# Copyright 2020 Authors of Cilium
# SPDX-License-Identifier: Apache-2.0

ifdef DOCKER_BUILDKIT

BUILD_DIR := _build
DOCKER_BUILD_DIR := $(BUILD_DIR)/context

# Export with value expected by docker
export DOCKER_BUILDKIT=1

# Clean the build directory and cache
clean-build:
	-$(QUIET) rm -rf _build
	-$(QUIET) docker builder prune --filter type=exec.cachemount -f

veryclean: clean-build

BUILDKIT_DOCKERFILE_FILTER := | sed -e "1s|^\#.*|\# syntax = docker/dockerfile:experimental|" -e "s|^RUN\(.*\)make|RUN --mount=type=cache,target=/root/.cache/go-build\1make|"

# _build/.git is a shallow bare clone of the main repo
# - mkdir can fail if the directory exists already
# - git clone will fail if _build.git already exists.
#   In this case the following 'build-context-update' will update it
# If the _build directory gets into bad shape 'make veryclean' will nuke it.
_build/.git:
	-mkdir -p _build
	-git clone --bare --no-local --depth 1 . _build/.git && cd _build && git remote set-url origin ..

#
# Create _build context:
# _build/context/.git will be a file (rather than directory) that contains git specific
# symbolic link to _build/.git (--separate-git-dir)
#
_build/context: _build/.git
	git init --separate-git-dir=$< $@

#
# Update the docker build context by:
# 1. shallow fetch from the main repo to _build/.git
# 2. check out FETCH_HEAD into _build/context. Hard reset seems to be a best way of doing this.
# 3. remove the .git file from _build/context/.git so that make running in docker knows this is
#    no a git repo (as _build/.git is NOT part of the docker context)
#
# Dependencies:
# - check that git status is clean
# - make sure docker build context exists
# - update GIT_VERSION in the build context if needed
# - update BPF_SRCFILES in the build context if needed
#
build-context-update: check-status _build/context _build/context/GIT_VERSION _build/context/BPF_SRCFILES
	@echo "gitdir: ../.git" > _build/context/.git
	cd _build && git fetch --depth=1 --no-tags
	cd _build/context && git reset --hard FETCH_HEAD && git clean -fd
	@rm _build/context/.git

#
# Docker build context does not contain the actual git repo, so we need to pass
# GIT_VERSION and/or BPF_SRCFILES to the build context separately.
#
_build/context/GIT_VERSION: GIT_VERSION _build/context
	cp $< $@
_build/context/BPF_SRCFILES: BPF_SRCFILES _build/context
	cp $< $@

# Generic rule for Dockerfiles. For 'Dockerfile' the stem ('%') matches just the 'D'.
_build/%ockerfile: %ockerfile force
	@-mkdir -p $(dir $@)
	@cat $< $(BUILDKIT_DOCKERFILE_FILTER) > $@
	@-grep "^FROM " $@ | cut -d ' ' -f2 | grep -v "scratch" | xargs -P4 -n1 docker pull

check-status:
	@if [ -n "`git status --porcelain`" ] ; then git status && echo "These changes will not be included in build, aborting. Define IGNORE_GIT_STATUS to build anyway." && test $(IGNORE_GIT_STATUS); fi

endif