#!/bin/bash

# Check Snapshot Size
# Determine how much space the snapshot is actually using

set -e

echo "=== Check Snapshot Size ==="
echo ""

# Current disk space
FREE_SPACE=$(df / | tail -1 | awk '{print $4}')
FREE_SPACE_GB=$(echo "scale=2; $FREE_SPACE / 1024 / 1024" | bc)
USED_SPACE=$(df / | tail -1 | awk '{print $3}')
USED_SPACE_GB=$(echo "scale=2; $USED_SPACE / 1024 / 1024" | bc)

echo "📊 Current Disk Status:"
echo "   Used: ${USED_SPACE_GB}GB"
echo "   Free: ${FREE_SPACE_GB}GB"
echo ""

# Check if snapshot exists in APFS
echo "🔍 Checking if snapshot exists in APFS..."
APFS_CHECK=$(diskutil apfs listSnapshots / 2>/dev/null | grep -i "timemachine" || echo "NOT_FOUND")
if [ "$APFS_CHECK" = "NOT_FOUND" ]; then
    echo "   ❌ Snapshot NOT found in APFS"
    echo "   This means it's a GHOST ENTRY - not taking any space!"
    echo ""
    echo "   The snapshot entry you see is just a stale database record."
    echo "   It's not actually consuming disk space."
    echo ""
    echo "   ✅ Your space is already available!"
    echo "   The ghost entry will clear on restart."
else
    echo "   ✅ Snapshot found in APFS"
    echo "   $APFS_CHECK"
    echo ""
    echo "   This snapshot IS taking up space."
fi
echo ""

# Try to get snapshot size
SNAPSHOT=$(tmutil listlocalsnapshots / 2>/dev/null | grep -v "Snapshots for disk" | grep -v "^$" | head -1)
if [ -n "$SNAPSHOT" ]; then
    echo "📸 Snapshot Details:"
    echo "   Name: $SNAPSHOT"
    echo ""
    
    echo "   Attempting to calculate snapshot size..."
    SNAP_DATE=$(echo "$SNAPSHOT" | sed 's/.*\.\([0-9]\{4\}-[0-9]\{2\}-[0-9]\{2\}-[0-9]\{6\}\)\.backup/\1/')
    
    # Try calculatedrift
    DRIFT_OUTPUT=$(sudo tmutil calculatedrift "$SNAPSHOT" 2>&1 || echo "ERROR")
    if echo "$DRIFT_OUTPUT" | grep -qi "size\|bytes\|GB\|MB"; then
        echo "   Size information:"
        echo "$DRIFT_OUTPUT" | grep -i "size\|bytes\|GB\|MB" | head -5 | sed 's/^/     /'
    else
        echo "   ⚠️  Could not calculate size (snapshot may be corrupted/stuck)"
    fi
    echo ""
fi

# Container vs Volume analysis
echo "📦 Container Analysis:"
CONTAINER_TOTAL=$(diskutil info / | grep 'Container Total' | awk '{print $4, $5}')
CONTAINER_FREE=$(diskutil info / | grep 'Container Free' | awk '{print $4, $5}')
VOLUME_USED=$(diskutil info / | grep 'Volume Used Space' | awk '{print $4, $5, $6}')

echo "   Container Total: $CONTAINER_TOTAL"
echo "   Container Free:  $CONTAINER_FREE"
echo "   Volume Used:     $VOLUME_USED"
echo ""

# Calculate if there's unaccounted space
CONTAINER_TOTAL_GB=$(diskutil info / | grep 'Container Total' | awk '{print $3}' | tr -d 'GB')
CONTAINER_FREE_GB=$(diskutil info / | grep 'Container Free' | awk '{print $3}' | tr -d 'GB')
VOLUME_USED_GB=$(diskutil info / | grep 'Volume Used Space' | awk '{print $4}' | tr -d 'GB')

CONTAINER_USED_GB=$(echo "$CONTAINER_TOTAL_GB - $CONTAINER_FREE_GB" | bc)
DISCREPANCY=$(echo "$CONTAINER_USED_GB - $VOLUME_USED_GB" | bc)

echo "   Container Used: ~${CONTAINER_USED_GB}GB"
echo "   Volume Used: ~${VOLUME_USED_GB}GB"
if (( $(echo "$DISCREPANCY > 1" | bc -l) )); then
    echo "   ⚠️  Unaccounted: ~${DISCREPANCY}GB"
    echo "      This could be:"
    echo "      - APFS snapshots"
    echo "      - Other volumes"
    echo "      - Reserved space"
else
    echo "   ✅ Space accounting looks normal"
fi
echo ""

# Summary
echo "=== Summary ==="
echo ""
if [ "$APFS_CHECK" = "NOT_FOUND" ]; then
    echo "✅ The snapshot is a GHOST ENTRY - it's NOT taking any space!"
    echo ""
    echo "   Your disk space is already available."
    echo "   The entry will clear on restart."
    echo ""
    echo "   If 'System Data' is still growing when you delete files,"
    echo "   it's because Time Machine is creating NEW snapshots,"
    echo "   not because of this old ghost entry."
else
    echo "⚠️  The snapshot IS in APFS and may be taking space."
    echo ""
    echo "   To free the space, you need to:"
    echo "   1. Remove Time Machine destination"
    echo "   2. Restart your Mac"
    echo "   3. The snapshot should be cleared"
fi
echo ""