package host

import (
	"bytes"
	"context"
	"crypto/sha256"
	"encoding/hex"
	"encoding/json"

	"github.com/carlosframework/platform/internal/hostactors"
	"github.com/carlosframework/platform/internal/hostbox"
	"github.com/carlosframework/platform/internal/hostclaim"
	"github.com/carlosframework/platform/internal/hostevidence"
	"github.com/carlosframework/platform/internal/release"
)

// RelocationReleaseReceipts discharges only the stop obligation. The region
// worker still owns the journal and executor transfer after this CAS.
type RelocationReleaseReceipts struct {
	Store     release.Store
	Directory hostactors.Directory
}

func (r RelocationReleaseReceipts) Complete(ctx context.Context, observed hostclaim.Observed, key, digest string) (hostclaim.Observed, error) {
	if ctx == nil || r.Store == nil || observed.Absent || observed.Claim == nil || observed.Claim.Holder == nil || observed.ETag == "" {
		return hostclaim.Observed{}, ErrClaimStopIdentity
	}
	c := observed.Claim
	if c.Op.Kind != hostclaim.KindRelocating || c.Op.Phase != "releasing" || c.Op.ID == "" || c.Op.Exec != c.Op.Intent["source_box"] || c.Op.Exec == "" {
		return hostclaim.Observed{}, ErrClaimStopIdentity
	}
	raw, _, err := r.Store.Get(ctx, key)
	if err != nil {
		return hostclaim.Observed{}, err
	}
	sum := sha256.Sum256(raw)
	if hex.EncodeToString(sum[:]) != digest {
		return hostclaim.Observed{}, ErrClaimStopReceipt
	}
	var receipt StopReceipt
	if json.Unmarshal(raw, &receipt) != nil {
		return hostclaim.Observed{}, ErrClaimStopReceipt
	}
	canonical, err := json.Marshal(receipt)
	if err != nil || !bytes.Equal(raw, canonical) {
		return hostclaim.Observed{}, ErrClaimStopReceipt
	}
	h := c.Holder
	if receipt.V != 1 || key != stopEvidenceKey(c.Host, c.Op.ID, c.Op.Exec, receipt.ID) || receipt.Host != c.Host || receipt.Incarnation != h.Incarnation || receipt.InstallationStamp != h.Stamp || receipt.WriterSession != h.Session || receipt.OperationID != c.Op.ID || receipt.Phase != c.Op.Phase || receipt.ObligationID != "relocation-release" || receipt.Box != c.Op.Exec || receipt.Region != c.Op.Intent["region"] || receipt.Enrollment != c.Op.Intent["source_enrollment"] || receipt.EvidenceAt.IsZero() || receipt.RequestLimitNS != int64(hostbox.RequestLimit) || receipt.ClaimGen == 0 || len(receipt.CgroupIdentities) == 0 || !stopDigest(receipt.InventorySHA256) || !stopDigest(receipt.LocalJournalSHA256) {
		return hostclaim.Observed{}, ErrClaimStopReceipt
	}
	if h.Session == 0 {
		replayed := c.Op.Journal["release_stop_receipt"] == key && c.Op.Journal["release_stop_sha256"] == digest
		if receipt.Kind != StopReceiptNoProcess || receipt.FenceID != "" || receipt.ProducerDrainDigest != "" || receipt.ClaimETag == "" || (!replayed && receipt.ClaimETag != observed.ETag) || h.WriterBox != "" || h.Generation != "" || len(h.Admissions) != 0 {
			return hostclaim.Observed{}, ErrClaimStopReceipt
		}
	} else if receipt.Kind != "stopped" || receipt.FenceID == "" || !stopDigest(receipt.ProducerDrainDigest) {
		return hostclaim.Observed{}, ErrClaimStopReceipt
	}
	roster, err := r.Directory.Read(ctx)
	if err != nil {
		return hostclaim.Observed{}, err
	}
	box, ok := roster.Roster.Boxes[receipt.Box]
	if !ok || box.Enrollment != receipt.Enrollment || box.Region != receipt.Region {
		return hostclaim.Observed{}, ErrClaimStopIdentity
	}
	signature, _, err := r.Store.Get(ctx, key+".sig")
	if err != nil {
		return hostclaim.Observed{}, err
	}
	if err = hostevidence.Verify(box.CensusPublicKey, key, raw, signature); err != nil {
		return hostclaim.Observed{}, err
	}
	if c.Op.Journal["release_stop_receipt"] == key && c.Op.Journal["release_stop_sha256"] == digest {
		for _, ob := range c.Obligations {
			if ob.ID == receipt.ObligationID && ob.Op == receipt.OperationID {
				return hostclaim.Observed{}, ErrClaimStopReceipt
			}
		}
		return observed, nil
	}
	if c.Op.Journal["release_stop_receipt"] != "" || c.Op.Journal["release_stop_sha256"] != "" {
		return hostclaim.Observed{}, ErrClaimStopReceipt
	}
	return hostclaim.Update(ctx, r.Store, observed, func(next *hostclaim.Claim) error {
		for i, ob := range next.Obligations {
			if ob.ID == receipt.ObligationID && ob.Op == receipt.OperationID && ob.Kind == "relocation-release" && ob.Park == nil && ob.Box == receipt.Box && ob.Region == receipt.Region && ob.Owner == "region:"+receipt.Region {
				if next.Op.Journal == nil {
					next.Op.Journal = map[string]string{}
				}
				next.Op.Journal["release_stop_receipt"] = key
				next.Op.Journal["release_stop_sha256"] = digest
				next.Obligations = append(next.Obligations[:i], next.Obligations[i+1:]...)
				return nil
			}
		}
		return hostclaim.ErrWrongState
	})
}