package hostbox

import (
	"context"
	"crypto/sha256"
	"encoding/hex"
	"encoding/json"
	"github.com/carlosframework/platform/internal/hostguard"
	"math"
	"slices"
)

type ProducerCompletion struct {
	Count  uint64
	Digest string
}

func (c ProducerCompletion) Valid() bool {
	if c.Count == 0 {
		return c.Digest == ""
	}
	b, err := hex.DecodeString(c.Digest)
	return err == nil && len(b) == sha256.Size
}

// CompleteProducer atomically removes a joined producer and extends its durable
// completion chain. The previous value permits replay after a lost commit reply.
func (j *LaunchJournal) CompleteProducer(ctx context.Context, t hostguard.FenceTarget, id string, previous ProducerCompletion) (ProducerCompletion, error) {
	if j == nil {
		return previous, ErrUnsupported
	}
	if j.remote != nil {
		out, err := journalCall(ctx, j.remote, JournalRequest{Op: "complete", Target: t, Producer: id, Previous: previous})
		return out.Completion, err
	}

	if !component(id) || !previous.Valid() || previous.Count == math.MaxUint64 {
		return previous, ErrTypedInventory
	}
	raw, _ := json.Marshal(struct {
		Previous ProducerCompletion
		ID       string
	}{previous, id})
	digest := sha256.Sum256(raw)
	next := ProducerCompletion{Count: previous.Count + 1, Digest: hex.EncodeToString(digest[:])}
	err := j.mutate(ctx, t, func(in *LaunchInventory) error {
		i := slices.Index(in.ProducerIDs, id)
		if i < 0 && in.Completed == next {
			return nil
		}
		if i < 0 || in.Completed != previous {
			return ErrChanged
		}
		in.ProducerIDs = slices.Delete(in.ProducerIDs, i, i+1)
		in.Completed = next
		return nil
	})
	if err != nil {
		return previous, err
	}
	return next, nil
}

func (j *LaunchJournal) RecordProducer(ctx context.Context, t hostguard.FenceTarget, id string) error {
	if j == nil {
		return ErrUnsupported
	}
	if j.remote != nil {
		out, err := journalCall(ctx, j.remote, JournalRequest{Op: "producer", Target: t, Producer: id})
		_ = out
		return err
	}

	if !component(id) {
		return ErrTypedInventory
	}
	return j.mutate(ctx, t, func(in *LaunchInventory) error {
		for _, old := range in.ProducerIDs {
			if old == id {
				return ErrTypedInventory
			}
		}
		in.ProducerIDs = append(in.ProducerIDs, id)
		return nil
	})
}