package proxy

import (
	"context"
	"net/http"
	"net/netip"

	"sneak.berlin/go/smallwebwaf/internal/lookup"
)

// The headers in which the app is passed the client's AS number and
// country while SWWAF_ADD_LOOKUP_HEADERS is set. Go sends a header name in
// this form, so X-Client-ASN arrives as X-Client-Asn; header names are not
// case-sensitive.
const (
	asnHeader     = "X-Client-Asn"
	countryHeader = "X-Client-Country"
)

// lookUp looks up the client's AS number and country, and notes them for
// the log line, unless SWWAF_LOOKUP_SOURCE is off or the client is on a
// private, loopback or link-local address, which no lookup can place.
// While a setting needs the answer, a new client's request waits for it.
// ctx is the request's own context.
func (rq *request) lookUp(ctx context.Context) {
	if rq.h.config.LookupSource == "off" || !canBePlaced(rq.client) {
		return
	}

	answer := rq.h.geojs.LookUp(ctx, clientGroup(rq.client))
	rq.lookedUp = true
	rq.line.ASN = answer.ASN
	rq.line.ASName = answer.ASName
	rq.line.Country = answer.Country
}

// addLookup adds answer, GeoJS's answer about a client, to the client's
// history, and to the notes of the bans on its netblock that have no AS
// number, AS name or country yet.
func (h *handler) addLookup(answer lookup.Answer) {
	h.limiter.AddLookup(answer.Client, answer.Answered,
		answer.ASN, answer.ASName, answer.Country)
	h.ledger.AddLookup(h.netblock(answer.Client.Addr()),
		answer.ASN, answer.ASName, answer.Country)
}

// setLookupHeaders sets the headers in which the app is passed the
// client's AS number and country, leaving out one that is unknown. Any
// the client sent are removed, so that the app can believe them.
func setLookupHeaders(header http.Header, asn, country string) {
	header.Del(asnHeader)
	header.Del(countryHeader)

	if asn != "" {
		header.Set(asnHeader, asn)
	}

	if country != "" {
		header.Set(countryHeader, country)
	}
}

// canBePlaced reports whether a lookup can place addr: private, loopback
// and link-local addresses have no AS number or country.
func canBePlaced(addr netip.Addr) bool {
	return !addr.IsPrivate() && !addr.IsLoopback() && !addr.IsLinkLocalUnicast()
}