package acl

import (
	"crypto/ecdsa"
	"crypto/elliptic"
	"errors"
	"fmt"

	"github.com/nspcc-dev/neo-go/pkg/crypto/keys"
	"github.com/nspcc-dev/neofs-node/pkg/core/container"
	"github.com/nspcc-dev/neofs-node/pkg/core/netmap"
	"github.com/nspcc-dev/neofs-node/pkg/local_object_storage/engine"
	"github.com/nspcc-dev/neofs-node/pkg/services/object/acl/eacl"
	eaclV2 "github.com/nspcc-dev/neofs-node/pkg/services/object/acl/eacl/v2"
	v2 "github.com/nspcc-dev/neofs-node/pkg/services/object/acl/v2"
	bearerSDK "github.com/nspcc-dev/neofs-sdk-go/bearer"
	eaclSDK "github.com/nspcc-dev/neofs-sdk-go/eacl"
	addressSDK "github.com/nspcc-dev/neofs-sdk-go/object/address"
	"github.com/nspcc-dev/neofs-sdk-go/owner"
)

// CheckerPrm groups parameters for Checker
// constructor.
type CheckerPrm struct {
	eaclSrc      eacl.Source
	validator    *eaclSDK.Validator
	localStorage *engine.StorageEngine
	state        netmap.State
}

func (c *CheckerPrm) SetEACLSource(v eacl.Source) *CheckerPrm {
	c.eaclSrc = v
	return c
}

func (c *CheckerPrm) SetValidator(v *eaclSDK.Validator) *CheckerPrm {
	c.validator = v
	return c
}

func (c *CheckerPrm) SetLocalStorage(v *engine.StorageEngine) *CheckerPrm {
	c.localStorage = v
	return c
}

func (c *CheckerPrm) SetNetmapState(v netmap.State) *CheckerPrm {
	c.state = v
	return c
}

// Checker implements v2.ACLChecker interfaces and provides
// ACL/eACL validation functionality.
type Checker struct {
	eaclSrc      eacl.Source
	validator    *eaclSDK.Validator
	localStorage *engine.StorageEngine
	state        netmap.State
}

// Various EACL check errors.
var (
	errEACLDeniedByRule       = errors.New("denied by rule")
	errBearerExpired          = errors.New("bearer token has expired")
	errBearerInvalidSignature = errors.New("bearer token has invalid signature")
	errBearerNotSignedByOwner = errors.New("bearer token is not signed by the container owner")
	errBearerInvalidOwner     = errors.New("bearer token owner differs from the request sender")
)

// NewChecker creates Checker.
// Panics if at least one of the parameter is nil.
func NewChecker(prm *CheckerPrm) *Checker {
	panicOnNil := func(fieldName string, field interface{}) {
		if field == nil {
			panic(fmt.Sprintf("incorrect field %s (%T): %v", fieldName, field, field))
		}
	}

	panicOnNil("EACLSource", prm.eaclSrc)
	panicOnNil("EACLValidator", prm.validator)
	panicOnNil("LocalStorageEngine", prm.localStorage)
	panicOnNil("NetmapState", prm.state)

	return &Checker{
		eaclSrc:      prm.eaclSrc,
		validator:    prm.validator,
		localStorage: prm.localStorage,
		state:        prm.state,
	}
}

// CheckBasicACL is a main check function for basic ACL.
func (c *Checker) CheckBasicACL(info v2.RequestInfo) bool {
	// check basic ACL permissions
	var checkFn func(eaclSDK.Operation) bool

	switch info.RequestRole() {
	case eaclSDK.RoleUser:
		checkFn = basicACLHelper(info.BasicACL()).UserAllowed
	case eaclSDK.RoleSystem:
		checkFn = basicACLHelper(info.BasicACL()).SystemAllowed
		if info.IsInnerRing() {
			checkFn = basicACLHelper(info.BasicACL()).InnerRingAllowed
		}
	case eaclSDK.RoleOthers:
		checkFn = basicACLHelper(info.BasicACL()).OthersAllowed
	default:
		// log there
		return false
	}

	return checkFn(info.Operation())
}

// StickyBitCheck validates owner field in the request if sticky bit is enabled.
func (c *Checker) StickyBitCheck(info v2.RequestInfo, owner *owner.ID) bool {
	// According to NeoFS specification sticky bit has no effect on system nodes
	// for correct intra-container work with objects (in particular, replication).
	if info.RequestRole() == eaclSDK.RoleSystem {
		return true
	}

	if !basicACLHelper(info.BasicACL()).Sticky() {
		return true
	}

	if owner == nil || len(info.SenderKey()) == 0 {
		return false
	}

	requestSenderKey := unmarshalPublicKey(info.SenderKey())

	return isOwnerFromKey(owner, requestSenderKey)
}

// CheckEACL is a main check function for extended ACL.
func (c *Checker) CheckEACL(msg interface{}, reqInfo v2.RequestInfo) error {
	if basicACLHelper(reqInfo.BasicACL()).Final() {
		return nil
	}

	// if bearer token is not allowed, then ignore it
	if !basicACLHelper(reqInfo.BasicACL()).BearerAllowed(reqInfo.Operation()) {
		reqInfo.CleanBearer()
	}

	var table eaclSDK.Table

	bearerTok := reqInfo.Bearer()
	if bearerTok == nil {
		pTable, err := c.eaclSrc.GetEACL(reqInfo.ContainerID())
		if err != nil {
			if errors.Is(err, container.ErrEACLNotFound) {
				return nil
			}
			return err
		}

		table = *pTable
	} else {
		table = bearerTok.EACLTable()
	}

	// if bearer token is not present, isValidBearer returns true
	if err := isValidBearer(reqInfo, c.state); err != nil {
		return err
	}

	hdrSrcOpts := make([]eaclV2.Option, 0, 3)

	addr := addressSDK.NewAddress()
	addr.SetContainerID(*reqInfo.ContainerID())
	addr.SetObjectID(*reqInfo.ObjectID())

	hdrSrcOpts = append(hdrSrcOpts,
		eaclV2.WithLocalObjectStorage(c.localStorage),
		eaclV2.WithAddress(addr),
	)

	if req, ok := msg.(eaclV2.Request); ok {
		hdrSrcOpts = append(hdrSrcOpts, eaclV2.WithServiceRequest(req))
	} else {
		hdrSrcOpts = append(hdrSrcOpts,
			eaclV2.WithServiceResponse(
				msg.(eaclV2.Response),
				reqInfo.Request().(eaclV2.Request),
			),
		)
	}

	action := c.validator.CalculateAction(new(eaclSDK.ValidationUnit).
		WithRole(reqInfo.RequestRole()).
		WithOperation(reqInfo.Operation()).
		WithContainerID(reqInfo.ContainerID()).
		WithSenderKey(reqInfo.SenderKey()).
		WithHeaderSource(
			eaclV2.NewMessageHeaderSource(hdrSrcOpts...),
		).
		WithEACLTable(&table),
	)

	if action != eaclSDK.ActionAllow {
		return errEACLDeniedByRule
	}
	return nil
}

// isValidBearer checks whether bearer token was correctly signed by authorized
// entity. This method might be defined on whole ACL service because it will
// require fetching current epoch to check lifetime.
func isValidBearer(reqInfo v2.RequestInfo, st netmap.State) error {
	token := reqInfo.Bearer()

	// 0. Check if bearer token is present in reqInfo.
	if token == nil {
		return nil
	}

	// 1. First check token lifetime. Simplest verification.
	if !isValidLifetime(token, st.CurrentEpoch()) {
		return errBearerExpired
	}

	// 2. Then check if bearer token is signed correctly.
	if err := token.VerifySignature(); err != nil {
		return errBearerInvalidSignature
	}

	// 3. Then check if container owner signed this token.
	issuer, ok := token.Issuer()
	if !ok {
		panic("unexpected false return from Issuer method on signed bearer token")
	}

	if !issuer.Equal(reqInfo.ContainerOwner()) {
		// TODO: #767 in this case we can issue all owner keys from neofs.id and check once again
		return errBearerNotSignedByOwner
	}

	// 4. Then check if request sender has rights to use this token.
	tokenOwner := token.OwnerID()
	requestSenderKey := unmarshalPublicKey(reqInfo.SenderKey())

	if !isOwnerFromKey(&tokenOwner, requestSenderKey) {
		// TODO: #767 in this case we can issue all owner keys from neofs.id and check once again
		return errBearerInvalidOwner
	}

	return nil
}

func isValidLifetime(t *bearerSDK.Token, epoch uint64) bool {
	// The "exp" (expiration time) claim identifies the expiration time on
	// or after which the JWT MUST NOT be accepted for processing.
	// The "nbf" (not before) claim identifies the time before which the JWT
	// MUST NOT be accepted for processing
	// RFC 7519 sections 4.1.4, 4.1.5
	return epoch >= t.NotBefore() && epoch <= t.Expiration()
}

func isOwnerFromKey(id *owner.ID, key *keys.PublicKey) bool {
	if id == nil || key == nil {
		return false
	}

	return id.Equal(owner.NewIDFromPublicKey((*ecdsa.PublicKey)(key)))
}

func unmarshalPublicKey(bs []byte) *keys.PublicKey {
	pub, err := keys.NewPublicKeyFromBytes(bs, elliptic.P256())
	if err != nil {
		return nil
	}
	return pub
}