# Multi-stage build for the backend service. Mirrors platform/telegram/Dockerfile:
# a golang-alpine builder yields a static binary shipped on distroless nonroot.
#
# The dictionary DAWGs are baked in from the scrabble-dictionary release artifact
# — the same set the Go CI downloads — and BACKEND_DICT_DIR points the
# binary at them. The published solver module is fetched directly from Gitea
# (GOPRIVATE), so the build stage needs git and network.
#
# Build from the repository root so go.work, go.work.sum, pkg/ and backend/ are all
# in the Docker context. DICT_VERSION has no default — the caller supplies the
# scrabble-dictionary release tag (compose/CI pass it; see deploy/README.md
# "Bumping the dictionary version"):
#   docker build --build-arg DICT_VERSION=v1.3.0 -f backend/Dockerfile -t scrabble-backend .

# --- dictionary artifact -----------------------------------------------------
FROM alpine:3.20 AS dawg
ARG DICT_VERSION
RUN apk add --no-cache curl tar
RUN mkdir -p /dawg \
 && curl -fsSL -o /tmp/dawg.tar.gz \
      "https://gitea.iliadenisov.ru/developer/scrabble-dictionary/releases/download/${DICT_VERSION}/scrabble-dawg-${DICT_VERSION}.tar.gz" \
 && tar xzf /tmp/dawg.tar.gz -C /dawg

# --- build -------------------------------------------------------------------
FROM golang:1.26.3-alpine AS build
WORKDIR /src
# git: the published solver module is fetched from Gitea directly (GOPRIVATE).
RUN apk add --no-cache git
ENV GOPRIVATE=gitea.iliadenisov.ru/*

COPY go.work go.work.sum ./
COPY pkg ./pkg
COPY backend ./backend

# Reduce the workspace to what the backend needs: backend + pkg. loadtest and the
# gateway replace it requires are not in this context, so drop both.
RUN go work edit -dropuse=./gateway -dropuse=./platform/telegram -dropuse=./loadtest -dropreplace=scrabble/gateway@v0.0.0
# VERSION (the deploy passes the git tag) is stamped into the binary via the linker.
ARG VERSION=dev
RUN CGO_ENABLED=0 GOOS=linux go build -trimpath -ldflags "-X scrabble/pkg/version.Version=${VERSION}" -o /out/backend ./backend/cmd/backend

# --- runtime -----------------------------------------------------------------
FROM gcr.io/distroless/static-debian12:nonroot
# Re-declare the build arg in this stage so it labels the seed dictionary. One
# DICT_VERSION drives both the artifact the dawg stage downloads and the version
# label the binary pins, so the resident version equals the release tag.
ARG DICT_VERSION
COPY --from=build /out/backend /usr/local/bin/backend
# Own the seed dictionary as the nonroot runtime user (UID 65532): a named volume
# mounted at /opt/dawg inherits this ownership on first use, so the admin console
# can write new version subdirectories at runtime. The volume preserves uploaded
# versions across deploys and, once seeded, is not re-seeded (ARCHITECTURE.md §5).
COPY --from=dawg --chown=65532:65532 /dawg /opt/dawg
# A second, UNSHADOWED copy of the build's DAWGs: the /opt/dawg volume mount hides the
# image's copy there, so this is where engine.DeliverVersion reads the build version from
# to add it (add-only) to the volume on boot — the deploy-delivers path that lets a bumped
# BACKEND_DICT_VERSION go live for new games without an admin upload (ARCHITECTURE.md §5).
COPY --from=dawg --chown=65532:65532 /dawg /opt/dawg-seed
ENV BACKEND_DICT_DIR=/opt/dawg
ENV BACKEND_DICT_SEED_DIR=/opt/dawg-seed
ENV BACKEND_DICT_VERSION=${DICT_VERSION}
ENTRYPOINT ["/usr/local/bin/backend"]
