// Copyright © 2023 Ory Corp
// SPDX-License-Identifier: Apache-2.0

package code

import (
	"context"
	"encoding/json"
	"net/http"
	"time"

	"github.com/gofrs/uuid"
	"github.com/pkg/errors"
	"go.opentelemetry.io/otel/attribute"

	"github.com/ory/kratos/identity"
	"github.com/ory/kratos/schema"
	"github.com/ory/kratos/selfservice/flow"
	"github.com/ory/kratos/selfservice/flow/settings"
	"github.com/ory/kratos/selfservice/flow/verification"
	"github.com/ory/kratos/text"
	"github.com/ory/kratos/ui/container"
	"github.com/ory/kratos/ui/node"
	"github.com/ory/kratos/x"
	"github.com/ory/x/decoderx"
	"github.com/ory/x/otelx"
	"github.com/ory/x/sqlcon"
	"github.com/ory/x/sqlxx"
)

func (s *Strategy) VerificationStrategyID() string {
	return string(verification.VerificationStrategyCode)
}

// PopulateVerificationMethod set's the appropriate UI nodes on this flow
//
// If the flow's state is `sent_email`, the `code` input and the success notification is set
// Otherwise, the default email input is added.
// If the flow is a browser flow, the CSRF token is added to the UI.
func (s *Strategy) PopulateVerificationMethod(r *http.Request, f *verification.Flow) error {
	return s.PopulateMethod(r, f)
}

func (s *Strategy) decodeVerification(r *http.Request) (*updateVerificationFlowWithCodeMethod, error) {
	var body updateVerificationFlowWithCodeMethod

	compiler, err := decoderx.HTTPRawJSONSchemaCompiler(verificationMethodSchema)
	if err != nil {
		return nil, errors.WithStack(err)
	}

	if err := decoderx.Decode(r, &body, compiler,
		decoderx.HTTPDecoderUseQueryAndBody(),
		decoderx.HTTPKeepRequestBody(true),
		decoderx.HTTPDecoderAllowedMethods("POST", "GET"),
		decoderx.HTTPDecoderSetValidatePayloads(true),
		decoderx.HTTPDecoderJSONFollowsFormFormat(),
	); err != nil {
		return nil, errors.WithStack(err)
	}

	return &body, nil
}

// handleVerificationError is a convenience function for handling all types of errors that may occur (e.g. validation error).
func (s *Strategy) handleVerificationError(r *http.Request, f *verification.Flow, body *updateVerificationFlowWithCodeMethod, err error) error {
	if f != nil {
		f.UI.SetCSRF(s.deps.GenerateCSRFToken(r))
		email := ""
		if body != nil {
			email = body.Email
		}
		label := text.NewInfoNodeInputEmail()
		inputType := node.InputAttributeTypeEmail
		if channels, chErr := s.deps.Config().CourierChannels(r.Context()); chErr == nil {
			for _, ch := range channels {
				if ch.ID == "sms" {
					label = text.NewInfoNodeInputEmailOrPhone()
					inputType = node.InputAttributeTypeText
					break
				}
			}
		}
		f.UI.GetNodes().Upsert(
			node.NewInputField("email", email, node.CodeGroup, inputType, node.WithRequiredInputAttribute).WithMetaLabel(label),
		)
	}

	return err
}

// swagger:model updateVerificationFlowWithCodeMethod
type updateVerificationFlowWithCodeMethod struct {
	// The email address or phone number to verify
	//
	// If the provided address belongs to a valid account, a verification email or SMS will be sent.
	//
	// If you want to notify the email address if the account does not exist, see
	// the [notify_unknown_recipients flag](https://www.ory.com/docs/kratos/self-service/flows/verify-email-account-activation#attempted-verification-notifications)
	//
	// If a code was already sent, including this field in the payload will invalidate the sent code and re-send a new code.
	//
	// required: false
	Email string `form:"email" json:"email"`

	// Sending the anti-csrf token is only required for browser login flows.
	CSRFToken string `form:"csrf_token" json:"csrf_token"`

	// Method is the method that should be used for this verification flow
	//
	// Allowed values are `link` and `code`.
	//
	// required: true
	Method verification.VerificationStrategy `json:"method"`

	// Code from the recovery email
	//
	// If you want to submit a code, use this field, but make sure to _not_ include the email field, as well.
	//
	// required: false
	Code string `json:"code" form:"code"`

	// The id of the flow
	Flow string `json:"-" form:"-"`

	// Transient data to pass along to any webhooks
	//
	// required: false
	TransientPayload json.RawMessage `json:"transient_payload,omitempty" form:"transient_payload"`
}

// getMethod returns the method of this submission or "" if no method could be found
func (body *updateVerificationFlowWithCodeMethod) getMethod() verification.VerificationStrategy {
	if body.Method != "" {
		return body.Method
	}
	if body.Code != "" {
		return verification.VerificationStrategyCode
	}

	return ""
}

func (s *Strategy) Verify(w http.ResponseWriter, r *http.Request, f *verification.Flow) (err error) {
	ctx, span := s.deps.Tracer(r.Context()).Tracer().Start(r.Context(), "selfservice.strategy.code.Strategy.Verify")
	span.SetAttributes(attribute.String("selfservice_flows_verification_use", s.deps.Config().SelfServiceFlowVerificationUse(ctx)))
	defer otelx.End(span, &err)

	body, err := s.decodeVerification(r)
	if err != nil {
		return s.handleVerificationError(r, nil, body, err)
	}

	f.TransientPayload = body.TransientPayload

	if err := flow.MethodEnabledAndAllowed(ctx, f.GetFlowName(), s.VerificationStrategyID(), string(body.getMethod()), s.deps); err != nil {
		return s.handleVerificationError(r, f, body, err)
	}

	if err := f.Valid(s.deps.Clock()); err != nil {
		return s.handleVerificationError(r, f, body, err)
	}

	switch f.State {
	case flow.StateChooseMethod:
		fallthrough
	case flow.StateEmailSent:
		return s.verificationHandleFormSubmission(ctx, w, r, f, body)
	case flow.StatePassedChallenge:
		return s.retryVerificationFlowWithMessage(ctx, w, r, f.Type, text.NewErrorValidationVerificationRetrySuccess())
	default:
		return s.retryVerificationFlowWithMessage(ctx, w, r, f.Type, text.NewErrorValidationVerificationStateFailure())
	}
}

func (s *Strategy) handleLinkClick(ctx context.Context, w http.ResponseWriter, r *http.Request, f *verification.Flow, code string) error {
	// Pre-fill the code
	if codeField := f.UI.Nodes.Find("code"); codeField != nil {
		codeField.Attributes.SetValue(code)
	}

	// In the verification flow, we can't enforce CSRF if the flow is opened from an email, so we initialize the CSRF
	// token here, so all subsequent interactions are protected
	csrfToken := s.deps.CSRFHandler().RegenerateToken(w, r)
	f.UI.SetCSRF(csrfToken)
	f.CSRFToken = csrfToken

	if err := s.deps.VerificationFlowPersister().UpdateVerificationFlow(ctx, f); err != nil {
		return err
	}

	// we always redirect to the browser UI here to allow API flows to complete aswell
	// TODO: In the future, we might want to redirect to a custom URI scheme here, to allow to open an app on the device of
	// the user to handle the flow directly.
	http.Redirect(w, r, f.AppendTo(s.deps.Config().SelfServiceFlowVerificationUI(ctx)).String(), http.StatusSeeOther)

	return errors.WithStack(flow.ErrCompletedByStrategy)
}

func (s *Strategy) verificationHandleFormSubmission(ctx context.Context, w http.ResponseWriter, r *http.Request, f *verification.Flow, body *updateVerificationFlowWithCodeMethod) error {
	if len(body.Code) > 0 {
		if r.Method == http.MethodGet {
			// Special case: in the code strategy we send out links as well, that contain the code
			return s.handleLinkClick(ctx, w, r, f, body.Code)
		}

		// If not GET: try to use the submitted code
		return s.verificationUseCode(ctx, w, r, body.Code, f)
	} else if len(body.Email) == 0 {
		// If no code and no email was provided, fail with a validation error
		return s.handleVerificationError(r, f, body, schema.NewRequiredError("#/email", "email"))
	}

	if err := flow.EnsureCSRF(s.deps, r, f.Type, s.deps.Config().DisableAPIFlowEnforcement(ctx), s.deps.GenerateCSRFToken, body.CSRFToken); err != nil {
		return s.handleVerificationError(r, f, body, err)
	}

	if err := s.deps.VerificationCodePersister().DeleteVerificationCodesOfFlow(ctx, f.ID); err != nil {
		return s.handleVerificationError(r, f, body, err)
	}

	via := hackyInferChannel(body.Email)

	ptc, ptcErr := s.deps.PendingTraitsChangePersister().GetPendingTraitsChangeByVerificationFlow(ctx, f.ID)
	if ptcErr != nil {
		if !errors.Is(ptcErr, sqlcon.ErrNoRows()) {
			return s.handleVerificationError(r, f, body, ptcErr)
		}
		if err := s.deps.CodeSender().SendVerificationCode(ctx, f, via, body.Email); err != nil {
			if !errors.Is(err, ErrUnknownAddress()) {
				return s.handleVerificationError(r, f, body, err)
			}
			// Continue execution
		}
	} else {
		// Re-check whether the proposed address is still unclaimed before resending.
		// Another identity may have claimed it between the failed code submission and this resend.
		existingAddr, addrErr := s.deps.PrivilegedIdentityPool().FindVerifiableAddressByValue(ctx, ptc.NewAddressVia, ptc.NewAddressValue)
		if addrErr != nil && !errors.Is(addrErr, sqlcon.ErrNoRows()) {
			return s.handleVerificationError(r, f, body, addrErr)
		}
		if addrErr == nil && existingAddr.IdentityID != ptc.IdentityID {
			if err := s.updateVerificationFlowWithMessage(ctx, w, r, f, text.NewErrorValidationDuplicateCredentials(), http.StatusBadRequest); err != nil {
				return s.retryVerificationFlowWithError(ctx, w, r, f.Type, err)
			}
			return errors.WithStack(flow.ErrCompletedByStrategy)
		}

		proposedIdentity, err := s.deps.IdentityPool().GetIdentity(ctx, ptc.IdentityID, identity.ExpandDefault)
		if err != nil {
			return s.handleVerificationError(r, f, body, err)
		}
		if err := s.SendVerificationCode(ctx, f, proposedIdentity, ptc); err != nil {
			return s.handleVerificationError(r, f, body, err)
		}
	}

	f.State = flow.StateEmailSent

	if err := s.PopulateVerificationMethod(r, f); err != nil {
		return s.handleVerificationError(r, f, body, err)
	}

	// PopulateVerificationMethod sets the email "code sent" message unconditionally.
	// Override it with the message that matches the channel the code was sent over.
	f.UI.Messages.Set(text.VerificationCodeSentMessage(via))

	if body.Email != "" {
		f.UI.Nodes.Append(
			node.NewInputField("email", body.Email, node.CodeGroup, node.InputAttributeTypeSubmit).
				WithMetaLabel(text.NewInfoNodeResendOTP()),
		)
	}

	if err := s.deps.VerificationFlowPersister().UpdateVerificationFlow(ctx, f); err != nil {
		return s.handleVerificationError(r, f, body, err)
	}

	return nil
}

func (s *Strategy) updateVerificationFlowWithMessage(ctx context.Context, w http.ResponseWriter, r *http.Request, f *verification.Flow, message *text.Message, statusCode int) error {
	f.UI.Messages.Clear()
	f.UI.Messages.Add(message)

	if err := s.deps.VerificationFlowPersister().UpdateVerificationFlow(ctx, f); err != nil {
		return err
	}

	if x.IsBrowserRequest(r) {
		http.Redirect(w, r, f.AppendTo(s.deps.Config().SelfServiceFlowVerificationUI(ctx)).String(), http.StatusSeeOther)
	} else {
		s.deps.Writer().WriteCode(w, r, statusCode, f)
	}
	return nil
}

func (s *Strategy) verificationUseCode(ctx context.Context, w http.ResponseWriter, r *http.Request, codeString string, f *verification.Flow) error {
	code, err := s.deps.VerificationCodePersister().UseVerificationCode(ctx, f.ID, codeString)
	if errors.Is(err, ErrCodeNotFound()) {
		if err := s.updateVerificationFlowWithMessage(ctx, w, r, f, text.NewErrorValidationVerificationCodeInvalidOrAlreadyUsed(), http.StatusOK); err != nil {
			return s.retryVerificationFlowWithError(ctx, w, r, f.Type, err)
		}
		return errors.WithStack(flow.ErrCompletedByStrategy)
	} else if err != nil {
		return s.retryVerificationFlowWithError(ctx, w, r, f.Type, err)
	}

	var identityID uuid.UUID
	var addressVia string
	var ptcIdentity *identity.Identity

	if code.VerifiableAddress == nil {
		// Pending-change path: no persisted address — look up by verification flow ID.
		ptc, ptcErr := s.deps.PendingTraitsChangePersister().GetPendingTraitsChangeByVerificationFlow(ctx, f.ID)
		if ptcErr != nil {
			if !errors.Is(ptcErr, sqlcon.ErrNoRows()) {
				return s.retryVerificationFlowWithError(ctx, w, r, f.Type, ptcErr)
			}
			// PTC vanished between code issuance and use — show the standard
			// "invalid or already used" message.
			if err := s.updateVerificationFlowWithMessage(ctx, w, r, f, text.NewErrorValidationVerificationCodeInvalidOrAlreadyUsed(), http.StatusOK); err != nil {
				return s.retryVerificationFlowWithError(ctx, w, r, f.Type, err)
			}
			return errors.WithStack(flow.ErrCompletedByStrategy)
		}

		// Security note: the verification flow is unauthenticated by design. The
		// user clicks a link from email/SMS. The pending change is bound to the
		// identity via IdentityID, but we cannot validate session ownership at
		// completion time. The security model relies on:
		//   1. The verification code is sent to the *new* address (attacker needs inbox access).
		//   2. The verification flow has a TTL (enforced by the flow handler).
		//   3. The one-time code is consumed on use (cannot be replayed).
		// Creation of pending changes is gated by a privileged session check;
		// ApplyPendingTraitsChange revalidates the session atomically with the apply.
		updatedIdentity, applyErr := s.deps.SettingsHookExecutor().ApplyPendingTraitsChange(ctx, w, r, ptc)
		if applyErr != nil {
			if errors.Is(applyErr, identity.ErrConcurrentModification) ||
				errors.Is(applyErr, settings.ErrPendingTraitsChangeSessionInvalid) {
				if err := s.updateVerificationFlowWithMessage(ctx, w, r, f, text.NewErrorValidationVerificationCodeInvalidOrAlreadyUsed(), http.StatusOK); err != nil {
					return s.retryVerificationFlowWithError(ctx, w, r, f.Type, err)
				}
				return errors.WithStack(flow.ErrCompletedByStrategy)
			}
			if errors.Is(applyErr, sqlcon.ErrUniqueViolation()) {
				if err := s.updateVerificationFlowWithMessage(ctx, w, r, f, text.NewErrorValidationDuplicateCredentials(), http.StatusBadRequest); err != nil {
					return s.retryVerificationFlowWithError(ctx, w, r, f.Type, err)
				}
				return errors.WithStack(flow.ErrCompletedByStrategy)
			}
			return s.retryVerificationFlowWithError(ctx, w, r, f.Type, applyErr)
		}

		ptcIdentity = updatedIdentity
		addressVia = ptc.NewAddressVia
		identityID = ptc.IdentityID
	} else {
		// Normal path: update the existing verifiable address directly.
		address := code.VerifiableAddress
		address.Verified = true
		verifiedAt := sqlxx.NullTime(time.Now().UTC())
		address.VerifiedAt = &verifiedAt
		address.Status = identity.VerifiableAddressStatusCompleted
		if err := s.deps.PrivilegedIdentityPool().UpdateVerifiableAddress(ctx, address, "verified", "verified_at", "status"); err != nil {
			return s.retryVerificationFlowWithError(ctx, w, r, f.Type, err)
		}

		addressVia = address.Via
		identityID = code.VerifiableAddress.IdentityID
	}

	var i *identity.Identity
	if ptcIdentity != nil {
		i = ptcIdentity
	} else {
		i, err = s.deps.IdentityPool().GetIdentity(ctx, identityID, identity.ExpandDefault)
		if err != nil {
			return s.retryVerificationFlowWithError(ctx, w, r, f.Type, err)
		}
	}

	// Remainder is shared between both paths.
	returnTo := f.ContinueURL(ctx, s.deps.Config())

	f.UI = &container.Container{
		Method: "GET",
		Action: returnTo.String(),
	}

	f.State = flow.StatePassedChallenge
	f.SetCSRFToken(flow.GetCSRFToken(s.deps, w, r, f.Type))
	if addressVia == identity.AddressTypeSMS {
		f.UI.Messages.Set(text.NewInfoSelfServiceVerificationPhoneSuccessful())
	} else {
		f.UI.Messages.Set(text.NewInfoSelfServiceVerificationSuccessful())
	}
	f.UI.Nodes.Append(node.NewAnchorField("continue", returnTo.String(), node.CodeGroup, text.NewInfoNodeLabelContinue()).
		WithMetaLabel(text.NewInfoNodeLabelContinue()))

	if err := s.deps.VerificationFlowPersister().UpdateVerificationFlow(ctx, f); err != nil {
		return s.retryVerificationFlowWithError(ctx, w, r, flow.TypeBrowser, err)
	}

	if err := s.deps.VerificationExecutor().PostVerificationHook(w, r, f, i); err != nil {
		return s.retryVerificationFlowWithError(ctx, w, r, f.Type, err)
	}

	return nil
}

func (s *Strategy) retryVerificationFlowWithMessage(ctx context.Context, w http.ResponseWriter, r *http.Request, ft flow.Type, message *text.Message) error {
	s.deps.
		Logger().
		WithRequest(r).
		WithField("message", message).
		Debug("A verification flow is being retried because a validation error occurred.")

	f, err := verification.NewFlow(s.deps,
		s.deps.Config().SelfServiceFlowVerificationRequestLifespan(ctx), s.deps.CSRFHandler().RegenerateToken(w, r), r, verification.Strategies{s}, ft)
	if err != nil {
		return s.handleVerificationError(r, f, nil, err)
	}

	f.UI.Messages.Add(message)

	if err := s.deps.VerificationFlowPersister().CreateVerificationFlow(ctx, f); err != nil {
		return s.handleVerificationError(r, f, nil, err)
	}

	if x.IsJSONRequest(r) {
		s.deps.Writer().WriteError(w, r, flow.NewFlowReplacedError(text.NewErrorSystemGeneric("An error occured, please use the new flow.")).WithFlow(f))
	} else {
		http.Redirect(w, r, f.AppendTo(s.deps.Config().SelfServiceFlowVerificationUI(ctx)).String(), http.StatusSeeOther)
	}

	return errors.WithStack(flow.ErrCompletedByStrategy)
}

func (s *Strategy) retryVerificationFlowWithError(ctx context.Context, w http.ResponseWriter, r *http.Request, ft flow.Type, verErr error) error {
	s.deps.
		Logger().
		WithRequest(r).
		WithError(verErr).
		Debug("A verification flow is being retried because an error occurred.")

	f, err := verification.NewFlow(s.deps,
		s.deps.Config().SelfServiceFlowVerificationRequestLifespan(ctx), s.deps.CSRFHandler().RegenerateToken(w, r), r, verification.Strategies{s}, ft)
	if err != nil {
		return s.handleVerificationError(r, f, nil, err)
	}

	var toReturn error

	if expired := new(flow.ExpiredError); errors.As(verErr, &expired) {
		f.UI.Messages.Add(text.NewErrorValidationVerificationFlowExpired(s.deps.Clock(), expired.ExpiredAt))
		toReturn = expired.WithFlow(f)
	} else if err := f.UI.ParseError(node.LinkGroup, verErr); err != nil {
		return err
	}

	if err := s.deps.VerificationFlowPersister().CreateVerificationFlow(ctx, f); err != nil {
		return s.handleVerificationError(r, f, nil, err)
	}

	if x.IsJSONRequest(r) {
		if toReturn == nil {
			toReturn = flow.NewFlowReplacedError(text.NewErrorSystemGeneric("An error occured, please retry the flow.")).
				WithFlow(f)
		}
		s.deps.Writer().WriteError(w, r, toReturn)
	} else {
		http.Redirect(w, r, f.AppendTo(s.deps.Config().SelfServiceFlowVerificationUI(ctx)).String(), http.StatusSeeOther)
	}

	return errors.WithStack(flow.ErrCompletedByStrategy)
}

func (s *Strategy) SendVerificationCode(ctx context.Context, f *verification.Flow, i *identity.Identity, a identity.VerifiableAddressLike) (err error) {
	rawCode := GenerateCode()

	if _, err = s.deps.VerificationCodePersister().CreateVerificationCode(ctx, &CreateVerificationCodeParams{
		RawCode:           rawCode,
		ExpiresIn:         s.deps.Config().SelfServiceCodeMethodLifespan(ctx),
		VerifiableAddress: a,
		FlowID:            f.ID,
	}); err != nil {
		return err
	}

	return s.deps.CodeSender().SendVerificationCodeTo(ctx, f, i, rawCode, a)
}