package ape

import (
	"context"
	"fmt"

	objectV2 "git.frostfs.info/TrueCloudLab/frostfs-api-go/v2/object"
	apistatus "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/client/status"
	cid "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/container/id"
	oid "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object/id"
	apechain "git.frostfs.info/TrueCloudLab/policy-engine/pkg/chain"
	policyengine "git.frostfs.info/TrueCloudLab/policy-engine/pkg/engine"
)

type checkerImpl struct {
	chainRouter policyengine.ChainRouter

	headerProvider HeaderProvider
}

func NewChecker(chainRouter policyengine.ChainRouter, headerProvider HeaderProvider) Checker {
	return &checkerImpl{
		chainRouter: chainRouter,

		headerProvider: headerProvider,
	}
}

type Prm struct {
	Namespace string

	Container cid.ID

	// Object ID is omitted for some methods.
	Object *oid.ID

	// If Header is set, then object attributes and properties will be parsed from
	// a request/response's header.
	Header *objectV2.Header

	// Method must be represented only as a constant represented in native schema.
	Method string

	// Role must be representedonly as a constant represented in native schema.
	Role string

	// An encoded sender's public key string.
	SenderKey string
}

var (
	errMissingOID = fmt.Errorf("object ID is not set")
)

// CheckAPE checks if a request or a response is permitted creating an ape request and passing
// it to chain router.
func (c *checkerImpl) CheckAPE(ctx context.Context, prm Prm) error {
	r, err := c.newAPERequest(ctx, prm)
	if err != nil {
		return fmt.Errorf("failed to create ape request: %w", err)
	}

	status, ruleFound, err := c.chainRouter.IsAllowed(apechain.Ingress,
		policyengine.NewRequestTarget(prm.Namespace, prm.Container.EncodeToString()), r)
	if err != nil {
		return err
	}

	if !ruleFound || status == apechain.Allow {
		return nil
	}

	return apeErr(prm.Method, status)
}

const accessDeniedAPEReasonFmt = "access to operation %s is denied by access policy engine: %s"

func apeErr(op string, status apechain.Status) error {
	errAccessDenied := &apistatus.ObjectAccessDenied{}
	errAccessDenied.WriteReason(fmt.Sprintf(accessDeniedAPEReasonFmt, op, status.String()))
	return errAccessDenied
}