package dkms

import (
	"os"
	"path"
	"path/filepath"
	"testing"

	"github.com/google/go-cmp/cmp"
)

func TestFindKernelModules(t *testing.T) {
	installDir := t.TempDir()

	paths := []string{
		"a.ko",
		"b.txt",
		"x/c.ko",
		"x/d.ko",
		"x/e.txt",
		"x/y/f.ko",
		"x/y/g.txt",
	}
	for _, p := range paths {
		installPath := path.Join(installDir, p)
		if err := os.MkdirAll(filepath.Dir(installPath), 0777); err != nil {
			t.Fatalf("%v", err)
		}
		if _, err := os.Create(path.Join(installDir, p)); err != nil {
			t.Fatalf("%v", err)
		}
	}

	kernelModules, err := FindKernelModules(installDir)
	if err != nil {
		t.Fatalf("could not find kernel modules: %v", err)
	}

	expected := map[string]string{
		"a.ko": path.Join(installDir, "a.ko"),
		"c.ko": path.Join(installDir, "x/c.ko"),
		"d.ko": path.Join(installDir, "x/d.ko"),
		"f.ko": path.Join(installDir, "x/y/f.ko"),
	}

	diff := cmp.Diff(expected, kernelModules)
	if diff != "" {
		t.Errorf("found kernel modules did not match expected:\ndiff: %s", diff)
	}
}

func TestModuleDependencies(t *testing.T) {
	deps, err := ModuleDependencies("ext4")
	if err != nil {
		t.Fatalf("error getting dependencies for module ext4: %v", err)
	}
	if len(deps) == 0 {
		t.Fatalf("expected to find at least one dependency for module ext4; found none")
	}
	t.Logf("ext4 dependencies: %v", deps)
}

func TestModuleDependencyGraph(t *testing.T) {
	insertedModules, err := InsertedModules()
	if err != nil {
		t.Fatalf("failed to get inserted modules: %v", err)
	}

	var moduleNames []string
	for module := range insertedModules {
		moduleNames = append(moduleNames, module)
	}

	// Technically, this wouldn't be fully correct if there are multiple kernels
	// installed, but any nontrivial dependency graph suffices for this test.
	modulePaths, err := FindKernelModules("/lib/modules/")
	if err != nil {
		t.Fatalf("failed to get kernel module paths")
	}

	graph, err := ModuleDependencyGraph(moduleNames, modulePaths)
	if err != nil {
		t.Fatalf("failed to build module dependency graph: %v", err)
	}

	any_non_empty_deps := false
	for _, deps := range graph {
		if len(deps) > 0 {
			any_non_empty_deps = true
		}
	}
	t.Logf("module dependency graph: %v", graph)

	if !any_non_empty_deps {
		t.Fatalf("expected to find at least one module with dependencies; found none")
	}
}

func TestModuleInsertionOrder(t *testing.T) {
	testCases := []struct {
		modules  []string
		graph    map[string][]string
		expected []string
	}{
		{
			modules: []string{"a", "b", "c", "d"},
			graph: map[string][]string{
				"a": {},
				"b": {"d"},
				"c": {"b", "a"},
				"d": {},
			},
			expected: []string{"a", "d", "b", "c"},
		},
		// This test case is the Lustre kernel module dependency graph, which has
		// a non-trivial structure and important tie-breaking.
		{
			modules: []string{
				"ksocklnd",
				"in-kernel-ko2iblnd",
				"ec",
				"fid",
				"fld",
				"libcfs",
				"lmv",
				"lnet",
				"lov",
				"lustre",
				"mdc",
				"mgc",
				"obdclass",
				"obdecho",
				"osc",
				"ptlrpc",
			},
			graph: map[string][]string{
				"ec":                 {},
				"fid":                {"obdclass", "ptlrpc", "libcfs"},
				"fld":                {"obdclass", "ptlrpc", "libcfs"},
				"in-kernel-ko2iblnd": {"ib_core", "rdma_cm", "libcfs", "lnet"},
				"ksocklnd":           {"lnet", "libcfs"},
				"libcfs":             {},
				"lmv":                {"fld", "obdclass", "fid", "ptlrpc", "libcfs", "lnet"},
				"lnet":               {"sunrpc", "libcfs"},
				"lov":                {"obdclass", "ptlrpc", "fld", "libcfs"},
				"lustre":             {"lnet", "obdclass", "ptlrpc", "libcfs", "lov", "mdc", "lmv", "fid"},
				"mdc":                {"ptlrpc", "libcfs", "osc", "obdclass", "lov", "fid"},
				"mgc":                {"ptlrpc", "obdclass", "libcfs", "lnet"},
				"obdclass":           {"lnet", "libcfs"},
				"obdecho":            {"obdclass", "libcfs"},
				"osc":                {"libcfs", "obdclass", "ptlrpc", "lnet"},
				"ptlrpc":             {"lnet", "libcfs", "obdclass"},
			},
			expected: []string{
				"libcfs",
				"sunrpc",
				"lnet",
				"ksocklnd",
				"ib_core",
				"rdma_cm",
				"in-kernel-ko2iblnd",
				"ec",
				"obdclass",
				"ptlrpc",
				"fid",
				"fld",
				"lmv",
				"lov",
				"osc",
				"mdc",
				"lustre",
				"mgc",
				"obdecho",
			},
		},
	}

	for _, testCase := range testCases {
		order := ModuleInsertionOrder(testCase.modules, testCase.graph)

		diff := cmp.Diff(order, testCase.expected)
		if len(diff) > 0 {
			t.Fatalf("order differs from expected: %s", diff)
		}
	}
}