package graph

import (
	"sync"

	"gitea.unbound.se/unboundsoftware/schemas/graph/model"
)

// PubSub handles publishing schema updates to subscribers
type PubSub struct {
	mu          sync.RWMutex
	subscribers map[string][]chan *model.SchemaUpdate
}

func NewPubSub() *PubSub {
	return &PubSub{
		subscribers: make(map[string][]chan *model.SchemaUpdate),
	}
}

// Subscribe creates a new subscription channel for a given schema ref
func (ps *PubSub) Subscribe(ref string) chan *model.SchemaUpdate {
	ps.mu.Lock()
	defer ps.mu.Unlock()

	ch := make(chan *model.SchemaUpdate, 10)
	ps.subscribers[ref] = append(ps.subscribers[ref], ch)

	return ch
}

// Unsubscribe removes a subscription channel
func (ps *PubSub) Unsubscribe(ref string, ch chan *model.SchemaUpdate) {
	ps.mu.Lock()
	defer ps.mu.Unlock()

	subs := ps.subscribers[ref]
	for i, sub := range subs {
		if sub == ch {
			// Remove this subscriber
			ps.subscribers[ref] = append(subs[:i], subs[i+1:]...)
			close(sub)
			break
		}
	}

	// Clean up empty subscriber lists
	if len(ps.subscribers[ref]) == 0 {
		delete(ps.subscribers, ref)
	}
}

// Publish sends a schema update to all subscribers of a given ref
func (ps *PubSub) Publish(ref string, update *model.SchemaUpdate) {
	ps.mu.RLock()
	defer ps.mu.RUnlock()

	for _, ch := range ps.subscribers[ref] {
		// Non-blocking send - if subscriber is slow, skip
		select {
		case ch <- update:
		default:
			// Channel full, subscriber is too slow - skip this update
		}
	}
}