package edge

import (
	"context"
	"net"
	"net/http"
	"net/http/httputil"

	"github.com/carlosframework/platform/internal/geoip"
	"github.com/carlosframework/platform/internal/tunnelclient"
)

// geoResultKey carries the request's one geo answer (spec §8.2): computed
// at ingress or adopted from a trusted transport, read by setGeo, the cache
// path (through r.Header) and analytics.
type geoResultKey struct{}

func geoAnswerFrom(ctx context.Context) (geoip.Answer, bool) {
	a, ok := ctx.Value(geoResultKey{}).(geoip.Answer)
	return a, ok
}

// fromTunnel is the tunnel client's mark (geoip spec §8.4, D2): set on
// every request tunnelclient serves, never by anything a client sends.
var fromTunnel = tunnelclient.FromTunnel

// decideGeo is step 3 of spec §8.1. hopPresent says the request ARRIVED
// carrying X-Carlos-Hop (captured before acceptHop strips it); hopped says
// acceptHop verified it.
func (e *Edge) decideGeo(r *http.Request, c geoip.Captured, hopPresent, hopped, isDoor bool) geoip.Answer {
	switch {
	case isDoor:
		return geoip.Off() // RemoteAddr is this box (door.go)
	case hopped:
		return c.Adopt() // the sending edge looked up; never trust our own peer
	case hopPresent:
		return geoip.Off() // rejected hop: RemoteAddr is the sending edge (codex R2-1)
	case fromTunnel(r.Context()):
		return c.Adopt() // the hub looked up (spec §8.4)
	}
	ip := net.ParseIP(clientIP(r))
	return geoip.FromSnapshot(e.geoLookup(ip))
}

// setGeo is every Rewrite's geo step (spec §8.3): after hop-by-hop removal,
// delete every geo header from the outbound request and write the answer
// back from the context. forwardsToEdge adds X-Carlos-Hop-Geo for the next
// edge; an app never receives it.
func setGeo(pr *httputil.ProxyRequest, forwardsToEdge bool) {
	geoip.StripAll(pr.Out.Header)
	a, ok := geoAnswerFrom(pr.In.Context())
	if !ok {
		a = geoip.Off() // scheduler calls through UnixProxy and anything else that never passed ServeHTTP
	}
	a.WriteApp(pr.Out.Header)
	if forwardsToEdge {
		pr.Out.Header.Set(geoip.HeaderHop, a.HopValue())
	}
}