#!/usr/bin/env bash
export LC_ALL=C
set -e -o pipefail

# Source the common prelude, which:
#   1. Checks if we're at the top directory of the Dash Core repository
#   2. Defines a few common functions and variables
#
# shellcheck source=libexec/prelude.bash
source "$(dirname "${BASH_SOURCE[0]}")/libexec/prelude.bash"


###################
## Sanity Checks ##
###################

################
# Required non-builtin commands should be invokable
################

check_tools cat diff gpg

################
# Required env vars should be non-empty
################

cmd_usage() {
cat <<EOF
Synopsis:

    env GUIX_SIGS_REPO=<path/to/guix.sigs> ./contrib/guix/guix-verify

EOF
}

if [ -z "$GUIX_SIGS_REPO" ]; then
    cmd_usage
    exit 1
fi

################
# GUIX_SIGS_REPO should exist as a directory
################

if [ ! -d "$GUIX_SIGS_REPO" ]; then
cat << EOF
ERR: The specified GUIX_SIGS_REPO is not an existent directory:

    '$GUIX_SIGS_REPO'

Hint: Please clone the guix.sigs repository and point to it with the
      GUIX_SIGS_REPO environment variable.

EOF
cmd_usage
exit 1
fi

##############
##  Verify  ##
##############

OUTSIGDIR_BASE="${GUIX_SIGS_REPO}/${VERSION}"
echo "Looking for signature directories in '${OUTSIGDIR_BASE}'"
echo ""

# Usage: verify compare_manifest current_manifest
verify() {
    local compare_manifest="$1"
    local current_manifest="$2"
    if ! gpg --quiet --batch --verify "$current_manifest".asc "$current_manifest" 1>&2; then
        echo "ERR: Failed to verify GPG signature in '${current_manifest}'"
        echo ""
        echo "Hint: Either the signature is invalid or the public key is missing"
        echo ""
        failure=1
    elif ! diff --report-identical "$compare_manifest" "$current_manifest" 1>&2; then
        echo "ERR: The SHA256SUMS attestation in these two directories differ:"
        echo "    '${compare_manifest}'"
        echo "    '${current_manifest}'"
        echo ""
        failure=1
    else
        echo "Verified: '${current_manifest}'"
        echo ""
    fi
}

shopt -s nullglob
all_noncodesigned=( "$OUTSIGDIR_BASE"/*/noncodesigned.SHA256SUMS )
shopt -u nullglob

echo "--------------------"
echo ""
if (( ${#all_noncodesigned[@]} )); then
    compare_noncodesigned="${all_noncodesigned[0]}"

    for current_manifest in "${all_noncodesigned[@]}"; do
        verify "$compare_noncodesigned" "$current_manifest"
    done

    echo "DONE: Checking output signatures for noncodesigned.SHA256SUMS"
    echo ""
else
    echo "WARN: No signature directories with noncodesigned.SHA256SUMS found"
    echo ""
fi

shopt -s nullglob
all_all=( "$OUTSIGDIR_BASE"/*/all.SHA256SUMS )
shopt -u nullglob

echo "--------------------"
echo ""
if (( ${#all_all[@]} )); then
    compare_all="${all_all[0]}"

    for current_manifest in "${all_all[@]}"; do
        verify "$compare_all" "$current_manifest"
    done

    # Sanity check: there should be no entries that exist in
    # noncodesigned.SHA256SUMS that doesn't exist in all.SHA256SUMS
    if [[ "$(comm -23 <(sort "$compare_noncodesigned") <(sort "$compare_all") | wc -c)" -ne 0 ]]; then
        echo "ERR: There are unique lines in noncodesigned.SHA256SUMS which"
        echo "     do not exist in all.SHA256SUMS, something went very wrong."
        exit 1
    fi

    echo "DONE: Checking output signatures for all.SHA256SUMS"
    echo ""
else
    echo "WARN: No signature directories with all.SHA256SUMS found"
    echo ""
fi

echo "===================="
echo ""
if (( ${#all_noncodesigned[@]} + ${#all_all[@]} == 0 )); then
    echo "ERR: Unable to perform any verifications as no signature directories"
    echo "     were found"
    echo ""
    exit 1
fi

if [ -n "$failure" ]; then
    exit 1
fi