package command

import (
	"context"
	"crypto/rand"
	"crypto/x509"
	"crypto/x509/pkix"
	"encoding/pem"
	"fmt"
	"math/big"
	"net/http"
	"strconv"
	"sync"
	"time"

	"github.com/go-jose/go-jose/v4"
	"github.com/zitadel/logging"

	"github.com/zitadel/zitadel/internal/api/authz"
	api_http "github.com/zitadel/zitadel/internal/api/http"
	"github.com/zitadel/zitadel/internal/cache/connector"
	"github.com/zitadel/zitadel/internal/command/preparation"
	sd "github.com/zitadel/zitadel/internal/config/systemdefaults"
	"github.com/zitadel/zitadel/internal/crypto"
	"github.com/zitadel/zitadel/internal/domain"
	"github.com/zitadel/zitadel/internal/eventstore"
	"github.com/zitadel/zitadel/internal/id"
	"github.com/zitadel/zitadel/internal/notification/senders"
	"github.com/zitadel/zitadel/internal/static"
	"github.com/zitadel/zitadel/internal/telemetry/tracing"
	webauthn_helper "github.com/zitadel/zitadel/internal/webauthn"
	"github.com/zitadel/zitadel/internal/zerrors"
)

type Commands struct {
	httpClient *http.Client

	jobs sync.WaitGroup

	checkPermission             domain.PermissionCheck
	newEncryptedCode            encrypedCodeFunc
	newEncryptedCodeWithDefault encryptedCodeWithDefaultFunc
	newHashedSecret             hashedSecretFunc

	eventstore     *eventstore.Eventstore
	static         static.Storage
	idGenerator    id.Generator
	zitadelRoles   []authz.RoleMapping
	externalDomain string
	externalSecure bool
	externalPort   uint16

	idpConfigEncryption             crypto.EncryptionAlgorithm
	smtpEncryption                  crypto.EncryptionAlgorithm
	smsEncryption                   crypto.EncryptionAlgorithm
	userEncryption                  crypto.EncryptionAlgorithm
	targetEncryption                crypto.EncryptionAlgorithm
	userPasswordHasher              *crypto.Hasher
	secretHasher                    *crypto.Hasher
	machineKeySize                  int
	applicationKeySize              int
	domainVerificationAlg           crypto.EncryptionAlgorithm
	domainVerificationGenerator     crypto.Generator
	domainVerificationValidator     func(domain, token, verifier string, checkType api_http.CheckType) error
	sessionTokenCreator             func(sessionID string) (id string, token string, err error)
	sessionTokenVerifier            func(ctx context.Context, sessionToken, sessionID, tokenID string) (err error)
	defaultAccessTokenLifetime      time.Duration
	defaultRefreshTokenLifetime     time.Duration
	defaultRefreshTokenIdleLifetime time.Duration
	phoneCodeVerifier               func(ctx context.Context, id string) (senders.CodeGenerator, error)

	multifactors            domain.MultifactorConfigs
	webauthnConfig          *webauthn_helper.Config
	keySize                 int
	keyAlgorithm            crypto.EncryptionAlgorithm
	certificateAlgorithm    crypto.EncryptionAlgorithm
	certKeySize             int
	privateKeyLifetime      time.Duration
	publicKeyLifetime       time.Duration
	certificateLifetime     time.Duration
	defaultSecretGenerators *SecretGenerators

	samlCertificateAndKeyGenerator func(id string) ([]byte, []byte, error)
	webKeyGenerator                func(keyID string, alg crypto.EncryptionAlgorithm, genConfig crypto.WebKeyConfig) (encryptedPrivate *crypto.CryptoValue, public *jose.JSONWebKey, err error)

	GrpcMethodExisting     func(method string) bool
	GrpcServiceExisting    func(method string) bool
	ActionFunctionExisting func(function string) bool
	EventExisting          func(event string) bool
	EventGroupExisting     func(group string) bool

	GenerateDomain func(instanceName, domain string) (string, error)

	caches *Caches
	// Store instance IDs where all milestones are reached (except InstanceDeleted).
	// These instance's milestones never need to be invalidated,
	// so the query and cache overhead can completely eliminated.
	milestonesCompleted sync.Map
}

func StartCommands(
	ctx context.Context,
	es *eventstore.Eventstore,
	cacheConnectors connector.Connectors,
	defaults sd.SystemDefaults,
	zitadelRoles []authz.RoleMapping,
	staticStore static.Storage,
	webAuthN *webauthn_helper.Config,
	externalDomain string,
	externalSecure bool,
	externalPort uint16,
	idpConfigEncryption, otpEncryption, smtpEncryption, smsEncryption, userEncryption, domainVerificationEncryption, oidcEncryption, samlEncryption, targetEncryption crypto.EncryptionAlgorithm,
	httpClient *http.Client,
	permissionCheck domain.PermissionCheck,
	sessionTokenVerifier func(ctx context.Context, sessionToken string, sessionID string, tokenID string) (err error),
	defaultAccessTokenLifetime,
	defaultRefreshTokenLifetime,
	defaultRefreshTokenIdleLifetime time.Duration,
	defaultSecretGenerators *SecretGenerators,
) (repo *Commands, err error) {
	if externalDomain == "" {
		return nil, zerrors.ThrowInvalidArgument(nil, "COMMAND-Df21s", "no external domain specified")
	}
	idGenerator := id.SonyFlakeGenerator()
	// reuse the oidcEncryption to be able to handle both tokens in the interceptor later on
	sessionAlg := oidcEncryption

	secretHasher, err := defaults.SecretHasher.NewHasher()
	if err != nil {
		return nil, fmt.Errorf("secret hasher: %w", err)
	}
	userPasswordHasher, err := defaults.PasswordHasher.NewHasher()
	if err != nil {
		return nil, fmt.Errorf("password hasher: %w", err)
	}
	caches, err := startCaches(ctx, cacheConnectors)
	if err != nil {
		return nil, fmt.Errorf("caches: %w", err)
	}
	repo = &Commands{
		eventstore:                      es,
		static:                          staticStore,
		idGenerator:                     idGenerator,
		zitadelRoles:                    zitadelRoles,
		externalDomain:                  externalDomain,
		externalSecure:                  externalSecure,
		externalPort:                    externalPort,
		keySize:                         defaults.KeyConfig.Size,
		certKeySize:                     defaults.KeyConfig.CertificateSize,
		privateKeyLifetime:              defaults.KeyConfig.PrivateKeyLifetime,
		publicKeyLifetime:               defaults.KeyConfig.PublicKeyLifetime,
		certificateLifetime:             defaults.KeyConfig.CertificateLifetime,
		idpConfigEncryption:             idpConfigEncryption,
		smtpEncryption:                  smtpEncryption,
		smsEncryption:                   smsEncryption,
		userEncryption:                  userEncryption,
		targetEncryption:                targetEncryption,
		userPasswordHasher:              userPasswordHasher,
		secretHasher:                    secretHasher,
		machineKeySize:                  int(defaults.SecretGenerators.MachineKeySize),
		applicationKeySize:              int(defaults.SecretGenerators.ApplicationKeySize),
		domainVerificationAlg:           domainVerificationEncryption,
		domainVerificationGenerator:     crypto.NewEncryptionGenerator(defaults.DomainVerification.VerificationGenerator, domainVerificationEncryption),
		domainVerificationValidator:     api_http.ValidateDomain,
		keyAlgorithm:                    oidcEncryption,
		certificateAlgorithm:            samlEncryption,
		webauthnConfig:                  webAuthN,
		httpClient:                      httpClient,
		checkPermission:                 permissionCheck,
		newEncryptedCode:                newEncryptedCode,
		newEncryptedCodeWithDefault:     newEncryptedCodeWithDefaultConfig,
		sessionTokenCreator:             sessionTokenCreator(idGenerator, sessionAlg),
		sessionTokenVerifier:            sessionTokenVerifier,
		defaultAccessTokenLifetime:      defaultAccessTokenLifetime,
		defaultRefreshTokenLifetime:     defaultRefreshTokenLifetime,
		defaultRefreshTokenIdleLifetime: defaultRefreshTokenIdleLifetime,
		defaultSecretGenerators:         defaultSecretGenerators,
		samlCertificateAndKeyGenerator:  samlCertificateAndKeyGenerator(defaults.KeyConfig.CertificateSize, defaults.KeyConfig.CertificateLifetime),
		webKeyGenerator:                 crypto.GenerateEncryptedWebKey,
		// always true for now until we can check with an eventlist
		EventExisting: func(event string) bool { return true },
		// always true for now until we can check with an eventlist
		EventGroupExisting:     func(group string) bool { return true },
		GrpcServiceExisting:    func(service string) bool { return false },
		GrpcMethodExisting:     func(method string) bool { return false },
		ActionFunctionExisting: domain.FunctionExists(),
		multifactors: domain.MultifactorConfigs{
			OTP: domain.OTPConfig{
				CryptoMFA: otpEncryption,
				Issuer:    defaults.Multifactors.OTP.Issuer,
			},
		},
		GenerateDomain: domain.NewGeneratedInstanceDomain,
		caches:         caches,
	}

	if defaultSecretGenerators != nil && defaultSecretGenerators.ClientSecret != nil {
		repo.newHashedSecret = newHashedSecretWithDefault(secretHasher, defaultSecretGenerators.ClientSecret)
	}
	repo.phoneCodeVerifier = repo.phoneCodeVerifierFromConfig
	return repo, nil
}

type AppendReducer interface {
	AppendEvents(...eventstore.Event)
	// TODO: Why is it allowed to return an error here?
	Reduce() error
}

func (c *Commands) pushAppendAndReduce(ctx context.Context, object AppendReducer, cmds ...eventstore.Command) error {
	if len(cmds) == 0 {
		return nil
	}
	events, err := c.eventstore.Push(ctx, cmds...)
	if err != nil {
		return err
	}
	return AppendAndReduce(object, events...)
}

type AppendReducerDetails interface {
	AppendEvents(...eventstore.Event)
	// TODO: Why is it allowed to return an error here?
	Reduce() error
	GetWriteModel() *eventstore.WriteModel
}

func (c *Commands) pushAppendAndReduceDetails(ctx context.Context, object AppendReducerDetails, cmds ...eventstore.Command) (*domain.ObjectDetails, error) {
	if err := c.pushAppendAndReduce(ctx, object, cmds...); err != nil {
		return nil, err
	}
	return writeModelToObjectDetails(object.GetWriteModel()), nil
}

func AppendAndReduce(object AppendReducer, events ...eventstore.Event) error {
	object.AppendEvents(events...)
	return object.Reduce()
}

func queryAndReduce(ctx context.Context, filter preparation.FilterToQueryReducer, wm eventstore.QueryReducer) error {
	events, err := filter(ctx, wm.Query())
	if err != nil {
		return err
	}
	if len(events) == 0 {
		return nil
	}
	wm.AppendEvents(events...)
	return wm.Reduce()
}

type existsWriteModel interface {
	Exists() bool
	eventstore.QueryReducer
}

func exists(ctx context.Context, filter preparation.FilterToQueryReducer, wm existsWriteModel) (bool, error) {
	err := queryAndReduce(ctx, filter, wm)
	if err != nil {
		return false, err
	}
	return wm.Exists(), nil
}

func samlCertificateAndKeyGenerator(keySize int, lifetime time.Duration) func(id string) ([]byte, []byte, error) {
	return func(id string) ([]byte, []byte, error) {
		priv, pub, err := crypto.GenerateKeyPair(keySize)
		if err != nil {
			return nil, nil, err
		}

		serial, err := strconv.Atoi(id)
		if err != nil {
			return nil, nil, err
		}
		now := time.Now()
		template := x509.Certificate{
			SerialNumber: big.NewInt(int64(serial)),
			Subject: pkix.Name{
				Organization: []string{"ZITADEL"},
				SerialNumber: id,
			},
			NotBefore:             now,
			NotAfter:              now.Add(lifetime),
			KeyUsage:              x509.KeyUsageKeyEncipherment | x509.KeyUsageDigitalSignature,
			ExtKeyUsage:           []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
			BasicConstraintsValid: true,
		}

		derBytes, err := x509.CreateCertificate(rand.Reader, &template, &template, pub, priv)
		if err != nil {
			return nil, nil, zerrors.ThrowInternalf(err, "COMMAND-x92u101j", "failed to create certificate")
		}

		keyBlock := &pem.Block{Type: "RSA PRIVATE KEY", Bytes: x509.MarshalPKCS1PrivateKey(priv)}
		certBlock := &pem.Block{Type: "CERTIFICATE", Bytes: derBytes}
		return pem.EncodeToMemory(keyBlock), pem.EncodeToMemory(certBlock), nil
	}
}

// Close blocks until all async jobs are finished,
// the context expires or after eventstore.PushTimeout.
func (c *Commands) Close(ctx context.Context) error {
	if c.eventstore.PushTimeout != 0 {
		var cancel context.CancelFunc
		ctx, cancel = context.WithTimeout(ctx, c.eventstore.PushTimeout)
		defer cancel()
	}

	done := make(chan struct{})
	go func() {
		c.jobs.Wait()
		close(done)
	}()
	select {
	case <-done:
		return nil
	case <-ctx.Done():
		return ctx.Err()
	}
}

// asyncPush attempts to push events to the eventstore in a separate Go routine.
// This can be used to speed up request times when the outcome of the push is
// not important for business logic but have a pure logging function.
// For example this can be used for Secret Check Success and Failed events.
// On push error, a log line describing the error will be emitted.
func (c *Commands) asyncPush(ctx context.Context, cmds ...eventstore.Command) {
	// Create a new context, as the request scoped context might get
	// canceled before we where able to push.
	// The eventstore has its own PushTimeout setting,
	// so we don't need to have a context with timeout here.
	ctx = context.WithoutCancel(ctx)

	c.jobs.Add(1)

	go func() {
		defer c.jobs.Done()
		localCtx, span := tracing.NewSpan(ctx)

		_, err := c.eventstore.Push(localCtx, cmds...)
		if err != nil {
			for _, cmd := range cmds {
				logging.WithError(err).Warnf("could not push event %q", cmd.Type())
			}
		}

		span.EndWithError(err)
	}()
}