package proxy_test

import (
	"encoding/json"
	"maps"
	"net/http"
	"net/http/httptest"
	"slices"
	"strings"
	"sync"
	"sync/atomic"
	"testing"

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

// The clients the stand-in for GeoJS knows about.
const (
	// fromDE is placed in Germany.
	fromDE = client
	// fromKP is placed in North Korea.
	fromKP = "198.51.100.7"
	// unplaced cannot be placed in any country.
	unplaced = "192.0.2.1"
)

func TestCountryLists(t *testing.T) {
	t.Parallel()

	for _, tc := range []struct {
		name    string
		env     map[string]string
		refused []string
	}{
		{"denied", map[string]string{deniedCountries: "kp"}, []string{fromKP}},
		{
			"exclusively allowed", map[string]string{allowedCountries: "DE"},
			[]string{fromKP, unplaced},
		},
		{
			"both", map[string]string{deniedCountries: "kp", allowedCountries: "de,fr"},
			[]string{fromKP, unplaced},
		},
	} {
		t.Run(tc.name, func(t *testing.T) {
			t.Parallel()

			var calls atomic.Int32

			app := startApp(t, func(http.ResponseWriter, *http.Request) {
				calls.Add(1)
			})
			geojsURL, _ := startGeoJS(t)
			env := map[string]string{trustedProxies: trustLocalhost}
			maps.Copy(env, tc.env)
			addr, out := startProxyWithGeoJS(t, app.URL, geojsURL, env)

			for i, sent := range []struct{ client, country string }{
				{fromDE, "DE"}, {fromKP, "KP"}, {unplaced, ""},
			} {
				req := newRequest(t, http.MethodGet, addr, "/", http.NoBody)
				req.Header.Set(forwardedFor, sent.client)
				got := do(t, req)

				line := out.requestLines(t, i+1)[i]
				if line.Country != sent.country {
					t.Errorf("log line has country %q, want %q", line.Country, sent.country)
				}

				if slices.Contains(tc.refused, sent.client) {
					wantStatus(t, got, http.StatusForbidden)
					wantLine(t, line, http.StatusForbidden, requestlog.ActionCountryDenied)
				} else {
					wantStatus(t, got, http.StatusOK)
					wantLine(t, line, http.StatusOK, requestlog.ActionForward)
				}
			}

			if int(calls.Load()) != 3-len(tc.refused) {
				t.Errorf("the app was called %d times, want %d",
					calls.Load(), 3-len(tc.refused))
			}
		})
	}
}

func TestCountryRefusalComesBeforeTheBodyAndTheRateLimits(t *testing.T) {
	t.Parallel()

	var calls atomic.Int32

	app := startApp(t, func(http.ResponseWriter, *http.Request) {
		calls.Add(1)
	})
	geojsURL, _ := startGeoJS(t)
	addr, out := startProxyWithGeoJS(t, app.URL, geojsURL, map[string]string{
		trustedProxies:     trustLocalhost,
		deniedCountries:    "kp",
		rateLimitPerMinute: "1",
	})

	// With a limit of one request a minute, the second request would be
	// over it, were refused requests counted.
	for i := range 2 {
		req := newRequest(t, http.MethodPost, addr, "/", strings.NewReader("a body"))
		req.Header.Set(forwardedFor, fromKP)
		wantStatus(t, do(t, req), http.StatusForbidden)

		line := out.requestLines(t, i+1)[i]
		wantLine(t, line, http.StatusForbidden, requestlog.ActionCountryDenied)

		if line.RequestBytes != 0 || line.LimitHit != "" {
			t.Errorf("log line has request_bytes %d and limit_hit %q, want 0 and none",
				line.RequestBytes, line.LimitHit)
		}
	}

	if calls.Load() != 0 {
		t.Errorf("the app was called %d times, want none", calls.Load())
	}
}

func TestCountryNotLookedUpWithoutAListOrForAPrivateAddress(t *testing.T) {
	t.Parallel()

	for _, tc := range []struct {
		name    string
		env     map[string]string
		clients []string // "" sends no X-Forwarded-For: the client is 127.0.0.1
	}{
		{"no country list is set", nil, []string{fromKP, fromDE}},
		{
			"private, loopback and link-local addresses",
			map[string]string{allowedCountries: "de"},
			[]string{"10.0.0.5", "192.168.1.9", "fd00::5", "", "169.254.0.9", "fe80::9"},
		},
	} {
		t.Run(tc.name, func(t *testing.T) {
			t.Parallel()

			app := startApp(t, func(http.ResponseWriter, *http.Request) {})
			geojsURL, asked := startGeoJS(t)
			env := map[string]string{trustedProxies: trustLocalhost}
			maps.Copy(env, tc.env)
			addr, out := startProxyWithGeoJS(t, app.URL, geojsURL, env)

			for i, sent := range tc.clients {
				req := newRequest(t, http.MethodGet, addr, "/", http.NoBody)
				if sent != "" {
					req.Header.Set(forwardedFor, sent)
				}

				wantStatus(t, do(t, req), http.StatusOK)

				line := out.requestLines(t, i+1)[i]
				wantLine(t, line, http.StatusOK, requestlog.ActionForward)

				country, present := line.fields["country"]
				if !present || country != "" {
					t.Errorf("log line for %q has country %v, want an empty one",
						line.ClientIP, country)
				}
			}

			if len(asked()) != 0 {
				t.Errorf("GeoJS was asked about %v, want nothing", asked())
			}
		})
	}
}

// startGeoJS starts a stand-in for GeoJS, which places fromDE and fromKP
// and no other address. It returns its URL, and what returns the
// addresses it has been asked about.
func startGeoJS(t *testing.T) (string, func() []string) {
	t.Helper()

	places := map[string]string{fromDE: "DE", fromKP: "KP"}

	var asked struct {
		mu    sync.Mutex
		addrs []string
	}

	geojs := httptest.NewServer(http.HandlerFunc(
		func(w http.ResponseWriter, r *http.Request) {
			addrs := strings.Split(r.URL.Query().Get("ip"), ",")

			asked.mu.Lock()
			asked.addrs = append(asked.addrs, addrs...)
			asked.mu.Unlock()

			answers := make([]map[string]string, 0, len(addrs))
			for _, addr := range addrs {
				answers = append(answers, map[string]string{
					"ip": addr, "country": places[addr],
				})
			}

			err := json.NewEncoder(w).Encode(answers)
			if err != nil {
				http.Error(w, err.Error(), http.StatusInternalServerError)
			}
		}))
	t.Cleanup(geojs.Close)

	return geojs.URL, func() []string {
		asked.mu.Lock()
		defer asked.mu.Unlock()

		return slices.Clone(asked.addrs)
	}
}