#!/bin/bash

# LVM Block-Level Backup Script
# Creates consistent snapshots and clones entire volumes block-for-block
# This is the ONLY backup script you need!

set -e

# Colors
RED='\033[0;31m'
GREEN='\033[0;32m'
YELLOW='\033[1;33m'
BLUE='\033[0;34m'
NC='\033[0m'

# Configuration
SOURCE_VG="internal-vg"
TARGET_VG="migration-vg"
SNAPSHOT_SIZE="2G"
LOG_FILE="/var/log/lvm-block-backup.log"

log() {
    local message="[$(date '+%Y-%m-%d %H:%M:%S')] $1"
    echo -e "${BLUE}$message${NC}"
    echo "$message" >> "$LOG_FILE"
}

error() {
    local message="[ERROR] $1"
    echo -e "${RED}$message${NC}" >&2
    echo "$message" >> "$LOG_FILE"
    exit 1
}

success() {
    local message="[SUCCESS] $1"
    echo -e "${GREEN}$message${NC}"
    echo "$message" >> "$LOG_FILE"
}

warning() {
    local message="[WARNING] $1"
    echo -e "${YELLOW}$message${NC}"
    echo "$message" >> "$LOG_FILE"
}

check_requirements() {
    log "Checking system requirements..."
    
    # Check if running as root
    if [ "$EUID" -ne 0 ]; then
        error "This script must be run as root. Use: sudo $0"
    fi
    
    # Check if source VG exists
    if ! vgs "$SOURCE_VG" >/dev/null 2>&1; then
        error "Source volume group '$SOURCE_VG' not found"
    fi
    
    # Check if target VG exists
    if ! vgs "$TARGET_VG" >/dev/null 2>&1; then
        error "Target volume group '$TARGET_VG' not found"
    fi
    
    # Check if volumes exist
    local volumes=("root" "home" "boot")
    for vol in "${volumes[@]}"; do
        if ! lvs "$SOURCE_VG/$vol" >/dev/null 2>&1; then
            error "Source logical volume '$SOURCE_VG/$vol' not found"
        fi
        if ! lvs "$TARGET_VG/$vol" >/dev/null 2>&1; then
            error "Target logical volume '$TARGET_VG/$vol' not found"
        fi
    done
    
    # Check available space for snapshots
    local vg_free=$(vgs --noheadings -o vg_free --units g "$SOURCE_VG" | tr -d ' G')
    local vg_free_int=${vg_free%.*}
    
    if [ "$vg_free_int" -lt 6 ]; then
        error "Insufficient free space for snapshots. Need at least 6GB, have ${vg_free}GB"
    fi
    
    success "System requirements check passed"
}

cleanup_snapshots() {
    log "Cleaning up any existing snapshots..."
    lvremove -f "$SOURCE_VG/root-backup-snap" 2>/dev/null || true
    lvremove -f "$SOURCE_VG/home-backup-snap" 2>/dev/null || true
    lvremove -f "$SOURCE_VG/boot-backup-snap" 2>/dev/null || true
}

create_snapshots() {
    log "Creating LVM snapshots for consistent backup..."
    
    cleanup_snapshots
    
    # Create snapshots
    lvcreate -L "$SNAPSHOT_SIZE" -s -n root-backup-snap "$SOURCE_VG/root" || error "Failed to create root snapshot"
    lvcreate -L "$SNAPSHOT_SIZE" -s -n home-backup-snap "$SOURCE_VG/home" || error "Failed to create home snapshot"  
    lvcreate -L 1G -s -n boot-backup-snap "$SOURCE_VG/boot" || error "Failed to create boot snapshot"
    
    success "Snapshots created successfully"
}

clone_volumes() {
    log "Starting block-level volume cloning..."
    
    # Unmount target volumes if mounted
    umount "/dev/$TARGET_VG/home" 2>/dev/null || true
    umount "/dev/$TARGET_VG/root" 2>/dev/null || true
    umount "/dev/$TARGET_VG/boot" 2>/dev/null || true
    
    # Clone root volume
    log "Cloning root volume (this may take a while)..."
    dd if="/dev/$SOURCE_VG/root-backup-snap" of="/dev/$TARGET_VG/root" bs=64M status=progress || error "Failed to clone root volume"
    success "Root volume cloned"
    
    # Clone home volume  
    log "Cloning home volume (this will take the longest)..."
    dd if="/dev/$SOURCE_VG/home-backup-snap" of="/dev/$TARGET_VG/home" bs=64M status=progress || error "Failed to clone home volume"
    success "Home volume cloned"
    
    # Clone boot volume
    log "Cloning boot volume..."
    dd if="/dev/$SOURCE_VG/boot-backup-snap" of="/dev/$TARGET_VG/boot" bs=64M status=progress || error "Failed to clone boot volume"
    success "Boot volume cloned"
}

verify_backup() {
    log "Verifying backup integrity..."
    
    # Check filesystem integrity
    fsck -n "/dev/$TARGET_VG/root" || warning "Root filesystem check showed issues"
    fsck -n "/dev/$TARGET_VG/boot" || warning "Boot filesystem check showed issues"
    
    # Note: Can't check encrypted home volume without decryption
    
    success "Backup verification completed"
}

show_backup_info() {
    log "Creating backup information..."
    
    cat << EOF

=====================================
LVM Block-Level Backup Complete
=====================================
Date: $(date)
Source: $SOURCE_VG
Target: $TARGET_VG

Volume Information:
$(lvs $SOURCE_VG $TARGET_VG)

The external drive now contains an exact block-level copy of your internal drive.
You can boot from the external drive by selecting it in your BIOS/UEFI boot menu.

To mount the backup volumes:
  sudo mount /dev/$TARGET_VG/root /mnt/backup-root
  sudo mount /dev/$TARGET_VG/boot /mnt/backup-boot
  # Home volume needs LUKS decryption first

EOF
}

main() {
    echo -e "${GREEN}=== LVM Block-Level Backup Tool ===${NC}"
    echo "This will create an exact copy of your internal LVM volumes to the external drive."
    echo
    
    read -p "Are you sure you want to proceed? This will OVERWRITE data on $TARGET_VG! [y/N]: " confirm
    if [[ ! "$confirm" =~ ^[Yy]$ ]]; then
        echo "Backup cancelled."
        exit 0
    fi
    
    check_requirements
    create_snapshots
    clone_volumes
    cleanup_snapshots
    verify_backup
    show_backup_info
    
    success "Backup completed successfully!"
}

# Trap to cleanup on exit
trap cleanup_snapshots EXIT

main "$@"