package worker

import (
	"context"
	"crypto/ed25519"
	"crypto/tls"
	"crypto/x509"
	"errors"
	"fmt"
	"strings"
	"time"

	"github.com/hashicorp/boundary/internal/gen/controller/servers/services"
	pbs "github.com/hashicorp/boundary/internal/gen/controller/servers/services"
)

const (
	validateSessionTimeout = 90 * time.Second
)

func (w *Worker) getSessionTls(hello *tls.ClientHelloInfo) (*tls.Config, error) {
	var sessionId string
	switch {
	case strings.HasPrefix(hello.ServerName, "s_"):
		w.logger.Trace("got valid session in SNI", "session_id", hello.ServerName)
		sessionId = hello.ServerName
	default:
		w.logger.Trace("invalid session in SNI", "session_id", hello.ServerName)
		return nil, fmt.Errorf("could not find session ID in SNI")
	}

	rawConn := w.controllerSessionConn.Load()
	if rawConn == nil {
		w.logger.Trace("could not get a controller client", "session_id", sessionId)
		return nil, errors.New("could not get a controller client")
	}
	conn, ok := rawConn.(pbs.SessionServiceClient)
	if !ok {
		w.logger.Trace("could not cast controller client to the real thing", "session_id", sessionId)
		return nil, errors.New("could not cast atomic controller client to the real thing")
	}
	if conn == nil {
		w.logger.Trace("controller client is nil", "session_id", sessionId)
		return nil, errors.New("controller client is nil")
	}

	timeoutContext, cancel := context.WithTimeout(w.baseContext, validateSessionTimeout)
	defer cancel()

	w.logger.Trace("looking up session", "session_id", sessionId)
	resp, err := conn.LookupSession(timeoutContext, &pbs.LookupSessionRequest{
		SessionId: sessionId,
	})
	if err != nil {
		return nil, fmt.Errorf("error validating session: %w", err)
	}

	if resp.GetExpiration().AsTime().Before(time.Now()) {
		return nil, fmt.Errorf("session is expired")
	}

	parsedCert, err := x509.ParseCertificate(resp.GetAuthorization().Certificate)
	if err != nil {
		return nil, fmt.Errorf("error parsing session certificate: %w", err)
	}

	if len(parsedCert.DNSNames) != 1 {
		return nil, fmt.Errorf("invalid length of DNS names (%d) in parsed certificate", len(parsedCert.DNSNames))
	}

	certPool := x509.NewCertPool()
	certPool.AddCert(parsedCert)

	tlsConf := &tls.Config{
		Certificates: []tls.Certificate{
			{
				Certificate: [][]byte{resp.GetAuthorization().Certificate},
				PrivateKey:  ed25519.PrivateKey(resp.GetAuthorization().PrivateKey),
				Leaf:        parsedCert,
			},
		},
		ServerName: parsedCert.DNSNames[0],
		ClientAuth: tls.RequireAndVerifyClientCert,
		ClientCAs:  certPool,
		MinVersion: tls.VersionTLS13,
	}

	// TODO: Periodicially clean this up. We can't rely on things in here but
	// not in cancellation because they could be on the way to being
	// established. However, since cert lifetimes are short, we can simply range
	// through and remove values that are expired.
	w.sessionInfoMap.Store(sessionId, resp)

	w.logger.Trace("returning TLS configuration", "session_id", sessionId)
	return tlsConf, nil
}

func (w *Worker) activateSession(ctx context.Context, tofuToken string, sess *services.LookupSessionResponse) error {
	rawConn := w.controllerSessionConn.Load()
	if rawConn == nil {
		return errors.New("could not get a controller client")
	}
	conn, ok := rawConn.(pbs.SessionServiceClient)
	if !ok {
		return errors.New("could not cast atomic controller client to the real thing")
	}
	if conn == nil {
		return errors.New("controller client is nil")
	}

	_, err := conn.ActivateSession(ctx, &pbs.ActivateSessionRequest{
		SessionId: sess.GetAuthorization().GetSessionId(),
		TofuToken: tofuToken,
		Version:   sess.GetVersion(),
		WorkerId:  w.conf.RawConfig.Worker.Name,
	})
	if err != nil {
		return fmt.Errorf("error activating session: %w", err)
	}
	return nil
}