package catalogue

import (
	"encoding/json"
	"strings"
	"testing"
)

// Where the answer to a requirement is allowed to live.
//
// A shell, a display server and a private network have to be on the machine that needs them. A
// database does not — it runs somewhere and is reached over the network. Both were written
// `requires`, so both were answered the same way, and the second answer was to install PostgreSQL
// on every machine that runs a web application.

// onNetwork is a set of providers, all of them reachable. Written as a helper because a machine
// that cannot reach the one answering its requirement is its own case, tested separately.
// reachable is this machine, on the private network.
func reachable() Node {
	n := workstation()
	n.At = "workstation.internal"
	return n
}

func onNetwork(nodes ...string) map[string][]Provider {
	out := make([]Provider, 0, len(nodes))
	for _, n := range nodes {
		out = append(out, Provider{Node: n, At: n + ".internal"})
	}
	return map[string][]Provider{"postgres-database": out}
}

func brokeredShelf() map[string]Manifest {
	return shelf(
		Manifest{Module: "postgres", Version: "1", Provides: FromAnywhere("postgres-database")},
		Manifest{Module: "meshboard", Version: "1", Requires: []string{"postgres-database"}},
	)
}

func TestADatabaseIsNotInstalledOnEveryMachineThatUsesOne(t *testing.T) {
	// The fault this whole distinction exists for.
	got, err := Resolve(brokeredShelf(), []string{"meshboard"}, reachable(),
		World{Offered: onNetwork("anchor")})
	if err != nil {
		t.Fatal(err)
	}
	if have := strings.Join(names(got), " "); strings.Contains(have, "postgres") {
		t.Fatalf("using a database installed one here: %s", have)
	}
}

func TestWhatAMachineTakesFromElsewhereIsRecorded(t *testing.T) {
	// It is the only part of a node's set that stops working when a *different* machine goes
	// away, and it is where a credential will have to be handed back.
	got, err := Resolve(brokeredShelf(), []string{"meshboard"}, reachable(),
		World{Offered: onNetwork("anchor")})
	if err != nil {
		t.Fatal(err)
	}
	if len(got.Needs) != 1 {
		t.Fatalf("got %v", got.Needs)
	}
	if got.Needs[0].Name != "postgres-database" || got.Needs[0].From != "anchor" {
		t.Fatalf("got %v", got.Needs[0])
	}
	if got.Needs[0].For != "meshboard" {
		t.Fatalf("it does not say what wanted it: %v", got.Needs[0])
	}
}

func TestNothingInTheMeshProvidingItIsRefusedWithSomewhereToPutIt(t *testing.T) {
	// Refused rather than installed here. Choosing a machine to put a database on is a decision
	// with consequences, and nothing resolving a web application should make it silently.
	_, err := Resolve(brokeredShelf(), []string{"meshboard"}, workstation(), World{})
	if err == nil {
		t.Fatal("a database was found in a mesh that has none")
	}
	if !strings.Contains(err.Error(), "assign") || !strings.Contains(err.Error(), "postgres") {
		t.Fatalf("the refusal does not say what to do: %v", err)
	}
}

func TestTwoNodesProvidingItIsRefusedRatherThanPicked(t *testing.T) {
	// Same rule as everywhere else. Picking one would be a guess about which database a person
	// meant, and the wrong guess is somebody's data in the wrong place.
	_, err := Resolve(brokeredShelf(), []string{"meshboard"}, reachable(),
		World{Offered: onNetwork("anchor", "archive")})
	if err == nil {
		t.Fatal("one of two databases was picked silently")
	}
	for _, want := range []string{"anchor", "archive", "pin"} {
		if !strings.Contains(err.Error(), want) {
			t.Fatalf("the refusal does not name %s: %v", want, err)
		}
	}
}

func TestSayingWhichOneSettlesIt(t *testing.T) {
	got, err := Resolve(brokeredShelf(), []string{"meshboard"}, reachable(),
		World{
			Offered: onNetwork("anchor", "archive"),
			Pinned:  map[string]string{"postgres-database": "archive"},
		})
	if err != nil {
		t.Fatal(err)
	}
	if len(got.Needs) != 1 || got.Needs[0].From != "archive" {
		t.Fatalf("the choice was not taken: %v", got.Needs)
	}
}

func TestBeingPointedAtAMachineThatDoesNotProvideItIsRefused(t *testing.T) {
	// Rather than falling back to one that does. A fallback would quietly move somebody's data to
	// a machine they did not choose, which is the whole reason the question is asked.
	_, err := Resolve(brokeredShelf(), []string{"meshboard"}, reachable(),
		World{
			Offered: onNetwork("anchor", "archive"),
			Pinned:  map[string]string{"postgres-database": "somewhere-else"},
		})
	if err == nil {
		t.Fatal("a machine was silently given a different database from the one chosen")
	}
	if !strings.Contains(err.Error(), "somewhere-else") {
		t.Fatalf("the refusal does not say what was chosen: %v", err)
	}
}

func TestOneProviderDoesNotOverruleAChoice(t *testing.T) {
	// A single answer is normally taken silently. Not when somebody said they wanted a different
	// one -- that is the mesh overruling a person, which it does nowhere else.
	_, err := Resolve(brokeredShelf(), []string{"meshboard"}, reachable(),
		World{
			Offered: onNetwork("anchor"),
			Pinned:  map[string]string{"postgres-database": "archive"},
		})
	if err == nil {
		t.Fatal("the only database was used although another was chosen")
	}
	if !strings.Contains(err.Error(), "only anchor provides it") {
		t.Fatalf("the refusal does not say what is available: %v", err)
	}
}

func TestACatalogueThatDisagreesAboutScopeIsRefused(t *testing.T) {
	// If one module says a database is local and another says it is anywhere, the same
	// requirement means two things depending on which one happens to answer it.
	_, err := Resolve(shelf(
		Manifest{Module: "postgres", Version: "1", Provides: FromAnywhere("postgres-database")},
		Manifest{Module: "sqlite", Version: "1", Provides: Offers("postgres-database")},
		Manifest{Module: "meshboard", Version: "1", Requires: []string{"postgres-database"}},
	), []string{"meshboard"}, workstation(), World{})
	if err == nil {
		t.Fatal("a catalogue that disagrees about where a database lives was accepted")
	}
	if !strings.Contains(err.Error(), "two things") {
		t.Fatalf("unhelpful refusal: %v", err)
	}
}

func TestALocalRequirementIsStillAnsweredLocally(t *testing.T) {
	// The change must not have made everything brokered. A shell is still installed here.
	got, err := Resolve(shelf(
		Manifest{Module: "zsh", Version: "1", Provides: Offers("shell")},
		Manifest{Module: "tools", Version: "1", Requires: []string{"shell"}},
	), []string{"tools"}, workstation(), World{})
	if err != nil {
		t.Fatal(err)
	}
	if have := strings.Join(names(got), " "); !strings.Contains(have, "zsh") {
		t.Fatalf("a shell was not installed on the machine that needs one: %s", have)
	}
}

func TestTheShortFormStillMeansHere(t *testing.T) {
	// `"provides": ["shell"]` must keep meaning what it meant, or every existing manifest
	// silently changes meaning.
	m, err := ParseManifest([]byte(`{"module":"zsh","version":"1","provides":["shell"]}`))
	if err != nil {
		t.Fatal(err)
	}
	if len(m.Provides) != 1 || m.Provides[0].At() != ScopeNode {
		t.Fatalf("a plain name is no longer node-scoped: %v", m.Provides)
	}
}

func TestASiteScopedProvisionIsRefused(t *testing.T) {
	// Meaningful for a claim — one DHCP server per segment — and not yet meaningful for a
	// provision, because nothing knows how to reach "the one at my site".
	_, err := ParseManifest([]byte(
		`{"module":"dns","version":"1","provides":[{"name":"resolver","scope":"site"}]}`))
	if err == nil {
		t.Fatal("a site-scoped provision was accepted")
	}
	if !strings.Contains(err.Error(), "site") {
		t.Fatalf("unhelpful refusal: %v", err)
	}
}

// Being told, which is the difference between knowing and being able to.

func boundShelf() map[string]Manifest {
	return shelf(
		Manifest{Module: "postgres", Version: "1", Provides: FromAnywhere("postgres-database"),
			Serves: map[string]map[string]any{"postgres-database": {"port": 5432, "driver": "postgres"}}},
		Manifest{Module: "meshboard", Version: "1", Requires: []string{"postgres-database"},
			Binds: map[string]string{"postgres-database": "/etc/meshboard/database.json"}},
	)
}

func binding(t *testing.T, out []map[string]any) map[string]any {
	t.Helper()
	for _, r := range out {
		if r["path"] != "/etc/meshboard/database.json" {
			continue
		}
		var parsed map[string]any
		if err := json.Unmarshal([]byte(r["content"].(string)), &parsed); err != nil {
			t.Fatalf("what the app is told is not readable: %v", err)
		}
		return parsed
	}
	t.Fatalf("the app was told nothing: %v", out)
	return nil
}

func TestAnAppIsToldWhereItsDatabaseIs(t *testing.T) {
	// Knowing it needs the anchor's database is useless to the program that needs it unless the
	// program is told. This is the whole point of the field.
	got, err := Resolve(boundShelf(), []string{"meshboard"}, reachable(),
		World{Offered: map[string][]Provider{"postgres-database": {{Node: "anchor", At: "anchor.internal",
			Serves: map[string]any{"port": 5432, "driver": "postgres"}}}}})
	if err != nil {
		t.Fatal(err)
	}
	told := binding(t, mustDeclare(t, got))
	if told["from"] != "anchor" || told["at"] != "anchor.internal" {
		t.Fatalf("it was not told where: %v", told)
	}
	serves, _ := told["serves"].(map[string]any)
	if serves["port"] != float64(5432) || serves["driver"] != "postgres" {
		t.Fatalf("it was not told how: %v", serves)
	}
}

func TestItSaysItCarriesNoCredential(t *testing.T) {
	// A missing field looks like a bug; a stated absence looks like a boundary. Somebody wiring
	// this up must not spend an afternoon looking for the password field.
	got, _ := Resolve(boundShelf(), []string{"meshboard"}, reachable(),
		World{Offered: map[string][]Provider{"postgres-database": {{Node: "anchor", At: "anchor.internal"}}}})
	told := binding(t, mustDeclare(t, got))
	note, _ := told["generated"].(string)
	if !strings.Contains(note, "no credential") {
		t.Fatalf("the file does not say what it does not carry: %v", note)
	}
	for key := range told {
		if strings.Contains(key, "password") || strings.Contains(key, "secret") {
			t.Fatalf("something that looks like a credential appeared: %q", key)
		}
	}
}

func TestTwoMachinesThatCannotReachEachOtherAreRefused(t *testing.T) {
	// An app on one machine and a database on another that share no private network is a mesh
	// that reports itself configured and does not work. Said here rather than discovered as a
	// connection timing out.
	_, err := Resolve(boundShelf(), []string{"meshboard"}, workstation(), // not on the network
		World{Offered: map[string][]Provider{"postgres-database": {{Node: "anchor", At: "anchor.internal"}}}})
	if err == nil {
		t.Fatal("an app was pointed at a database it has no path to")
	}
	if !strings.Contains(err.Error(), "private network") {
		t.Fatalf("the refusal does not say what is wrong: %v", err)
	}
	if !strings.Contains(err.Error(), meshNetwork) {
		t.Fatalf("the refusal does not say what to assign: %v", err)
	}
}

func TestTheProviderBeingOffTheNetworkIsAlsoRefused(t *testing.T) {
	// Both directions, because the failure is identical from either end and the remedy differs.
	_, err := Resolve(boundShelf(), []string{"meshboard"}, reachable(),
		World{Offered: map[string][]Provider{"postgres-database": {{Node: "anchor"}}}})
	if err == nil {
		t.Fatal("an app was pointed at a database that is not on the private network")
	}
	if !strings.Contains(err.Error(), "anchor") {
		t.Fatalf("the refusal does not name the unreachable end: %v", err)
	}
}

func TestBindingSomethingAnsweredHereWritesNothing(t *testing.T) {
	// A file saying "it is on this node" is a fact nobody needs and one more thing to keep true.
	got, err := Resolve(shelf(
		Manifest{Module: "zsh", Version: "1", Provides: Offers("shell")},
		Manifest{Module: "tools", Version: "1", Requires: []string{"shell"},
			Binds: map[string]string{"shell": "/etc/tools/shell.json"}},
	), []string{"tools"}, reachable(), World{})
	if err != nil {
		t.Fatal(err)
	}
	for _, r := range mustDeclare(t, got) {
		if r["path"] == "/etc/tools/shell.json" {
			t.Fatalf("a binding was written for something on this machine: %v", r)
		}
	}
}

func TestBindingWhatYouDoNotRequireIsRefused(t *testing.T) {
	_, err := ParseManifest([]byte(`{"module":"app","version":"1",
		"binds":{"postgres-database":"/etc/app/db.json"}}`))
	if err == nil {
		t.Fatal("a module was told about something it never asked for")
	}
	if !strings.Contains(err.Error(), "does not require") {
		t.Fatalf("unhelpful refusal: %v", err)
	}
}

func TestServingWhatYouDoNotProvideIsRefused(t *testing.T) {
	_, err := ParseManifest([]byte(`{"module":"app","version":"1",
		"serves":{"postgres-database":{"port":5432}}}`))
	if err == nil {
		t.Fatal("a module served something it does not provide")
	}
	if !strings.Contains(err.Error(), "does not provide") {
		t.Fatalf("unhelpful refusal: %v", err)
	}
}