#!/bin/sh
set -eu

project_dir=$(CDPATH= cd -- "$(dirname -- "$0")" && pwd)

find_legacy_volume() {
    volume_label=$1
    paired_label=$2
    volumes=$(docker volume ls -q --filter "label=com.docker.compose.volume=$volume_label")

    if [ -z "$volumes" ]; then
        echo "No legacy '$volume_label' Docker volume was found." >&2
        exit 1
    fi

    matching_volumes=''
    for volume in $volumes; do
        project=$(docker volume inspect --format '{{ index .Labels "com.docker.compose.project" }}' "$volume")
        paired_volume=$(docker volume ls -q \
            --filter "label=com.docker.compose.project=$project" \
            --filter "label=com.docker.compose.volume=$paired_label")
        if [ -n "$paired_volume" ]; then
            matching_volumes="$matching_volumes $volume"
        fi
    done

    set -- $matching_volumes
    if [ "$#" -ne 1 ]; then
        echo "Could not identify one '$volume_label' volume paired with the legacy '$paired_label' volume." >&2
        echo "Set LEGACY_GITEA_VOLUME and LEGACY_POSTGRES_VOLUME explicitly and rerun." >&2
        exit 1
    fi

    printf '%s\n' "$1"
}

gitea_volume=${LEGACY_GITEA_VOLUME:-$(find_legacy_volume gitea_data postgres_data)}
postgres_volume=${LEGACY_POSTGRES_VOLUME:-$(find_legacy_volume postgres_data gitea_data)}

for destination in "$project_dir/docker/gitea" "$project_dir/docker/postgres"; do
    mkdir -p "$destination"
    if [ -n "$(find "$destination" -mindepth 1 -print -quit)" ]; then
        echo "Migration destination '$destination' is not empty; refusing to overwrite data." >&2
        exit 1
    fi
done

docker compose down

docker run --rm \
    --volume "$gitea_volume:/source/gitea:ro" \
    --volume "$postgres_volume:/source/postgres:ro" \
    --volume "$project_dir/docker:/destination" \
    alpine:3.21 sh -ec '
        cp -a /source/gitea/. /destination/gitea/
        cp -a /source/postgres/. /destination/postgres/
    '

echo "Migration complete. Start the server with: docker compose up -d"