// Package crawler discovers Nostr relays by extracting relay URLs
// from kind 10002 (relay list metadata) events stored locally.
package crawler

import (
	"git.smesh.lol/moxie/pkg/mxutil"
	"git.smesh.lol/nostr/pkg/filter"
	"git.smesh.lol/nostr/pkg/kind"
	"git.smesh.lol/morly/pkg/store"
)

// Crawler discovers relay URLs from the local store.
type Crawler struct {
	store *store.Engine
}

// New creates a crawler.
func New(s *store.Engine) (c *Crawler) { return &Crawler{store: s} }

// Relay is a discovered relay with its usage hints.
type Relay struct {
	URL   string
	Read  bool
	Write bool
}

// Discover scans the store for kind 10002 events and extracts relay URLs.
// Returns deduplicated relays.
func (c *Crawler) Discover() (rs []Relay) {
	kind.Ensure()
	f := &filter.F{
		Kinds: kind.NewS(kind.RelayListMetadata),
	}
	events, err := c.store.QueryEvents(f)
	if err != nil {
		return nil
	}

	seen := map[string]*Relay{}
	for _, ev := range events {
		if ev.Tags == nil {
			continue
		}
		rTags := ev.Tags.GetAll([]byte("r"))
		for _, rt := range rTags {
			if rt.Len() < 2 {
				continue
			}
			url := string(rt.Value())
			if url == "" {
				continue
			}
			r, ok := seen[url]
			if !ok {
				r = &Relay{URL: url}
				seen[url] = r
			}
			// Third element is optional: "read", "write", or absent (both).
			hint := rt.Relay()
			if len(hint) == 0 {
				r.Read = true
				r.Write = true
			} else if string(hint) == "read" {
				r.Read = true
			} else if string(hint) == "write" {
				r.Write = true
			}
		}
	}

	out := []Relay{:0:len(seen)}
	for _, r := range seen {
		out = mxutil.Ensure(out, 1)
		out = push(out, *r)
	}
	return out
}

// DiscoverURLs returns just the relay URL strings.
func (c *Crawler) DiscoverURLs() (ss []string) {
	relays := c.Discover()
	urls := []string{:len(relays)}
	for i, r := range relays {
		urls[i] = r.URL
	}
	return urls
}