#!/bin/bash
# maravento.com
#
################################################################################
#
# checkmd5 - Verify MD5 checksum of selected file
#
# Nautilus Path: ~/.local/share/nautilus/scripts or ~/.config/nautilus/scripts
# Caja Path: ~/.config/caja/scripts
# Thunar Path: ~/.local/share/Thunar/scripts or ~/.config/Thunar/scripts
# Nemo Path: ~/.local/share/nemo/scripts
#
################################################################################

set -uo pipefail

# check no-root
if [ "$(id -u)" == "0" ]; then
    echo "[ERROR] This script should not be run as root."
    exit 1
fi

echo "Start CheckMD5. Wait..."

# Function to show error and exit
show_error() {
    zenity --error --title="MD5 Verification" --text="$1"
    exit 1
}

# Function to show info
show_info() {
    zenity --info --title="MD5 Verification" --text="$1"
}

# Check if zenity is available
if ! command -v zenity &> /dev/null; then
    echo "Error: zenity is required but not installed."
    exit 1
fi

# Check if md5sum is available
if ! command -v md5sum &> /dev/null; then
    show_error "Error: md5sum is required but not installed."
fi

# Get the selected file (universal file manager detection)
if [ -n "${NAUTILUS_SCRIPT_SELECTED_FILE_PATHS:-}" ]; then
    # Nautilus or Caja - get first line only
    original_file=$(echo "$NAUTILUS_SCRIPT_SELECTED_FILE_PATHS" | head -n1)
elif [ -n "${THUNAR_SELECTION:-}" ]; then
    # Thunar - get first line only
    original_file=$(echo "$THUNAR_SELECTION" | head -n1)
elif [ -n "${NEMO_SCRIPT_SELECTED_FILE_PATHS:-}" ]; then
    # Nemo (Linux Mint) - get first line only
    original_file=$(echo "$NEMO_SCRIPT_SELECTED_FILE_PATHS" | head -n1)
elif [ $# -eq 1 ]; then
    # Called from command line with argument
    original_file="$1"
else
    # No file provided, ask user to select
    original_file=$(zenity --file-selection \
                           --title="Select the original file to verify")
    [ $? -ne 0 ] && exit 0
fi

# Check if original file exists and is readable
if [ ! -f "$original_file" ]; then
    show_error "File does not exist: $original_file"
fi

if [ ! -r "$original_file" ]; then
    show_error "Cannot read file: $original_file"
fi

# Get file info for display
original_filename=$(basename "$original_file")

# Look for checksum file with same name + .md5 extension
checksum_file="${original_file}.md5"

# If not found, ask user to locate it
if [ ! -f "$checksum_file" ]; then
    zenity --info \
           --title="MD5 Verification" \
           --text="Checksum file not found:\n$(basename "$checksum_file")\n\nPlease select the .md5 checksum file manually."

    checksum_file=$(zenity --file-selection \
                           --title="Select the .md5 checksum file for: $original_filename" \
                           --file-filter="MD5 files (*.md5) | *.md5" \
                           --file-filter="All files | *")

    # If user cancelled the file selection
    if [ $? -ne 0 ] || [ -z "$checksum_file" ]; then
        show_error "No checksum file selected. Verification cancelled."
    fi
fi

# Validate checksum file
if [ ! -f "$checksum_file" ]; then
    show_error "Checksum file does not exist: $(basename "$checksum_file")"
fi

if [ ! -r "$checksum_file" ]; then
    show_error "Cannot read checksum file: $(basename "$checksum_file")"
fi

if [ ! -s "$checksum_file" ]; then
    show_error "Checksum file is empty: $(basename "$checksum_file")"
fi

# Extract hash from checksum file
line_count=$(grep -c '' "$checksum_file")
if [ "$line_count" -le 1 ]; then
    # Single-entry file: no ambiguity, use it as-is (covers plain "hash"
    # or "hash filename" sidecar files)
    hash=$(head -n1 "$checksum_file" | awk '{print $1}')
else
    # Multi-file manifest (e.g. generated by makemd5): match the entry
    # whose filename corresponds to the file being verified
    target_basename=$(basename "$original_file")
    hash=""
    while IFS= read -r line; do
        [ -z "$line" ] && continue
        line_file="${line#* }"
        if [ "$(basename "$line_file")" = "$target_basename" ]; then
            hash="${line%% *}"
            break
        fi
    done < "$checksum_file"
    if [ -z "$hash" ]; then
        show_error "No checksum entry found for '$target_basename' in $(basename "$checksum_file")."
    fi
fi

# Clean any whitespace
hash=$(echo "$hash" | tr -d '[:space:]')

# Validate hash format (MD5 should be 32 hex characters)
if [[ ! "$hash" =~ ^[a-fA-F0-9]{32}$ ]]; then
    show_error "Invalid MD5 hash format in checksum file.\n\nExpected: 32 hexadecimal characters\nFound: $hash\n\nChecksum file: $(basename "$checksum_file")"
fi

# Show progress dialog while calculating
(
echo "10" ; echo "# Reading checksum file..." ; sleep 0.3
echo "40" ; echo "# Calculating MD5 hash..." ; sleep 0.5
echo "90" ; echo "# Comparing checksums..." ; sleep 0.3
echo "100" ; echo "# Complete!"
) | zenity --progress \
           --title="MD5 Verification" \
           --text="Verifying: $original_filename" \
           --percentage=0 \
           --auto-close \
           --no-cancel &

progress_pid=$!

# Calculate actual hash of the file
actual_hash=$(md5sum "$original_file" | awk '{print $1}')

# Kill progress dialog
kill $progress_pid 2>/dev/null
wait $progress_pid 2>/dev/null

# Compare hashes directly (case insensitive)
if [ "$(echo "$hash" | tr '[:upper:]' '[:lower:]')" = "$(echo "$actual_hash" | tr '[:upper:]' '[:lower:]')" ]; then
    show_info "VERIFICATION SUCCESSFUL\n\nFile: $original_filename\nHash: $hash\nStatus: INTEGRITY VERIFIED\n\nThe file has not been corrupted or modified."
else
    show_error "VERIFICATION FAILED\n\nFile: $original_filename\nExpected: $hash\nActual: $actual_hash\nStatus: CHECKSUMS DO NOT MATCH\n\nThe file may be corrupted, incomplete, or modified."
fi