package main

import (
	"crypto/ed25519"
	"crypto/rand"
	"crypto/sha256"
	"crypto/tls"
	"crypto/x509"
	"crypto/x509/pkix"
	"encoding/hex"
	"math/big"
	"net"
	"os"
	"path/filepath"
	"strings"
	"testing"
	"time"

	"github.com/novox/mesh-controller/internal/broker"
)

// Where a builder publishes.
//
// Preferably from the mesh: a builder that is a module requires an artifact store, and the mesh
// writes it a binding saying which machine answers and on what port. Reading it means the address
// is not a setting somebody keeps in step by hand.

func binding(t *testing.T, body string) string {
	t.Helper()
	path := filepath.Join(t.TempDir(), "artifact-store.json")
	if err := os.WriteFile(path, []byte(body), 0o644); err != nil {
		t.Fatal(err)
	}
	return path
}

func TestTheMeshSaysWhereToPublish(t *testing.T) {
	t.Setenv("MESH_BINDING", binding(t, `{"binding":1,"provision":"artifact-store",
		"from":"anchor","at":"anchor.internal","serves":{"port":5000,"scheme":"http"}}`))
	where, err := whereToPublish()
	if err != nil {
		t.Fatal(err)
	}
	if where != "anchor.internal:5000" {
		t.Fatalf("got %q", where)
	}
}

func TestABindingWithNoAddressIsRefused(t *testing.T) {
	// The provider is not on the private network, so there is no name to reach it by. Falling
	// back to anything would publish to a store on the wrong machine and be found out much later.
	t.Setenv("MESH_BINDING", binding(t, `{"binding":1,"from":"anchor","serves":{"port":5000}}`))
	_, err := whereToPublish()
	if err == nil {
		t.Fatal("a binding with nowhere to reach was accepted")
	}
	if !strings.Contains(err.Error(), "anchor") {
		t.Fatalf("the failure does not name the machine: %v", err)
	}
}

func TestABindingWithNoPortIsRefused(t *testing.T) {
	t.Setenv("MESH_BINDING", binding(t, `{"binding":1,"from":"a","at":"a.internal","serves":{}}`))
	if _, err := whereToPublish(); err == nil {
		t.Fatal("a binding saying nothing about a port was accepted")
	}
}

func TestTheVariableStillWorksForABuilderRunByAPerson(t *testing.T) {
	// Which is how this started and how it is still run while being developed.
	t.Setenv("MESH_BINDING", "")
	t.Setenv("MESH_REGISTRY", "127.0.0.1:5000")
	where, err := whereToPublish()
	if err != nil {
		t.Fatal(err)
	}
	if where != "127.0.0.1:5000" {
		t.Fatalf("got %q", where)
	}
}

func TestNeitherIsRefusedRatherThanGuessed(t *testing.T) {
	t.Setenv("MESH_BINDING", "")
	t.Setenv("MESH_REGISTRY", "")
	if _, err := whereToPublish(); err == nil {
		t.Fatal("a builder with nowhere to publish reported somewhere")
	}
}

func TestTheCredentialComesFromAFileTheMeshSealed(t *testing.T) {
	// A builder that is a module is given its credential the way every module is: sealed to the
	// machine and written by the host. An environment variable instead would put the one copy
	// that matters through a terminal and a process listing.
	path := filepath.Join(t.TempDir(), "broker")
	if err := os.WriteFile(path, []byte("amqps://a-builder:secret@broker.internal:5671/\n"), 0o600); err != nil {
		t.Fatal(err)
	}
	t.Setenv("MESH_BROKER_FILE", path)
	t.Setenv("MESH_BROKER_AMQP", "amqp://should-not-be-used@nowhere/")

	got, err := brokerFrom()
	if err != nil {
		t.Fatal(err)
	}
	if got.URL != "amqps://a-builder:secret@broker.internal:5671/" {
		t.Fatalf("got %q", got.URL)
	}
}

// The credential the mesh seals carries what to check the broker's certificate against, because a
// mesh's broker presents a certificate of the mesh's own and no public trust store has it. A URL
// alone can only reach a broker somebody else vouches for.
func TestTheSealedCredentialCarriesWhatVerifiesTheBroker(t *testing.T) {
	path := filepath.Join(t.TempDir(), "broker")
	if err := os.WriteFile(path, []byte(
		`{"url":"amqps://a-builder:secret@broker.internal:5671/","fingerprint":"abc123"}`),
		0o600); err != nil {
		t.Fatal(err)
	}
	t.Setenv("MESH_BROKER_FILE", path)
	t.Setenv("MESH_BROKER_AMQP", "")

	got, err := brokerFrom()
	if err != nil {
		t.Fatal(err)
	}
	if got.URL != "amqps://a-builder:secret@broker.internal:5671/" {
		t.Fatalf("the url was lost: %q", got.URL)
	}
	if got.Fingerprint != "abc123" {
		t.Fatal("the builder was given nothing to check the broker against, so it can only " +
			"connect to a broker some public authority vouches for")
	}
}

func TestAnEmptyCredentialFileIsRefused(t *testing.T) {
	// Otherwise the builder connects as nobody and is refused, with the reason three layers away.
	path := filepath.Join(t.TempDir(), "broker")
	if err := os.WriteFile(path, []byte("\n"), 0o600); err != nil {
		t.Fatal(err)
	}
	t.Setenv("MESH_BROKER_FILE", path)
	t.Setenv("MESH_BROKER_AMQP", "")
	if _, err := brokerFrom(); err == nil {
		t.Fatal("an empty credential was accepted")
	}
}

func TestABuilderWithNoCredentialAtAllSaysSo(t *testing.T) {
	t.Setenv("MESH_BROKER_FILE", "")
	t.Setenv("MESH_BROKER_AMQP", "")
	if _, err := brokerFrom(); err == nil {
		t.Fatal("a builder with no broker reported one")
	}
}

// The pin is compared in the spelling the mesh writes it.
//
// A bare digest against a written fingerprint never matches, and the failure is indistinguishable
// from being pointed at the wrong broker — which is the one thing this check exists to report
// truthfully. It cost a lab run.
func TestThePinIsComparedInTheSpellingTheMeshWritesIt(t *testing.T) {
	certificate, key := aServerCertificate(t)
	der := certificate.Certificate[0]
	sum := sha256.Sum256(der)
	written := "sha256:" + hex.EncodeToString(sum[:])

	listener, err := tls.Listen("tcp", "127.0.0.1:0", &tls.Config{
		Certificates: []tls.Certificate{certificate}, MinVersion: tls.VersionTLS12,
	})
	if err != nil {
		t.Fatal(err)
	}
	defer listener.Close()
	go func() {
		for {
			conn, err := listener.Accept()
			if err != nil {
				return
			}
			_ = conn.(*tls.Conn).Handshake()
			conn.Close()
		}
	}()
	_ = key

	// The pin the mesh wrote must be accepted.
	if err := handshakeWith(listener.Addr().String(), written); err != nil {
		t.Fatalf("the broker this builder was told about was refused: %v", err)
	}
	// And a different one refused, or the check reports nothing.
	other := "sha256:" + strings.Repeat("ab", 32)
	if err := handshakeWith(listener.Addr().String(), other); err == nil {
		t.Fatal("a broker this builder was not told about was accepted")
	}
}

// handshakeWith runs the pin check the builder dials with against an address.
func handshakeWith(address, pin string) error {
	conn, err := tls.Dial("tcp", address, broker.PinnedToFingerprint(pin))
	if err != nil {
		return err
	}
	return conn.Close()
}

func aServerCertificate(t *testing.T) (tls.Certificate, ed25519.PrivateKey) {
	t.Helper()
	public, private, err := ed25519.GenerateKey(rand.Reader)
	if err != nil {
		t.Fatal(err)
	}
	template := &x509.Certificate{
		SerialNumber: big.NewInt(1),
		Subject:      pkix.Name{CommonName: "a broker"},
		NotBefore:    time.Now().Add(-time.Hour),
		NotAfter:     time.Now().Add(time.Hour),
		IPAddresses:  []net.IP{net.ParseIP("127.0.0.1")},
	}
	der, err := x509.CreateCertificate(rand.Reader, template, template, public, private)
	if err != nil {
		t.Fatal(err)
	}
	return tls.Certificate{Certificate: [][]byte{der}, PrivateKey: private}, private
}