#!/bin/bash
# pxe-netplan-apply.sh - install the two-NIC netplan config without ever
# leaving the box unreachable on the corporate NIC.
#
# Usage: pxe-netplan-apply.sh STAGED_YAML PXE_NAME PXE_MAC CORP_NAME CORP_MAC
#
# Called by pxe_server_setup.yml. Steps:
#   1. validate STAGED_YAML in a scratch root (netplan generate --root-dir);
#      nothing on the box changes if it is invalid
#   2. stop here (prints UNCHANGED) if it is already installed, no other
#      file configures wired NICs, and both NICs carry their stable names
#   3. back up /etc/netplan to /var/backups/netplan-<timestamp>/
#   4. install it (other wired configs moved aside), netplan generate
#      (restore on failure)
#   5. rename the NICs to their stable names (the .link files netplan
#      writes do it on every later boot), netplan apply (restore on failure)
#   6. check the imaging address and the corp NIC (warning only: the corp
#      cable may simply be unplugged)
# Prints CHANGED or UNCHANGED as the last line. Exit 1 = nothing applied
# (the previous config is back in place).

set -u

if [ $# -ne 5 ]; then
    echo "usage: $0 STAGED_YAML PXE_NAME PXE_MAC CORP_NAME CORP_MAC" >&2
    exit 2
fi
STAGED=$1
PXE_NAME=$2
PXE_MAC=${3,,}
CORP_NAME=$4
CORP_MAC=${5,,}
NETPLAN_DIR=${NETPLAN_DIR:-/etc/netplan}
TARGET=$NETPLAN_DIR/50-cloud-init.yaml

log() { echo "pxe-netplan-apply: $*"; }

# Name of the physical NIC that has MAC $1 (empty if none).
iface_of() {
    local d
    for d in /sys/class/net/*; do
        [ -e "$d/device" ] || continue
        if [ "$(cat "$d/address" 2>/dev/null)" = "$1" ]; then
            basename "$d"
            return 0
        fi
    done
    return 0
}

names_ok() {
    [ "$(iface_of "$PXE_MAC")" = "$PXE_NAME" ] &&
        [ "$(iface_of "$CORP_MAC")" = "$CORP_NAME" ]
}

# Other netplan files that configure wired NICs (installer leftovers, an
# en* DHCP match): they would put a second config on the two NICs. Files
# without "ethernets" (WiFi, NetworkManager wifi profiles) are left alone.
other_files() {
    find "$NETPLAN_DIR" -maxdepth 1 -type f \( -name '*.yaml' -o -name '*.yml' \) \
        ! -path "$TARGET" -exec grep -l 'ethernets' {} + 2>/dev/null | sort
}

# 1. validate in a scratch root
SCRATCH=$(mktemp -d)
trap 'rm -rf "$SCRATCH"' EXIT
mkdir -p "$SCRATCH/etc/netplan"
install -m 600 "$STAGED" "$SCRATCH/etc/netplan/50-cloud-init.yaml"
if ! netplan generate --root-dir "$SCRATCH"; then
    log "ERROR: $STAGED does not validate; nothing changed"
    exit 1
fi

# 2. already in place?
if cmp -s "$STAGED" "$TARGET" && [ -z "$(other_files)" ] && names_ok; then
    log "netplan already in place, $PXE_NAME and $CORP_NAME present"
    echo UNCHANGED
    exit 0
fi

# 3. back up
BACKUP=/var/backups/netplan-$(date +%Y%m%d-%H%M%S)
mkdir -p "$BACKUP"
cp -a "$NETPLAN_DIR/." "$BACKUP/"
log "previous config saved in $BACKUP"

restore() {
    log "restoring the previous config from $BACKUP"
    find "$NETPLAN_DIR" -maxdepth 1 -type f \( -name '*.yaml' -o -name '*.yml' \) -delete
    cp -a "$BACKUP/." "$NETPLAN_DIR/"
    netplan generate && netplan apply
}

# 4. install, moving aside the other wired configs (an en* DHCP match would
#    put a DHCP client on the imaging NIC too)
other_files | while IFS= read -r f; do
    log "moving aside $f (copy in $BACKUP)"
    rm -f "$f"
done
install -m 600 "$STAGED" "$TARGET"
if ! netplan generate; then
    log "ERROR: netplan generate failed"
    restore
    exit 1
fi

# 5. stable names now, so dnsmasq/UFW/Samba (which use them) work before
#    the next reboot. Does not depend on the netplan version renaming.
rename() {
    local mac=$1 want=$2 cur
    cur=$(iface_of "$mac")
    if [ -z "$cur" ]; then
        log "WARNING: no NIC with MAC $mac"
        return 0
    fi
    [ "$cur" = "$want" ] && return 0
    log "renaming $cur ($mac) to $want"
    if ! { ip link set dev "$cur" down &&
           ip link set dev "$cur" name "$want" &&
           ip link set dev "$want" up; }; then
        log "WARNING: rename $cur -> $want failed; it applies at the next reboot"
        ip link set dev "$cur" up 2>/dev/null
    fi
    return 0
}
rename "$PXE_MAC" "$PXE_NAME"
rename "$CORP_MAC" "$CORP_NAME"

if ! netplan apply; then
    log "ERROR: netplan apply failed"
    restore
    exit 1
fi

# 6. check
for _ in $(seq 1 20); do
    ip -4 -br addr show dev "$PXE_NAME" 2>/dev/null | grep -q ' [0-9]' && break
    sleep 1
done
ip -br addr show dev "$PXE_NAME" 2>/dev/null ||
    log "WARNING: $PXE_NAME not present yet (reboot to apply the .link names)"
for _ in $(seq 1 30); do
    ip -4 -br addr show dev "$CORP_NAME" 2>/dev/null | grep -q ' [0-9]' && break
    sleep 1
done
ip -4 -br addr show dev "$CORP_NAME" 2>/dev/null | grep -q ' [0-9]' ||
    log "WARNING: $CORP_NAME has no IPv4 address yet (corp cable unplugged or DHCP slow)"
echo CHANGED
exit 0