#!/bin/sh

PATH=/sbin:/bin:/usr/sbin:/usr/bin

TARGET_ETH0_NODE="ethernet@fe010000"
TARGET_ETH1_NODE="ethernet@fe2a0000"
TEMP_NAME="tera-swap0"

log_message() {
    echo "tera-ethernet-map: $*"
}

node_for_interface() {
    node_path=$(readlink -f "/sys/class/net/$1/device/of_node" 2>/dev/null) || return 1
    echo "${node_path##*/}"
}

wait_for_interfaces() {
    attempt=0
    while [ "$attempt" -lt 5 ]; do
        if [ -e /sys/class/net/eth0 ] && [ -e /sys/class/net/eth1 ]; then
            return 0
        fi
        attempt=$((attempt + 1))
        sleep 1
    done
    return 1
}

start_mapping() {
    if ! wait_for_interfaces; then
        log_message "eth0/eth1 did not appear"
        return 1
    fi

    eth0_node=$(node_for_interface eth0) || {
        log_message "cannot resolve eth0 device-tree node"
        return 1
    }
    eth1_node=$(node_for_interface eth1) || {
        log_message "cannot resolve eth1 device-tree node"
        return 1
    }

    if [ "$eth0_node" = "$TARGET_ETH0_NODE" ] && \
       [ "$eth1_node" = "$TARGET_ETH1_NODE" ]; then
        log_message "target mapping is already active"
        return 0
    fi

    if [ "$eth0_node" != "$TARGET_ETH1_NODE" ] || \
       [ "$eth1_node" != "$TARGET_ETH0_NODE" ]; then
        log_message "unexpected mapping: eth0=$eth0_node eth1=$eth1_node"
        return 1
    fi

    if ip link show dev "$TEMP_NAME" >/dev/null 2>&1; then
        log_message "temporary interface $TEMP_NAME already exists"
        return 1
    fi

    ip link set dev eth0 down || return 1
    ip link set dev eth1 down || return 1
    ip link set dev eth0 name "$TEMP_NAME" || return 1

    if ! ip link set dev eth1 name eth0; then
        ip link set dev "$TEMP_NAME" name eth0 >/dev/null 2>&1
        log_message "failed to rename original eth1 to eth0; rolled back"
        return 1
    fi

    if ! ip link set dev "$TEMP_NAME" name eth1; then
        ip link set dev eth0 name eth1 >/dev/null 2>&1
        ip link set dev "$TEMP_NAME" name eth0 >/dev/null 2>&1
        log_message "failed to finish interface swap; rolled back"
        return 1
    fi

    eth0_node=$(node_for_interface eth0)
    eth1_node=$(node_for_interface eth1)
    if [ "$eth0_node" != "$TARGET_ETH0_NODE" ] || \
       [ "$eth1_node" != "$TARGET_ETH1_NODE" ]; then
        log_message "post-swap verification failed: eth0=$eth0_node eth1=$eth1_node"
        return 1
    fi

    log_message "mapping applied: eth0=$eth0_node eth1=$eth1_node"
    return 0
}

case "${1:-start}" in
    start|restart)
        start_mapping
        ;;
    stop)
        ;;
    status)
        eth0_node=$(node_for_interface eth0 2>/dev/null || echo missing)
        eth1_node=$(node_for_interface eth1 2>/dev/null || echo missing)
        echo "eth0=$eth0_node"
        echo "eth1=$eth1_node"
        if [ "$eth0_node" = "$TARGET_ETH0_NODE" ] && \
           [ "$eth1_node" = "$TARGET_ETH1_NODE" ]; then
            exit 0
        fi
        exit 1
        ;;
    *)
        echo "Usage: $0 {start|stop|restart|status}" >&2
        exit 2
        ;;
esac