package ape

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

	refsV2 "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/api/refs"
	sessionV2 "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/api/session"
	"git.frostfs.info/TrueCloudLab/frostfs-sdk-go/bearer"
	cid "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/container/id"
	oid "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object/id"
	sessionSDK "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/session"
	"git.frostfs.info/TrueCloudLab/frostfs-sdk-go/user"
	nativeschema "git.frostfs.info/TrueCloudLab/policy-engine/schema/native"
	"github.com/nspcc-dev/neo-go/pkg/crypto/keys"
)

func getAddressParamsSDK(cidV2 *refsV2.ContainerID, objV2 *refsV2.ObjectID) (cnrID cid.ID, objID *oid.ID, err error) {
	if cidV2 != nil {
		if err = cnrID.ReadFromV2(*cidV2); err != nil {
			return
		}
	} else {
		err = errMissingContainerID
		return
	}

	if objV2 != nil {
		objID = new(oid.ID)
		if err = objID.ReadFromV2(*objV2); err != nil {
			return
		}
	}
	return
}

// originalBearerToken goes down to original request meta header and fetches
// bearer token from there.
func originalBearerToken(header *sessionV2.RequestMetaHeader) (*bearer.Token, error) {
	for header.GetOrigin() != nil {
		header = header.GetOrigin()
	}

	tokV2 := header.GetBearerToken()
	if tokV2 == nil {
		return nil, nil
	}

	var tok bearer.Token
	return &tok, tok.ReadFromV2(*tokV2)
}

func ownerFromToken(token *sessionSDK.Object) (*user.ID, *keys.PublicKey, error) {
	// 1. First check signature of session token.
	if !token.VerifySignature() {
		return nil, nil, errInvalidSessionSig
	}

	// 2. Then check if session token owner issued the session token
	// TODO(@cthulhu-rider): #468 implement and use another approach to avoid conversion
	var tokV2 sessionV2.Token
	token.WriteToV2(&tokV2)

	tokenIssuerKey, err := unmarshalPublicKey(tokV2.GetSignature().GetKey())
	if err != nil {
		return nil, nil, fmt.Errorf("invalid key in session token signature: %w", err)
	}

	tokenIssuer := token.Issuer()

	if !isOwnerFromKey(tokenIssuer, tokenIssuerKey) {
		// TODO: #767 in this case we can issue all owner keys from frostfs.id and check once again
		return nil, nil, errInvalidSessionOwner
	}

	return &tokenIssuer, tokenIssuerKey, nil
}

func originalBodySignature(v *sessionV2.RequestVerificationHeader) *refsV2.Signature {
	if v == nil {
		return nil
	}

	for v.GetOrigin() != nil {
		v = v.GetOrigin()
	}

	return v.GetBodySignature()
}

func unmarshalPublicKey(bs []byte) (*keys.PublicKey, error) {
	return keys.NewPublicKeyFromBytes(bs, elliptic.P256())
}

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

	var id2 user.ID
	user.IDFromKey(&id2, (ecdsa.PublicKey)(*key))

	return id2.Equals(id)
}

// assertVerb checks that token verb corresponds to the method.
func assertVerb(tok sessionSDK.Object, method string) bool {
	switch method {
	case nativeschema.MethodPutObject:
		return tok.AssertVerb(sessionSDK.VerbObjectPut, sessionSDK.VerbObjectDelete, sessionSDK.VerbObjectPatch)
	case nativeschema.MethodDeleteObject:
		return tok.AssertVerb(sessionSDK.VerbObjectDelete)
	case nativeschema.MethodGetObject:
		return tok.AssertVerb(sessionSDK.VerbObjectGet)
	case nativeschema.MethodHeadObject:
		return tok.AssertVerb(
			sessionSDK.VerbObjectHead,
			sessionSDK.VerbObjectGet,
			sessionSDK.VerbObjectDelete,
			sessionSDK.VerbObjectRange,
			sessionSDK.VerbObjectRangeHash,
			sessionSDK.VerbObjectPatch,
		)
	case nativeschema.MethodSearchObject:
		return tok.AssertVerb(sessionSDK.VerbObjectSearch, sessionSDK.VerbObjectDelete)
	case nativeschema.MethodRangeObject:
		return tok.AssertVerb(sessionSDK.VerbObjectRange, sessionSDK.VerbObjectRangeHash, sessionSDK.VerbObjectPatch)
	case nativeschema.MethodHashObject:
		return tok.AssertVerb(sessionSDK.VerbObjectRangeHash)
	case nativeschema.MethodPatchObject:
		return tok.AssertVerb(sessionSDK.VerbObjectPatch)
	}
	return false
}

// assertSessionRelation checks if given token describing the FrostFS session
// relates to the given container and optional object. Missing object
// means that the context isn't bound to any FrostFS object in the container.
// Returns no error iff relation is correct. Criteria:
//
//	session is bound to the given container
//	object is not specified or session is bound to this object
//
// Session MUST be bound to the particular container, otherwise behavior is undefined.
func assertSessionRelation(tok sessionSDK.Object, cnr cid.ID, obj *oid.ID) error {
	if !tok.AssertContainer(cnr) {
		return errors.New("requested container is not related to the session")
	}

	if obj != nil && !tok.AssertObject(*obj) {
		return errors.New("requested object is not related to the session")
	}

	return nil
}

func unmarshalPublicKeyWithOwner(rawKey []byte) (*user.ID, *keys.PublicKey, error) {
	key, err := unmarshalPublicKey(rawKey)
	if err != nil {
		return nil, nil, fmt.Errorf("invalid signature key: %w", err)
	}

	var idSender user.ID
	user.IDFromKey(&idSender, (ecdsa.PublicKey)(*key))

	return &idSender, key, nil
}