#!/bin/env bash

function die() { echo "$*" >&2; exit 1; }

function check_preconditions() {
	test -d /secrets || die "no /secrets directory"
	test -d /depot || die "no /depot directory"
}

function clone_depot() {
	echo Cloning depot to /depot/depot >&2
	hg clone ssh://hg/lukegb/depot /depot/depot
	cd /depot/depot
}

function update_depot() {
	echo Updating depot checkout in /depot/depot >&2
	cd /depot/depot
	hg revert -a
	hg pull
	hg update -r default -C
	hg purge --all
	hg strip --no-backup 'roots(outgoing())' || true
}

function make_depot_fresh() {
	if test -d /depot/depot; then
		update_depot
	else
		clone_depot
	fi
}

function clone_nixpkgs() {
	echo Cloning nixpkgs to /depot/nixpkgs >&2
	git clone --bare https://github.com/NixOS/nixpkgs.git /depot/nixpkgs
}

function update_nixpkgs() {
	echo Updating nixpkgs checkout in /depot/nixpkgs >&2
	pushd /depot/nixpkgs
	git fetch origin nixos-unstable
	git branch -f master FETCH_HEAD
	popd
}

function make_nixpkgs_fresh() {
	if test -d /depot/nixpkgs; then
		update_nixpkgs
	else
		clone_nixpkgs
	fi
}

function main() {
	set -euxo pipefail
	check_preconditions
	make_depot_fresh
	make_nixpkgs_fresh

	# Pre-seed the copybara cache directory, so it doesn't try to do the clone itself.
	mkdir -p $HOME/copybara/cache/{git_repos,hg_repos}
	hg clone --noupdate /depot/depot $HOME/copybara/cache/hg_repos/file%3A%2F%2F%2Fdepot%2Fdepot
	git clone --mirror /depot/nixpkgs $HOME/copybara/cache/git_repos/https%3A%2F%2Fgithub%2Ecom%2FNixOS%2Fnixpkgs%2Egit

	sed -i 's,file:///home/lukegb/depot,file:///depot/depot,g' ./third_party/nixpkgs/copy.bara.sky
	copybara migrate --verbose ./third_party/nixpkgs/copy.bara.sky || exit 0

	# Reset to a clean state.
	hg update -r default -C
	hg purge --all

	# And push, if it that worked.
	hg push -r .
}

main