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scripts/de-undochange.sh

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+#!/bin/bash
+
+# ==============================================================================
+# undochange.sh - Emergency System Rollback Tool (Btrfs Assistant Edition)
+# ==============================================================================
+# Usage: sudo ./undochange.sh
+# Description: Reverts system to "Before Shorin Setup" using btrfs-assistant
+#              This performs a Subvolume Rollback, not just a file diff undo.
+# ==============================================================================
+
+RED='\033[0;31m'
+GREEN='\033[0;32m'
+YELLOW='\033[1;33m'
+NC='\033[0m' # No Color
+
+TARGET_DESC="Before Desktop Environments"
+
+# 1. Check Root
+if [ "$EUID" -ne 0 ]; then
+    echo -e "${RED}Error: Please run as root (sudo ./undochange.sh)${NC}"
+    exit 1
+fi
+
+# 2. Check Dependencies
+if ! command -v snapper &> /dev/null; then
+    echo -e "${RED}Error: Snapper is not installed.${NC}"
+    exit 1
+fi
+
+if ! command -v btrfs-assistant &> /dev/null; then
+    echo -e "${RED}Error: btrfs-assistant is not installed.${NC}"
+    echo "Cannot perform subvolume rollback."
+    exit 1
+fi
+
+echo -e "${YELLOW}>>> Initializing Emergency Rollback (Target: '$TARGET_DESC')...${NC}"
+
+# --- Helper Function: Rollback Logic from quickload ---
+# Args: $1 = Subvolume Name (e.g., @ or @home), $2 = Snapper Config (e.g., root or home)
+perform_rollback() {
+    local subvol="$1"
+    local snap_conf="$2"
+    
+    echo -e "Checking config: ${YELLOW}$snap_conf${NC} for subvolume: ${YELLOW}$subvol${NC}..."
+
+    # 1. Get Snapper ID
+    # logic: list snapshots -> filter by description -> take the last one -> get ID
+    local snap_id=$(snapper -c "$snap_conf" list --columns number,description | grep "$TARGET_DESC" | tail -n 1 | awk '{print $1}')
+
+    if [ -z "$snap_id" ]; then
+        echo -e "${RED}  [SKIP] Snapshot '$TARGET_DESC' not found in config '$snap_conf'.${NC}"
+        return 1
+    fi
+
+    echo -e "  Found Snapshot ID: ${GREEN}$snap_id${NC}"
+
+    # 2. Map to Btrfs-Assistant Index
+    # Logic from quickload: Match Subvolume Name ($2) and Snapper ID ($3) to get Index ($1)
+    local ba_index=$(btrfs-assistant -l | awk -v v="$subvol" -v s="$snap_id" '$2==v && $3==s {print $1}')
+
+    if [ -z "$ba_index" ]; then
+        echo -e "${RED}  [FAIL] Could not map Snapper ID $snap_id to Btrfs-Assistant index.${NC}"
+        return 1
+    fi
+
+    # 3. Execute Restore
+    echo -e "  Executing rollback (Index: $ba_index)..."
+    if btrfs-assistant -r "$ba_index"; then
+        echo -e "  ${GREEN}Success.${NC}"
+        return 0
+    else
+        echo -e "  ${RED}Restore command failed.${NC}"
+        return 1
+    fi
+}
+
+# --- Main Execution ---
+
+# 3. Rollback Root (Critical)
+# Arch layout usually maps config 'root' to subvolume '@'
+echo -e "${YELLOW}>>> Restoring Root Filesystem...${NC}"
+if ! perform_rollback "@" "root"; then
+    echo -e "${RED}CRITICAL FAILURE: Failed to restore root partition.${NC}"
+    echo "Aborting operation to prevent partial system state."
+    exit 1
+fi
+
+# 4. Rollback Home (Optional)
+# Only attempt if 'home' config exists
+if snapper list-configs | grep -q "^home "; then
+    echo -e "${YELLOW}>>> Restoring Home Filesystem...${NC}"
+    # Arch layout usually maps config 'home' to subvolume '@home'
+    perform_rollback "@home" "home"
+else
+    echo -e "No 'home' snapper config found, skipping home restore."
+fi
+
+# 5. Reboot
+echo -e "${GREEN}System rollback successful.${NC}"
+echo -e "${YELLOW}Rebooting in 3 seconds...${NC}"
+sleep 3
+reboot