#!/usr/bin/env bash
# SPDX-License-Identifier: MIT-0
# Copyright (C) 2024 by Gero Schwäricke <gero.schwaericke@grandcentrix.net>
#
# Permission is hereby granted, free of charge, to any person obtaining a copy of this
# software and associated documentation files (the "Software"), to deal in the Software
# without restriction, including without limitation the rights to use, copy, modify,
# merge, publish, distribute, sublicense, and/or sell copies of the Software, and to
# permit persons to whom the Software is furnished to do so.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
# INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
# PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
# LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT
# OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
# OTHER DEALINGS IN THE SOFTWARE.

# Check for updates to Linux stable releases. The script uses the versions found in
# linux/linux.hash. For each of the versions it downloads the related hash list and tries
# to find an updated stable release. If found it updates all related files and hashes.

set -euo pipefail

latest_version=$(sed -rn 's|^\tdefault "(.+)" if BR2_LINUX_KERNEL_LATEST_VERSION$|\1|p' linux/Config.in)
latest_release_version=$(echo "${latest_version}" | cut -f 1-2 -d .)
echo "${latest_version} -> ${latest_release_version}"

updated_releases_list=''

hash_list=
while read -r line; do
    # e.g.: # From https://www.kernel.org/pub/linux/kernel/v6.x/sha256sums.asc
    url=$(echo "${line}" | sed -n 's|^# From \(https://www\.kernel\.org/pub/linux/kernel/.*/sha256sums.asc\)|\1|p')
    # e.g.: sha256  f905f1238ea7a8e85314bacf283302e8097006010d25fcea726d0de0ea5bc9b6  linux-6.8.9.tar.xz
    old_hash=$(echo "${line}" | sed -rn 's|^sha256 +([0-9a-f]+) +linux-.*$|\1|p')
    old_version=$(echo "${line}" | sed -rn 's|^sha256 +[0-9a-f]+ +linux-(.+)\.tar\.xz$|\1|p')
    if [ -n "${url}" ]; then
        # Line contained a URL: Download hash list and use it.
        if [ -a "${hash_list}" ]; then
            rm "${hash_list}"
        fi

        hash_list=$(basename "${url}")
        echo ">>> Downloading hash list from ${url}"
        wget --no-verbose "${url}"
        gpg --verify "${hash_list}"

        echo "${line}" >> linux/linux.hash.new
    elif [ -n "${old_version}" ]; then
        # Line contained a hash entry: Search for newer versions.
        release_version=$(echo "${old_version}" | cut -f 1-2 -d .) # e.g.: 6.8 instead of 6.8.9
        # e.g.: 19b31956d229b5b9ca5671fa1c74320179682a3d8d00fc86794114b21da86039  linux-6.8.12.tar.xz
        new_hash_entry=$(grep "^[0-9a-f]\+ \+linux-${release_version//./\\.}\.[0-9]\+\.tar\.xz$" "${hash_list}" | sort -V --key '2' | tail -1)
        new_hash=$(echo "${new_hash_entry}" | cut -f 1 -d ' ')
        new_version=$(echo "${new_hash_entry}" | cut -f 3 -d ' ' | sed -rn 's|linux-(.+)\.tar\.xz|\1|p')

        if [ "$new_version" == "$old_version" ]; then
            # Same version as before
            echo ">>> Release ${release_version}.x already on newest version ${new_version}."
            echo "${line}" >> linux/linux.hash.new

            if [ "${old_hash}" != "${new_hash}" ]; then
                # Hash changed! This should never happen!
                echo ">>> Version hash changed for ${release_version}.x!"
                echo ">>> It was: ${old_hash}"
                echo ">>> It is:  ${new_hash}"
                exit 1
            fi
        else
            # Different version: update hash list, default headers, and possibly latest
            # version.
            echo ">>> Updating hash for ${release_version}.x in linux/linux.hash"
            echo "sha256  ${new_hash}  linux-${new_version}.tar.xz" >> linux/linux.hash.new

            echo ">>> Updating version from ${old_version} to ${new_version} in Config.in files"
            sed -Ei "s/\tdefault \"${old_version}\"([\t ]+)if /\tdefault \"${new_version}\"\1if /" \
                package/linux-headers/Config.in.host linux/Config.in

            updated_releases_list="${updated_releases_list} ${release_version}.x"
        fi
    else
        # Different line: Reset hash list and just copy this line over as is.
        if [ -a "${hash_list}" ]; then
            rm "${hash_list}"
            hash_list=
        fi
        echo "${line}" >> linux/linux.hash.new
    fi
done < linux/linux.hash

# We were iterating over this file so we could not edit in-place.
mv linux/linux.hash.new linux/linux.hash

if [ -n "${updated_releases_list}" ]; then
    echo ">>> Suggested subject: {linux, linux-headers}: bump${updated_releases_list//.x /.x, } series"
else
    echo '>>> Nothing happened.'
fi