package handlers

import (
	"errors"
	"fmt"
	"net/http"
	"net/url"
	"path"
	"strings"

	"github.com/google/uuid"
	"github.com/ory/fosite"

	"github.com/authelia/authelia/v4/internal/authentication"
	"github.com/authelia/authelia/v4/internal/authorization"
	"github.com/authelia/authelia/v4/internal/middlewares"
	"github.com/authelia/authelia/v4/internal/model"
	"github.com/authelia/authelia/v4/internal/oidc"
	"github.com/authelia/authelia/v4/internal/session"
	"github.com/authelia/authelia/v4/internal/utils"
)

func handleOIDCAuthorizationConsent(ctx *middlewares.AutheliaCtx, issuer *url.URL, client *oidc.Client,
	userSession session.UserSession,
	rw http.ResponseWriter, r *http.Request, requester fosite.AuthorizeRequester) (consent *model.OAuth2ConsentSession, handled bool) {
	var (
		subject uuid.UUID
		err     error
	)

	var handler handlerAuthorizationConsent

	switch {
	case userSession.IsAnonymous():
		handler = handleOIDCAuthorizationConsentNotAuthenticated
	case client.IsAuthenticationLevelSufficient(userSession.AuthenticationLevel):
		if subject, err = ctx.Providers.OpenIDConnect.GetSubject(ctx, client.GetSectorIdentifier(), userSession.Username); err != nil {
			ctx.Logger.Errorf(logFmtErrConsentCantGetSubject, requester.GetID(), client.GetID(), client.Consent, userSession.Username, client.GetSectorIdentifier(), err)

			ctx.Providers.OpenIDConnect.WriteAuthorizeError(ctx, rw, requester, oidc.ErrSubjectCouldNotLookup)

			return nil, true
		}

		switch client.Consent.Mode {
		case oidc.ClientConsentModeExplicit:
			handler = handleOIDCAuthorizationConsentModeExplicit
		case oidc.ClientConsentModeImplicit:
			handler = handleOIDCAuthorizationConsentModeImplicit
		case oidc.ClientConsentModePreConfigured:
			handler = handleOIDCAuthorizationConsentModePreConfigured
		default:
			ctx.Logger.Errorf(logFmtErrConsentCantDetermineConsentMode, requester.GetID(), client.GetID())

			ctx.Providers.OpenIDConnect.WriteAuthorizeError(ctx, rw, requester, fosite.ErrServerError.WithHint("Could not determine the client consent mode."))

			return nil, true
		}
	default:
		if subject, err = ctx.Providers.OpenIDConnect.GetSubject(ctx, client.GetSectorIdentifier(), userSession.Username); err != nil {
			ctx.Logger.Errorf(logFmtErrConsentCantGetSubject, requester.GetID(), client.GetID(), client.Consent, userSession.Username, client.GetSectorIdentifier(), err)

			ctx.Providers.OpenIDConnect.WriteAuthorizeError(ctx, rw, requester, oidc.ErrSubjectCouldNotLookup)

			return nil, true
		}

		handler = handleOIDCAuthorizationConsentGenerate
	}

	return handler(ctx, issuer, client, userSession, subject, rw, r, requester)
}

func handleOIDCAuthorizationConsentNotAuthenticated(_ *middlewares.AutheliaCtx, issuer *url.URL, _ *oidc.Client,
	_ session.UserSession, _ uuid.UUID,
	rw http.ResponseWriter, r *http.Request, requester fosite.AuthorizeRequester) (consent *model.OAuth2ConsentSession, handled bool) {
	redirectionURL := handleOIDCAuthorizationConsentGetRedirectionURL(issuer, nil, requester)

	http.Redirect(rw, r, redirectionURL.String(), http.StatusFound)

	return nil, true
}

func handleOIDCAuthorizationConsentGenerate(ctx *middlewares.AutheliaCtx, issuer *url.URL, client *oidc.Client,
	userSession session.UserSession, subject uuid.UUID,
	rw http.ResponseWriter, r *http.Request, requester fosite.AuthorizeRequester) (consent *model.OAuth2ConsentSession, handled bool) {
	var (
		err error
	)

	ctx.Logger.Debugf(logFmtDbgConsentGenerate, requester.GetID(), client.GetID(), client.Consent)

	if len(ctx.QueryArgs().PeekBytes(qryArgConsentID)) != 0 {
		ctx.Logger.Errorf(logFmtErrConsentGenerateError, requester.GetID(), client.GetID(), client.Consent, "generating", errors.New("consent id value was present when it should be absent"))

		ctx.Providers.OpenIDConnect.WriteAuthorizeError(ctx, rw, requester, oidc.ErrConsentCouldNotGenerate)

		return nil, true
	}

	if consent, err = model.NewOAuth2ConsentSession(subject, requester); err != nil {
		ctx.Logger.Errorf(logFmtErrConsentGenerateError, requester.GetID(), client.GetID(), client.Consent, "generating", err)

		ctx.Providers.OpenIDConnect.WriteAuthorizeError(ctx, rw, requester, oidc.ErrConsentCouldNotGenerate)

		return nil, true
	}

	if err = ctx.Providers.StorageProvider.SaveOAuth2ConsentSession(ctx, *consent); err != nil {
		ctx.Logger.Errorf(logFmtErrConsentGenerateError, requester.GetID(), client.GetID(), client.Consent, "saving", err)

		ctx.Providers.OpenIDConnect.WriteAuthorizeError(ctx, rw, requester, oidc.ErrConsentCouldNotSave)

		return nil, true
	}

	handleOIDCAuthorizationConsentRedirect(ctx, issuer, consent, client, userSession, rw, r, requester)

	return consent, true
}

func handleOIDCAuthorizationConsentRedirect(ctx *middlewares.AutheliaCtx, issuer *url.URL, consent *model.OAuth2ConsentSession, client *oidc.Client,
	userSession session.UserSession, rw http.ResponseWriter, r *http.Request, requester fosite.AuthorizeRequester) {
	var location *url.URL

	if client.IsAuthenticationLevelSufficient(userSession.AuthenticationLevel) {
		location, _ = url.ParseRequestURI(issuer.String())
		location.Path = path.Join(location.Path, oidc.EndpointPathConsent)

		query := location.Query()
		query.Set(queryArgID, consent.ChallengeID.String())

		location.RawQuery = query.Encode()

		ctx.Logger.Debugf(logFmtDbgConsentAuthenticationSufficiency, requester.GetID(), client.GetID(), client.Consent, authentication.LevelToString(userSession.AuthenticationLevel), "sufficient", authorization.LevelToString(client.Policy))
	} else {
		location = handleOIDCAuthorizationConsentGetRedirectionURL(issuer, consent, requester)

		ctx.Logger.Debugf(logFmtDbgConsentAuthenticationSufficiency, requester.GetID(), client.GetID(), client.Consent, authentication.LevelToString(userSession.AuthenticationLevel), "insufficient", authorization.LevelToString(client.Policy))
	}

	ctx.Logger.Debugf(logFmtDbgConsentRedirect, requester.GetID(), client.GetID(), client.Consent, location)

	http.Redirect(rw, r, location.String(), http.StatusFound)
}

func handleOIDCAuthorizationConsentGetRedirectionURL(issuer *url.URL, consent *model.OAuth2ConsentSession, requester fosite.AuthorizeRequester) (redirectURL *url.URL) {
	iss := issuer.String()

	if !strings.HasSuffix(iss, "/") {
		iss += "/"
	}

	redirectURL, _ = url.ParseRequestURI(iss)

	query := redirectURL.Query()
	query.Set(queryArgWorkflow, workflowOpenIDConnect)

	switch {
	case consent != nil:
		query.Set(queryArgWorkflowID, consent.ChallengeID.String())
	case requester != nil:
		rd, _ := url.ParseRequestURI(iss)
		rd.Path = path.Join(rd.Path, oidc.EndpointPathAuthorization)
		rd.RawQuery = requester.GetRequestForm().Encode()

		query.Set(queryArgRD, rd.String())
	}

	redirectURL.RawQuery = query.Encode()

	return redirectURL
}

func verifyOIDCUserAuthorizedForConsent(ctx *middlewares.AutheliaCtx, client *oidc.Client, userSession session.UserSession, consent *model.OAuth2ConsentSession, subject uuid.UUID) (err error) {
	var sid uint32

	if client == nil {
		if client, err = ctx.Providers.OpenIDConnect.GetFullClient(consent.ClientID); err != nil {
			return fmt.Errorf("failed to retrieve client: %w", err)
		}
	}

	if sid = subject.ID(); sid == 0 {
		if subject, err = ctx.Providers.OpenIDConnect.GetSubject(ctx, client.GetSectorIdentifier(), userSession.Username); err != nil {
			return fmt.Errorf("failed to lookup subject: %w", err)
		}

		sid = subject.ID()
	}

	if !consent.Subject.Valid {
		if sid == 0 {
			return fmt.Errorf("the consent subject is null for consent session with id '%d' for anonymous user", consent.ID)
		}

		consent.Subject = uuid.NullUUID{UUID: subject, Valid: true}

		if err = ctx.Providers.StorageProvider.SaveOAuth2ConsentSessionSubject(ctx, *consent); err != nil {
			return fmt.Errorf("failed to update the consent subject: %w", err)
		}
	}

	if consent.Subject.UUID.ID() != sid {
		return fmt.Errorf("the consent subject identifier '%s' isn't owned by user '%s' who has a subject identifier of '%s' with sector identifier '%s'", consent.Subject.UUID, userSession.Username, subject, client.GetSectorIdentifier())
	}

	return nil
}

func getOIDCExpectedScopesAndAudienceFromRequest(requester fosite.Requester) (scopes, audience []string) {
	return getOIDCExpectedScopesAndAudience(requester.GetClient().GetID(), requester.GetRequestedScopes(), requester.GetRequestedAudience())
}

func getOIDCExpectedScopesAndAudience(clientID string, scopes, audience []string) (expectedScopes, expectedAudience []string) {
	if !utils.IsStringInSlice(clientID, audience) {
		audience = append(audience, clientID)
	}

	return scopes, audience
}