#!/bin/bash

export SOURCE_DIR=${SOURCE_DIR:=root}
# Fix basename / showing up as "/" -> change to "root"
if [ $(basename $SOURCE_DIR) = / ]; then
    export SNAPSHOT_PREFIX=${SNAPSHOT_PREFIX:=root}
else
    export SNAPSHOT_PREFIX=${SNAPSHOT_PREFIX:=$(basename $SOURCE_DIR)}
fi
# Set snapshot prefix based on basename
export SNAPSHOT_TIME=$(date +"%y_%m_%d-%H.%M")
export SNAPSHOT_NAME=$SNAPSHOT_PREFIX-$SNAPSHOT_TIME
export SNAPSHOT_DIR=${SNAPSHOT_DIR:=/.snapshots}
export LATEST=$SNAPSHOT_PREFIX-latest
export BACKUP_DRIVE_MNT=${BACKUP_DRIVE_MNT:=/mnt/backup0}
export BACKUP_DIR=${BACKUP_DIR:=/mnt/backup0/DucoBacktop}

# Show snapshot settings
echo "SOURCE_DIR: $SOURCE_DIR"
echo "SNAPSHOT_PREFIX: $SNAPSHOT_PREFIX"
echo "SNAPSHOT_TIME: $SNAPSHOT_TIME"
echo "SNAPSHOT_NAME: $SNAPSHOT_NAME"
echo "SNAPSHOT_DIR: $SNAPSHOT_DIR"
echo "LATEST: $LATEST"
echo "BACKUP_DRIVE_MNT: $BACKUP_DRIVE_MNT"
echo "BACKUP_DIR: $BACKUP_DIR"

# Create readonly snapshot
btrfs subvolume snapshot -r $SOURCE_DIR $SNAPSHOT_DIR/$SNAPSHOT_NAME

# Check if backup disk is mounted
mount $BACKUP_DRIVE_MNT
mountpoint $BACKUP_DRIVE_MNT

if [ $? = 0 ]; then
    if [ -d $BACKUP_DIR/$LATEST ]; then
        btrfs send -p $SNAPSHOT_DIR/$LATEST $SNAPSHOT_DIR/$SNAPSHOT_NAME | btrfs receive $BACKUP_DIR
    else
        btrfs send $SNAPSHOT_DIR/$SNAPSHOT_NAME | btrfs receive $BACKUP_DIR
    fi

    # Update latest in snapshot dir
    rm -f $SNAPSHOT_DIR/$LATEST
    ln -s $SNAPSHOT_DIR/$SNAPSHOT_NAME $SNAPSHOT_DIR/$LATEST
    
    # Update latest in backup dir
    rm -f $BACKUP_DIR/$LATEST
    ln -s $BACKUP_DIR/$SNAPSHOT_NAME $BACKUP_DIR/$LATEST
else
    echo "Backup location $BACKUP_DRIVE_MNT not mounted. Snapshot $SNAPSHOT_NAME not synced"
fi