#!/bin/bash

# Log file for tracking changes
LOGFILE="/var/log/fix-ownership.log"
echo "Starting ownership change process on $(date)" > "$LOGFILE"

# Cache to track unchanged users and groups
UNCHANGED_USERS=()
UNCHANGED_GROUPS=()
USER_EXISTS=false
GROUP_EXISTS=false

# function to check if a user is unchanged
is_user_unchanged() {
    local user="$1"
    [[ " ${UNCHANGED_USERS[@]} " =~ " ${user} " ]]
}

# function to check if a group is unchanged
is_group_unchanged() {
    local group="$1"
    [[ " ${UNCHANGED_GROUPS[@]} " =~ " ${group} " ]]
}

# function to process a single file
process_file() {
    local filepath="$1"

    # gather username, UID, group name, and GID of the file/folder
    FILE_UID=$(stat -c "%u" "$filepath")
    FILE_GID=$(stat -c "%g" "$filepath")
    FILE_USER=$(stat -c "%U" "$filepath")
    FILE_GROUP=$(stat -c "%G" "$filepath")

    # skip files owned by unchanged users and groups
    if is_user_unchanged "$FILE_USER" && is_group_unchanged "$FILE_GROUP"; then
        return
    fi

    # check if the user exists in /lib/passwd
    if grep -q "^${FILE_USER}:" /lib/passwd; then
        EXPECTED_UID=$(getent passwd "$FILE_USER" | cut -d: -f3)
        USER_EXISTS=true
    fi

    # check if the group exists in /lib/group
    if grep -q "^${FILE_GROUP}:" /lib/group; then
        EXPECTED_GID=$(getent group "$FILE_GROUP" | cut -d: -f3)
        GROUP_EXISTS=true
    fi

    # compare UID
   if $USER_EXISTS then
        if [[ "$FILE_UID" != "$EXPECTED_UID" ]]; then
            echo "Fixing UID for $filepath: $FILE_UID -> $EXPECTED_UID" >> "$LOGFILE"
            chown "$EXPECTED_UID" "$filepath"
        else
        # mark user as unchanged
        UNCHANGED_USERS+=("$FILE_USER")
        fi
    fi

     # compare GID
   if $GROUP_EXISTS then
        if [[ "$FILE_GID" != "$EXPECTED_GID" ]]; then
            echo "Fixing GID for $filepath: $FILE_GID -> $EXPECTED_GID" >> "$LOGFILE"
            chgrp "$EXPECTED_GID" "$filepath"
        else
        # mark group as unchanged
        UNCHANGED_GROUPS+=("$FILE_GROUP")
        fi
    fi

}

export -f process_file
export LOGFILE
export UNCHANGED_USERS
export UNCHANGED_GROUPS

# Parallelized processing with find and xargs
find / -path /sysroot -prune -o -print 2>/dev/null | xargs -P "$(nproc)" -I {} bash -c 'process_file "$@"' _ {}
echo "ownership chnage process completed on $(date)" >> "$LOGFILE"