function make_ca() {
    local CA_DAYS=3650 # Default validity period for CA certificates

    # CA defaults to the main CA if not specified, but can be overridden with --issuing-ca
    local CA_FILE_PREFIX="ca"
    local PATHLEN=0

    while [[ $# -gt 0 ]]; do
        case "$1" in
            --days)
                if [[ -z "$2" || ! "$2" =~ ^[0-9]+$ ]]; then
                    echo "ERROR: Invalid value for --days. Must be a positive integer." >&2
                    return 1
                fi
                CA_DAYS="$2"
                shift 2
                ;;
            --issuing-ca)
                if [[ -z "$2" ]]; then
                    echo "ERROR: Missing value for --issuing-ca." >&2
                    return 1
                fi
                if [[ "$2" == "ca" ]]; then
                    echo "ERROR: --issuing-ca cannot be 'ca' as it is reserved for the root CA." >&2
                    return 1
                fi
                CA_FILE_PREFIX="$2"
                shift 2
                ;;
            --path-len)
                if [[ -z "$2" || ! "$2" =~ ^[0-9]+$ ]]; then
                    echo "ERROR: Invalid value for --path-len. Must be a non-negative integer." >&2
                    return 1
                fi
                PATHLEN="$2"
                shift 2
                ;;
            *)
                break
                ;;
        esac
    done

    # Use the provided directory argument
    local CA_DIR="$1"
    local CA_NAME="$2"
    shift 2

    if [[ -z "$CA_DIR" || -z "$CA_NAME" || ! -d "$CA_DIR" ]]; then
        echo "ERROR: Certificate directory $CA_DIR does not exist."
        return 1
    fi

    local ROOT_CA_CERT="ca_cert.pem"
    local ROOT_CA_KEY="ca_key.pem"
    local CA_CERT="${CA_FILE_PREFIX}_cert.pem"
    local CA_KEY="${CA_FILE_PREFIX}_key.pem"

    # Generate CA certificate and key if they don't exist
    if [[ ! -f "$CA_DIR/$ROOT_CA_CERT" || ! -f "$CA_DIR/$ROOT_CA_KEY" ]]; then
        # Check, if the user requested a non-root CA without an existing root CA, which is not possible.
        if [[ "$ROOT_CA_CERT" != "$CA_CERT" ]]; then
            echo "ERROR: Cannot create issuing CA '$CA_NAME' without existing root CA certificate and key. Please create the root CA first." >&2
            return 1
        fi
        echo "Generating CA certificate '$CA_NAME' and key..."
        if ! openssl req \
            -quiet \
            -x509 \
            -newkey rsa:4096 \
            -keyout "$CA_DIR/$ROOT_CA_KEY" \
            -out "$CA_DIR/$ROOT_CA_CERT" \
            -days "$CA_DAYS" \
            -noenc \
            -subj "/CN=${CA_NAME}" \
            -text \
            -addext "basicConstraints=critical,CA:TRUE,pathlen:${PATHLEN}"; then
            echo "ERROR: Failed to generate CA certificate and key." >&2
            return 1
        fi

        return 0
    fi

    if [[ ! -f "$CA_DIR/$CA_CERT" || ! -f "$CA_DIR/$CA_KEY" ]]; then
        echo "Generating issuing CA certificate '$CA_NAME' and key..."
        if ! openssl req \
            -quiet \
            -newkey rsa:4096 \
            -keyout "$CA_DIR/${CA_KEY}" \
            -noenc \
            -subj "/CN=${CA_NAME}" \
            -addext "basicConstraints=critical,CA:TRUE,pathlen:0" \
        | openssl x509 \
            -req \
            -CA "$CA_DIR/$ROOT_CA_CERT" \
            -CAkey "$CA_DIR/$ROOT_CA_KEY" \
            -copy_extensions copyall \
            -days "$CA_DAYS" \
            -text \
            -out "$CA_DIR/${CA_CERT}"; then
            echo "ERROR: Failed to generate issuing CA certificate and key." >&2
            return 1
        fi
    fi

    return 0
}

function _is_ip() {
    if [[ "$1" =~ ^[0-9]{1,3}(\.[0-9]{1,3}){3}$ ]]; then
        return 0
    else
        return 1
    fi
}

function _is_dns() {
    if [[ "$1" =~ ^[a-z0-9-]+(\.[a-z0-9-]+)*$ ]]; then
        return 0
    else
        return 1
    fi
}

function make_server_cert() {
    local CA_FILE_PREFIX="ca" # Default to CA if no issuing CA is used
    local CERT_DAYS=365 # Default validity period for leaf certificates

    while [[ $# -gt 0 ]]; do
        case "$1" in
            --issuing-ca)
                if [[ -z "$2" ]]; then
                    echo "ERROR: Missing value for --issuing-ca." >&2
                    return 1
                fi
                if [[ "$2" == "ca" ]]; then
                    echo "ERROR: --issuing-ca cannot be 'ca' as it is reserved for the root CA." >&2
                    return 1
                fi
                CA_FILE_PREFIX="$2"
                shift 2
                ;;
            --days)
                if [[ -z "$2" || ! "$2" =~ ^[0-9]+$ ]]; then
                    echo "ERROR: Invalid value for --days. Must be a positive integer." >&2
                    return 1
                fi
                CERT_DAYS="$2"
                shift 2
                ;;
            *) break ;;
        esac
    done

    local CERT_DIR="$1"
    local CERT_SUBJECT_NAME="$2"
    shift 2

    local CA_CERT="${CA_FILE_PREFIX}_cert.pem"
    local CA_KEY="${CA_FILE_PREFIX}_key.pem"

    if [[ -z "$CERT_DIR" || ! -d "$CERT_DIR" ]]; then
        echo "ERROR: Certificate directory $CERT_DIR does not exist."
        return 1
    fi

    if [[ -z "$CERT_SUBJECT_NAME" ]]; then
        echo "ERROR: Subject name is required." >&2
        return 1
    fi

    if ! _is_dns "$CERT_SUBJECT_NAME"; then
        echo "ERROR: Invalid subject name '$CERT_SUBJECT_NAME'. Must be a valid DNS name." >&2
        return 1
    fi

    if [[ ! -f "$CERT_DIR/$CA_CERT" || ! -f "$CERT_DIR/$CA_KEY" ]]; then
        echo "ERROR: Signing CA certificate and key not found in $CERT_DIR. Please call setup a signing CA first." >&2
        return 1
    fi

    # Calculate the "account" name from the subject name, the hostname part before the first dot
    local CERT_NAME="${CERT_SUBJECT_NAME%%.*}"

    # Start with the subjectAltName extension containing the main DNS name
    local SANS=("DNS:${CERT_SUBJECT_NAME}")

    # Combine the remaining arguments into a single string for the subjectAltName extension
    while [[ $# -gt 0 ]]; do
        if _is_ip "$1"; then
            SANS+=("IP:$1")
        elif _is_dns "$1"; then
            SANS+=("DNS:$1")
        else
            echo "ERROR: Invalid SAN entry '$1'" >&2
            return 1
        fi
        shift
    done

    # Join the SAN entries with commas for the OpenSSL command
    local SANS_EXT="subjectAltName=$(IFS=,; echo "${SANS[*]}")"

    echo "Generating server certificate for '$CERT_SUBJECT_NAME' with SANs:"
    for san in "${SANS[@]}"; do
        echo "  - $san"
    done

    # Generate server certificate and key if they don't exist
    if [[ ! -f "$CERT_DIR/${CERT_NAME}_cert.pem" || ! -f "$CERT_DIR/${CERT_NAME}_key.pem" ]]; then
        echo "Generating server certificate and key..."
        if ! openssl req \
            -quiet \
            -newkey rsa:4096 \
            -keyout "$CERT_DIR/${CERT_NAME}_key.pem" \
            -noenc \
            -subj "/CN=${CERT_SUBJECT_NAME}" \
            -addext "basicConstraints=critical,CA:FALSE" \
            -addext "keyUsage=digitalSignature,keyEncipherment" \
            -addext "extendedKeyUsage=serverAuth,clientAuth" \
            -addext "$SANS_EXT" \
        | openssl x509 \
            -req \
            -CA "$CERT_DIR/$CA_CERT" \
            -CAkey "$CERT_DIR/$CA_KEY" \
            -copy_extensions copyall \
            -days $CERT_DAYS \
            -text \
            -out "$CERT_DIR/${CERT_NAME}_cert.pem"; then
            echo "ERROR: Failed to generate server certificate and key." >&2
            return 1
        fi
    fi

    return 0
}

function make_pfx() {
    local CERT_DIR="$1"
    local CERT_NAME="$2"
    local PFX_PASSWORD="${3:-}"

    if [[ -z "$CERT_DIR" || ! -d "$CERT_DIR" ]]; then
        echo "ERROR: Certificate directory $CERT_DIR does not exist."
        return 1
    fi

    if [[ -z "$CERT_NAME" ]]; then
        echo "ERROR: Certificate name is required." >&2
        return 1
    fi

    if [[ ! -f "$CERT_DIR/${CERT_NAME}_cert.pem" || ! -f "$CERT_DIR/${CERT_NAME}_key.pem" ]]; then
        echo "ERROR: Server certificate and key not found in $CERT_DIR. Please call make_server_cert first." >&2
        return 1
    fi

    if [[ ! -f "$CERT_DIR/ca_cert.pem" || ! -f "$CERT_DIR/ca_key.pem" ]]; then
        echo "ERROR: CA certificate and key not found in $CERT_DIR. Please call make_ca first." >&2
        return 1
    fi

    if [[ -z "$PFX_PASSWORD" ]]; then
        PFX_PASSWORD="changeit"
    fi

    if [[ ! -f "$CERT_DIR/${CERT_NAME}.pfx" ]]; then
        echo -n "Generating PKCS#12 (PFX) file..."
        if ! openssl pkcs12 \
            -export -out "$CERT_DIR/${CERT_NAME}.pfx" \
            -inkey "$CERT_DIR/${CERT_NAME}_key.pem" \
            -in "$CERT_DIR/${CERT_NAME}_cert.pem" \
            -certfile "$CERT_DIR/ca_cert.pem" \
            -password pass:"$PFX_PASSWORD"; then
            echo "ERROR: Failed to generate PKCS#12 (PFX) file." >&2
            return 1
        fi
        echo "done."
    else
        echo "PKCS#12 (PFX) file already exists, aborting generation."
        return 1
    fi

    return 0
}