#!/bin/bash
set -euo pipefail

# copyfast — 快速拷贝最新文件到绑定的U盘
#
# 模式:
#   (无参数)        正常模式: 找到绑定的U盘, 拷贝最新匹配文件并弹出
#   --count N        指定拷贝最新的 N 个文件 (默认1)
#   --no-unmount     拷贝后不弹出U盘
#   --bind           绑定当前插入的U盘 (自动选最大分区, 可绑定多个)
#   --unbind         解除已绑定的U盘
#   --install-udev   安装 udev 规则, 插入U盘时自动运行
#   --uninstall-udev 移除 udev 规则
#   --config         打印当前配置
#   --help           帮助信息

# 真实用户检测: sudo → $SUDO_USER, 否则 → $USER, --user 可覆盖
# 真实 HOME 根据最终 REAL_USER 推导
_resolve_home() {
    getent passwd "$1" 2>/dev/null | cut -d: -f6
}
if [[ -n "${SUDO_USER:-}" ]]; then
    REAL_USER="$SUDO_USER"
    REAL_HOME="$(_resolve_home "$SUDO_USER")"
else
    REAL_USER="$USER"
    REAL_HOME="$HOME"
fi

CONFIG_DIR="${XDG_CONFIG_HOME:-$REAL_HOME/.config}/copyfast"
CONFIG_FILE="$CONFIG_DIR/config"
SCRIPT_PATH="$(realpath "$0")"

# ============================================================
# 默认配置
# ============================================================
SOURCE_DIR="$REAL_HOME/Downloads"
EXTENSIONS=""           # 逗号分隔, 空=所有文件
USB_UUIDS=""            # 绑定的U盘UUID列表 (空格分隔)
AUTO_UNMOUNT="true"     # 拷贝后自动弹出 (默认开启)
FILE_COUNT="1"          # 拷贝最新文件的数量

# ============================================================
# 加载配置
# ============================================================
load_config() {
    if [[ -f "$CONFIG_FILE" ]]; then
        source "$CONFIG_FILE"
    fi
    # 迁移旧格式: USB_UUID → USB_UUIDS
    if [[ -z "$USB_UUIDS" ]] && [[ -n "${USB_UUID:-}" ]]; then
        USB_UUIDS="$USB_UUID"
        save_config
    fi
}

# ============================================================
# 保存配置
# ============================================================
save_config() {
    mkdir -p "$CONFIG_DIR"
    cat > "$CONFIG_FILE" <<EOF
# copyfast 配置文件
# 由 copyfast --bind / --unbind 写入, 也可手动编辑

SOURCE_DIR="$SOURCE_DIR"
EXTENSIONS="$EXTENSIONS"
USB_UUIDS="$USB_UUIDS"
AUTO_UNMOUNT="$AUTO_UNMOUNT"
FILE_COUNT="$FILE_COUNT"
EOF
}

# ============================================================
# 将USB_UUIDS字符串转为数组
# ============================================================
get_bound_uuids() {
    local -a result=()
    if [[ -n "$USB_UUIDS" ]]; then
        for uuid in $USB_UUIDS; do
            [[ -n "$uuid" ]] && result+=("$uuid")
        done
    fi
    echo "${result[@]:-}"
}

# ============================================================
# 列出当前插入的USB设备 — 每磁盘只返回最大分区
# 输出格式: DISK_NAME|UUID|LABEL|MOUNTPOINT|SIZE
# ============================================================
list_usb_disks() {
    # 获取USB磁盘名称
    local usb_disks
    usb_disks=$(lsblk -o NAME,TRAN -d -l -n 2>/dev/null | awk '$2=="usb"{print $1}')
    [[ -z "$usb_disks" ]] && return

    for disk in $usb_disks; do
        # 获取此磁盘下的分区
        local parts best_uuid best_label best_mp best_size_bytes best_size_str
        local part_size_bytes part_size_str part_uuid part_label part_mp
        best_size_bytes=0

        local parts_list
        parts_list=$(lsblk -o NAME -l -n "/dev/$disk" 2>/dev/null | grep -v "^$disk\$")
        while IFS= read -r part; do
            local dev="/dev/$part"
            part_uuid=$(lsblk -o UUID -n "$dev" | tr -d '[:space:]')
            [[ -z "$part_uuid" ]] && continue
            part_size_str=$(lsblk -o SIZE -n "$dev" | tr -d '[:space:]')
            part_label=$(lsblk -o LABEL -n "$dev" | tr -d '[:space:]')
            part_mp=$(lsblk -o MOUNTPOINT -n "$dev" | tr -d '[:space:]')

            # 解析 SIZE (用 awk 处理浮点数, 如 "57.3G")
            part_size_bytes=$(awk -v s="$part_size_str" '
                BEGIN {
                    u = substr(s, length(s))
                    v = substr(s, 1, length(s)-1) + 0
                    if (u == "T")      printf "%d", v * 1099511627776
                    else if (u == "G") printf "%d", v * 1073741824
                    else if (u == "M") printf "%d", v * 1048576
                    else if (u == "K") printf "%d", v * 1024
                    else               printf "%d", v
                }')

            if [[ "$part_size_bytes" -gt "$best_size_bytes" ]]; then
                best_size_bytes=$part_size_bytes
                best_uuid=$part_uuid
                best_label=$part_label
                best_mp=$part_mp
                best_size_str=$part_size_str
            fi
        done <<< "$parts_list"

        if [[ -n "${best_uuid:-}" ]]; then
            echo "$disk|$best_uuid|${best_label:-}|${best_mp:-}|${best_size_str:-}"
        fi
    done
}

# ============================================================
# 通过UUID查找设备 (不管是否挂载)
# 返回 "MOUNTPOINT|KNAME" 或 "|KNAME" (未挂载时挂载点为空)
# 通过 /dev/disk/by-uuid/ 和 lsblk 单列输出, 避免空列解析问题
# ============================================================
find_device_by_uuid() {
    local uuid="$1"
    local dev_path

    # 优先使用 udev 直接传递的设备路径 (避免 /dev/disk/by-uuid 未就绪)
    if [[ -n "${UDEV_DEVICE:-}" ]] && [[ -e "$UDEV_DEVICE" ]]; then
        dev_path="$UDEV_DEVICE"
    else
        dev_path="/dev/disk/by-uuid/$uuid"
        [[ -e "$dev_path" ]] || { return 1; }
    fi

    local mp k
    mp=$(lsblk -o MOUNTPOINT -n "$dev_path" | head -1 | tr -d '[:space:]')
    k=$(basename "$(readlink -f "$dev_path")")

    echo "$mp|$k"
}

# ============================================================
# 挂载设备, 返回挂载点
# 多级保底: root直接用mount, 普通用户用udisksctl
# ============================================================
mount_device() {
    local uuid="$1"
    local dev_path

    if [[ -n "${UDEV_DEVICE:-}" ]] && [[ -e "$UDEV_DEVICE" ]]; then
        dev_path="$UDEV_DEVICE"
    else
        dev_path="/dev/disk/by-uuid/$uuid"
        [[ -e "$dev_path" ]] || return 1
    fi

    # 已挂载则直接返回挂载点
    local mp
    mp=$(lsblk -o MOUNTPOINT -n "$dev_path" 2>/dev/null | head -1 | tr -d '[:space:]')
    if [[ -n "$mp" ]]; then
        echo "$mp"
        return 0
    fi

    # 尝试1: udisksctl (需要D-Bus会话, 适用于桌面环境)
    if udisksctl mount -b "$dev_path" 2>/dev/null; then
        return 0
    fi

    # 尝试2: root 直接 mount (适用于udev触发场景)
    if [[ "$(id -u)" == "0" ]]; then
        local mnt="/run/media/copyfast/$uuid"
        mkdir -p "$mnt"
        if mount "$dev_path" "$mnt" 2>/dev/null; then
            echo "$mnt"
            return 0
        fi
    fi

    # 尝试3: sudo mount
    local mnt="/run/media/copyfast/$uuid"
    mkdir -p "$mnt" 2>/dev/null || true
    if sudo mount "$dev_path" "$mnt" 2>/dev/null; then
        echo "$mnt"
        return 0
    fi

    return 1
}

# ============================================================
# 获取挂载点 (设备可能已挂载或需挂载)
# ============================================================
get_mountpoint() {
    local uuid="$1"
    local dev_info
    dev_info=$(find_device_by_uuid "$uuid")

    if [[ -z "$dev_info" ]]; then
        return 1
    fi

    local mp="${dev_info%%|*}"

    if [[ -z "$mp" ]]; then
        if [[ "${UDEV_MODE:-false}" == "true" ]]; then
            # udev模式: 不挂载, 等待桌面环境自动挂载 (最长10秒)
            local i
            for i in {1..10}; do
                sleep 1
                dev_info=$(find_device_by_uuid "$uuid")
                mp="${dev_info%%|*}"
                [[ -n "$mp" ]] && break
            done
        else
            # 正常模式: 主动挂载
            mount_device "$uuid" > /dev/null 2>&1 || return 1
            sleep 1
            dev_info=$(find_device_by_uuid "$uuid")
            mp="${dev_info%%|*}"
        fi
    fi

    if [[ -n "$mp" ]]; then
        echo "$mp"
        return 0
    fi

    return 1
}

# ============================================================
# 获取源目录中最新的 N 个文件 (每行一个路径)
# $1: 源目录, $2: 逗号分隔的扩展名 (空=所有文件), $3: 数量 (默认1)
# ============================================================
get_latest_files() {
    local src="$1"
    local exts="$2"
    local count="${3:-1}"

    if [[ ! -d "$src" ]]; then
        echo ""
        return 1
    fi

    if [[ -z "$exts" ]]; then
        find "$src" -maxdepth 1 -type f -printf '%T@ %p\n' 2>/dev/null \
            | sort -rn | head -n "$count" | cut -d' ' -f2-
        return
    fi

    local IFS=','
    local args=()
    local ext_count=0
    for ext in $exts; do
        ext=$(echo "$ext" | tr -d '[:space:]')
        [[ -z "$ext" ]] && continue
        if [[ $ext_count -gt 0 ]]; then
            args+=(-o)
        fi
        args+=(-iname "*.$ext")
        ext_count=$((ext_count+1))
    done

    if [[ $ext_count -eq 0 ]]; then
        echo ""
        return 1
    fi

    if [[ $ext_count -gt 1 ]]; then
        find "$src" -maxdepth 1 -type f \( "${args[@]}" \) -printf '%T@ %p\n' 2>/dev/null \
            | sort -rn | head -n "$count" | cut -d' ' -f2-
    else
        find "$src" -maxdepth 1 -type f "${args[@]}" -printf '%T@ %p\n' 2>/dev/null \
            | sort -rn | head -n "$count" | cut -d' ' -f2-
    fi
}

# ============================================================
# 日志 (udev触发时写入logger, 否则写入stderr)
# ============================================================
log() {
    if [[ "${UDEV_MODE:-false}" == "true" ]]; then
        logger -t "copyfast" "$@"
    else
        echo "$@" >&2
    fi
}

# ============================================================
# 桌面通知 (通过 real user 的 D-Bus)
# ============================================================
_notify() {
    local uid
    uid=$(id -u "$REAL_USER" 2>/dev/null) || { log "通知: 无法获取用户UID"; return 0; }

    local bus="/run/user/$uid/bus"
    if [[ ! -S "$bus" ]]; then
        log "通知: D-Bus 会话总线不可用 ($bus)"
        return 0
    fi

    export DBUS_SESSION_BUS_ADDRESS="unix:path=$bus"

    # 尝试多种方式获取 DISPLAY
    if [[ -z "${DISPLAY:-}" ]]; then
        # 从 loginctl 获取用户会话的 display
        local display
        display=$(loginctl show-user "$REAL_USER" -p Display 2>/dev/null | cut -d= -f2)
        # 兜底: 常见的 display 值
        for d in "${display:-}" ":0" ":1"; do
            [[ -z "$d" ]] && continue
            export DISPLAY="$d"
            break
        done
    fi

    if notify-send -i drive-removable-media "copyfast" "$*" -t 5000 2>/dev/null; then
        log "通知: 桌面通知已发送"
    else
        log "通知: notify-send 执行失败"
    fi
    return 0
}

# ============================================================
# 正常模式: 查找USB并拷贝最新文件
# ============================================================
do_copy() {
    if [[ -z "$USB_UUIDS" ]]; then
        log "错误: 未绑定U盘。请先插入U盘并运行: $(basename "$0") --bind"
        exit 1
    fi

    if [[ ! "$FILE_COUNT" =~ ^[1-9][0-9]*$ ]]; then
        log "错误: 文件数量不是有效的正整数: $FILE_COUNT"
        exit 1
    fi

    # 遍历已绑定UUID, 找到第一个可用的
    log "正在查找已绑定的U盘..."
    local uuids uuid mountpoint was_mounted
    uuids=($(get_bound_uuids))

    for uuid in "${uuids[@]}"; do
        # 检查设备是否存在
        local dev_info
        dev_info=$(find_device_by_uuid "$uuid")
        [[ -z "$dev_info" ]] && continue

        local current_mp="${dev_info%%|*}"
        was_mounted="$current_mp"

        mountpoint=$(get_mountpoint "$uuid" 2>/dev/null) || {
            log "警告: 无法挂载 UUID=$uuid, 尝试下一个..."
            continue
        }
        break
    done

    if [[ -z "${mountpoint:-}" ]]; then
        log "错误: 未找到任何已绑定的U盘, 请确认U盘已插入"
        exit 1
    fi

    log "找到已绑定U盘: UUID=$uuid, 挂载点=$mountpoint"

    if [[ ! -d "$SOURCE_DIR" ]]; then
        log "错误: 源目录不存在: $SOURCE_DIR"
        exit 1
    fi

    log "正在 $SOURCE_DIR 中查找最新 $FILE_COUNT 个文件..."
    local files
    files=$(get_latest_files "$SOURCE_DIR" "$EXTENSIONS" "$FILE_COUNT")

    if [[ -z "$files" ]]; then
        if [[ -n "$EXTENSIONS" ]]; then
            log "错误: 未在 $SOURCE_DIR 中找到匹配扩展名 ($EXTENSIONS) 的文件"
        else
            log "错误: $SOURCE_DIR 中没有文件"
        fi
        exit 1
    fi

    local copied=0
    while IFS= read -r f; do
        [[ -z "$f" ]] && continue
        log "拷贝 ($((copied+1))/$FILE_COUNT): $(basename "$f") -> $mountpoint"
        cp "$f" "$mountpoint/"
        copied=$((copied+1))
    done <<< "$files"

    log "拷贝完成: 共 $copied 个文件 -> $mountpoint"

    # udev模式下发送桌面通知
    if [[ "${UDEV_MODE:-false}" == "true" ]]; then
        _notify "拷贝完成: 共 $copied 个文件"
    fi

    if [[ "$AUTO_UNMOUNT" == "true" ]]; then
        log "正在弹出U盘..."

        # udev模式下设置 D-Bus 环境以便 udisksctl 工作
        if [[ "${UDEV_MODE:-false}" == "true" ]]; then
            local uid
            uid=$(id -u "$REAL_USER" 2>/dev/null)
            if [[ -n "${uid:-}" ]] && [[ -S "/run/user/$uid/bus" ]]; then
                export DBUS_SESSION_BUS_ADDRESS="unix:path=/run/user/$uid/bus"
            fi
        fi

        local dev_to_unmount="${UDEV_DEVICE:-/dev/disk/by-uuid/$uuid}"
        if udisksctl unmount -b "$dev_to_unmount" 2>/dev/null; then
            log "已弹出U盘 (unmount)"
        elif udisksctl power-off -b "$dev_to_unmount" 2>/dev/null; then
            log "已弹出U盘 (power-off)"
        elif umount "$mountpoint" 2>/dev/null; then
            log "已弹出U盘 (umount)"
        elif sudo umount "$mountpoint" 2>/dev/null; then
            log "已弹出U盘 (sudo umount)"
        else
            log "警告: 弹出 $mountpoint 失败 (可能有其他程序正在使用)"
        fi
    fi
}

# ============================================================
# 绑定模式: 自动选择每个U盘的最大分区, 加入绑定列表
# ============================================================
do_bind() {
    local devices
    devices=$(list_usb_disks)

    if [[ -z "$devices" ]]; then
        echo "错误: 未检测到插入的USB设备, 请先插入U盘"
        exit 1
    fi

    local disk uuid label mp size

    # 收集当前已绑定的UUID
    local -A bound_map
    if [[ -n "$USB_UUIDS" ]]; then
        for bid in $USB_UUIDS; do
            bound_map["$bid"]=1
        done
    fi

    # 过滤掉已绑定的, 收集可绑定的
    local candidates=()
    while IFS='|' read -r disk uuid label mp size; do
        if [[ -n "${bound_map[$uuid]:-}" ]]; then
            echo "跳过已绑定: $uuid (标签=${label:-(无)}, 挂载点=${mp:-(未挂载)})"
            continue
        fi
        candidates+=("$disk|$uuid|$label|$mp|$size")
    done <<< "$devices"

    if [[ ${#candidates[@]} -eq 0 ]]; then
        echo "所有已插入的U盘都已绑定。"
        echo "当前绑定: $USB_UUIDS"
        echo "如需解绑, 请运行: $(basename "$0") --unbind"
        exit 0
    fi

    local chosen_uuid chosen_label chosen_disk
    local count=${#candidates[@]}

    if [[ "$count" -eq 1 ]]; then
        IFS='|' read -r chosen_disk chosen_uuid chosen_label _ _ <<< "${candidates[0]}"
        echo "检测到1个新U盘, 自动选择最大分区:"
        echo "  磁盘: $chosen_disk"
        echo "  标签: ${chosen_label:-(无)}"
        echo "  UUID: $chosen_uuid"
        echo ""
    else
        echo "检测到 $count 个新U盘, 请选择要绑定的设备:"
        echo ""
        local i=1
        local lines=()
        for cand in "${candidates[@]}"; do
            IFS='|' read -r disk uuid label mp size <<< "$cand"
            echo "  [$i] 磁盘=$disk  标签=${label:-(无)}  UUID=$uuid  挂载点=${mp:-(未挂载)}"
            lines+=("$cand")
            ((i++))
        done
        echo ""
        read -rp "请选择要绑定的编号 [1-$count]: " choice
        if [[ ! "$choice" =~ ^[0-9]+$ ]] || [[ "$choice" -lt 1 ]] || [[ "$choice" -gt "$count" ]]; then
            echo "错误: 无效选择"
            exit 1
        fi
        IFS='|' read -r chosen_disk chosen_uuid chosen_label _ _ <<< "${lines[$((choice-1))]}"
    fi

    # 添加到绑定列表
    if [[ -z "$USB_UUIDS" ]]; then
        USB_UUIDS="$chosen_uuid"
    else
        USB_UUIDS="$USB_UUIDS $chosen_uuid"
    fi
    save_config

    echo "已绑定U盘:"
    echo "  磁盘: $chosen_disk"
    echo "  标签: ${chosen_label:-(无)}"
    echo "  UUID: $chosen_uuid"
    echo ""
    echo "当前所有绑定: $USB_UUIDS"
    echo "配置已保存到 $CONFIG_FILE"
    echo ""
    echo "后续可直接运行 $(basename "$0") 或安装 udev 规则以实现自动运行:"
    echo "  $(basename "$0") --install-udev"
}

# ============================================================
# 解绑模式: 交互选择已绑定的U盘并移除
# ============================================================
do_unbind() {
    if [[ -z "$USB_UUIDS" ]]; then
        echo "当前没有绑定的U盘。"
        exit 0
    fi

    local uuids
    uuids=($USB_UUIDS)

    echo "当前绑定列表:"
    local i=1
    for uuid in "${uuids[@]}"; do
        # 查询标签信息
        local info
        info=$(lsblk -o UUID,LABEL,MOUNTPOINT -l -n 2>/dev/null | awk -v u="$uuid" '$1==u {print "标签=" $2 " 挂载点=" $3}')
        echo "  [$i] UUID=$uuid  ${info:-未插入}"
        ((i++))
    done
    echo ""

    if [[ ${#uuids[@]} -eq 1 ]]; then
        read -rp "确认解除此绑定? [y/N]: " confirm
        if [[ ! "$confirm" =~ ^[Yy]$ ]]; then
            echo "已取消"
            exit 0
        fi
        USB_UUIDS=""
    else
        read -rp "请选择要解除的编号 [1-${#uuids[@]}] (留空取消): " choice
        if [[ -z "$choice" ]]; then
            echo "已取消"
            exit 0
        fi
        if [[ ! "$choice" =~ ^[1-9][0-9]*$ ]] || [[ "$choice" -gt "${#uuids[@]}" ]]; then
            echo "错误: 无效选择"
            exit 1
        fi
        unset 'uuids[$((choice-1))]'
        USB_UUIDS="${uuids[*]}"
    fi

    save_config
    echo "已解除绑定。"
    if [[ -n "$USB_UUIDS" ]]; then
        echo "当前绑定: $USB_UUIDS"
    else
        echo "当前没有任何绑定。"
    fi
}

# ============================================================
# 安装 udev 规则 — 为每个已绑定UUID生成一条规则
# ============================================================
do_install_udev() {
    if [[ -z "$USB_UUIDS" ]]; then
        echo "错误: 尚未绑定U盘, 请先运行: $(basename "$0") --bind"
        exit 1
    fi

    local udev_rule="/etc/udev/rules.d/99-copyfast.rules"

    if [[ -f "$udev_rule" ]]; then
        echo "udev 规则已存在于 $udev_rule"
        read -rp "是否覆盖? [y/N]: " confirm
        if [[ ! "$confirm" =~ ^[Yy]$ ]]; then
            echo "已取消"
            exit 0
        fi
        sudo rm "$udev_rule"
    fi

    echo "正在生成 udev 规则..."

    local uuids
    uuids=($USB_UUIDS)

    {
        echo "# copyfast udev rules — 插入已绑定U盘时自动运行"
        echo "# 安装时间: $(date)"
        for uuid in "${uuids[@]}"; do
            echo "ACTION==\"add\", SUBSYSTEM==\"block\", ENV{ID_FS_UUID}==\"$uuid\", RUN+=\"/usr/bin/systemd-run --uid=$REAL_USER --gid=$(id -g "$REAL_USER") --collect -- $SCRIPT_PATH --udev-triggered --device /dev/\$kernel\""
        done
    } | sudo tee "$udev_rule" > /dev/null

    echo "正在重新加载 udev 规则..."
    sudo udevadm control --reload-rules
    sudo udevadm trigger

    echo ""
    echo "udev 规则安装完成: $udev_rule"
    echo "已为 ${#uuids[@]} 个U盘生成规则。"
    echo ""
    echo "规则内容:"
    cat "$udev_rule"
    echo ""
    echo "现在插入任意已绑定的U盘, 脚本将自动运行。"
}

# ============================================================
# 卸载 udev 规则
# ============================================================
do_uninstall_udev() {
    local udev_rule="/etc/udev/rules.d/99-copyfast.rules"

    if [[ ! -f "$udev_rule" ]]; then
        echo "udev 规则不存在: $udev_rule"
        exit 0
    fi

    echo "正在移除 udev 规则..."
    sudo rm "$udev_rule"

    echo "正在重新加载 udev 规则..."
    sudo udevadm control --reload-rules

    echo "已移除 udev 规则。"
}

# ============================================================
# 打印配置
# ============================================================
do_config() {
    echo "当前配置:"
    echo "  配置文件:   $CONFIG_FILE"
    echo "  源目录:     $SOURCE_DIR"
    echo "  文件后缀:   ${EXTENSIONS:-(所有文件)}"
    echo "  拷贝数量:   最新的 $FILE_COUNT 个文件"
    echo "  拷贝后弹出: $AUTO_UNMOUNT"
    echo ""
    if [[ -z "$USB_UUIDS" ]]; then
        echo "  已绑定U盘:  (无)"
    else
        echo "  已绑定U盘 ($(echo "$USB_UUIDS" | wc -w) 个):"
        local uuids
        uuids=($USB_UUIDS)
        for uuid in "${uuids[@]}"; do
            local info
            info=$(lsblk -o UUID,LABEL,MOUNTPOINT -l -n 2>/dev/null \
                | awk -v u="$uuid" '$1==u {printf "标签=%s, 挂载点=%s", ($2?$2:"无"), ($3?$3:"未挂载")}')
            echo "    UUID=$uuid  ${info:-未插入}"
        done
    fi
}

# ============================================================
# 帮助
# ============================================================
do_help() {
    cat <<HELP
copyfast — 从指定目录快速拷贝最新文件到绑定的U盘

用法: $(basename "$0") [选项]

正常使用:
  直接运行即可将 SOURCE_DIR 中最新的 FILE_COUNT 个匹配文件
  拷贝到已绑定的U盘 (第一个检测到的), 拷贝完成后自动弹出U盘。

选项:
  -n, --count N      拷贝最新的 N 个文件 (默认: 1)
                     例: $(basename "$0") --count 3
  -N, --no-unmount   拷贝后不弹出U盘
                     例: $(basename "$0") --no-unmount

绑定与管理:
  -b, --bind         绑定当前插入的U盘到配置文件
                     每个U盘只选最大分区, 可重复执行绑定多个U盘
                     例: $(basename "$0") --bind
  -u, --unbind       解除已绑定的U盘, 交互选择要移除的绑定
                     例: $(basename "$0") --unbind
  -i, --install-udev 安装 udev 规则 (需 sudo 权限)
                     为所有已绑定U盘生成规则, 插入任意一个即自动运行
  -U, --uninstall-udev 移除 udev 规则 (需 sudo 权限)
  -c, --config       打印当前所有配置项及其值
  -h, --help         显示此帮助信息

配置文件: $CONFIG_FILE
  配置项说明:
    SOURCE_DIR     要拷贝哪个目录下的最新文件
                   默认: ~/Downloads
    EXTENSIONS     只拷贝这些后缀的文件, 逗号分隔, 大小写不敏感
                   留空表示所有文件
                   例: "ppt,pptx,pdf" 或 "zip,tar.gz,7z"
    FILE_COUNT     每次拷贝最新的几个文件, 必须是正整数 (默认1)
    USB_UUIDS      绑定的U盘UUID列表 (空格分隔), 由 --bind/--unbind 维护
                   请不要手动修改此项
    AUTO_UNMOUNT   拷贝后是否自动弹出U盘
                   true=弹出 (默认), false=不弹出
                   命令行 --no-unmount 可临时覆盖为不弹出

使用示例:
  # 首次配置
  $(basename "$0") --bind           # 插入U盘后绑定 (自动选最大分区)
  $(basename "$0") --count 3       # 拷贝最新3个文件到U盘
  $(basename "$0") --no-unmount    # 拷贝但不弹出

  # 管理多个U盘
  $(basename "$0") --bind           # 插入另一个U盘, 再次绑定
  $(basename "$0") --config         # 查看所有绑定
  $(basename "$0") --unbind         # 解除某个绑定

  # 修改默认行为: 编辑配置文件
  # 将 EXTENSIONS 设为 "ppt,pptx" 则之后只拷贝这两种文件
  # 将 FILE_COUNT 设为 "5" 则之后每次拷贝5个文件

  # 安装自动运行后, 插入任意已绑定U盘自动拷贝并弹出
  $(basename "$0") --install-udev

技术说明:
  - USB设备通过文件系统UUID识别, 不受挂载点路径变化影响
  - 每个U盘只选最大分区, 避免绑定到启动分区等小分区
  - 支持绑定多个不同U盘, 运行时使用最先检测到的那个
  - udev模式下轮询等待挂载 (最长10秒), 日志写入 syslog
  - 文件匹配使用 find -iname, 扩展名匹配不区分大小写
HELP
}

# ============================================================
# 入口与参数解析
# ============================================================

# 先加载配置文件, 后续命令行参数可覆盖配置值
load_config

UDEV_MODE=false
UDEV_DEVICE=""

# 使用 while+shift 解析参数, 支持 --count N 这种带值参数
while [[ $# -gt 0 ]]; do
    case "$1" in
        --udev-triggered)
            UDEV_MODE=true
            shift
            ;;
        --user)
            if [[ -z "${2:-}" ]] || [[ "${2:0:1}" == "-" ]]; then
                echo "错误: --user 需要指定用户名"
                exit 1
            fi
            REAL_USER="$2"
            REAL_HOME="$(_resolve_home "$2")"
            shift 2
            ;;
        --device)
            if [[ -z "${2:-}" ]] || [[ "${2:0:1}" == "-" ]]; then
                echo "错误: --device 需要指定设备路径"
                exit 1
            fi
            UDEV_DEVICE="$2"
            shift 2
            ;;
        --count|-n)
            if [[ -z "${2:-}" ]] || [[ "${2:0:1}" == "-" ]]; then
                echo "错误: --count 需要指定一个正整数"
                exit 1
            fi
            FILE_COUNT="$2"
            shift 2
            ;;
        --no-unmount|-N)
            AUTO_UNMOUNT="false"
            shift
            ;;
        --bind|-b)
            do_bind
            exit 0
            ;;
        --unbind|-u)
            do_unbind
            exit 0
            ;;
        --install-udev|-i)
            do_install_udev
            exit 0
            ;;
        --uninstall-udev|-U)
            do_uninstall_udev
            exit 0
            ;;
        --config|-c)
            do_config
            exit 0
            ;;
        --help|-h)
            do_help
            exit 0
            ;;
        *)
            echo "错误: 未知选项 '$1'"
            echo "运行 $(basename "$0") --help 查看用法"
            exit 1
            ;;
    esac
done

# 进入正常拷贝模式
# 注意: udev 模式下由 systemd-run 管理生命周期, 无需后台化
do_copy