#!/bin/bash
# Point the OpenWrt build at an installed Go toolchain.
#
# Go based packages (tailscale, adguardhome, easytier, cloudflared, ...) need a
# host Go. By default OpenWrt builds the whole bootstrap chain from source; an
# already installed Go can replace part or all of that:
#
#   --external      GOLANG_BUILD_BOOTSTRAP=n, host Go is built with the
#                   installed toolchain directly (skips the entire chain,
#                   requires a Go new enough for the target version)
#   default         keep GOLANG_BUILD_BOOTSTRAP=y and only set the root, which
#                   skips the initial bootstrap step
#
# Usage: ./update-go-path.sh [options]
#
#       --external        skip the bootstrap chain entirely (recommended)
#       --go-root <dir>   use this Go instead of auto-detecting
#       --skip-defconfig  do not run make defconfig afterwards
#   -n, --dry-run         show what would change, write nothing
#   -h, --help            show this help
#
# Run it from the OpenWrt root:  ./helper/update-go-path.sh
#
# Author: Zhe Yuan

set -euo pipefail
umask 022

CONFIG_FILE=".config"
EXTERNAL=false
GO_ROOT=""
RUN_DEFCONFIG=true
DRY_RUN=false

info() { echo "[INFO] $*"; }
warn() { echo "[WARN] $*"; }
err()  { echo "[ERROR] $*" >&2; }

usage() { sed -n '2,25p' "$0" | sed 's/^# \{0,1\}//;s/^#$//'; }

while [ $# -gt 0 ]; do
  case "$1" in
    --external) EXTERNAL=true ;;
    --go-root)
      if [ $# -lt 2 ] || [ -z "${2:-}" ]; then err "--go-root requires a directory."; exit 1; fi
      GO_ROOT="$2"; shift ;;
    --skip-defconfig) RUN_DEFCONFIG=false ;;
    -n|--dry-run) DRY_RUN=true ;;
    -h|--help) usage; exit 0 ;;
    *) err "Unknown option: $1"; echo "Run '$0 --help' for usage." >&2; exit 1 ;;
  esac
  shift
done

echo "========================================"
echo " Go Toolchain Setup for OpenWrt"
echo "========================================"

if [ ! -f "$CONFIG_FILE" ]; then
  err "No .config in the current directory."
  err "From the OpenWrt root, run it as: ./helper/$(basename "$0")"
  exit 1
fi

# --- Locate a Go installation --------------------------------------------
if [ -z "$GO_ROOT" ]; then
  # nullglob only drops words that actually contain a wildcard; a literal path
  # such as /usr/local/go/ survives even when it does not exist. So collect
  # candidates and keep only the directories that are really there.
  shopt -s nullglob
  CANDIDATES=(/usr/lib/go-*/ /usr/local/go/ /usr/lib/golang/)
  shopt -u nullglob

  GO_DIRS=()
  for dir in "${CANDIDATES[@]}"; do
    [ -d "$dir" ] && GO_DIRS+=("$dir")
  done

  if [ ${#GO_DIRS[@]} -eq 0 ]; then
    err "No Go installation found under /usr/lib/go-*, /usr/local/go or /usr/lib/golang."
    err "Install one with:  sudo apt install golang-1.24-go"
    err "or keep the default, where OpenWrt builds its own bootstrap chain."
    exit 1
  fi

  BEST_VER=""
  for dir in "${GO_DIRS[@]}"; do
    [ -x "${dir}bin/go" ] || continue
    ver="$("${dir}bin/go" version 2>/dev/null | awk '{print $3}' | sed 's/^go//')"
    [ -n "$ver" ] || continue
    if [ -z "$BEST_VER" ] ||
      [ "$(printf '%s\n%s\n' "$BEST_VER" "$ver" | sort -V | tail -n 1)" = "$ver" ]; then
      BEST_VER="$ver"
      GO_ROOT="$dir"
    fi
  done

  if [ -z "$GO_ROOT" ]; then
    err "Found Go directories but none contained a working bin/go."
    exit 1
  fi

  if [ ${#GO_DIRS[@]} -gt 1 ]; then
    info "Go installations found: ${GO_DIRS[*]}"
    info "Using the newest; override with --go-root <dir>."
  fi
fi

GO_ROOT="${GO_ROOT%/}/"
if [ ! -x "${GO_ROOT}bin/go" ]; then
  err "No usable Go compiler at ${GO_ROOT}bin/go"
  exit 1
fi
GO_VER="$("${GO_ROOT}bin/go" version | awk '{print $3}' | sed 's/^go//')"

info "Go toolchain: $GO_ROOT (version $GO_VER)"

# --- Warn if it is older than what the tree wants -------------------------
BOOTSTRAP_MK="feeds/packages/lang/golang/golang-bootstrap/Makefile"
if [ -f "$BOOTSTRAP_MK" ]; then
  NEED="$(awk -F':=' '/^GO_VERSION_MAJOR_MINOR/ {print $2; exit}' "$BOOTSTRAP_MK" | tr -d ' ')"
  if [ -n "$NEED" ] &&
    [ "$(printf '%s\n%s\n' "$NEED" "$GO_VER" | sort -V | head -n 1)" != "$NEED" ]; then
    warn "Installed Go $GO_VER is older than the bootstrap version $NEED this tree expects."
    warn "The build may fail; consider installing golang-$NEED-go."
  fi
fi

# --- Apply ----------------------------------------------------------------
set_config() {
  local key="$1" val="$2"
  if [ "$DRY_RUN" = true ]; then
    echo "[DRY-RUN] $key=$val"
    return
  fi
  # Drop every existing form of the symbol, then append once.
  sed -i "/^${key}=/d;/^# ${key} is not set$/d" "$CONFIG_FILE"
  if [ "$val" = "n" ]; then
    echo "# $key is not set" >> "$CONFIG_FILE"
  else
    echo "$key=$val" >> "$CONFIG_FILE"
  fi
}

set_config CONFIG_GOLANG_EXTERNAL_BOOTSTRAP_ROOT "\"$GO_ROOT\""

if [ "$EXTERNAL" = true ]; then
  set_config CONFIG_GOLANG_BUILD_BOOTSTRAP n
  info "Bootstrap chain disabled; host Go is built with the installed toolchain."
else
  set_config CONFIG_GOLANG_BUILD_BOOTSTRAP y
  info "Bootstrap chain kept (only the initial step is skipped)."
  info "Pass --external to skip it entirely."
fi

if [ "$DRY_RUN" = true ]; then
  echo
  info "Dry run complete; .config was not modified."
  exit 0
fi

if [ "$RUN_DEFCONFIG" = true ]; then
  info "Running make defconfig..."
  make defconfig >/dev/null
fi

echo
echo "========================================"
echo "OK  Go configuration updated."
echo "========================================"
grep -E '^(CONFIG_GOLANG_EXTERNAL_BOOTSTRAP_ROOT|CONFIG_GOLANG_BUILD_BOOTSTRAP)|^# CONFIG_GOLANG_BUILD_BOOTSTRAP' "$CONFIG_FILE" | sed 's/^/   /'
echo