# ensure compatability with Spack v0.18.0
try:
    from spack.package_base import PackageStillNeededError
except:
    from spack.package import PackageStillNeededError

needed = set()
# keep packages that are part of an environment
for e in spack.environment.all_environments():
    needed.update(e.all_hashes())
# also keep packages that provide compilers (and their dependencies)
for c in spack.compilers.all_compiler_specs():
    pkg_spec = spack.compilers.pkg_spec_for_compiler(c)
    needed.update([dep.dag_hash() for pkg in spack.store.db.query(pkg_spec) for dep in pkg.traverse()])

installed = {spec.dag_hash(): spec for spec in spack.store.db.query()}
to_remove = set(installed) - needed

# this will try to uninstall ANY package that is not part of an environment
# including test dependencies
# for a list of all the packages that will be uninstalled:
print('The following packages will be uninstalled:')
print('\n'.join(sorted([installed[h].short_spec+' ('+h+')' for h in to_remove])))

# iteratively uninstall packages with no dependents
while to_remove:
    # print('New iteration')
    for hash in to_remove.copy():
        spec = installed[hash]
        try:
            spec.package.do_uninstall()
            to_remove.discard(hash)
        except PackageStillNeededError:
            pass
            # print('Not ready to remove', spec.short_spec, 'in this iteration')