#! /usr/bin/env sh

# nixos-config - My current NixOS configuration
#
# Copyright (C) 2025 Benedikt Peetz <benedikt.peetz@b-peetz.de>
# SPDX-License-Identifier: GPL-3.0-or-later
#
# This file is part of my nixos-config.
#
# You should have received a copy of the License along with this program.
# If not, see <https://www.gnu.org/licenses/gpl-3.0.txt>.

UPDATE_SCRIPT_NAME="update.sh"

info() {
    echo "Info: $1"
}
dbg() {
    if [ "${DEBUG_ENABLE-unset}" != "unset" ]; then
        echo "Debug: $1" >&2
    fi
}
die() {
    echo "Error: $1"
    exit 1
}

# Search for a file “upwards”.
# This will return the relative path from "$1" to the found file.
#
# # Type
# upfind :: Path -> String -> Path
#
# # Arguments
# $1
# : The directory to use as start of your search.
#
# $2
# : The file to search for.
#
# # Example
# upfind "/home/user1" "/usr"
# => /usr
upfind() {
    starting_directory="$(readlink --canonicalize "$1")"
    search_string="$2"

    current_directory="$starting_directory"

    while
        search_result=$(fd "$search_string" "$current_directory/" --max-depth 1)
        dbg "upfind - search in $current_directory gives: $search_result"
        [ -z "$search_result" ] && [ "$current_directory" != "/" ]
    do current_directory=$(dirname "$current_directory"); done

    realpath --relative-to="$1" "$search_result"
}

# Construct the storage path for the update script allowed hashes.
#
# # Type
# get_storage_path :: Path -> Path
#
# # Arguments
# $1
# : The path to the update script
#
# # Returns
# The constructed storage path.
get_storage_path() {
    update_script="$(realpath "$1")"

    storage_path="$XDG_DATA_HOME/fupdate-flake/$update_script"
    echo "$storage_path"
}

# Checks if a given path to the update script is allowed.
#
# # Type
# is_allowed :: Path -> bool
#
# # Arguments
# $1
# : The path to the update script to check.
#
# # Return exit code
# 0
# : If the update script is allowed
#
# 1
# : If it is not.
is_allowed() {
    update_script="$(realpath "$1")"

    storage_path="$(get_storage_path "$update_script")"

    # Use this invocation, to also include the path to the `$update_script`
    update_script_hash="$(sha256sum "$update_script")"

    if [ -f "$storage_path" ]; then
        if [ "$(cat "$storage_path")" = "$update_script_hash" ]; then
            return 0
        else
            return 1
        fi
    else
        return 1
    fi
}

# Asks the user if they want to allow a given script.
#
# # Type
# ask_to_allow_update_script :: Path
#
# # Arguments
# $1
# : The path to the update script to ask for.
ask_to_allow_update_script() {
    update_script="$(realpath "$1")"

    printf "\033[2J" # clear the screen
    cat "$update_script"

    printf "Do you want to allow this script?[N/y]: "
    read -r allow

    case "$allow" in
    [yY])
        info "Update script allowed."

        storage_path="$(get_storage_path "$update_script")"
        update_script_hash="$(sha256sum "$update_script")"

        mkdir --parents "$(dirname "$storage_path")"
        printf "%s" "$update_script_hash" >"$storage_path"
        ;;
    *)
        info "Update script not allowed."
        ;;
    esac
}

# Performs a full update.
# This consists of running an update script.
# Additionally, it also checks for duplicated inputs in a `flake.lock` file, if it exists.
#
# # Type
# update :: Path -> Path -> [String]
#
# # Arguments
# $1
# : The path to the update script to execute.
#
# $2
# : The base directory from which to start the update.
#
# $3
# : Arguments to pass to the update script.
update() {
    update_script="$1"
    base_directory="$2"
    shift 2

    cd "$base_directory" || die "The provided base directory '$base_directory' cannot be accessed"
    dbg "Changed directory to: $base_directory"

    dbg "Executing update script ('$update_script') following args: '$*'"
    "$update_script" "$@"

    if [ -f "flake.lock" ] && grep '[^0-9]_[0-9]' flake.lock --quiet; then
        batgrep '[^0-9]_[0-9]' flake.lock
        die "Your flake.nix contains duplicate inputs!"
    fi
}

main() {
    base_directory="$(git rev-parse --show-toplevel)"
    update_script="$(upfind "$PWD" "$UPDATE_SCRIPT_NAME")"
    dbg "update_script is: $update_script"

    if [ "$update_script" = "" ]; then
        die "Failed to find update script."
    elif is_allowed "$update_script"; then
        update "$update_script" "$base_directory" "$@"
    else
        ask_to_allow_update_script "$update_script"
        is_allowed "$update_script" && main "$@"
    fi
}

main

# vim: ft=sh