package delivery_test

import (
	"context"
	"encoding/json"
	"log/slog"
	"net/http"
	"net/http/httptest"
	"net/url"
	"sync"
	"sync/atomic"
	"testing"
	"time"

	"github.com/google/uuid"
	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"
	"sneak.berlin/go/webhooker/internal/database"
	"sneak.berlin/go/webhooker/internal/delivery"
)

// The headers these tests drive stand in for the two classes the
// off-origin rule covers: an operator-configured credential and an
// inbound header the delivery path forwards. net/http withholds
// Authorization and Cookie across a host change, and nothing else.
const (
	probeHeaderName    = "X-Api-Key"
	probeHeaderValue   = "QQNEVERONTHEWIREQQ"
	inboundHeaderName  = "X-Hub-Signature"
	inboundHeaderValue = "sha1=QQINBOUNDQQ"
)

// redirectProbe records what the last hop of a redirect chain
// actually received.
type redirectProbe struct {
	mu   sync.Mutex
	seen http.Header
	hits int
}

func (p *redirectProbe) serve(
	w http.ResponseWriter, r *http.Request,
) {
	p.mu.Lock()
	p.seen = r.Header.Clone()
	p.hits++
	p.mu.Unlock()

	w.WriteHeader(http.StatusOK)
}

func (p *redirectProbe) result() (http.Header, int) {
	p.mu.Lock()
	defer p.mu.Unlock()

	return p.seen, p.hits
}

// deliverWithProbeHeaders runs one real delivery of a new task
// through the engine to targetURL, carrying both probe headers —
// probeHeaderName configured on the target, inboundHeaderName
// forwarded from the event — and returns the delivery status the
// engine recorded.
func deliverWithProbeHeaders(
	t *testing.T, targetURL string,
) database.DeliveryStatus {
	t.Helper()

	s := newISetup(t)

	event := iSeedEvent(
		t, s.WebhookDB, s.WebhookID, `{"hello":"world"}`,
	)
	targetID := uuid.New().String()

	inbound, err := json.Marshal(map[string][]string{
		inboundHeaderName: {inboundHeaderValue},
	})
	require.NoError(t, err)

	event.Headers = string(inbound)

	d := iSeedDelivery(
		t, s.WebhookDB, event.ID, targetID,
		database.DeliveryStatusPending,
	)

	cfg, err := json.Marshal(delivery.HTTPTargetConfig{
		URL: targetURL,
		Headers: map[string]string{
			probeHeaderName: probeHeaderValue,
		},
	})
	require.NoError(t, err)

	body := event.Body
	task := iTask(
		d, event, s.WebhookID, targetID,
		"redirect-target", string(cfg), 0, 1, &body,
	)

	s.Engine.ExportProcessNewTask(context.TODO(), &task)

	var updated database.Delivery

	require.NoError(t, s.WebhookDB.First(
		&updated, "id = ?", d.ID,
	).Error)

	return updated.Status
}

// A 302 to an origin the operator never configured must not carry
// the credential they configured for the one they did, nor the
// inbound header this delivery forwarded — one rule for both
// classes. The chain is still followed, so the delivery is recorded
// from the final hop.
func TestDelivery_CrossOriginRedirectDropsOriginScopedHeaders(
	t *testing.T,
) {
	t.Parallel()

	var probe redirectProbe

	final := httptest.NewServer(
		http.HandlerFunc(probe.serve),
	)
	defer final.Close()

	// httptest listens on loopback, so reach the second server
	// under loopback's other name: the hop then differs in
	// hostname as well as port and is cross-host by any reading.
	finalURL, err := url.Parse(final.URL)
	require.NoError(t, err)

	finalURL.Host = "localhost:" + finalURL.Port()
	finalURL.Path = "/moved"

	origin := httptest.NewServer(http.HandlerFunc(
		func(w http.ResponseWriter, r *http.Request) {
			http.Redirect(
				w, r, finalURL.String(),
				http.StatusFound,
			)
		},
	))
	defer origin.Close()

	status := deliverWithProbeHeaders(t, origin.URL)

	seen, hits := probe.result()

	assert.Equal(t, 1, hits,
		"the redirect must still be followed",
	)
	assert.Empty(t, seen.Get(probeHeaderName),
		"a configured credential header must not reach an "+
			"origin the operator did not configure",
	)
	assert.Empty(t, seen.Get(inboundHeaderName),
		"a forwarded inbound header must not reach an origin "+
			"the operator did not configure",
	)
	assert.Equal(t,
		database.DeliveryStatusDelivered, status,
		"the final hop's 200 is the delivery's result",
	)
}

// Stripping must not fire within the configured origin, or every
// destination that redirects its own path would lose its
// credential and start answering 401 — and would lose the inbound
// signature the receiver verifies.
func TestDelivery_SameOriginRedirectKeepsOriginScopedHeaders(
	t *testing.T,
) {
	t.Parallel()

	var probe redirectProbe

	srv := httptest.NewServer(http.HandlerFunc(
		func(w http.ResponseWriter, r *http.Request) {
			if r.URL.Path == "/moved" {
				probe.serve(w, r)

				return
			}

			http.Redirect(
				w, r, "/moved", http.StatusFound,
			)
		},
	))
	defer srv.Close()

	status := deliverWithProbeHeaders(t, srv.URL+"/hook")

	seen, hits := probe.result()

	assert.Equal(t, 1, hits)
	assert.Equal(t, probeHeaderValue, seen.Get(probeHeaderName),
		"a redirect within the configured origin must keep "+
			"the configured header",
	)
	assert.Equal(t,
		inboundHeaderValue, seen.Get(inboundHeaderName),
		"a redirect within the configured origin must keep "+
			"the forwarded inbound header",
	)
	assert.Equal(t,
		database.DeliveryStatusDelivered, status,
	)
}

// The origin comparison is deliberately stricter than the one
// net/http applies to Authorization: the port counts and a
// subdomain does not inherit. Only the default-port spellings of
// one origin are the same origin.
func TestSameDeliveryOrigin(t *testing.T) {
	t.Parallel()

	// The configured target URL every case redirects away from.
	// Destination paths differ only so that no literal repeats.
	const configured = "https://h/a"

	cases := map[string]struct {
		origin string
		dest   string
		want   bool
	}{
		"other path":           {configured, "https://h/b", true},
		"default port spelled": {configured, "https://h:443/c", true},
		"host in another case": {configured, "https://H/d", true},
		"http default port":    {"http://h:80/a", "http://h/e", true},
		"upgrade to https":     {"http://h/a", "https://h/f", true},
		"downgrade to http":    {configured, "http://h/g", false},
		"another host":         {configured, "https://i/h", false},
		"a subdomain":          {configured, "https://x.h/i", false},
		"the parent domain":    {"https://x.h/a", "https://h/j", false},
		"another port":         {configured, "https://h:8443/k", false},

		// Hostname() unwraps an IPv6 literal's brackets, so a
		// bracketed host whose last group is the origin's port
		// renders identically to the origin unless the port is
		// re-joined with brackets. Each dest below differs from
		// its origin in address AND in port.
		"ipv6 port as final group": {
			"https://[2001:db8::1]:8080/a",
			"https://[2001:db8::1:8080]/l",
			false,
		},
		"ipv6 loopback port as final group": {
			"https://[::1]:8080/a",
			"https://[::1:8080]/m",
			false,
		},
		"ipv6 same origin": {
			"https://[2001:db8::1]:8080/a",
			"https://[2001:DB8::1]:8080/n",
			true,
		},
	}

	for name, tc := range cases {
		t.Run(name, func(t *testing.T) {
			t.Parallel()

			origin, err := url.Parse(tc.origin)
			require.NoError(t, err)

			dest, err := url.Parse(tc.dest)
			require.NoError(t, err)

			assert.Equal(t, tc.want,
				delivery.ExportSameDeliveryOrigin(
					origin, dest,
				),
			)
		})
	}
}

// Installing a CheckRedirect discards net/http's own redirect
// limit, so the cap this policy restates is the only thing between
// a self-redirecting destination and an unbounded chain. A
// destination that always redirects must be cut off after exactly
// maxDeliveryRedirects requests, with the sentinel surfacing to the
// caller rather than a generic net/http error.
func TestRedirectPolicy_StopsAtHopCap(t *testing.T) {
	t.Parallel()

	var hits atomic.Int64

	srv := httptest.NewServer(http.HandlerFunc(
		func(w http.ResponseWriter, r *http.Request) {
			hits.Add(1)
			http.Redirect(
				w, r, "/loop", http.StatusFound,
			)
		},
	))
	defer srv.Close()

	engine := delivery.NewTestEngine(
		slog.New(slog.DiscardHandler),
		&http.Client{Timeout: 10 * time.Second},
		1,
	)

	client := engine.ExportClientForRequest(
		&delivery.HTTPTargetConfig{URL: srv.URL},
		[]string{probeHeaderName},
	)
	require.NotNil(t, client.CheckRedirect)

	req, err := http.NewRequestWithContext(
		context.Background(), http.MethodGet, srv.URL, http.NoBody,
	)
	require.NoError(t, err)

	resp, doErr := client.Do(req)
	if resp != nil {
		_ = resp.Body.Close()
	}

	require.Error(t, doErr,
		"an endless redirect chain must not be followed forever",
	)
	require.ErrorIs(t, doErr, delivery.ErrExportTooManyRedirects)

	assert.Equal(t,
		int64(delivery.ExportMaxDeliveryRedirects), hits.Load(),
		"the chain must stop after exactly %d hops",
		delivery.ExportMaxDeliveryRedirects,
	)
}

// The set the redirect policy strips is whatever the delivery path
// actually put on the wire, so a header added to the forward set is
// covered without a second edit. A header the event never carried
// is not in the set, and the delivery path's own two are deliberately
// excluded: Content-Type describes the body, which a 307 carries
// across hosts, and the inbound User-Agent every real sender supplies
// is overwritten before the request goes out.
func TestApplyRequestHeaders_ReportsOriginScopedNames(t *testing.T) {
	t.Parallel()

	inbound, err := json.Marshal(map[string][]string{
		inboundHeaderName: {inboundHeaderValue},
		"Content-Type":    {testContentType},
		"User-Agent":      {"curl/8.7.1"},
		"Host":            {"inbound.example.com"},
	})
	require.NoError(t, err)

	req, err := http.NewRequestWithContext(
		context.Background(),
		http.MethodPost,
		"https://target.example.com/hook",
		http.NoBody,
	)
	require.NoError(t, err)

	names := delivery.ExportApplyRequestHeaders(
		req,
		&database.Event{
			Headers:     string(inbound),
			ContentType: testContentType,
		},
		&delivery.HTTPTargetConfig{
			Headers: map[string]string{
				probeHeaderName: probeHeaderValue,
			},
		},
	)

	assert.Equal(t,
		[]string{probeHeaderName, inboundHeaderName}, names,
		"both header classes are reported, and only those: "+
			"Host is never forwarded, Content-Type and "+
			"User-Agent are the delivery path's own",
	)
}