#!/bin/bash

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 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

    add_binary /usr/bin/kmod /usr/bin/modprobe
    add_binary /usr/bin/mount
    add_binary /usr/bin/sulogin
    add_binary /usr/bin/umount
    add_binary /usr/lib/systemd/systemd /init

    map add_binary \
        /usr/bin/journalctl \
        /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
    map add_udev_rule "$rules" \
        50-udev-default.rules \
        60-persistent-storage.rules \
        64-btrfs.rules \
        80-drivers.rules \
        99-systemd.rules

    # systemd units
    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-udevadm-cleanup-db.service \
        initrd.target \
        kmod-static-nodes.service \
        local-fs.target \
        local-fs-pre.target \
        paths.target \
        reboot.target \
        slices.target \
        sockets.target \
        swap.target \
        systemd-battery-check.service \
        systemd-bsod.service \
        systemd-fsck@.service \
        systemd-hibernate-resume.service \
        systemd-journald-audit.socket \
        systemd-journald-dev-log.socket \
        systemd-journald.service \
        systemd-modules-load.service \
        systemd-pcrphase-initrd.service \
        systemd-tmpfiles-setup-dev.service \
        systemd-udevd-control.socket \
        systemd-udevd-kernel.socket \
        systemd-udevd.service \
        systemd-udev-trigger.service \
        systemd-vconsole-setup.service \
        timers.target \
        rescue.target \
        emergency.target

    # add libraries dlopen()ed (hard and optional dependencies):
    #  kmod     -> systemd-shared
    #  qrencode -> bsod
    #  tss2-*   -> tpm2-util
    for LIB in kmod qrencode tss2-{esys,rc,mu,tcti-'*'}; do
        for FILE in $(find /usr/lib/ -maxdepth 1 -name "lib${LIB}.so*"); do
            if [[ -L "${FILE}" ]]; then
                add_symlink "${FILE}"
            else
                add_binary "${FILE}"
            fi
        done
    done

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

    printf '%s\n' >"$BUILDROOT/etc/nsswitch.conf" \
        'passwd: files' \
        'group: files' \
        'shadow: files'

    echo "root:x:0:0:root:/root:/bin/sh" >"$BUILDROOT/etc/passwd"
    echo 'root:*:::::::' >"$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"

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

    [[ -f /etc/fstab.initramfs ]] && add_file "/etc/fstab.initramfs" "/etc/fstab"
}

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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