#!/usr/bin/env bash
#
# Copyright (c) 2024 YunoHost Contributors
#
# This file is part of YunoHost (see https://yunohost.org)
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License as
# published by the Free Software Foundation, either version 3 of the
# License, or (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU Affero General Public License for more details.
#
# You should have received a copy of the GNU Affero General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
#

# Exit hook on subcommand error or unset variable
set -e

# Source YNH helpers
# shellcheck source=../../helpers/helpers
source /usr/share/yunohost/helpers

do_init_regen() {

    cd /usr/share/yunohost/conf/dnsmasq

    if jq -re '.dns_custom_resolvers_enabled' <<< "$YNH_SETTINGS"; then
        read -ra nameservers <<< "$(jq -r '.dns_custom_resolvers_list' <<< "$YNH_SETTINGS")"
        for nameserver in "${nameservers[@]}"; do
            echo "nameserver $nameserver" >> /etc/resolv.dnsmasq.conf
        done
    else
        # Use a seed derived from the machine id and current month
        # This way, the shuffle is random but should be stable accross the same month
        # and make sure the regenconf is idempotent (at least during the same month)
        # i.e. that it doesn't re-shuffle the file everytime we run the regenconf
        SEED=$( (
            cat /etc/machine-id || true
            date +%m%Y
        ) | md5sum)
        cat plain/resolv.dnsmasq.conf | grep "^nameserver" | shuf --random-source=<(echo "$SEED") > /etc/resolv.dnsmasq.conf
    fi
    chown root /etc/resolv.dnsmasq.conf
    chmod 644 /etc/resolv.dnsmasq.conf

    cp plain/etcdefault /etc/default/dnsmasq

    export wireless_interfaces=""
    ynh_render_template "dnsmasq.conf.tpl" "${pending_dir}/etc/dnsmasq.conf"

    # Remove / disable services likely to conflict with dnsmasq
    for SERVICE in systemd-resolved bind9; do
        systemctl is-enabled $SERVICE &> /dev/null && systemctl disable $SERVICE 2> /dev/null
        systemctl is-active $SERVICE &> /dev/null && systemctl stop $SERVICE
    done

    systemctl restart dnsmasq
}

do_pre_regen() {
    pending_dir=$1

    cd /usr/share/yunohost/conf/dnsmasq

    # create directory for pending conf
    dnsmasq_dir="${pending_dir}/etc/dnsmasq.d"
    mkdir -p "$dnsmasq_dir"
    etcdefault_dir="${pending_dir}/etc/default"
    mkdir -p "$etcdefault_dir"

    # add default conf files
    cp plain/etcdefault "${pending_dir}/etc/default/dnsmasq"

    # add resolver pool
    if jq -re '.dns_custom_resolvers_enabled' <<< "$YNH_SETTINGS"; then
        read -ra nameservers <<< "$(jq -r '.dns_custom_resolvers_list' <<< "$YNH_SETTINGS" | sed 's/,/ /g')"
        for nameserver in "${nameservers[@]}"; do
            echo "nameserver $nameserver" >> "${pending_dir}/etc/resolv.dnsmasq.conf"
        done
    else
        # Use a seed derived from the machine id and current month
        # This way, the shuffle is random but should be stable accross the same month
        # and make sure the regenconf is idempotent (at least during the same month)
        # i.e. that it doesn't re-shuffle the file everytime we run the regenconf
        SEED=$( (
            cat /etc/machine-id || true
            date +%m%Y
        ) | md5sum)
        cat plain/resolv.dnsmasq.conf | grep "^nameserver" | shuf --random-source=<(echo "$SEED") > "${pending_dir}/etc/resolv.dnsmasq.conf"
    fi

    # retrieve variables
    ipv4=$(curl --max-time 10 -s -4 https://ipv4.yunohost.org 2> /dev/null || true)
    ynh_validate_ip4 "$ipv4" || ipv4='127.0.0.1'
    ipv6=$(curl --max-time 10 -s -6 https://ipv6.yunohost.org 2> /dev/null || true)
    ynh_validate_ip6 "$ipv6" || ipv6=''
    interfaces="$(ip -j addr show | jq -r '[.[].ifname]|join(" ")')"
    wireless_interfaces="lo"
    for dev in /sys/class/net/*; do
        if [ -d "$dev/wireless" ] && grep -q "up" "$dev/operstate"; then
            wireless_interfaces+=" $(basename "$dev")"
        fi
    done

    # General configuration
    export wireless_interfaces
    ynh_render_template "dnsmasq.conf.tpl" "${pending_dir}/etc/dnsmasq.conf"

    # add domain conf files
    export interfaces
    export ipv4
    export ipv6
    for domain in $YNH_DOMAINS; do
        [[ ! $domain =~ \.local$ ]] || continue
        export domain

        if tr ' ' '\n' <<< "$YNH_DOMAINS_WITH_MAIL_IN" | grep -q "^$domain$"; then
            export mail_in="True"
        else
            export mail_in="False"
        fi
        ynh_render_template "domain.tpl" "${dnsmasq_dir}/${domain}"
    done

    # We arbitrarily pick 'c' for spamhaus NS but there's a/b/c/e
    SPAMHAUS_NS=c.gns.spamhaus.org
    # We need to perform a dig request ... but dnsmasq may not be up yet, and we'll get an empty result
    # It's not too dramatic because next time the regenconf is ran, dnsmasq should be up
    # Nevertheless it's good to try to make sure that this doesn't happen to avoid weird stuff where
    # the regenconf is not idempotent ...
    # So if dnsmasq is not up, try to pick the first IPv4 resolver from the shuffled list
    if systemctl --quiet is-active dnsmasq; then
        RESOLVER_FOR_DIG="127.0.0.1"
    else
        RESOLVER_FOR_DIG=$(grep '^nameserver.*\.' /etc/resolv.dnsmasq.conf | head -n1 | awk '{print $2}')
    fi

    cat << EOF > "${dnsmasq_dir}/spamhaus"
# Gotta force the usage of resolvers for spamhaus,
# Which will otherwise complain that we may be using an open resolver...
# cf https://www.spamhaus.com/resource-center/successfully-accessing-spamhauss-free-block-lists-using-a-public-dns/#yes-but-why-block-queries-from-public-recursive-name-servers
# We pick one of spamhaus' a/b/c/d/e nameservers, cf https://multirbl.valli.org/detail/zen.spamhaus.org.html
# And kind of hard-code the corresponding IPs because in practice dnsmasq doesn't allow to have a domain name for the resolver part of server= :| ...
# Fun-fact : did you know that AAAA is the name of IPv6 DNS records, but also the sound you make when debugging network and DNS??? #TheMoreYouKnow
EOF
    for IP in $( (
        dig +short A $SPAMHAUS_NS "@$RESOLVER_FOR_DIG" 2> /dev/null || true
        dig +short AAAA $SPAMHAUS_NS "@$RESOLVER_FOR_DIG" 2> /dev/null || true
    ) | grep -v '^;' | sort); do
        echo "server=/*.zen.spamhaus.org/$IP" >> "${dnsmasq_dir}/spamhaus"
    done

    # remove old domain conf files
    for conf_file in /etc/dnsmasq.d/*.*; do
        domain=$(basename "$conf_file")
        if [[ ! $YNH_DOMAINS =~ $domain ]] && [[ ! $domain =~ \.local$ ]] && [[ $domain != spamhaus ]]; then
            touch "${dnsmasq_dir}/${domain}"
        fi
    done
}

do_post_regen() {
    regen_conf_files=$1

    # Force permission (to cover some edge cases where root's umask is like 027 and then dnsmasq cant read this file)
    chown root /etc/resolv.dnsmasq.conf
    chmod 644 /etc/resolv.dnsmasq.conf

    # Fuck it, those domain/search entries from dhclient are usually annoying
    # lying shit from the ISP trying to MiTM
    if grep -q -E "^ *(domain|search)" /run/resolvconf/resolv.conf; then
        if grep -q -E "^ *(domain|search)" /run/resolvconf/interface/*.dhclient 2> /dev/null; then
            sed -E "s/^(domain|search)/#\1/g" -i /run/resolvconf/interface/*.dhclient
        fi

        grep -q '^supersede domain-name "";' /etc/dhcp/dhclient.conf 2> /dev/null || echo 'supersede domain-name "";' >> /etc/dhcp/dhclient.conf
        grep -q '^supersede domain-search "";' /etc/dhcp/dhclient.conf 2> /dev/null || echo 'supersede domain-search "";' >> /etc/dhcp/dhclient.conf
        grep -q '^supersede search "";' /etc/dhcp/dhclient.conf 2> /dev/null || echo 'supersede search "";' >> /etc/dhcp/dhclient.conf
        systemctl restart resolvconf
    fi

    # Some stupid things like rabbitmq-server used by onlyoffice won't work if
    # the *short* hostname doesn't exists in /etc/hosts -_-
    short_hostname=$(hostname -s)
    grep -q "127.0.0.1.*$short_hostname" /etc/hosts || echo -e "\n127.0.0.1\t$short_hostname" >> /etc/hosts

    [[ -n "$regen_conf_files" ]] || return 0

    # Remove / disable services likely to conflict with dnsmasq
    for SERVICE in systemd-resolved bind9; do
        systemctl is-enabled $SERVICE &> /dev/null && systemctl disable $SERVICE 2> /dev/null
        systemctl is-active $SERVICE &> /dev/null && systemctl stop $SERVICE
    done

    systemctl restart dnsmasq
}

"do_$1_regen" "$(echo "${*:2}" | xargs)"