package nip10

import "github.com/nbd-wtf/go-nostr"

func GetThreadRoot(tags nostr.Tags) *nostr.Tag {
	for _, tag := range tags {
		if len(tag) >= 4 && tag[0] == "e" && tag[3] == "root" {
			return &tag
		}
	}

	return tags.GetFirst([]string{"e", ""})
}

func GetImmediateReply(tags nostr.Tags) *nostr.Tag {
	var root *nostr.Tag
	var lastE *nostr.Tag

	for i := len(tags) - 1; i >= 0; i-- {
		tag := tags[i]

		if len(tag) < 2 {
			continue
		}
		if tag[0] != "e" {
			continue
		}

		if len(tag) >= 4 {
			if tag[3] == "reply" {
				return &tag
			}
			if tag[3] == "root" {
				// will be used as our first fallback
				root = &tag
				continue
			}
			if tag[3] == "mention" {
				// this invalidates this tag as a second fallback mechanism (clients that don't add markers)
				continue
			}
		}

		lastE = &tag // will be used as our second fallback (clients that don't add markers)
	}

	// if we reached this point we don't have a "reply", but if we have a "root"
	// that means this event is a direct reply to the root
	if root != nil {
		return root
	}

	// if we reached this point and we have at least one "e" we'll use that (the last)
	return lastE
}