package smallwebwaf_test

import (
	"bytes"
	"context"
	"encoding/json"
	"io"
	"net"
	"net/http"
	"net/http/httptest"
	"strings"
	"sync"
	"testing"
	"time"

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

const (
	// waitLimit bounds how long a test waits for what should happen.
	waitLimit = 10 * time.Second
	// pollInterval is how often a test looks for a line.
	pollInterval = 10 * time.Millisecond
	// testVersion is the version the tests give smallwebwaf.
	testVersion = "test"
	// localhost is where the tests listen.
	localhost  = "127.0.0.1"
	listenAddr = "SWWAF_LISTEN_ADDR"
)

// output collects what smallwebwaf writes on stdout.
type output struct {
	mu  sync.Mutex
	buf bytes.Buffer
}

// Write adds lines smallwebwaf writes.
func (o *output) Write(p []byte) (int, error) {
	o.mu.Lock()
	defer o.mu.Unlock()

	return o.buf.Write(p)
}

// line returns the first line whose field key is value, waiting for it.
func (o *output) line(t *testing.T, key, value string) map[string]any {
	t.Helper()

	deadline := time.Now().Add(waitLimit)
	for time.Now().Before(deadline) {
		o.mu.Lock()
		text := o.buf.String()
		o.mu.Unlock()

		for line := range strings.Lines(text) {
			var fields map[string]any

			err := json.Unmarshal([]byte(line), &fields)
			if err != nil {
				t.Fatalf("output line %q is not JSON: %v", line, err)
			}

			if fields[key] == value {
				return fields
			}
		}

		time.Sleep(pollInterval)
	}

	t.Fatalf("no line with %s %q in the output:\n%s", key, value, o.buf.String())

	return nil
}

// run runs smallwebwaf with the settings in env until ctx is done, and
// returns its exit status.
func run(ctx context.Context, env map[string]string, out *output) int {
	return smallwebwaf.Run(ctx, smallwebwaf.Params{
		Version: testVersion,
		LookupEnv: func(name string) (string, bool) {
			value, ok := env[name]

			return value, ok
		},
		Stdout: out,
	})
}

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

	out := &output{}

	status := run(t.Context(), map[string]string{"SWWAF_REQUEST_MAX_BYTES": "lots"}, out)
	if status != 1 {
		t.Errorf("exit status %d, want 1", status)
	}

	line := out.line(t, "msg", "invalid setting")
	message, _ := line["error"].(string)

	if line["type"] != "process" || line["level"] != "ERROR" ||
		!strings.HasPrefix(message, "SWWAF_REQUEST_MAX_BYTES: ") {
		t.Errorf("start refused with %v", line)
	}
}

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

	taken, err := (&net.ListenConfig{}).Listen(t.Context(), "tcp", localhost+":0")
	if err != nil {
		t.Fatalf("listen: %v", err)
	}

	defer func() {
		_ = taken.Close()
	}()

	out := &output{}

	status := run(t.Context(), map[string]string{listenAddr: taken.Addr().String()}, out)
	if status != 1 {
		t.Errorf("exit status %d, want 1", status)
	}

	out.line(t, "msg", "cannot listen on SWWAF_LISTEN_ADDR")
}

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

	app := httptest.NewServer(http.HandlerFunc(
		func(w http.ResponseWriter, _ *http.Request) {
			_, _ = io.WriteString(w, "hello from the app")
		}))
	defer app.Close()

	ctx, stop := context.WithCancel(t.Context())
	out := &output{}
	exited := make(chan int, 1)

	go func() {
		exited <- run(ctx, map[string]string{
			listenAddr:           localhost + ":0",
			"SWWAF_UPSTREAM_URL": app.URL,
		}, out)
	}()

	starting := out.line(t, "msg", "starting")
	wantStartingLine(t, starting, app.URL)

	addr, _ := starting["address"].(string)
	wantGreeting(t, "http://"+addr+"/")
	out.line(t, "type", "request")

	stop()

	select {
	case status := <-exited:
		if status != 0 {
			t.Errorf("exit status %d, want 0", status)
		}
	case <-time.After(waitLimit):
		t.Fatal("still running after being told to stop")
	}

	out.line(t, "msg", "stopped")
}

// wantStartingLine checks that the line at start gives the version and
// every setting's value.
func wantStartingLine(t *testing.T, line map[string]any, appURL string) {
	t.Helper()

	settings, _ := line["settings"].(map[string]any)
	want := map[string]any{
		listenAddr:                        localhost + ":0",
		"SWWAF_UPSTREAM_URL":              appURL,
		"SWWAF_TRUSTED_PROXIES":           "10.0.0.0/8,172.16.0.0/12,192.168.0.0/16",
		"SWWAF_CLIENT_REQUEST_TIMEOUT":    "60s",
		"SWWAF_CLIENT_RESPONSE_TIMEOUT":   "30m",
		"SWWAF_UPSTREAM_REQUEST_TIMEOUT":  "60s",
		"SWWAF_UPSTREAM_RESPONSE_TIMEOUT": "30m",
		"SWWAF_REQUEST_MAX_BYTES":         "100M",
		"SWWAF_RESPONSE_MAX_BYTES":        "5G",
	}

	for name, value := range want {
		if settings[name] != value {
			t.Errorf("starting line gives %s=%v, want %v", name, settings[name], value)
		}
	}

	if line["version"] != testVersion || line["type"] != "process" {
		t.Errorf("starting line %v", line)
	}
}

// wantGreeting checks that a request to url gets the app's answer.
func wantGreeting(t *testing.T, url string) {
	t.Helper()

	req, err := http.NewRequestWithContext(t.Context(), http.MethodGet, url,
		http.NoBody)
	if err != nil {
		t.Fatalf("new request: %v", err)
	}

	transport := &http.Transport{}
	defer transport.CloseIdleConnections()

	res, err := (&http.Client{Transport: transport}).Do(req)
	if err != nil {
		t.Fatalf("request: %v", err)
	}

	body, err := io.ReadAll(res.Body)
	_ = res.Body.Close()

	if err != nil || string(body) != "hello from the app" {
		t.Errorf("got %q (%v), want the app's answer", body, err)
	}
}