#!/bin/bash

# Simple LVM Backup Script
# Does exactly what it says: snapshot -> copy -> cleanup
# NO complex logic, just the essentials

set -e

# Colors
RED='\033[0;31m'
GREEN='\033[0;32m'
YELLOW='\033[1;33m'
NC='\033[0m'

usage() {
    echo "Usage: $0 SOURCE_LV TARGET_DEVICE"
    echo ""
    echo "Example: $0 /dev/internal-vg/root /dev/sdb"
    echo ""
    echo "This will:"
    echo "1. Create a snapshot of SOURCE_LV"
    echo "2. Copy it block-for-block to TARGET_DEVICE"
    echo "3. Clean up the snapshot"
    echo ""
    echo "WARNING: TARGET_DEVICE will be completely overwritten!"
    exit 1
}

log() {
    echo -e "${GREEN}[$(date '+%H:%M:%S')] $1${NC}"
}

error() {
    echo -e "${RED}[ERROR] $1${NC}" >&2
    cleanup_and_exit 1
}

warn() {
    echo -e "${YELLOW}[WARNING] $1${NC}"
}

cleanup_and_exit() {
    local exit_code=${1:-0}
    
    if [ -n "$SNAPSHOT_PATH" ] && lvs "$SNAPSHOT_PATH" >/dev/null 2>&1; then
        warn "Cleaning up snapshot: $SNAPSHOT_PATH"
        lvremove -f "$SNAPSHOT_PATH" || warn "Failed to remove snapshot"
    fi
    
    exit $exit_code
}

# Trap for cleanup
trap 'cleanup_and_exit 130' INT TERM

# Check arguments
if [ $# -ne 2 ]; then
    usage
fi

SOURCE_LV="$1"
TARGET_DEVICE="$2"

# Check if running as root
if [ "$EUID" -ne 0 ]; then
    error "This script must be run as root"
fi

# Basic validation
if [ ! -e "$SOURCE_LV" ]; then
    error "Source LV does not exist: $SOURCE_LV"
fi

if [ ! -e "$TARGET_DEVICE" ]; then
    error "Target device does not exist: $TARGET_DEVICE"
fi

# Extract VG and LV names
VG_NAME=$(lvs --noheadings -o vg_name "$SOURCE_LV" | tr -d ' ')
LV_NAME=$(lvs --noheadings -o lv_name "$SOURCE_LV" | tr -d ' ')
SNAPSHOT_NAME="${LV_NAME}_simple_backup"
SNAPSHOT_PATH="/dev/$VG_NAME/$SNAPSHOT_NAME"

log "Simple LVM Backup Starting"
log "Source: $SOURCE_LV"
log "Target: $TARGET_DEVICE"
log "Snapshot will be: $SNAPSHOT_PATH"

# Final confirmation
echo ""
echo -e "${YELLOW}WARNING: This will completely overwrite $TARGET_DEVICE${NC}"
echo -e "${YELLOW}All data on $TARGET_DEVICE will be lost!${NC}"
echo ""
read -p "Are you sure you want to continue? (yes/no): " confirm

if [ "$confirm" != "yes" ]; then
    echo "Backup cancelled."
    exit 0
fi

echo ""
log "Starting backup process..."

# Step 1: Create snapshot
log "Creating snapshot..."
if ! lvcreate -L1G -s -n "$SNAPSHOT_NAME" "$SOURCE_LV"; then
    error "Failed to create snapshot"
fi
log "Snapshot created: $SNAPSHOT_PATH"

# Step 2: Copy data
log "Starting copy operation..."
log "This may take a long time depending on the size of your data"

# Use pv if available for progress, otherwise dd with progress
if command -v pv >/dev/null 2>&1; then
    log "Using pv for progress monitoring"
    if ! pv "$SNAPSHOT_PATH" | dd of="$TARGET_DEVICE" bs=4M; then
        error "Copy operation failed"
    fi
else
    log "Using dd (install 'pv' for progress monitoring)"
    if ! dd if="$SNAPSHOT_PATH" of="$TARGET_DEVICE" bs=4M status=progress; then
        error "Copy operation failed"
    fi
fi

log "Copy completed successfully"

# Step 3: Clean up snapshot
log "Removing snapshot..."
if ! lvremove -f "$SNAPSHOT_PATH"; then
    warn "Failed to remove snapshot, but backup completed"
    warn "You may need to manually remove: $SNAPSHOT_PATH"
else
    log "Snapshot cleaned up"
fi

log "Backup completed successfully!"
log "Your data has been copied to: $TARGET_DEVICE"

echo ""
echo -e "${GREEN}SUCCESS: Backup completed!${NC}"
echo ""
echo "To verify the backup, you can:"
echo "1. Mount $TARGET_DEVICE and check the files"
echo "2. Boot from $TARGET_DEVICE if it's bootable"
echo ""