# Builds a single Python backend on top of the shared
# .docker/bases/Dockerfile.python base. The base bakes in apt-update + GPU
# SDK install + python toolchain (uv, pip, rustup, grpcio-tools), so this
# stage only carries the per-backend source COPY + `make`.
#
# CI orchestration (.github/workflows/backend.yml + backend_pr.yml) builds
# the right base flavour automatically via scripts/derive-build-matrix.js
# and passes BASE_IMAGE_PREBUILT here. For local builds, run:
#   make backend-image-base BUILD_TYPE=<...>     # build the base
#   make backend-image BACKEND=<...> BUILD_TYPE=<...>
# See .agents/ci-caching.md.

ARG BASE_IMAGE_PREBUILT

FROM ${BASE_IMAGE_PREBUILT} AS builder

ARG BACKEND=rerankers
ARG BUILD_TYPE
ENV BUILD_TYPE=${BUILD_TYPE}
ARG CUDA_MAJOR_VERSION
ARG CUDA_MINOR_VERSION
ENV CUDA_MAJOR_VERSION=${CUDA_MAJOR_VERSION}
ENV CUDA_MINOR_VERSION=${CUDA_MINOR_VERSION}

COPY backend/python/${BACKEND} /${BACKEND}
COPY backend/backend.proto /${BACKEND}/backend.proto
COPY backend/python/common/ /${BACKEND}/common
COPY scripts/build/package-gpu-libs.sh /package-gpu-libs.sh

# Optional per-backend source build toggle (e.g. vllm on CPU can set
# FROM_SOURCE=true to compile against the build host SIMD instead of
# pulling a prebuilt wheel). Default empty — most backends ignore it.
ARG FROM_SOURCE=""
ENV FROM_SOURCE=${FROM_SOURCE}

# Cache-buster for the per-backend `make` step. Most Python backends list
# unpinned deps (torch, transformers, vllm, ...), so a warm registry cache
# would otherwise freeze upstream versions indefinitely. CI passes a value
# that rolls weekly so the install layer is rebuilt at most once per week
# and picks up newer wheels from PyPI / nightly indexes.
ARG DEPS_REFRESH=initial

RUN cd /${BACKEND} && PORTABLE_PYTHON=true make

# Package GPU libraries into the backend's lib directory
RUN mkdir -p /${BACKEND}/lib && \
    TARGET_LIB_DIR="/${BACKEND}/lib" BUILD_TYPE="${BUILD_TYPE}" CUDA_MAJOR_VERSION="${CUDA_MAJOR_VERSION}" \
    bash /package-gpu-libs.sh "/${BACKEND}/lib"

# Run backend-specific packaging if a package.sh exists
RUN if [ -f "/${BACKEND}/package.sh" ]; then \
        cd /${BACKEND} && bash package.sh; \
    fi

FROM scratch
ARG BACKEND=rerankers
COPY --from=builder /${BACKEND}/ /