#!/bin/bash

# Domain reconciliation for a restore.
#
# A backup carries the domains the OLD machine served. After adoption they are
# this machine's domains — but DNS still points at a server that may not exist
# any more. Nothing in the restore path checked this, so the first sign of
# trouble was Traefik failing to get a certificate long after the installer had
# said it was finished.
#
# This is a report, never a refusal. A domain that does not resolve here is a
# perfectly normal state five minutes into a rebuild: the user is about to go
# and repoint it. What is not acceptable is not being told.
#
# Emits one record per domain on stdout:
#
#     <verdict>\t<domain>\t<domain_ip>\t<detail>
#
# verdict is ok | elsewhere | unresolved.

# Every CFG_DOMAIN_N actually set, in slot order.
restoreDomainList()
{
    local f="${configs_dir%/}/network/network_domains"
    [[ -r "$f" ]] || return 0
    local line v
    while IFS= read -r line; do
        [[ "$line" =~ ^CFG_DOMAIN_[0-9]+= ]] || continue
        v="${line#*=}"
        # The config files carry a trailing comment column; strip it and the
        # whitespace that pads it, or every domain arrives with an essay
        # attached and no DNS lookup ever matches.
        v="${v%%#*}"
        v="${v#"${v%%[![:space:]]*}"}"
        v="${v%"${v##*[![:space:]]}"}"
        # updateConfigOption writes an empty value as a literal "" — without
        # stripping the quotes every cleared slot reads back as a two-character
        # domain, and a config with nine empty slots reports nine failures.
        v="${v%\"}"; v="${v#\"}"
        v="${v%\'}"; v="${v#\'}"
        v="${v#"${v%%[![:space:]]*}"}"
        v="${v%"${v##*[![:space:]]}"}"
        [[ -n "$v" ]] && printf '%s\n' "$v"
    done < "$f"
}

# This server's public address, or empty when it cannot be established.
#
# Kept apart from the LAN address on purpose. setupCheckDomainPointsHere falls
# back to `hostname -I` when the public lookup fails, which is fine for its own
# purposes but wrong here: comparing a public A record against a private
# 10.x address makes every correctly-pointed domain look misconfigured, and
# LibrePortal is explicitly a LAN/VPN-first product where that lookup failing
# is ordinary rather than exceptional.
restoreServerPublicIp()
{
    local ip
    ip=$(dig +short +time=3 +tries=1 myip.opendns.com @resolver1.opendns.com 2>/dev/null | head -1)
    [[ "$ip" =~ ^[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+$ ]] || return 1
    printf '%s' "$ip"
}

_restoreIsPrivateIp()
{
    case "${1:-}" in
        10.*|127.*|192.168.*|169.254.*) return 0 ;;
        172.1[6-9].*|172.2[0-9].*|172.3[01].*) return 0 ;;
        *) return 1 ;;
    esac
}

# Check one domain against a known server address.
#
# The server address is passed in rather than resolved here: it is the same for
# every domain, and looking it up per domain meant a network round trip each
# time for an answer that could not have changed.
restoreDomainCheck()
{
    local domain="$1" server_ip="$2"
    local ip
    ip=$(dig +short +time=3 +tries=1 "$domain" A 2>/dev/null | grep -E '^[0-9.]+$' | head -1)

    if [[ -z "$ip" ]]; then
        # A literal '-' rather than an empty field: tab is IFS whitespace, so
        # `IFS=$'\t' read` collapses two adjacent tabs into one and every
        # column after the gap shifts left — which silently emptied the detail.
        printf 'unresolved\t%s\t-\t%s\n' "$domain" "no DNS record found"
    elif [[ -z "$server_ip" ]]; then
        printf 'unknown\t%s\t%s\t%s\n' "$domain" "$ip" "resolves to $ip — could not check this server's public address"
    elif [[ "$ip" == "$server_ip" ]]; then
        printf 'ok\t%s\t%s\t%s\n' "$domain" "$ip" "points at this server"
    else
        printf 'elsewhere\t%s\t%s\t%s\n' "$domain" "$ip" "points at $ip, not this server"
    fi
}

# Report on every restored domain. Leaves the ones that resolve here in
# RESTORE_DOMAINS_OK and the rest in RESTORE_DOMAINS_ELSEWHERE, so a caller can
# offer to leave the strays out of the Traefik config rather than shipping a
# router for a name that cannot reach this box.
restoreDomainReport()
{
    RESTORE_DOMAINS_OK=()
    RESTORE_DOMAINS_ELSEWHERE=()
    RESTORE_DOMAINS_UNKNOWN=()

    local -a domains=()
    local d
    while IFS= read -r d; do [[ -n "$d" ]] && domains+=("$d"); done < <(restoreDomainList)

    if (( ${#domains[@]} == 0 )); then
        isNotice "No domains in the restored config — nothing to check."
        return 0
    fi

    # Resolved once rather than per domain: it cannot change between them.
    local server_ip=""
    server_ip=$(restoreServerPublicIp) || server_ip=""

    local lan_ip; lan_ip=$(hostname -I 2>/dev/null | awk '{print $1}')
    if [[ -n "$server_ip" ]]; then
        isNotice "Checking ${#domains[@]} restored domain(s) against this server ($server_ip)…"
    else
        isNotice "Checking ${#domains[@]} restored domain(s)…"
    fi
    echo ""

    local rec verdict domain ip detail
    for domain in "${domains[@]}"; do
        rec=$(restoreDomainCheck "$domain" "$server_ip")
        IFS=$'\t' read -r verdict domain ip detail <<< "$rec"
        case "$verdict" in
            ok)
                printf '    \033[0;32m✓\033[0m %-28s %s\n' "$domain" "$detail"
                RESTORE_DOMAINS_OK+=("$domain") ;;
            elsewhere)
                printf '    \033[0;33m!\033[0m %-28s %s\n' "$domain" "$detail"
                RESTORE_DOMAINS_ELSEWHERE+=("$domain") ;;
            unknown)
                # Unverifiable is not the same as wrong, and offering to delete
                # a domain on the strength of a failed lookup would be.
                printf '    \033[0;33m?\033[0m %-28s %s\n' "$domain" "$detail"
                RESTORE_DOMAINS_UNKNOWN+=("$domain") ;;
            *)
                printf '    \033[0;33m?\033[0m %-28s %s\n' "$domain" "$detail"
                RESTORE_DOMAINS_ELSEWHERE+=("$domain") ;;
        esac
    done

    echo ""
    if (( ${#RESTORE_DOMAINS_UNKNOWN[@]} > 0 )); then
        isNotice "Could not work out this server's public address, so ${#RESTORE_DOMAINS_UNKNOWN[@]} domain(s) could not be checked."
        isNotice "That is expected on a LAN-only or VPN-only box${lan_ip:+ (this one answers on $lan_ip)}."
    fi
    if (( ${#RESTORE_DOMAINS_ELSEWHERE[@]} > 0 )); then
        isNotice "${#RESTORE_DOMAINS_ELSEWHERE[@]} of ${#domains[@]} do not point here yet."
        isNotice "That is normal mid-rebuild — update the DNS A records to this server and they will work."
        isNotice "Until then Traefik cannot get a certificate for them, so those sites stay unreachable."
    else
        isSuccessful "Every restored domain already points at this server."
    fi
    return 0
}

# Drop the domains that do not point here out of the live config, keeping their
# slot order for the ones that stay.
#
# Offered rather than done: a user who is about to repoint DNS wants them kept,
# and a user rebuilding onto a box that will never own those names wants them
# gone. Guessing either way is worse than asking.
restoreDomainsDropElsewhere()
{
    local f="${configs_dir%/}/network/network_domains"
    [[ -r "$f" ]] || return 1
    (( ${#RESTORE_DOMAINS_ELSEWHERE[@]} > 0 )) || return 0

    local d slot=1
    for d in "${RESTORE_DOMAINS_OK[@]}"; do
        updateConfigOption "CFG_DOMAIN_$slot" "$d" >/dev/null 2>&1
        slot=$((slot + 1))
    done
    while (( slot <= 9 )); do
        updateConfigOption "CFG_DOMAIN_$slot" "" >/dev/null 2>&1
        slot=$((slot + 1))
    done
    isSuccessful "Kept ${#RESTORE_DOMAINS_OK[@]} domain(s); removed ${#RESTORE_DOMAINS_ELSEWHERE[@]} that do not point here."
    isNotice "Add them back on the Domains page once DNS is updated."
    return 0
}