#!/bin/bash

add_udev_rule() {
    # Add an udev rules file to the initcpio image. Dependencies on binaries
    # will be discovered and added.
    #   $1: path to rules file (or name of rules file)

    local rules="$1" rule= key= value= binary=

    if [[ ${rules:0:1} != '/' ]]; then
        rules=$(PATH=/usr/lib/udev/rules.d:/lib/udev/rules.d type -P "$1")
    fi
    if [[ -z $rules ]]; then
        # complain about not found rules
        return 1
    fi

    add_file "$rules" /usr/lib/udev/rules.d/"${rules##*/}"

    while IFS=, read -ra rule; do
        # skip empty lines, comments
        [[ -z $rule || $rule = @(+([[:space:]])|#*) ]] && continue

        for pair in "${rule[@]}"; do
            IFS=' =' read -r key value <<< "$pair"
            case $key in
                RUN@({program}|+)|IMPORT{program}|ENV{REMOVE_CMD})
                    # strip quotes
                    binary=${value//[\"\']/}
                    # just take the first word as the binary name
                    binary=${binary%% *}
                    [[ ${binary:0:1} == '$' ]] && continue
                    if [[ ${binary:0:1} != '/' ]]; then
                        binary=$(PATH=/usr/lib/udev:/lib/udev type -P "$binary")
                    fi
                    add_binary "$binary"
                    ;;
            esac
        done
    done <"$rules"
}

add_systemd_unit() {
    # Add a systemd unit file to the initcpio image. Hard dependencies on binaries
    # and other unit files will be discovered and added.
    #   $1: path to rules file (or name of rules file)

    local unit= rule= entry= key= value= binary= dep=

    unit=$(PATH=/usr/lib/systemd/system:/lib/systemd/system:/usr/lib64/systemd/system:/lib64/systemd/system type -P "$1")
    if [[ -z $unit ]]; then
        # complain about not found unit file
        return 1
    fi

    add_file "$unit"

    while IFS='=' read -r key values; do
        read -ra values <<< "$values"

        case $key in
            Requires|OnFailure)
                # only add hard dependencies (not Wants)
                map add_systemd_unit "${values[@]}"
                ;;
            Exec*)
                # do not add binaries unless they are required,
                # strip special executable prefixes
                case ${values[0]} in
                    -*)  ;;
                    !!*) add_binary "${values[0]#!!}" ;;
                    *)   add_binary "${values[0]#[@!:+]}" ;;
                esac
                ;;
        esac

    done <"$unit"

    # preserve reverse soft dependency
    for dep in {/usr,}/lib/systemd/system/*.wants/${unit##*/}; do
        if [[ -L $dep ]]; then
            add_symlink "$dep"
        fi
    done

    # add hard dependencies
    if [[ -d $unit.requires ]]; then
        for dep in "$unit".requires/*; do
            add_systemd_unit ${dep##*/}
        done
    fi
}

add_systemd_drop_in() {
    local unit=$1 dropin_name=$2

    mkdir -p "$BUILDROOT/etc/systemd/system/$unit.d"
    cat >"$BUILDROOT/etc/systemd/system/$unit.d/$2.conf"
}

build() {
    local rules unit

    local libdir

    if [ -e /usr/lib64 ] ; then
        libdir="lib64"
    else
        libdir="lib"
    fi

    add_binary /usr/lib/initcpio/busybox /usr/bin/busybox
    add_symlink "/bin" /usr/bin

    for applet in $(/usr/lib/initcpio/busybox --list | grep -v busybox); do
        add_symlink "/usr/bin/$applet" /usr/bin/busybox
    done

    add_binary /usr/bin/sulogin
    add_binary /usr/lib/systemd/systemd /init
    add_file /etc/os-release
    add_file /etc/machine-id
    add_file /etc/machine-info

    map add_binary \
        /usr/bin/systemd-tmpfiles \
        /usr/lib/systemd/systemd-executor \
        /usr/lib/systemd/systemd-hibernate-resume \
        /usr/lib/systemd/systemd-shutdown \
        /usr/lib/systemd/systemd-sulogin-shell \
        /usr/lib/systemd/system-generators/systemd-fstab-generator \
        /usr/lib/systemd/system-generators/systemd-gpt-auto-generator \
        /usr/lib/systemd/system-generators/systemd-hibernate-resume-generator

    # udev rules and systemd units
    map add_udev_rule "$rules" \
            50-udev-default.rules \
            60-persistent-storage.rules \
            64-btrfs.rules \
            80-drivers.rules \
            99-systemd.rules

    map add_systemd_unit \
            initrd-cleanup.service \
            initrd-fs.target \
            initrd-parse-etc.service \
            initrd-root-fs.target \
            initrd-root-device.target \
            initrd-switch-root.service \
            initrd-switch-root.target \
            initrd.target \
            local-fs.target \
            local-fs-pre.target \
            paths.target \
            reboot.target \
            slices.target \
            sockets.target \
            systemd-fsck@.service \
            systemd-hibernate-resume@.service \
            systemd-modules-load.service \
            systemd-udev-trigger.service \
            systemd-udevd-control.socket \
            systemd-udevd-kernel.socket \
            systemd-udevd.service \
            timers.target \
            rescue.target \
            emergency.target

    add_symlink "/usr/lib/systemd/system/default.target" "initrd.target"
    add_symlink "/usr/lib/systemd/system/ctrl-alt-del.target" "reboot.target"

    add_binary "$(readlink -f /usr/$libdir/libnss_files.so.2)"
    add_binary "$(readlink -f /usr/$libdir/libnss_systemd.so.2)"
    printf '%s\n' >"$BUILDROOT/etc/nsswitch.conf" \
        'passwd: files systemd' \
        'group: files [SUCCESS=merge] systemd' \
        'shadow: files [UNAVAIL=return] systemd'

    echo "root:x:0:0:root:/root:/bin/sh" >"$BUILDROOT/etc/passwd"
    echo 'root::18684::::::' >"$BUILDROOT/etc/shadow"
    getent group root audio disk input kmem kvm lp optical render sgx storage tty uucp video | awk -F: ' { print $1 ":x:" $3 ":" }' >"$BUILDROOT/etc/group"

    for sysuserfile in $(ls /usr/lib/sysusers.d/) ; do
        add_file /usr/lib/sysusers.d/${sysuserfile}
    done

    add_dir "/etc/modules-load.d"
    (
      . "$_f_config"
      set -f
      printf '%s\n' ${MODULES[@]} >"$BUILDROOT/etc/modules-load.d/MODULES.conf"
    )

    add_dir /etc/systemd
    echo -e "[Manager]\\nDefaultStandardOutput=inherit" > $BUILDROOT/etc/systemd/system.conf
}

help() {
    cat <<HELPEOF
This will install a basic systemd setup in your initramfs, and is meant to
replace the 'base', 'usr', 'udev' and 'resume' hooks. Other hooks with runtime
components will need to be ported, and will not work as intended. You also may
wish to still include the 'base' hook (before this hook) to ensure that a
rescue shell exists on your initramfs.
HELPEOF
}

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