package relay

import (
	"git.mleku.dev/mleku/dendrite/pkg/axiom"
	"git.mleku.dev/mleku/dendrite/pkg/nostr"
)

// CoherenceFilter rejects events whose decomposed elements don't bond
// to any existing lattice structure. An event that produces zero
// elements matching any known constraint is structurally incoherent
// with the relay's content — noise, not signal.
type CoherenceFilter struct {
	// KnownTypes is the set of element type tags that the lattice
	// currently has sites for. Events must produce at least one
	// element with a type in this set to pass the filter.
	KnownTypes map[string]bool
}

// Admits returns true if the event's decomposed elements include at
// least one element type known to the lattice. An event that bonds
// nowhere is spam — it has no structural relationship to the content
// the relay serves.
func (f *CoherenceFilter) Admits(ev *nostr.Event) bool {
	if len(f.KnownTypes) == 0 {
		return true // no filter configured → admit all
	}

	elems := nostr.EventToElements(ev)
	for _, e := range elems {
		if f.KnownTypes[e.Type()] {
			return true
		}
	}
	return false
}

// NewCoherenceFilter creates a filter from a set of constraints.
// The filter admits events that produce elements matching any of
// the constraint tags.
func NewCoherenceFilter(constraints []axiom.Constraint) *CoherenceFilter {
	types := make(map[string]bool, len(constraints))
	for _, c := range constraints {
		types[c.Tag()] = true
	}
	return &CoherenceFilter{KnownTypes: types}
}