// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at http://mozilla.org/MPL/2.0/.

// Package provider provides TLS config for client & server.
package provider

import (
	"context"
	stdlibtls "crypto/tls"
	"fmt"
	"log"
	"sync"

	"github.com/cosi-project/runtime/pkg/resource"
	"github.com/cosi-project/runtime/pkg/state"
	"github.com/siderolabs/crypto/tls"

	"github.com/siderolabs/talos/pkg/machinery/resources/secrets"
)

// TLSConfig provides client & server TLS configs for trustd.
type TLSConfig struct {
	certificateProvider *certificateProvider
}

// NewTLSConfig builds provider from configuration and endpoints.
//
//nolint:gocyclo
func NewTLSConfig(resources state.State) (*TLSConfig, error) {
	watchCh := make(chan state.Event)

	if err := resources.Watch(context.TODO(), resource.NewMetadata(secrets.NamespaceName, secrets.TrustdType, secrets.TrustdID, resource.VersionUndefined), watchCh); err != nil {
		return nil, fmt.Errorf("error setting up watch: %w", err)
	}

	// wait for the first event to set up certificate provider
	provider := &certificateProvider{}

	for {
		event := <-watchCh

		switch event.Type {
		case state.Created, state.Updated:
			// expected
		case state.Destroyed, state.Bootstrapped:
			// ignore, we'll get another event
			continue
		case state.Errored:
			return nil, fmt.Errorf("error watching for trustd certificates: %w", event.Error)
		}

		trustdCerts := event.Resource.(*secrets.Trustd) //nolint:errcheck,forcetypeassert

		if err := provider.Update(trustdCerts); err != nil {
			return nil, err
		}

		break
	}

	go func() {
		for {
			event := <-watchCh

			switch event.Type {
			case state.Created, state.Updated:
				// expected
			case state.Destroyed, state.Bootstrapped:
				// ignore, we'll get another event
				continue
			case state.Errored:
				log.Printf("error watching for trustd certificates: %s", event.Error)
			}

			trustdCerts := event.Resource.(*secrets.Trustd) //nolint:errcheck,forcetypeassert

			if err := provider.Update(trustdCerts); err != nil {
				log.Printf("failed updating cert: %v", err)
			}
		}
	}()

	return &TLSConfig{
		certificateProvider: provider,
	}, nil
}

// ServerConfig generates server-side tls.Config.
func (tlsConfig *TLSConfig) ServerConfig() (*stdlibtls.Config, error) {
	ca, err := tlsConfig.certificateProvider.GetCA()
	if err != nil {
		return nil, fmt.Errorf("failed to get root CA: %w", err)
	}

	return tls.New(
		tls.WithClientAuthType(tls.ServerOnly),
		tls.WithCACertPEM(ca),
		tls.WithServerCertificateProvider(tlsConfig.certificateProvider),
	)
}

type certificateProvider struct {
	mu sync.Mutex

	trustdCerts *secrets.Trustd
	serverCert  *stdlibtls.Certificate
}

func (p *certificateProvider) Update(trustdCerts *secrets.Trustd) error {
	p.mu.Lock()
	defer p.mu.Unlock()

	p.trustdCerts = trustdCerts

	serverCert, err := stdlibtls.X509KeyPair(p.trustdCerts.TypedSpec().Server.Crt, p.trustdCerts.TypedSpec().Server.Key)
	if err != nil {
		return fmt.Errorf("failed to parse server cert and key into a TLS Certificate: %w", err)
	}

	p.serverCert = &serverCert

	return nil
}

func (p *certificateProvider) GetCA() ([]byte, error) {
	p.mu.Lock()
	defer p.mu.Unlock()

	return p.trustdCerts.TypedSpec().CA.Crt, nil
}

func (p *certificateProvider) GetCertificate(h *stdlibtls.ClientHelloInfo) (*stdlibtls.Certificate, error) {
	p.mu.Lock()
	defer p.mu.Unlock()

	return p.serverCert, nil
}

func (p *certificateProvider) GetClientCertificate(*stdlibtls.CertificateRequestInfo) (*stdlibtls.Certificate, error) {
	return nil, nil
}
