#!/bin/bash

strip_quotes() {
  local len=${#1} quotes=$'[\'"]' str=${!1}

  if [[ ${str:0:1} = ${str: -1} && ${str:0:1} = $quotes ]]; then
    printf -v "$1" %s "${str:1:-1}"
  fi
}

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= rule= key= value= binary=

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

    add_file "$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 $key in
                RUN@({program}|+)|IMPORT{program}|ENV{REMOVE_CMD})
                    strip_quotes 'value'
                    # just take the first word as the binary name
                    binary=${value%% *}
                    [[ ${binary:0:1} == '$' ]] && 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 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*)
                # don't add binaries unless they are required
                if [[ ${values[0]:0:1} != '-' ]]; then
                    add_binary "${values[0]}"
                fi
                ;;
        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
}

build() {
    local rules unit

    # from base
    add_binary /bin/mount
    add_binary /usr/bin/kmod /usr/bin/modprobe
    add_binary /usr/lib/systemd/systemd /init

    map add_binary \
        /usr/lib/systemd/systemd-hibernate-resume \
        /usr/lib/systemd/system-generators/systemd-hibernate-resume-generator \
        /usr/bin/systemd-tmpfiles

    # generators
    map add_file \
        /usr/lib/systemd/system-generators/systemd-fstab-generator \
        /usr/lib/systemd/system-generators/systemd-gpt-auto-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-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-fsck@.service \
            systemd-hibernate-resume@.service \
            systemd-journald.service \
            systemd-journald-audit.socket \
            systemd-journald-dev-log.socket \
            systemd-tmpfiles-setup-dev.service \
            systemd-udev-trigger.service \
            systemd-udevd-control.socket \
            systemd-udevd-kernel.socket \
            systemd-udevd.service \
            timers.target

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

    # udev wants /etc/group since it doesn't launch with --resolve-names=never
    add_file "/etc/nsswitch.conf"
    add_binary "$(readlink -f /usr/lib/libnss_files.so)"
    add_file "/etc/passwd"
    add_file "/etc/group"
}

help() {
    cat <<HELPEOF
This will install a basic systemd setup in your initramfs, and is meant to
replace the 'base', 'usr', 'udev' and 'timestamp' 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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