package store

import (
	"os"
	"path/filepath"
	"strings"
	"testing"
	"time"
)

func TestAFreshMachineHasAnEmptyStateNotAnError(t *testing.T) {
	// The first apply on a machine that has never been touched is the ordinary case, not a
	// failure. A host that errored here could never bootstrap anything.
	s, err := Load(filepath.Join(t.TempDir(), "nothing-here.json"))
	if err != nil {
		t.Fatalf("a fresh machine produced an error: %v", err)
	}
	if len(s.Resources) != 0 {
		t.Errorf("a fresh machine claims to own %d resources", len(s.Resources))
	}
}

func TestAnUnreadableStateIsRefusedNotIgnored(t *testing.T) {
	// The dangerous one. Starting empty would make the host believe it owns nothing, so it
	// would remove nothing it should and re-apply everything it need not — silently.
	path := filepath.Join(t.TempDir(), "state.json")
	if err := os.WriteFile(path, []byte("{this is not json"), 0o600); err != nil {
		t.Fatal(err)
	}
	_, err := Load(path)
	if err == nil {
		t.Fatal("a corrupt state was read as an empty one")
	}
	if !strings.Contains(err.Error(), "believes it owns nothing") {
		t.Errorf("the error does not say why this matters: %v", err)
	}
}

func TestWhatIsSavedIsWhatIsLoaded(t *testing.T) {
	path := filepath.Join(t.TempDir(), "state.json")
	want := State{Resources: []Applied{
		{ID: "etc", Type: "directory", Target: "/etc/mesh", AppliedAt: time.Now().UTC().Truncate(time.Second)},
		{ID: "conf", Type: "file", Target: "/etc/mesh/host.conf", AppliedAt: time.Now().UTC().Truncate(time.Second)},
	}}
	if err := Save(path, want); err != nil {
		t.Fatal(err)
	}
	got, err := Load(path)
	if err != nil {
		t.Fatal(err)
	}
	if len(got.Resources) != 2 || got.Resources[0].ID != "etc" || got.Resources[1].ID != "conf" {
		t.Fatalf("order or content was lost: %+v", got.Resources)
	}
	if got.UpdatedAt.IsZero() {
		t.Error("the state does not say when it was written")
	}
}

func TestTheStateIsNotWorldReadable(t *testing.T) {
	// It records what is on the machine and where. Not secret, and not everyone's business.
	path := filepath.Join(t.TempDir(), "state.json")
	if err := Save(path, State{Resources: []Applied{{ID: "a", Type: "file", Target: "/a"}}}); err != nil {
		t.Fatal(err)
	}
	info, err := os.Stat(path)
	if err != nil {
		t.Fatal(err)
	}
	if mode := info.Mode().Perm(); mode&0o077 != 0 {
		t.Errorf("the state is readable by others: %o", mode)
	}
}

func TestSavingLeavesNoDebrisBehind(t *testing.T) {
	// The write is atomic through a temporary file. A run that left those behind would fill a
	// directory with near-copies of the truth, and the next reader would have to guess.
	dir := t.TempDir()
	path := filepath.Join(dir, "state.json")
	for i := 0; i < 3; i++ {
		if err := Save(path, State{Resources: []Applied{{ID: "a", Type: "file", Target: "/a"}}}); err != nil {
			t.Fatal(err)
		}
	}
	entries, err := os.ReadDir(dir)
	if err != nil {
		t.Fatal(err)
	}
	if len(entries) != 1 {
		names := []string{}
		for _, e := range entries {
			names = append(names, e.Name())
		}
		t.Errorf("expected only the state file, found: %v", names)
	}
}

func TestRecordReplacesRatherThanDuplicating(t *testing.T) {
	s := State{}
	s.Record(Applied{ID: "a", Type: "file", Target: "/old"})
	s.Record(Applied{ID: "a", Type: "file", Target: "/new"})

	if len(s.Resources) != 1 {
		t.Fatalf("one identity produced %d records", len(s.Resources))
	}
	if s.Resources[0].Target != "/new" {
		t.Errorf("the record was not updated: %+v", s.Resources[0])
	}
}

func TestOrphansAreWhatWasAppliedAndIsNoLongerDeclared(t *testing.T) {
	// The whole reason the store arrives at stage 2 rather than stage 3: removal is impossible
	// without knowing what was applied.
	s := State{Resources: []Applied{
		{ID: "dir", Type: "directory", Target: "/etc/mesh"},
		{ID: "file", Type: "file", Target: "/etc/mesh/a.conf"},
		{ID: "kept", Type: "file", Target: "/etc/mesh/b.conf"},
	}}
	orphans := s.Orphans(map[string]bool{"kept": true}, OriginCarried)

	if len(orphans) != 2 {
		t.Fatalf("expected two orphans, got %d: %+v", len(orphans), orphans)
	}
	// Reverse order: undoing in the order things were made would remove a directory before the
	// file inside it.
	if orphans[0].ID != "file" || orphans[1].ID != "dir" {
		t.Errorf("orphans are not in reverse order: %s then %s", orphans[0].ID, orphans[1].ID)
	}
}

func TestNothingIsAnOrphanWhenEverythingIsDeclared(t *testing.T) {
	s := State{Resources: []Applied{{ID: "a", Type: "file", Target: "/a"}}}
	if got := s.Orphans(map[string]bool{"a": true}, OriginCarried); len(got) != 0 {
		t.Errorf("a declared resource was treated as an orphan: %+v", got)
	}
}

func TestADeclarationDoesNotOrphanWhatTheBundleRaised(t *testing.T) {
	// 04-ISSUES/010. A first node raises its foundation from the bundle it carries, then enrols
	// and is sent a declaration naming two resources. Before origins, that removed the store, the
	// broker and the control plane that had sent it — the mesh deleting itself over the link the
	// message arrived on, in under a second, on the first end-to-end run.
	s := State{Resources: []Applied{
		{ID: "store", Type: "container", Target: "mesh-store", Origin: OriginCarried},
		{ID: "broker", Type: "container", Target: "mesh-broker", Origin: OriginCarried},
		{ID: "greeting", Type: "directory", Target: "/var/lib/demo", Origin: OriginDeclared},
	}}

	// The mesh declares nothing at all. Everything it previously declared is an orphan; nothing
	// the bundle raised is.
	orphans := s.Orphans(map[string]bool{}, OriginDeclared)
	if len(orphans) != 1 || orphans[0].ID != "greeting" {
		var got []string
		for _, o := range orphans {
			got = append(got, o.ID)
		}
		t.Fatalf("a declaration would remove %v; it may only remove what the mesh declared", got)
	}
}

func TestTheBundleDoesNotOrphanWhatTheMeshDeclared(t *testing.T) {
	// The same rule the other way. A host reconciling its carried bundle must not remove what the
	// mesh assigned to this node, or every restart would undo the node's actual work.
	s := State{Resources: []Applied{
		{ID: "store", Type: "container", Target: "mesh-store", Origin: OriginCarried},
		{ID: "workload", Type: "container", Target: "some-app", Origin: OriginDeclared},
	}}

	orphans := s.Orphans(map[string]bool{"store": true}, OriginCarried)
	if len(orphans) != 0 {
		t.Errorf("reconciling the bundle would remove %s, which the mesh declared", orphans[0].ID)
	}
}

func TestStateWrittenBeforeOriginsExistedIsTreatedAsCarried(t *testing.T) {
	// Every resource a host had applied before this field existed came from its bundle, because
	// there was no other way to tell it anything. Guessing the other way would have the first
	// declaration remove the foundation — which is the fault this exists to prevent, arriving
	// through the upgrade that fixes it.
	s := State{Resources: []Applied{{ID: "store", Type: "container", Target: "mesh-store"}}}

	if got := s.Orphans(map[string]bool{}, OriginDeclared); len(got) != 0 {
		t.Errorf("a declaration would remove %s, recorded before origins existed", got[0].ID)
	}
	if got := s.Orphans(map[string]bool{}, OriginCarried); len(got) != 1 {
		t.Error("the bundle cannot remove its own resource, so nothing could ever remove it")
	}
}