package versions

import (
	"context"
	"fmt"
)

// The registry seats' events the builder hears on its durable consumer of each `<seat>.events` (design 51 *How a
// publish ends*, DLV-B4).
const (
	HeardPublished = "published"
	HeardRefused   = "refused"
	HeardRemoved   = "removed"
	HeardKept      = "kept"
)

// Outcome is the body of a registry seat's published, refused and removed (mesh-contracts parts/registry Outcome), the
// fields the builder reads.
type Outcome struct {
	Name    string `json:"name"`
	Version string `json:"version,omitempty"`
	Digest  string `json:"digest"`
	Kind    string `json:"kind"`
	Holder  string `json:"holder"`
	Reason  string `json:"reason,omitempty"`
	// Tags are, on kept, the other tags still naming its digest.
	Tags []string `json:"tags,omitempty"`
}

// RemoveOutcome is what a seat's remove answered: kept whole (another tag names its digest), with why and those tags; or
// asked, the seat saying removed on its events.
type RemoveOutcome struct {
	Kept   bool
	Reason string
	Tags   []string
}

// keep marks a tagged version kept by its seat, so it is asked no more.
func (n *Numberer) keep(ctx context.Context, e Entry, reason string, tags []string) error {
	if reason == "" {
		reason = "shared-digest"
	}
	_, err := n.Versions.Mark(ctx, e.Name, e.Version, func(x *Entry) {
		x.State, x.Reason, x.KeptWith = Kept, reason, append([]string(nil), tags...)
	})
	return err
}

// Heard takes one seat event in: a numbered version's entry turns published (with its digest when it held none),
// refused with the holder's reason, removed with its reason and the event's id, or kept (another tag names its digest)
// with the other tags; a by-digest publish (no version)
// marks nothing. It answers the names waiting on their floor that the event wakes: a `published` says the seat
// answers (design 51 *The floor*).
func (n *Numberer) Heard(ctx context.Context, seat, event, id string, o Outcome) ([]string, error) {
	var wake []string
	if event == HeardPublished && n.Waits != nil {
		wake = n.Waits.Wake(WakePublished, seat, "", "")
	}
	if o.Version == "" {
		return wake, nil
	}
	var change func(*Entry)
	switch event {
	case HeardPublished:
		change = func(e *Entry) {
			e.State, e.Reason = Published, ""
			if e.Digest == "" {
				e.Digest = o.Digest
			}
		}
	case HeardRefused:
		change = func(e *Entry) {
			if e.State != Published {
				e.State, e.Reason, e.RefusedDigest = Refused, o.Reason, o.Digest
			}
		}
	case HeardRemoved:
		change = func(e *Entry) { e.State, e.Reason, e.RemovedBy = Removed, o.Reason, id }
	case HeardKept:
		change = func(e *Entry) {
			if e.State != Removed {
				e.State, e.Reason, e.KeptWith = Kept, o.Reason, append([]string(nil), o.Tags...)
				if e.Reason == "" {
					e.Reason = "shared-digest"
				}
			}
		}
	default:
		return wake, fmt.Errorf("%s says %q, which the builder does not hear", seat, event)
	}
	if _, err := n.Versions.Mark(ctx, o.Name, o.Version, change); err != nil {
		return wake, fmt.Errorf("%s's %s of %s@%s: %w", seat, event, o.Name, o.Version, err)
	}
	return wake, nil
}