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

package client

import (
	"context"
	"crypto/tls"
	"fmt"
	"os"
	"strings"
	"time"

	"golang.org/x/oauth2"

	"github.com/ory/x/flagx"

	"github.com/spf13/cobra"
	"github.com/spf13/pflag"
	"google.golang.org/grpc"
	"google.golang.org/grpc/credentials"
	"google.golang.org/grpc/credentials/insecure"
	"google.golang.org/grpc/credentials/oauth"
)

type contextKeys string

const (
	FlagReadRemote  = "read-remote"
	FlagWriteRemote = "write-remote"
	FlagOplRemote   = "syntax-remote"

	FlagInsecureNoTransportSecurity  = "insecure-disable-transport-security"
	FlagInsecureSkipHostVerification = "insecure-skip-hostname-verification"
	FlagAuthority                    = "authority"
	FlagBlock                        = "block"

	EnvReadRemote  = "KETO_READ_REMOTE"
	EnvWriteRemote = "KETO_WRITE_REMOTE"
	EnvAuthToken   = "KETO_BEARER_TOKEN" //nolint:gosec // just the key, not the value
	EnvAuthority   = "KETO_AUTHORITY"

	ContextKeyTimeout  contextKeys = "timeout"
	ContextKeyDialFunc contextKeys = "dial"
)

type connectionDetails struct {
	token, authority     string
	skipHostVerification bool
	noTransportSecurity  bool
	block                bool
}

func (d *connectionDetails) dialOptions() (opts []grpc.DialOption) {
	if d.token != "" {
		opts = append(opts,
			grpc.WithPerRPCCredentials(
				oauth.TokenSource{TokenSource: oauth2.StaticTokenSource(&oauth2.Token{AccessToken: d.token})},
			))
	}
	if d.authority != "" {
		opts = append(opts, grpc.WithAuthority(d.authority))
	}

	// TLS settings
	switch {
	case d.noTransportSecurity:
		opts = append(opts, grpc.WithTransportCredentials(insecure.NewCredentials()))
	case d.skipHostVerification:
		opts = append(opts, grpc.WithTransportCredentials(credentials.NewTLS(&tls.Config{
			//nolint:gosec // explicity set through scary flag
			InsecureSkipVerify: true,
		})))
	default:
		// Defaults to the default host root CA bundle
		opts = append(opts, grpc.WithTransportCredentials(credentials.NewTLS(nil)))
	}
	if d.block {
		opts = append(opts, grpc.WithBlock()) //nolint:staticcheck // SA1019 grpc.WithBlock is deprecated, but we actually want to block here until the connection is up.
	}
	return opts
}

func getRemote(cmd *cobra.Command, flagRemote, envRemote string) (remote string) {
	defer (func() {
		if strings.HasPrefix(remote, "http://") || strings.HasPrefix(remote, "https://") {
			_, _ = fmt.Fprintf(cmd.ErrOrStderr(), "remote %q seems to be an http URL instead of a remote address\n", remote)
		}
	})()

	if cmd.Flags().Changed(flagRemote) {
		return flagx.MustGetString(cmd, flagRemote)
	} else if remote, isSet := os.LookupEnv(envRemote); isSet {
		return remote
	}

	// no value is set, use fallback from the flag and warn about that
	remote = flagx.MustGetString(cmd, flagRemote)
	_, _ = fmt.Fprintf(cmd.ErrOrStderr(), "neither flag --%s nor env var %s are set, falling back to %s\n", flagRemote, envRemote, remote)
	return remote
}

func getAuthority(cmd *cobra.Command) string {
	if cmd.Flags().Changed(FlagAuthority) {
		return flagx.MustGetString(cmd, FlagAuthority)
	}
	return os.Getenv(EnvAuthority)
}

func getConnectionDetails(cmd *cobra.Command) connectionDetails {
	return connectionDetails{
		token:                os.Getenv(EnvAuthToken),
		authority:            getAuthority(cmd),
		skipHostVerification: flagx.MustGetBool(cmd, FlagInsecureSkipHostVerification),
		noTransportSecurity:  flagx.MustGetBool(cmd, FlagInsecureNoTransportSecurity),
		block:                flagx.MustGetBool(cmd, "block"),
	}
}

func GetReadConn(cmd *cobra.Command) (*grpc.ClientConn, error) {
	return Conn(cmd.Context(),
		getRemote(cmd, FlagReadRemote, EnvReadRemote),
		getConnectionDetails(cmd),
	)
}

func GetWriteConn(cmd *cobra.Command) (*grpc.ClientConn, error) {
	return Conn(cmd.Context(),
		getRemote(cmd, FlagWriteRemote, EnvWriteRemote),
		getConnectionDetails(cmd),
	)
}

func Conn(ctx context.Context, remote string, details connectionDetails) (*grpc.ClientConn, error) {
	if d, ok := ctx.Value(ContextKeyTimeout).(time.Duration); ok {
		var cancel context.CancelFunc
		ctx, cancel = context.WithTimeout(ctx, d)
		defer cancel()
	}

	if dial, ok := ctx.Value(ContextKeyDialFunc).(func(context.Context, string) (*grpc.ClientConn, error)); ok {
		return dial(ctx, remote)
	}

	return grpc.DialContext( // nolint:staticcheck // SA1019 grpc.DialContext is deprecated, but we actually want to connect here right away.
		ctx,
		remote,
		details.dialOptions()...,
	)
}

func RegisterRemoteURLFlags(flags *pflag.FlagSet) {
	flags.String(FlagReadRemote, "127.0.0.1:4466", "Remote address of the read API endpoint.")
	flags.String(FlagWriteRemote, "127.0.0.1:4467", "Remote address of the write API endpoint.")
	flags.String(FlagAuthority, "", "Set the authority header for the remote gRPC server.")
	flags.Bool(FlagInsecureNoTransportSecurity, false, "Disables transport security. Do not use this in production.")
	flags.Bool(FlagInsecureSkipHostVerification, false, "Disables hostname verification. Do not use this in production.")
	flags.Bool(FlagBlock, false, "Block until the connection is up.")
}