#!/bin/bash -e

package=0

process_preset() {
    if [[ -n "${pkgbase}" && -e $preset ]]; then
        if ! cmp $preset > /dev/null 2>&1 <(sed "s|%PKGBASE%|${pkgbase}|g" /usr/share/mkinitcpio/hook.preset); then
            if [[ ! -e $preset.pacsave ]]; then
                # save the preset as pacsave
                mv $preset $preset.pacsave && return 0
            fi
        else
            # remove the preset
            rm $preset && return 0
        fi
    fi
}

while read -r line; do
    if [[ $line != */vmlinuz ]]; then
        # triggers when it's a change to usr/lib/initcpio/*
        package=1
        continue
    fi

    if ! read -r pkgbase > /dev/null 2>&1 < "${line%/vmlinuz}/pkgbase"; then
        # if the kernel has no pkgbase, we skip it
        continue
    fi

    # remove the actual kernel and images for the package being removed
    kernel="/boot/vmlinuz-${pkgbase}"
    preset="/etc/mkinitcpio.d/${pkgbase}.preset"
    initramfs="/boot/initramfs-${pkgbase}.img"
    fallback_initramfs="/boot/initramfs-${pkgbase}-fallback.img"
    if [[ -e $kernel ]]; then
        # remove the installed kernel
        rm $kernel
    fi

    process_preset "${pkgbase}" $preset

    if [[ -e $initramfs ]]; then
        # remove the main image
        rm $initramfs
    fi
    if [[ -e $fallback_initramfs ]]; then
        # remove the fallback image
        rm $fallback_initramfs
    fi
done

if (( package )) && compgen -G /etc/mkinitcpio.d/"*.preset" > /dev/null; then
    shopt -s nullglob
    for preset in /etc/mkinitcpio.d/*.preset; do
        pkgbase=${preset##*/}
        pkgbase=${pkgbase%.preset}
        process_preset "${pkgbase}" $preset
    done
    shopt -u nullglob
fi