#!/usr/bin/env bash

# Exit script on error
set -e
# Exit on undeclared variable
set -u

# File used to track processed files
rebalance_db_file_name="rebalance_db.txt"

# Index used for progress
current_index=0

## Color Constants

# Reset
Color_Off='\033[0m' # Text Reset

# Regular Colors
Red='\033[0;31m'    # Red
Green='\033[0;32m'  # Green
Yellow='\033[0;33m' # Yellow
Cyan='\033[0;36m'   # Cyan

## Functions

# Print a help message
function print_usage() {
    echo "Usage: zfs-inplace-rebalancing.sh --checksum true --passes 1 --debug false /my/pool"
}

# Print a given text entirely in a given color
function color_echo() {
    color=$1
    text=$2
    echo -e "${color}${text}${Color_Off}"
}

# Print a given text entirely in a given color
function echo_debug() {
    if [ "$debug_flag" = true ]; then
        text=$*
        echo "${text}"
    fi
}

function get_rebalance_count() {
    file_path="$1"

    line_nr=$(grep -xF -n "${file_path}" "./${rebalance_db_file_name}" | head -n 1 | cut -d: -f1)
    if [ -z "${line_nr}" ]; then
        echo "0"
        return
    else
        rebalance_count_line_nr="$((line_nr + 1))"
        rebalance_count=$(awk "NR == ${rebalance_count_line_nr}" "./${rebalance_db_file_name}")
        echo "${rebalance_count}"
        return
    fi
}

# Rebalance a group of files that are hardlinked together
function process_inode_group() {
    paths=("$@")
    num_paths="${#paths[@]}"

    # Progress tracking
    current_index="$((current_index + 1))"
    progress_raw=$((current_index * 10000 / file_count))
    progress_percent=$(printf '%0.2f' "${progress_raw}e-2")
    color_echo "${Cyan}" "Progress -- Files: ${current_index}/${file_count} (${progress_percent}%)"

    echo_debug "Processing inode group with ${num_paths} paths:"
    for path in "${paths[@]}"; do
        echo_debug " - $path"
    done

    # Check rebalance counts for all files
    should_skip=false
    for path in "${paths[@]}"; do
        rebalance_count=$(get_rebalance_count "${path}")
        if [ "${rebalance_count}" -ge "${passes_flag}" ]; then
            should_skip=true
            break
        fi
    done

    if [ "${should_skip}" = true ]; then
        if [ "${num_paths}" -gt 1 ]; then
            color_echo "${Yellow}" "Rebalance count (${passes_flag}) reached, skipping group: ${paths[*]}"
        else
            color_echo "${Yellow}" "Rebalance count (${passes_flag}) reached, skipping: ${paths[0]}"
        fi
        return
    fi

    main_file="${paths[0]}"

    # Check if main_file exists
    if [[ ! -f "${main_file}" ]]; then
        color_echo "${Yellow}" "File is missing, skipping: ${main_file}"
        return
    fi

    tmp_extension=".balance"
    tmp_file_path="${main_file}${tmp_extension}"

    echo "Copying '${main_file}' to '${tmp_file_path}'..."
    echo_debug "Executing copy command:"

    if [[ "${OSName}" == "linux-gnu"* ]]; then
        # Linux

        # --reflink=never -- force standard copy (see ZFS Block Cloning)
        # -a -- keep attributes, includes -d -- keep symlinks (dont copy target) and
        #       -p -- preserve ACLs to
        # -x -- stay on one system
        cmd=(cp --reflink=never -ax "${main_file}" "${tmp_file_path}")
        echo_debug "${cmd[@]}"
        "${cmd[@]}"
    elif [[ "${OSName}" == "darwin"* ]] || [[ "${OSName}" == "freebsd"* ]]; then
        # Mac OS and FreeBSD

        # -a -- Archive mode.  Same as -RpP. Includes preservation of modification
        #       time, access time, file flags, file mode, ACL, user ID, and group
        #       ID, as allowed by permissions.
        # -x -- File system mount points are not traversed.
        cmd=(cp -ax "${main_file}" "${tmp_file_path}")
        echo_debug "${cmd[@]}"
        "${cmd[@]}"
    else
        echo "Unsupported OS type: $OSTYPE"
        exit 1
    fi

    # Compare copy against original to make sure nothing went wrong
    if [[ "${checksum_flag}" == "true"* ]]; then
        echo "Comparing copy against original..."
        if [[ "${OSName}" == "linux-gnu"* ]]; then
            # Linux

            # file attributes
            original_perms=$(lsattr "${main_file}")
            # remove anything after the last space
            original_perms=${original_perms% *}
            # file permissions, owner, group, size, modification time
            original_perms="${original_perms} $(stat -c "%A %U %G %s %Y" "${main_file}")"


            # file attributes
            copy_perms=$(lsattr "${tmp_file_path}")
            # remove anything after the last space
            copy_perms=${copy_perms% *}
            # file permissions, owner, group, size, modification time
            copy_perms="${copy_perms} $(stat -c "%A %U %G %s %Y" "${tmp_file_path}")"
        elif [[ "${OSName}" == "darwin"* ]] || [[ "${OSName}" == "freebsd"* ]]; then
            # Mac OS
            # FreeBSD

            # note: no lsattr on Mac OS or FreeBSD

            # file permissions, owner, group size, modification time
            original_perms="$(stat -f "%Sp %Su %Sg %z %m" "${main_file}")"

            # file permissions, owner, group size, modification time
            copy_perms="$(stat -f "%Sp %Su %Sg %z %m" "${tmp_file_path}")"
        else
            echo "Unsupported OS type: $OSTYPE"
            exit 1
        fi

        echo_debug "Original perms: $original_perms"
        echo_debug "Copy perms: $copy_perms"

        if [[ "${original_perms}" == "${copy_perms}"* ]]; then
            color_echo "${Green}" "Attribute and permission check OK"
        else
            color_echo "${Red}" "Attribute and permission check FAILED: ${original_perms} != ${copy_perms}"
            exit 1
        fi

        if cmp -s "${main_file}" "${tmp_file_path}"; then
            color_echo "${Green}" "File content check OK"
        else
            color_echo "${Red}" "File content check FAILED"
            exit 1
        fi
    fi

    echo "Removing original files..."
    for path in "${paths[@]}"; do
        echo_debug "Removing $path"
        rm "${path}"
    done

    echo "Renaming temporary copy to original '${main_file}'..."
    echo_debug "Moving ${tmp_file_path} to ${main_file}"
    mv "${tmp_file_path}" "${main_file}"

    # Only recreate hardlinks if there are multiple paths
    if [ "${num_paths}" -gt 1 ]; then
        echo "Recreating hardlinks..."
        for (( i=1; i<${#paths[@]}; i++ )); do
            echo_debug "Linking ${main_file} to ${paths[$i]}"
            ln "${main_file}" "${paths[$i]}"
        done
    fi

    if [ "${passes_flag}" -ge 1 ]; then
        # Update rebalance "database" for all files
        for path in "${paths[@]}"; do
            line_nr=$(grep -xF -n "${path}" "./${rebalance_db_file_name}" | head -n 1 | cut -d: -f1)
            if [ -z "${line_nr}" ]; then
                rebalance_count=1
                echo "${path}" >> "./${rebalance_db_file_name}"
                echo "${rebalance_count}" >> "./${rebalance_db_file_name}"
            else
                rebalance_count_line_nr="$((line_nr + 1))"
                rebalance_count=$(awk "NR == ${rebalance_count_line_nr}" "./${rebalance_db_file_name}")
                rebalance_count="$((rebalance_count + 1))"
                echo_debug "Updating rebalance count for ${path} to ${rebalance_count}"
                sed -i "${rebalance_count_line_nr}s/.*/${rebalance_count}/" "./${rebalance_db_file_name}"
            fi
        done
    fi
}

checksum_flag='true'
passes_flag='1'
debug_flag='false'

if [[ "$#" -eq 0 ]]; then
    print_usage
    exit 0
fi

while true; do
    case "$1" in
    -h | --help)
        print_usage
        exit 0
        ;;
    -c | --checksum)
        if [[ "$2" == 1 || "$2" =~ (on|true|yes) ]]; then
            checksum_flag="true"
        else
            checksum_flag="false"
        fi
        shift 2
        ;;
    -p | --passes)
        passes_flag=$2
        shift 2
        ;;
    --debug)
        if [[ "$2" == 1 || "$2" =~ (on|true|yes) ]]; then
            debug_flag="true"
        else
            debug_flag="false"
        fi
        shift 2
        ;;
    *)
        break
        ;;
    esac
done

root_path=$1

OSName=$(echo "$OSTYPE" | tr '[:upper:]' '[:lower:]')

color_echo "$Cyan" "Start rebalancing $(date):"
color_echo "$Cyan" "  Path: ${root_path}"
color_echo "$Cyan" "  Rebalancing Passes: ${passes_flag}"
color_echo "$Cyan" "  Use Checksum: ${checksum_flag}"
color_echo "$Cyan" "  Debug Mode: ${debug_flag}"

# Generate files_list.txt with device and inode numbers using stat, separated by a pipe '|'
if [[ "${OSName}" == "linux-gnu"* ]]; then
    # Linux
    find "$root_path" -type f -not -path '*/.zfs/*' -exec stat --printf '%d:%i|%n\n' {} \; > files_list.txt
elif [[ "${OSName}" == "darwin"* ]] || [[ "${OSName}" == "freebsd"* ]]; then
    # Mac OS and FreeBSD
    find "$root_path" -type f -not -path '*/.zfs/*' -exec stat -f "%d:%i|%N" {} \; > files_list.txt
else
    echo "Unsupported OS type: $OSTYPE"
    exit 1
fi

echo_debug "Contents of files_list.txt:"
if [ "$debug_flag" = true ]; then
    cat files_list.txt
fi

# Sort files_list.txt by device and inode number
sort -t '|' -k1,1 files_list.txt > sorted_files_list.txt

echo_debug "Contents of sorted_files_list.txt:"
if [ "$debug_flag" = true ]; then
    cat sorted_files_list.txt
fi

# Use awk to group paths by inode key and handle spaces in paths
awk -F'|' '{
    key = $1
    path = substr($0, length(key)+2)
    if (key == prev_key) {
        print "\t" path
    } else {
        if (NR > 1) {
            # Do nothing
        }
        print key
        print "\t" path
        prev_key = key
    }
}' sorted_files_list.txt > grouped_inodes.txt

echo_debug "Contents of grouped_inodes.txt:"
if [ "$debug_flag" = true ]; then
    cat grouped_inodes.txt
fi

# Count number of inode groups
file_count=$(grep -c '^\w' grouped_inodes.txt)

color_echo "$Cyan" "  Number of files to process: ${file_count}"

# Initialize current_index
current_index=0

# Create db file
if [ "${passes_flag}" -ge 1 ]; then
    touch "./${rebalance_db_file_name}"
fi

paths=()

# Read grouped_inodes.txt line by line
while IFS= read -r line; do
    if [[ "$line" == $'\t'* ]]; then
        # This is a path line
        path="${line#$'\t'}"
        paths+=("$path")
    else
        # This is a new inode key
        if [[ "${#paths[@]}" -gt 0 ]]; then
            # Process the previous group
            process_inode_group "${paths[@]}"
        fi
        paths=()
    fi
done < grouped_inodes.txt

# Process the last group after the loop ends
if [[ "${#paths[@]}" -gt 0 ]]; then
    process_inode_group "${paths[@]}"
fi

# Clean up temporary files
rm files_list.txt sorted_files_list.txt grouped_inodes.txt

echo ""
echo ""
color_echo "$Green" "Done!"