package getsvc

import (
	"context"
	"errors"

	"git.frostfs.info/TrueCloudLab/frostfs-node/internal/logs"
	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/util"
	apistatus "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/client/status"
	objectSDK "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object"
	"go.uber.org/zap"
)

// Get serves a request to get an object by address, and returns Streamer instance.
func (s *Service) Get(ctx context.Context, prm Prm) error {
	return s.get(ctx, RequestParameters{
		commonPrm: prm.commonPrm,
	})
}

// GetRange serves a request to get an object by address, and returns Streamer instance.
func (s *Service) GetRange(ctx context.Context, prm RangePrm) error {
	return s.get(ctx, RequestParameters{
		commonPrm: prm.commonPrm,
		rng:       prm.rng,
	})
}

func (s *Service) GetRangeHash(ctx context.Context, prm RangeHashPrm) (*RangeHashRes, error) {
	hashes := make([][]byte, 0, len(prm.rngs))

	for _, rng := range prm.rngs {
		h := prm.hashGen()

		// For big ranges we could fetch range-hashes from different nodes and concatenate them locally.
		// However,
		// 1. Potential gains are insignificant when operating in the Internet given typical latencies and losses.
		// 2. Parallel solution is more complex in terms of code.
		// 3. TZ-hash is likely to be disabled in private installations.
		reqPrm := RequestParameters{
			commonPrm: prm.commonPrm,
			rng:       &rng,
		}
		reqPrm.SetChunkWriter(&hasherWrapper{
			hash: util.NewSaltingWriter(h, prm.salt),
		})

		if err := s.get(ctx, reqPrm); err != nil {
			return nil, err
		}

		hashes = append(hashes, h.Sum(nil))
	}

	return &RangeHashRes{
		hashes: hashes,
	}, nil
}

// Head reads object header from container.
//
// Returns ErrNotFound if the header was not received for the call.
// Returns SplitInfoError if object is virtual and raw flag is set.
func (s *Service) Head(ctx context.Context, prm HeadPrm) error {
	return s.get(ctx, RequestParameters{
		head:      true,
		commonPrm: prm.commonPrm,
	})
}

func (s *Service) get(ctx context.Context, prm RequestParameters) error {
	exec := &request{
		keyStore:                 s.keyStore,
		traverserGenerator:       s.traverserGenerator,
		remoteStorageConstructor: s.remoteStorageConstructor,
		epochSource:              s.epochSource,
		localStorage:             s.localStorage,
		containerSource:          s.containerSource,

		prm:       prm,
		infoSplit: objectSDK.NewSplitInfo(),
		infoEC:    newECInfo(),
		log:       s.log,
	}

	exec.setLogger(s.log)

	exec.execute(ctx)

	return exec.statusError.err
}

func (exec *request) execute(ctx context.Context) {
	exec.log.Debug(ctx, logs.ServingRequest)

	// perform local operation
	exec.executeLocal(ctx)

	exec.analyzeStatus(ctx, true)
}

func (exec *request) analyzeStatus(ctx context.Context, execCnr bool) {
	// analyze local result
	switch exec.status {
	case statusOK:
		exec.log.Debug(ctx, logs.OperationFinishedSuccessfully)
	case statusINHUMED:
		exec.log.Debug(ctx, logs.GetRequestedObjectWasMarkedAsRemoved)
	case statusVIRTUAL:
		exec.log.Debug(ctx, logs.GetRequestedObjectIsVirtual)
		exec.assemble(ctx)
	case statusOutOfRange:
		exec.log.Debug(ctx, logs.GetRequestedRangeIsOutOfObjectBounds)
	case statusEC:
		exec.log.Debug(ctx, logs.GetRequestedObjectIsEC)
		if exec.isRaw() && execCnr {
			exec.executeOnContainer(ctx)
			exec.analyzeStatus(ctx, false)
		}
		exec.assembleEC(ctx)
	default:
		exec.log.Debug(ctx, logs.OperationFinishedWithError,
			zap.Error(exec.err),
		)
		var errAccessDenied *apistatus.ObjectAccessDenied
		if execCnr && errors.As(exec.err, &errAccessDenied) {
			// Local get can't return access denied error, so this error was returned by
			// write to the output stream. So there is no need to try to find object on other nodes.
			return
		}

		if execCnr {
			exec.executeOnContainer(ctx)
			exec.analyzeStatus(ctx, false)
		}
	}
}