package smallwebwaf_test

import (
	"bytes"
	"context"
	"encoding/json"
	"io"
	"net"
	"net/http"
	"net/http/httptest"
	"os"
	"path/filepath"
	"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"
	upstreamURL          = "SWWAF_UPSTREAM_URL"
	trustedProxies       = "SWWAF_TRUSTED_PROXIES"
	stateDir             = "SWWAF_STATE_DIR"
	stateWriteDelay      = "SWWAF_STATE_WRITE_DELAY"
	stateCounterInterval = "SWWAF_STATE_COUNTER_INTERVAL"
	rateLimitPerDay      = "SWWAF_RATE_LIMIT_PER_DAY"
	// greeting is what the tests' app answers.
	greeting = "hello from the app"
)

// 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.text())

	return nil
}

// text returns everything written so far.
func (o *output) text() string {
	o.mu.Lock()
	defer o.mu.Unlock()

	return o.buf.String()
}

// 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 TestShortMetricsTokenStopsTheStartUnshown(t *testing.T) {
	t.Parallel()

	const token = "a-token-of-31-characters-at-all" //nolint:gosec // too short to use

	out := &output{}

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

	line := out.line(t, "msg", "invalid setting")
	if line["error"] != "SWWAF_METRICS_TOKEN: is shorter than 32 characters" {
		t.Errorf("start refused with %v", line)
	}

	if strings.Contains(out.text(), token) {
		t.Errorf("the output shows the token:\n%s", out.text())
	}
}

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(),
		stateDir:   t.TempDir(),
	}, 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()

	appURL := startApp(t)
	dir := t.TempDir()

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

	go func() {
		exited <- run(ctx, map[string]string{
			listenAddr:  localhost + ":0",
			upstreamURL: appURL,
			stateDir:    dir,
		}, out)
	}()

	starting := out.line(t, "msg", "starting")
	wantStartingLine(t, starting, appURL, dir)

	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")
}

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

	env := map[string]string{
		listenAddr:      localhost + ":0",
		upstreamURL:     startApp(t),
		stateDir:        t.TempDir(),
		rateLimitPerDay: "2",
		// Neither comes due in the test: the files are written as
		// smallwebwaf stops.
		stateWriteDelay:      "1h",
		stateCounterInterval: "1h",
	}

	// The two requests a day allows, and a stop.
	runUntilStopped(t, env, func(url string) {
		wantGreeting(t, url)
		wantGreeting(t, url)
	})

	// After a restart the client has no fresh allowance: its third
	// request breaks the day limit, and bans it.
	out := runUntilStopped(t, env, func(url string) {
		wantRefused(t, url)
	})
	out.line(t, "action", "rate_limited")

	// After another, the ban still refuses it.
	out = runUntilStopped(t, env, func(url string) {
		wantRefused(t, url)
	})
	out.line(t, "action", "banned")
}

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

	const scope = "SWWAF_BAN_SCOPE_V4_PREFIX"

	env := map[string]string{
		listenAddr:      localhost + ":0",
		upstreamURL:     startApp(t),
		stateDir:        t.TempDir(),
		trustedProxies:  localhost + "/32",
		rateLimitPerDay: "1",
		scope:           "24",
	}

	// 203.0.113.9's second request breaks the day limit, and bans
	// 203.0.113.0/24.
	runUntilStopped(t, env, func(url string) {
		wantStatus(t, url, "203.0.113.9", http.StatusOK)
		wantStatus(t, url, "203.0.113.9", http.StatusForbidden)
	})

	// With each address a netblock of its own after a restart, that ban
	// still refuses all of 203.0.113.0/24. 198.51.100.7 is banned alone.
	env[scope] = "32"
	runUntilStopped(t, env, func(url string) {
		wantStatus(t, url, "203.0.113.200", http.StatusForbidden)
		wantStatus(t, url, "203.0.114.1", http.StatusOK)
		wantStatus(t, url, "198.51.100.7", http.StatusOK)
		wantStatus(t, url, "198.51.100.7", http.StatusForbidden)
	})

	// With /24 netblocks again, that ban still refuses 198.51.100.7, and
	// no other address.
	env[scope] = "24"
	runUntilStopped(t, env, func(url string) {
		wantStatus(t, url, "198.51.100.7", http.StatusForbidden)
		wantStatus(t, url, "198.51.100.8", http.StatusOK)
	})
}

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

	const (
		// bans.json as an admin writes it with a ban, permanent, on
		// 203.0.113.0/24, and with none.
		oneBan = `{"version": 1, "bans": [{"netblock": "203.0.113.0/24", ` +
			`"start": "2026-10-06T00:00:00Z", "expires": null}]}`
		noBan = `{"version": 1, "bans": []}`
	)

	dir := t.TempDir()
	env := map[string]string{
		listenAddr:     localhost + ":0",
		upstreamURL:    startApp(t),
		stateDir:       dir,
		trustedProxies: localhost + "/32",
		// No write comes due in the test, so only the watch on the
		// directory can take the edits in.
		stateWriteDelay:      "1h",
		stateCounterInterval: "1h",
	}

	runUntilStopped(t, env, func(url string) {
		path := filepath.Join(dir, "bans.json")

		saveUntilAnswered(t, path, oneBan, url, "203.0.113.9", http.StatusForbidden)
		wantStatus(t, url, "198.51.100.7", http.StatusOK)
		saveUntilAnswered(t, path, noBan, url, "203.0.113.9", http.StatusOK)
	})
}

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

	dir := t.TempDir()

	err := os.WriteFile(filepath.Join(dir, "bans.json"), []byte("{\n"), 0o600)
	if err != nil {
		t.Fatalf("write bans.json: %v", err)
	}

	// The file ends at the newline that is the second byte of its first
	// line.
	wantStartRefused(t, dir, filepath.Join(dir, "bans.json")+", line 1, column 2: ")
}

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

	wantStartRefused(t, filepath.Join(t.TempDir(), "missing"),
		"SWWAF_STATE_DIR cannot be written: ")
}

// wantStartRefused runs smallwebwaf with its state files in dir, and
// checks that it stops at start, with an error that starts with want. If
// it starts instead, it is stopped after waitLimit.
func wantStartRefused(t *testing.T, dir, want string) {
	t.Helper()

	ctx, stop := context.WithTimeout(t.Context(), waitLimit)
	defer stop()

	out := &output{}

	status := run(ctx, map[string]string{listenAddr: localhost + ":0", stateDir: dir}, out)
	if status != 1 {
		t.Fatalf("exit status %d, want 1", status)
	}

	line := out.line(t, "msg", "cannot use the state files")
	message, _ := line["error"].(string)

	if !strings.HasPrefix(message, want) {
		t.Errorf("start refused with %q, want an error starting %q", message, want)
	}
}

// startApp starts an app that answers every request with greeting, and
// returns its URL.
func startApp(t *testing.T) string {
	t.Helper()

	app := httptest.NewServer(http.HandlerFunc(
		func(w http.ResponseWriter, _ *http.Request) {
			_, _ = io.WriteString(w, greeting)
		}))
	t.Cleanup(app.Close)

	return app.URL
}

// runUntilStopped runs smallwebwaf with the settings in env, has use send
// it requests at url, then stops it as SIGTERM does, checks that it
// stopped in order, and returns its output.
func runUntilStopped(
	t *testing.T, env map[string]string, use func(url string),
) *output {
	t.Helper()

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

	go func() {
		exited <- run(ctx, env, out)
	}()

	addr, _ := out.line(t, "msg", "starting")["address"].(string)
	use("http://" + addr + "/")
	stop()

	select {
	case status := <-exited:
		if status != 0 {
			t.Fatalf("exit status %d, want 0; output:\n%s", status, out.text())
		}
	case <-time.After(waitLimit):
		t.Fatal("still running after being told to stop")
	}

	return out
}

// 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, dir string) {
	t.Helper()

	settings, _ := line["settings"].(map[string]any)
	want := map[string]any{
		listenAddr:                              localhost + ":0",
		upstreamURL:                             appURL,
		stateDir:                                dir,
		"SWWAF_MODE":                            "enforce",
		stateWriteDelay:                         "10s",
		stateCounterInterval:                    "15m",
		trustedProxies:                          "10.0.0.0/8,172.16.0.0/12,192.168.0.0/16",
		"SWWAF_CLIENT_REQUEST_TIMEOUT":          "60s",
		"SWWAF_CLIENT_REQUEST_HEADER_MAX_BYTES": "32K",
		"SWWAF_CLIENT_IDLE_TIMEOUT":             "120s",
		"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",
		"SWWAF_ALLOW_NETS":                      "",
		"SWWAF_RATE_LIMIT_EXEMPT_NETS":          "",
		"SWWAF_DENY_NETS":                       "",
		"SWWAF_RATE_LIMIT_PER_MINUTE":           "1000",
		"SWWAF_RATE_LIMIT_PER_HOUR":             "10000",
		rateLimitPerDay:                         "50000",
		"SWWAF_DENIED_COUNTRIES":                "",
		"SWWAF_EXCLUSIVELY_ALLOWED_COUNTRIES":   "",
		"SWWAF_BAN_RESPONSE":                    "403",
		"SWWAF_LIMIT_BAN_DURATION":              "1h",
		"SWWAF_LIMIT_BAN_REPEAT_WINDOW":         "24h",
		"SWWAF_MAX_BAN_DURATION":                "7d",
		"SWWAF_MAX_BANS":                        "5000",
		"SWWAF_BAN_SCOPE_V4_PREFIX":             "32",
	}

	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) != greeting {
		t.Errorf("got %q (%v), want the app's answer", body, err)
	}
}

// wantRefused checks that a request to url is refused with 403, the
// default SWWAF_BAN_RESPONSE.
func wantRefused(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)
	}

	_ = res.Body.Close()

	if res.StatusCode != http.StatusForbidden {
		t.Errorf("status %d, want %d", res.StatusCode, http.StatusForbidden)
	}
}

// wantStatus checks that a request to url from the client at from, as
// X-Forwarded-For names it, is answered with status.
func wantStatus(t *testing.T, url, from string, status int) {
	t.Helper()

	got := statusFrom(t, url, from)
	if got != status {
		t.Errorf("request from %s: status %d, want %d", from, got, status)
	}
}

// saveUntilAnswered writes content to the state file at path, as an
// admin saves an edit of it, until a request to url from the client at
// from is answered with status. The file is written again before each
// request, since smallwebwaf may not watch its directory yet when it is
// first written. It waits as long as that takes, so that a slow test
// process cannot fail the test.
func saveUntilAnswered(t *testing.T, path, content, url, from string, status int) {
	t.Helper()

	for {
		err := os.WriteFile(path, []byte(content), 0o600)
		if err != nil {
			t.Fatalf("write %s: %v", path, err)
		}

		if statusFrom(t, url, from) == status {
			return
		}

		time.Sleep(pollInterval)
	}
}

// statusFrom returns the status a request to url from the client at
// from, as X-Forwarded-For names it, is answered with.
func statusFrom(t *testing.T, url, from string) int {
	t.Helper()

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

	req.Header.Set("X-Forwarded-For", from)

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

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

	_ = res.Body.Close()

	return res.StatusCode
}