package client

import (
	"bytes"
	"context"
	"crypto/ecdsa"
	"crypto/tls"
	"errors"
	"fmt"
	"net/url"
	"time"

	v2accounting "git.frostfs.info/TrueCloudLab/frostfs-api-go/v2/accounting"
	"git.frostfs.info/TrueCloudLab/frostfs-api-go/v2/rpc"
	"git.frostfs.info/TrueCloudLab/frostfs-api-go/v2/rpc/client"
	"git.frostfs.info/TrueCloudLab/frostfs-sdk-go/netmap"
	"google.golang.org/grpc"
)

// Client represents virtual connection to the FrostFS network to communicate
// with FrostFS server using FrostFS API protocol. It is designed to provide
// an abstraction interface from the protocol details of data transfer over
// a network in FrostFS.
//
// Client can be created using simple Go variable declaration. Before starting
// work with the Client, it SHOULD BE correctly initialized (see Init method).
// Before executing the FrostFS operations using the Client, connection to the
// server MUST BE correctly established (see Dial method and pay attention
// to the mandatory parameters). Using the Client before connecting have
// been established can lead to a panic. After the work, the Client SHOULD BE
// closed (see Close method): it frees internal and system resources which were
// allocated for the period of work of the Client. Calling Init/Dial/Close method
// during the communication process step strongly discouraged as it leads to
// undefined behavior.
//
// Each method which produces a FrostFS API call may return a server response.
// Status responses are returned in the result structure, and can be cast
// to built-in error instance (or in the returned error if the client is
// configured accordingly). Certain statuses can be checked using `apistatus`
// and standard `errors` packages. Note that package provides some helper
// functions to work with status returns (e.g. IsErrContainerNotFound).
// All possible responses are documented in methods, however, some may be
// returned from all of them (pay attention to the presence of the pointer sign):
//   - *apistatus.ServerInternal on internal server error;
//   - *apistatus.NodeUnderMaintenance if a server is under maintenance;
//   - *apistatus.SuccessDefaultV2 on default success.
//
// Client MUST NOT be copied by value: use pointer to Client instead.
//
// See client package overview to get some examples.
type Client struct {
	prm PrmInit

	c client.Client

	server frostFSAPIServer
}

// Init brings the Client instance to its initial state.
//
// One-time method call during application init stage (before Dial) is expected.
// Calling multiple times leads to undefined behavior.
//
// See docs of PrmInit methods for details. See also Dial / Close.
func (c *Client) Init(prm PrmInit) {
	c.prm = prm
}

// Dial establishes a connection to the server from the FrostFS network.
// Returns an error describing failure reason. If failed, the Client
// SHOULD NOT be used.
//
// Uses the context specified by SetContext if it was called with non-nil
// argument, otherwise context.Background() is used. Dial returns context
// errors, see context package docs for details.
//
// Returns an error if required parameters are set incorrectly, look carefully
// at the method documentation.
//
// One-time method call during application start-up stage (after Init ) is expected.
// Calling multiple times leads to undefined behavior.
//
// See also Init / Close.
func (c *Client) Dial(ctx context.Context, prm PrmDial) error {
	if prm.Endpoint == "" {
		return errorServerAddrUnset
	}

	if prm.DialTimeout <= 0 {
		prm.DialTimeout = defaultDialTimeout
	}
	if prm.StreamTimeout <= 0 {
		prm.StreamTimeout = defaultStreamTimeout
	}

	c.c = *client.New(append(
		client.WithNetworkURIAddress(prm.Endpoint, prm.TLSConfig),
		client.WithDialTimeout(prm.DialTimeout),
		client.WithRWTimeout(prm.StreamTimeout),
		client.WithGRPCDialOptions(prm.GRPCDialOptions),
	)...)

	c.setFrostFSAPIServer((*coreServer)(&c.c))

	// TODO: (neofs-api-go#382) perform generic dial stage of the client.Client
	_, err := rpc.Balance(&c.c, new(v2accounting.BalanceRequest),
		client.WithContext(ctx),
	)
	// return context errors since they signal about dial problem
	if errors.Is(err, context.Canceled) || errors.Is(err, context.DeadlineExceeded) {
		return err
	}

	return nil
}

func (c *Client) netMapDialNode(ctx context.Context, node *netmap.NodeInfo, prm PrmNetMapDial) error {
	addresses := node.ExternalAddresses()

	dialAddr := func(addr string) error {
		err := c.Dial(ctx, PrmDial{Endpoint: addr, PrmDialOptions: prm.PrmDialOptions})
		if err != nil {
			if !prm.FallbackToAvailableAddress {
				return err
			}
			if !errors.Is(err, context.Canceled) && !errors.Is(err, context.DeadlineExceeded) {
				return err
			}
		}
		return nil
	}

	if prm.UseRandomAddress {
		// Use map for randomized iteration over addresses
		addressesMap := make(map[string]struct{})
		for _, addr := range addresses {
			addressesMap[addr] = struct{}{}
		}

		for addr := range addressesMap {
			err := dialAddr(addr)
			if err != nil {
				return err
			}
		}
	}

	for _, addr := range addresses {
		err := dialAddr(addr)
		if err != nil {
			return err
		}
	}
	return nil
}

func (c *Client) NetMapDial(ctx context.Context, endpoint string, prm PrmNetMapDial) error {
	u, err := url.Parse(endpoint)
	if err != nil {
		return err
	}

	if u.Scheme == "frostfs" {
		nodes := c.prm.NetMap.Nodes()
		for _, node := range nodes {
			if bytes.Equal([]byte(u.Host), node.PublicKey()) {
				return c.netMapDialNode(ctx, &node, prm)
			}
		}
	}
	return fmt.Errorf("dial failure: endpoint %s isn't valid", endpoint)
}

// sets underlying provider of frostFSAPIServer. The method is used for testing as an approach
// to skip Dial stage and override FrostFS API server. MUST NOT be used outside test code.
// In real applications wrapper over git.frostfs.info/TrueCloudLab/frostfs-api-go/v2/rpc/client
// is statically used.
func (c *Client) setFrostFSAPIServer(server frostFSAPIServer) {
	c.server = server
}

// Close closes underlying connection to the FrostFS server. Implements io.Closer.
// MUST NOT be called before successful Dial. Can be called concurrently
// with server operations processing on running goroutines: in this case
// they are likely to fail due to a connection error.
//
// One-time method call during application shutdown stage (after Init and Dial)
// is expected. Calling multiple times leads to undefined behavior.
//
// See also Init / Dial.
func (c *Client) Close() error {
	return c.c.Conn().Close()
}

// PrmInit groups initialization parameters of Client instances.
//
// See also Init.
type PrmInit struct {
	DisableFrostFSErrorResolution bool

	Key ecdsa.PrivateKey

	ResponseInfoCallback func(ResponseMetaInfo) error

	NetMap *netmap.NetMap

	NetMagic uint64
}

// SetDefaultPrivateKey sets Client private key to be used for the protocol
// communication by default.
//
// Required for operations without custom key parametrization (see corresponding Prm* docs).
//
// Deprecated: Use PrmInit.Key instead.
func (x *PrmInit) SetDefaultPrivateKey(key ecdsa.PrivateKey) {
	x.Key = key
}

// Deprecated: method is no-op. Option is default.
func (x *PrmInit) ResolveFrostFSFailures() {
}

// DisableFrostFSFailuresResolution makes the Client to preserve failure statuses of the
// FrostFS protocol only in resulting structure (see corresponding Res* docs).
// These errors are returned from each protocol operation. By default, statuses
// are resolved and returned as a Go built-in errors.
//
// Deprecated: Use PrmInit.DisableFrostFSErrorResolution instead.
func (x *PrmInit) DisableFrostFSFailuresResolution() {
	x.DisableFrostFSErrorResolution = true
}

// SetResponseInfoCallback makes the Client to pass ResponseMetaInfo from each
// FrostFS server response to f. Nil (default) means ignore response meta info.
//
// Deprecated: Use PrmInit.ResponseInfoCallback instead.
func (x *PrmInit) SetResponseInfoCallback(f func(ResponseMetaInfo) error) {
	x.ResponseInfoCallback = f
}

const (
	defaultDialTimeout   = 5 * time.Second
	defaultStreamTimeout = 10 * time.Second
)

type PrmDialOptions struct {
	TLSConfig *tls.Config

	// If DialTimeout is non-positive, then it's set to defaultDialTimeout.
	DialTimeout time.Duration

	// If StreamTimeout is non-positive, then it's set to defaultStreamTimeout.
	StreamTimeout time.Duration

	GRPCDialOptions []grpc.DialOption
}

// PrmDial groups connection parameters for the Dial call in the Client.
//
// See also Dial.
type PrmDial struct {
	Endpoint string

	PrmDialOptions
}

// PrmNetMapDial groups connection parameters for the NetMapDial call in the Client.
type PrmNetMapDial struct {
	UseExternalAddresses       bool
	UseRandomAddress           bool
	FallbackToAvailableAddress bool

	PrmDialOptions
}

// SetServerURI sets server URI in the FrostFS network.
// Required parameter.
//
// Format of the URI:
//
//	[scheme://]host:port
//
// Supported schemes:
//
//	grpc
//	grpcs
//
// See also SetTLSConfig.
//
// Deprecated: Use PrmDial.Endpoint instead.
func (x *PrmDial) SetServerURI(endpoint string) {
	x.Endpoint = endpoint
}

// SetTLSConfig sets tls.Config to open TLS client connection
// to the FrostFS server. Nil (default) means insecure connection.
//
// See also SetServerURI.
//
// Deprecated: Use PrmDialOptions.TLSConfig instead.
func (x *PrmDialOptions) SetTLSConfig(tlsConfig *tls.Config) {
	x.TLSConfig = tlsConfig
}

// SetTimeout sets the timeout for connection to be established.
// MUST BE positive. If not called, 5s timeout will be used by default.
//
// Deprecated: Use PrmDialOptions.DialTimeout instead.
func (x *PrmDialOptions) SetTimeout(timeout time.Duration) {
	x.DialTimeout = timeout
}

// SetStreamTimeout sets the timeout for individual operations in streaming RPC.
// MUST BE positive. If not called, 10s timeout will be used by default.
//
// Deprecated: Use PrmDialOptions.StreamTimeout instead.
func (x *PrmDialOptions) SetStreamTimeout(timeout time.Duration) {
	x.StreamTimeout = timeout
}

// SetGRPCDialOptions sets the gRPC dial options for new gRPC client connection.
//
// Deprecated: Use PrmDialOptions.GRPCDialOptions instead.
func (x *PrmDialOptions) SetGRPCDialOptions(opts ...grpc.DialOption) {
	x.GRPCDialOptions = opts
}