stockholm ?= .

export HOSTNAME ?= $(shell cat /proc/sys/kernel/hostname)

export STOCKHOLM_VERSION ?= $(shell \
	version=git.$$(git describe --always --dirty); \
	case $$version in (*-dirty) version=$$version@$$HOSTNAME; esac; \
	date=$$(date +%y.%m); \
	printf '%s' "$$date.$$version"; \
)

system ?= $(HOSTNAME)
$(if $(system),,$(error unbound variable: system))

nixos-config ?= $(stockholm)/$(LOGNAME)/1systems/$(system)/config.nix
ifneq ($(words $(wildcard $(nixos-config))),1)
$(error bad nixos-config: $(nixos-config))
endif

# target = [target_user@]target_host[:target_port][/target_path]
ifdef target
_target_user != echo $(target) | sed -n 's/@.*//p'
_target_path != echo $(target) | sed -n 's/^[^/]*//p'
_target_port != echo $(target) | sed -En 's|^.*:([^/]*)(/.*)?$$|\1|p'
_target_host != echo $(target) | sed -En 's/^(.*@)?([^:/]*).*/\2/p'
ifneq ($(_target_host),)
$(if $(target_host),$(error cannot define both, target_host and host in target))
target_host ?= $(_target_host)
endif
ifneq ($(_target_user),)
$(if $(target_user),$(error cannot define both, target_user and user in target))
target_user ?= $(_target_user)
endif
ifneq ($(_target_port),)
$(if $(target_port),$(error cannot define both, target_port and port in target))
target_port ?= $(_target_port)
endif
ifneq ($(_target_path),)
$(if $(target_path),$(error cannot define both, target_path and path in target))
target_path ?= $(_target_path)
endif
endif

target_host ?= $(system)
target_user ?= root
target_port ?= 22
target_path ?= /var/src

$(if $(target_host),,$(error unbound variable: target_host))
$(if $(target_user),,$(error unbound variable: target_user))
$(if $(target_port),,$(error unbound variable: target_port))
$(if $(target_path),,$(error unbound variable: target_path))

whatsupnix = \
	if type whatsupnix >/dev/null 2>&1; then \
	  whatsupnix $(1); \
	else \
	  cat; \
	fi

build = \
	nix-build \
		-Q \
		--no-out-link \
		--show-trace \
		-I nixos-config=$(nixos-config) \
		-I stockholm=$(stockholm) \
		-E "with import <stockholm>; $(1)" \
		$(2) \
	|& $(call whatsupnix)

evaluate = \
	nix-instantiate \
		--eval \
		--readonly-mode \
		--show-trace \
		-I nixos-config=$(nixos-config) \
		-I stockholm=$(stockholm) \
		-E "let eval = import <stockholm>; in with eval; $(1)" \
		$(2)

ifeq ($(MAKECMDGOALS),)
$(error No goals specified)
endif

# usage: make deploy system=foo [target_host=bar]
ifeq ($(debug),true)
deploy: rebuild-command = dry-activate
else
deploy: rebuild-command = switch
endif
deploy: ssh ?= ssh
deploy:
	$(MAKE) populate debug=false
	$(ssh) $(target_user)@$(target_host) -p $(target_port) \
		env STOCKHOLM_VERSION="$$STOCKHOLM_VERSION" \
			nixos-rebuild -Q $(rebuild-command) --show-trace -I $(target_path) \
	|& $(call whatsupnix,$(target_user)@$(target_host):$(target_port))

# usage: make populate system=foo
populate: populate-target = \
	$(target_user)@$(target_host):$(target_port)$(target_path)
ifeq ($(debug),true)
populate: populate-flags += --debug
endif
ifneq ($(ssh),)
populate: populate-flags += --ssh=$(ssh)
endif
populate:
	$(call evaluate,config.krebs.build.source) --json --strict | \
	populate $(populate-target) $(populate-flags)

# usage: make pkgs.populate
pkgs:;@$(error no package selected)
pkgs.%:;@$(call build,$@)

# usage: make LOGNAME=shared system=wolf eval.config.krebs.build.host.name
eval eval.:;@$(call evaluate,$${expr-eval})
eval.%:;@$(call evaluate,$@)

# usage: make install system=foo [target_host=bar]
install: ssh ?= ssh -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null
install:
	$(ssh) $(target_user)@$(target_host) -p $(target_port) \
		env target_path=$(target_path) \
			sh -s prepare < krebs/4lib/infest/prepare.sh
	$(MAKE) populate target_path=/mnt$(target_path)
	$(ssh) $(target_user)@$(target_host) -p $(target_port) \
		env NIXOS_CONFIG=$(target_path)/nixos-config \
				STOCKHOLM_VERSION="$$STOCKHOLM_VERSION" \
			nixos-install

# usage: make test system=foo [target=bar] [method={eval,build}]
method ?= eval
ifeq ($(method),build)
test: test = $(call build,$(1),$(2))
else
ifeq ($(method),eval)
test: test ?= $(call evaluate,$(1),$(2)) --json --strict | jq -r .
else
$(error bad method: $(method))
endif
endif
test: ssh ?= ssh
ifeq ($(target_user)@$(target_host),$(LOGNAME)@$(HOSTNAME))
test: wrapper = exec
else
test: wrapper = $(ssh) $(target_user)@$(target_host) -p $(target_port)
endif
test: populate
	$(wrapper) $(call test,config.system.build.toplevel,-I $(target_path))