#!/usr/bin/env bash
# SPDX-License-Identifier: GPL-2.0-only

build() {
    local m=''
    local -a md_devs mods
    local -i attempts_left

    # allow other hooks to customize behavior if autodetect is run them
    # shellcheck disable=SC2034
    declare -gri mkinitcpio_autodetect=1

    [[ "$KERNELVERSION" == 'none' ]] && return 0

    auto_modules() {
        # Perform auto detection of modules via sysfs.

        local mods=() uevents

        # Look for uevents
        for (( attempts_left=2; attempts_left; --attempts_left )); do
            if uevents="$(LC_ALL=C.UTF-8 find /sys/devices -name uevent -exec sort -u {} +)"; then
                break
            fi
            if (( attempts_left > 1 )); then
                # Sleep and try again to avoid a race condition with udev
                # NOTE: This is a best-effort workaround for what is assumed to be
                # a bug in `udevadm settle` where the command exits while the
                # devices have not yet settled. See
                # https://gitlab.archlinux.org/archlinux/mkinitcpio/mkinitcpio/-/issues/177
                # and https://bugs.archlinux.org/task/77789 for details.
                warning 'An error was encountered during device lookup. Retrying.'
                sleep 1
            else
                error 'An error was encountered during device lookup.'
                return 1
            fi
        done
        mapfile -t mods < <(sed -n 's/\(DRIVER\|MODALIAS\)=\(.\+\)/\2/p' <<<"$uevents")
        mapfile -t mods < <(modprobe -S "$KERNELVERSION" -qaR "${mods[@]}" | LC_ALL=C.UTF-8 sort -u)

        (( ${#mods[*]} )) && printf "%s\n" "${mods[@]//-/_}"
    }

    add_if_avail() {
        local r='' resolved=()

        # treat this as an alias, since ext3 might be aliased to ext4. also, as
        # of linux 3.9, we can find any filesystem by the alias "fs-$name"
        # rather than having to guess at the corresponding module name.
        mapfile -t resolved < <(modprobe -S "$KERNELVERSION" -qaR {fs-,}"$1")

        for r in "${resolved[@]}"; do
            _autodetect_cache["$r"]=1
        done
    }

    if [[ ! -d /sys/devices ]]; then
        error "/sys does not appear to be mounted. Unable to use autodetection"
        return 1
    fi

    mapfile -t mods < <(auto_modules)
    if (( ! ${#mods[@]} )); then
        error 'Cannot acquire used modules. Unable to use autodetection.'
        return 1
    fi

    for m in "${mods[@]}"; do
        _autodetect_cache["$m"]=1
    done

    # detect filesystem for root
    if rootfstype="$(findmnt -uno fstype -T '/')"; then
        if [[ "${rootfstype}" == "overlay" ]]; then
            warning "cannot detect type of overlayfs root filesystem"
            # fs_autodetect_failed is used by other hooks called after this one
            # shellcheck disable=SC2034
            fs_autodetect_failed=1
        else
            add_if_avail "$rootfstype"
        fi
    else
        error "failed to detect root filesystem"
        # fs_autodetect_failed is used by other hooks called after this one
        # shellcheck disable=SC2034
        fs_autodetect_failed=1
    fi

    # detect filesystem for separate /usr
    if usrfstype="$(findmnt -snero fstype -T '/usr')"; then
        add_if_avail "$usrfstype"
    fi

    # scan for md raid devices
    mapfile -t md_devs < <(compgen -G '/sys/class/block/md*/md/level')
    if (( ${#md_devs[@]} )); then
        quiet "found %d mdadm arrays to scan" "${#md_devs[*]}"
        mapfile -t mods < <(awk '{ gsub(/raid[456]/, "raid456"); print; }' "${md_devs[@]}")
        for m in "${mods[@]}"; do
            _autodetect_cache["$m"]=1
        done
    fi

    if (( ${#_autodetect_cache[*]} )); then
        quiet "caching %d modules" "${#_autodetect_cache[*]}"
    fi
}

help() {
    cat <<HELPEOF
This hook shrinks your initramfs to a smaller size by autodetecting the needed
modules. Be sure to verify included modules are correct and none are missing.
This hook must be run before other subsystem hooks in order to take advantage
of auto-detection.  Any hooks placed before 'autodetect' will be installed in
full.
HELPEOF
}

# vim: set ft=sh ts=4 sw=4 et: