#!/usr/bin/env bash
set -euo pipefail

# Repo root = directory where this script lives
ROOT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
WRAPPERS_DIR="$ROOT_DIR/gradle/wrappers"
BACKUP_ROOT="$WRAPPERS_DIR/backup"

# Parse Gradle version from gradle-wrapper.properties (distributionUrl)
extract_version() {
  local props="$1"
  local url
  url="$(grep -E '^\s*distributionUrl=' "$props" | head -n 1 | cut -d= -f2- || true)"
  # Match: gradle-9.2.1-bin.zip / gradle-8.14.3-all.zip / gradle-9.0-rc-1-bin.zip
  if [[ "$url" =~ gradle-([0-9A-Za-z.\-]+)-(bin|all)\.zip ]]; then
    echo "${BASH_REMATCH[1]}"
  else
    echo "unknown"
  fi
}

major_of() {
  local v="$1"
  # major = digits before first dot or dash
  if [[ "$v" =~ ^([0-9]+) ]]; then
    echo "${BASH_REMATCH[1]}"
  else
    echo "0"
  fi
}

list_wrappers() {
  shopt -s nullglob
  local d
  for d in "$WRAPPERS_DIR"/g[0-9]*; do
    [[ -d "$d" ]] || continue
    local name
    name="$(basename "$d")"
    [[ "$name" =~ ^g[0-9]+$ ]] || continue

    local props="$d/gradle/wrapper/gradle-wrapper.properties"
    local jar="$d/gradle/wrapper/gradle-wrapper.jar"
    local sh="$d/gradlew"
    local bat="$d/gradlew.bat"
    [[ -f "$props" && -f "$jar" && -f "$sh" && -f "$bat" ]] || continue

    local ver major
    ver="$(extract_version "$props")"
    major="$(major_of "$ver")"
    printf "%s|%s|%s\n" "$name" "$major" "$ver"
  done | sort -t'|' -k2,2n
}

backup_current() {
  mkdir -p "$BACKUP_ROOT"
  local stamp
  stamp="$(date +%Y%m%d-%H%M%S)"
  local dest="$BACKUP_ROOT/$stamp"
  mkdir -p "$dest/gradle/wrapper"

  # Backup only if exists
  [[ -f "$ROOT_DIR/gradlew" ]] && cp -f "$ROOT_DIR/gradlew" "$dest/" || true
  [[ -f "$ROOT_DIR/gradlew.bat" ]] && cp -f "$ROOT_DIR/gradlew.bat" "$dest/" || true
  [[ -f "$ROOT_DIR/gradle/wrapper/gradle-wrapper.jar" ]] && cp -f "$ROOT_DIR/gradle/wrapper/gradle-wrapper.jar" "$dest/gradle/wrapper/" || true
  [[ -f "$ROOT_DIR/gradle/wrapper/gradle-wrapper.properties" ]] && cp -f "$ROOT_DIR/gradle/wrapper/gradle-wrapper.properties" "$dest/gradle/wrapper/" || true

  echo "Backed up current wrapper to: $dest"

  # Cleanup old backups (keep last 10)
  local backups
  mapfile -t backups < <(ls -1dt "$BACKUP_ROOT"/*/ 2>/dev/null)
  if [[ ${#backups[@]} -gt 10 ]]; then
    local i
    for ((i=10; i<${#backups[@]}; i++)); do
      rm -rf "${backups[$i]}"
    done
    echo "Deleted $(( ${#backups[@]} - 10 )) old backup(s)."
  fi
}

apply_wrapper() {
  local wrapper_dir="$1"

  # Try to stop current Gradle daemon (best-effort)
  if [[ -x "$ROOT_DIR/gradlew" ]]; then
    "$ROOT_DIR/gradlew" --stop >/dev/null 2>&1 || true
  fi

  backup_current

  mkdir -p "$ROOT_DIR/gradle/wrapper"
  cp -f "$wrapper_dir/gradlew" "$ROOT_DIR/gradlew"
  cp -f "$wrapper_dir/gradlew.bat" "$ROOT_DIR/gradlew.bat"
  cp -f "$wrapper_dir/gradle/wrapper/gradle-wrapper.jar" "$ROOT_DIR/gradle/wrapper/gradle-wrapper.jar"
  cp -f "$wrapper_dir/gradle/wrapper/gradle-wrapper.properties" "$ROOT_DIR/gradle/wrapper/gradle-wrapper.properties"

  chmod +x "$ROOT_DIR/gradlew" || true
}

usage() {
  cat <<EOF
Usage:
  ./gradle-wrapper-switcher              # interactive menu
  ./gradle-wrapper-switcher --use g9     # switch to a specific wrapper directory
  ./gradle-wrapper-switcher --list       # list detected wrappers
EOF
}

main() {
  [[ -d "$WRAPPERS_DIR" ]] || { echo "Wrappers directory not found: $WRAPPERS_DIR"; exit 1; }

  if [[ "${1:-}" == "--list" ]]; then
    list_wrappers | while IFS='|' read -r name major ver; do
      echo "$name -> Gradle $major.x ($ver)"
    done
    exit 0
  fi

  if [[ "${1:-}" == "--use" ]]; then
    local target="${2:-}"
    [[ -n "$target" ]] || { usage; exit 1; }
    local dir="$WRAPPERS_DIR/$target"
    [[ -d "$dir" ]] || { echo "Wrapper not found: $dir"; exit 1; }
    apply_wrapper "$dir"
    local ver major
    ver="$(extract_version "$dir/gradle/wrapper/gradle-wrapper.properties")"
    major="$(major_of "$ver")"
    echo "Switched to: Gradle $major.x ($ver) from $target"
    echo "Tip: In IntelliJ IDEA or Android Studio, use \"Reload All Gradle Projects\" if needed."
    exit 0
  fi

  # interactive
  mapfile -t items < <(list_wrappers)
  [[ "${#items[@]}" -gt 0 ]] || { echo "No valid wrappers found under: $WRAPPERS_DIR"; exit 1; }

  echo "Please choose the Gradle version to switch to:"
  local i=1
  local names=()
  local line name major ver
  for line in "${items[@]}"; do
    IFS='|' read -r name major ver <<<"$line"
    names+=("$name")
    echo "$i. Gradle ${major}.x (Pinned version: $ver)"
    i=$((i+1))
  done

  echo -n "> "
  read -r choice
  [[ "$choice" =~ ^[0-9]+$ ]] || { echo "Invalid selection."; exit 1; }
  (( choice>=1 && choice<=${#names[@]} )) || { echo "Out of range."; exit 1; }

  local picked="${names[$((choice-1))]}"
  apply_wrapper "$WRAPPERS_DIR/$picked"
  local picked_ver
  picked_ver="$(extract_version "$WRAPPERS_DIR/$picked/gradle/wrapper/gradle-wrapper.properties")"
  echo "Switched to: Gradle ${picked//[^0-9]/}.x (Pinned version: $picked_ver)"
  echo "Tip: In IntelliJ IDEA or Android Studio, use \"Reload All Gradle Projects\" if needed."
}

main "$@"