#!/bin/bash
# Minimal snap CLI stub for snapcraft's pack flow. We avoid running
# snapd in this container, but snapcraft calls `snap pack --check-skeleton`
# to validate the prime tree and `snap pack [opts] <dir> <out-dir>` to
# build the .snap. We implement those two with a sanity check and
# mksquashfs respectively; nothing else is supported.
set -e

if [ "$1" != pack ]; then
    echo "snap stub: only 'pack' is supported, got: $*" >&2
    exit 1
fi
shift

check_skeleton=0
filename=""
compression=""
positional=()

while [ "$#" -gt 0 ]; do
    case "$1" in
        --check-skeleton) check_skeleton=1; shift ;;
        --filename)       filename="$2"; shift 2 ;;
        --filename=*)     filename="${1#--filename=}"; shift ;;
        --compression)    compression="$2"; shift 2 ;;
        --compression=*)  compression="${1#--compression=}"; shift ;;
        --)               shift; while [ "$#" -gt 0 ]; do positional+=("$1"); shift; done ;;
        --*)              shift ;;  # ignore unknown long opts
        *)                positional+=("$1"); shift ;;
    esac
done

snap_dir="${positional[0]:-}"
output_dir="${positional[1]:-.}"

if [ ! -f "$snap_dir/meta/snap.yaml" ]; then
    echo "snap stub: '$snap_dir/meta/snap.yaml' not found" >&2
    exit 1
fi

if [ "$check_skeleton" = 1 ]; then
    exit 0
fi

if [ -z "$filename" ]; then
    name=$(awk -F': ' '/^name:/    { print $2; exit }' "$snap_dir/meta/snap.yaml" | sed "s/[\"' ]//g")
    ver=$( awk -F': ' '/^version:/ { print $2; exit }' "$snap_dir/meta/snap.yaml" | sed "s/[\"' ]//g")
    arch=$(dpkg --print-architecture)
    filename="${name}_${ver}_${arch}.snap"
fi

mkdir -p "$output_dir"
output="$output_dir/$filename"

comp_args=()
if [ -n "$compression" ]; then
    comp_args=(-comp "$compression")
fi

# Mirror the squashfs options snapd's `snap pack` uses
# (see snap/squashfs/squashfs.go in snapd). The Snap Store re-packs the
# uploaded snap with these exact flags and rejects the upload if the
# resulting squashfs metadata differs from ours (the
# squashfs-package-v2_squashfs_repack_checksum review check). Missing
# -no-xattrs in particular trips that check even when file content is
# identical.
mksquashfs "$snap_dir" "$output" \
    -noappend -no-fragments -no-progress -no-xattrs -all-root \
    "${comp_args[@]}" >&2

# snapcraft parses our stdout as Path(stdout.partition(":")[2].strip()).name
echo "built: $(readlink -f "$output")"