos="windows"
      goarch="arm64"
      output="$DIST_DIR/sing-box-windows-arm64.exe"
      tags="$BUILD_TAGS_WINDOWS"
      ;;
    darwin-amd64)
      goos="darwin"
      goarch="amd64"
      output="$DIST_DIR/sing-box-darwin-amd64"
      tags="$BUILD_TAGS_OTHERS"
      ;;
    darwin-arm64)
      goos="darwin"
      goarch="arm64"
      output="$DIST_DIR/sing-box-darwin-arm64"
      tags="$BUILD_TAGS_OTHERS"
      ;;
    current)
      goos="$("$GO_BIN" env GOOS)"
      goarch="$("$GO_BIN" env GOARCH)"
      output="$DIST_DIR/sing-box-${goos}-${goarch}"
      if [[ "$goos" == "windows" ]]; then
        output="${output}.exe"
        tags="$BUILD_TAGS_WINDOWS"
      else
        tags="$BUILD_TAGS_OTHERS"
      fi
      ;;
    *)
      echo "Unsupported target: $target" >&2
      exit 1
      ;;
  esac

  echo "==> Building $target (jobs: $RESOLVED_BUILD_JOBS)"
  (
    cd "$ROOT_DIR"
    export CGO_ENABLED="$CGO_ENABLED_VALUE"
    export GOOS="$goos"
    export GOARCH="$goarch"
    if [[ -n "$goarm" ]]; then
      export GOARM="$goarm"
    else
      unset GOARM 2>/dev/null || true
    fi

    "$GO_BIN" build -v -p "$RESOLVED_BUILD_JOBS" -trimpath \
      -ldflags "-X 'github.com/sagernet/sing-box/constant.Version=$VERSION_VALUE' $LDFLAGS_SHARED -s -w -buildid=" \
      -tags "$tags" \
      -o "$output" \
      "$MAIN_PKG"
  )
}

if [[ "${1:-}" == "-h" || "${1:-}" == "--help" ]]; then
  usage
  exit 0
fi

require_file "$ROOT_DIR/release/DEFAULT_BUILD_TAGS_OTHERS"
require_file "$ROOT_DIR/release/DEFAULT_BUILD_TAGS_WINDOWS"
require_file "$ROOT_DIR/release/LDFLAGS"

if ! command -v "$GO_BIN" >/dev/null 2>&1; then
  echo "Go binary not found: $GO_BIN" >&2
  exit 1
fi

BUILD_TAGS_OTHERS="${BUILD_TAGS_OTHERS:-$(trim_file "$ROOT_DIR/release/DEFAULT_BUILD_TAGS_OTHERS")}"
BUILD_TAGS_WINDOWS="${BUILD_TAGS_WINDOWS:-$(trim_file "$ROOT_DIR/release/DEFAULT_BUILD_TAGS_WINDOWS")}"
LDFLAGS_SHARED="$(trim_file "$ROOT_DIR/release/LDFLAGS")"
VERSION_VALUE="$(resolve_version)"
RESOLVED_BUILD_JOBS="$(resolve_build_jobs)"

mkdir -p "$DIST_DIR"

if [[ "$#" -eq 0 || "${1:-}" == "all" ]]; then
  TARGETS=("${DEFAULT_TARGETS[@]}")
else
  TARGETS=("$@")
fi

for target in "${TARGETS[@]}"; do
  build_target "$target"
done

echo
echo "Build completed."
echo "Output directory: $DIST_DIR"