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 writes every header
// name in this form, as it sends it and as it receives it, so X-Client-ASN
// arrives as X-Client-Asn, and Del removes a client's own whatever their
// case; 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, in the lookup
// database or through GeoJS, 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. The lookup database
// answers at once. With GeoJS, 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
	}

	if rq.h.config.LookupSource == "file" {
		rq.lookupAnswer = rq.h.lookupFile.LookUp(clientGroup(rq.client))
	} else {
		rq.lookupAnswer = rq.h.geojs.LookUp(ctx, clientGroup(rq.client))
	}

	rq.lookedUp = true
	rq.line.ASN = rq.lookupAnswer.ASN
	rq.line.ASName = rq.lookupAnswer.ASName
	rq.line.Country = rq.lookupAnswer.Country
}

// addLookup adds answer, an answer about a client from the lookup
// database or GeoJS, 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.
func setLookupHeaders(header http.Header, asn, country string) {
	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()
}