package handlers

import (
	"log/slog"
	"net/http"
	"net/http/httptest"
	"net/url"
	"regexp"
	"strings"
	"testing"

	"sneak.berlin/go/pixa/internal/imgcache"
	"sneak.berlin/go/pixa/internal/session"
)

// formatField is the generator form's format field name.
const formatField = "format"

// Markers telling the login page from the generator page.
const (
	loginForm     = `action="/"`
	loginKeyInput = `name="key"`
	generatorForm = `action="/generate"`
)

// generatedURLPattern extracts the path of the URL the generator page shows.
// The test router runs with debug on, so the URL starts with http, and its
// host is httptest's default request host.
var generatedURLPattern = regexp.MustCompile(
	`value="http://example\.com(/v1/e/[^"]+)"`)

// findSessionCookie returns the session cookie rec sets, or nil if it sets
// none.
func findSessionCookie(rec *httptest.ResponseRecorder) *http.Cookie {
	for _, c := range rec.Result().Cookies() {
		if c.Name == session.CookieName {
			return c
		}
	}

	return nil
}

// TestHandleRoot_NoSession_ShowsLoginForm verifies that GET / without a
// login session shows the login form.
func TestHandleRoot_NoSession_ShowsLoginForm(t *testing.T) {
	t.Parallel()

	_, srv := newCSRFTestRouter(t)

	rec := httptest.NewRecorder()
	srv.ServeHTTP(rec, httptest.NewRequestWithContext(
		t.Context(), http.MethodGet, "/", nil))

	if rec.Code != http.StatusOK {
		t.Fatalf("status = %d, want %d", rec.Code, http.StatusOK)
	}

	body := rec.Body.String()
	if !strings.Contains(body, loginForm) || !strings.Contains(body, loginKeyInput) {
		t.Errorf("page is not the login form: %s", body)
	}
}

// TestLoginPost_WrongKey_ShowsErrorWithoutSession verifies that a wrong key
// shows the login form again with an error, and sets no session cookie.
func TestLoginPost_WrongKey_ShowsErrorWithoutSession(t *testing.T) {
	t.Parallel()

	_, srv := newCSRFTestRouter(t)

	cookies, token := csrfCredentials(t, srv, nil)

	rec := postForm(srv, "/", cookies, url.Values{
		loginKeyField:  {"wrong-signing-key-fedcba9876543210"},
		csrfTokenField: {token},
	})

	if rec.Code != http.StatusOK {
		t.Fatalf("status = %d, want %d", rec.Code, http.StatusOK)
	}

	body := rec.Body.String()
	if !strings.Contains(body, loginForm) || !strings.Contains(body, loginKeyInput) {
		t.Errorf("page is not the login form: %s", body)
	}

	if !strings.Contains(body, "Invalid signing key") {
		t.Error("login form does not show the error")
	}

	if c := findSessionCookie(rec); c != nil {
		t.Errorf("wrong key set a session cookie: %s", c)
	}
}

// TestLoginPost_RightKey_SetsSessionCookie verifies that the right key answers
// 303 to / with a session cookie marked Secure, HttpOnly and SameSite=Strict,
// and that GET / with that cookie shows the generator page.
func TestLoginPost_RightKey_SetsSessionCookie(t *testing.T) {
	t.Parallel()

	_, srv := newCSRFTestRouter(t)

	cookies, token := csrfCredentials(t, srv, nil)

	rec := postForm(srv, "/", cookies, url.Values{
		loginKeyField:  {testSigningKey},
		csrfTokenField: {token},
	})

	if rec.Code != http.StatusSeeOther || rec.Header().Get("Location") != "/" {
		t.Fatalf("status = %d, Location = %q, want %d to /",
			rec.Code, rec.Header().Get("Location"), http.StatusSeeOther)
	}

	sessionCookie := findSessionCookie(rec)
	if sessionCookie == nil {
		t.Fatal("right key set no session cookie")
	}

	t.Logf("Set-Cookie: %s", sessionCookie)

	if !sessionCookie.Secure {
		t.Error("session cookie is not Secure")
	}

	if !sessionCookie.HttpOnly {
		t.Error("session cookie is not HttpOnly")
	}

	if sessionCookie.SameSite != http.SameSiteStrictMode {
		t.Errorf("session cookie SameSite = %v, want Strict", sessionCookie.SameSite)
	}

	req := httptest.NewRequestWithContext(t.Context(), http.MethodGet, "/", nil)
	req.AddCookie(sessionCookie)

	rec = httptest.NewRecorder()
	srv.ServeHTTP(rec, req)

	if rec.Code != http.StatusOK ||
		!strings.Contains(rec.Body.String(), generatorForm) {
		t.Errorf("GET / with the session cookie: status = %d, "+
			"want %d and the generator page", rec.Code, http.StatusOK)
	}
}

// TestHandleLogout_ClearsSessionCookie verifies that GET /logout answers 303
// to / and replaces the session cookie with an empty one sent with
// Max-Age=0, which makes the browser delete it.
func TestHandleLogout_ClearsSessionCookie(t *testing.T) {
	t.Parallel()

	h, _ := newCSRFTestRouter(t)

	req := httptest.NewRequestWithContext(
		t.Context(), http.MethodGet, "/logout", nil)
	req.AddCookie(newSessionCookie(t, h))

	rec := httptest.NewRecorder()
	h.HandleLogout().ServeHTTP(rec, req)

	if rec.Code != http.StatusSeeOther || rec.Header().Get("Location") != "/" {
		t.Fatalf("status = %d, Location = %q, want %d to /",
			rec.Code, rec.Header().Get("Location"), http.StatusSeeOther)
	}

	t.Logf("Set-Cookie: %s", rec.Header().Get("Set-Cookie"))

	sessionCookie := findSessionCookie(rec)
	if sessionCookie == nil {
		t.Fatal("logout did not set the session cookie")
	}

	if sessionCookie.Value != "" {
		t.Errorf("session cookie value = %q, want empty", sessionCookie.Value)
	}

	// net/http reads a Max-Age=0 attribute back as MaxAge -1.
	if sessionCookie.MaxAge != -1 {
		t.Errorf("session cookie MaxAge = %d, want -1 (Max-Age=0)",
			sessionCookie.MaxAge)
	}
}

// TestGeneratePost_NoSession_RedirectsToLogin verifies that POST /generate
// with a valid CSRF token but no login session answers 303 to / and makes no
// URL.
func TestGeneratePost_NoSession_RedirectsToLogin(t *testing.T) {
	t.Parallel()

	_, srv := newCSRFTestRouter(t)

	cookies, token := csrfCredentials(t, srv, nil)

	rec := postForm(srv, "/generate", cookies, url.Values{
		sourceURLField: {testSourceURL},
		csrfTokenField: {token},
	})

	if rec.Code != http.StatusSeeOther || rec.Header().Get("Location") != "/" {
		t.Fatalf("status = %d, Location = %q, want %d to /",
			rec.Code, rec.Header().Get("Location"), http.StatusSeeOther)
	}

	if strings.Contains(rec.Body.String(), "/v1/e/") {
		t.Error("a URL was made without a login session")
	}
}

// TestGeneratePost_URLServesImage verifies that the URL the generator page
// makes is served by /v1/e/. The image route runs on handlers of its own,
// made with the same signing key.
func TestGeneratePost_URLServesImage(t *testing.T) {
	t.Parallel()

	_, imageSrv := newSignedHostServer(t, slog.New(slog.DiscardHandler))

	rec := generatePost(t, url.Values{
		sourceURLField: {"https://" + signedHost + photoPath},
		widthField:     {"50"},
		heightField:    {"50"},
		formatField:    {string(imgcache.FormatJPEG)},
	})

	if rec.Code != http.StatusOK {
		t.Fatalf("POST /generate status = %d, want %d", rec.Code, http.StatusOK)
	}

	match := generatedURLPattern.FindStringSubmatch(rec.Body.String())
	if match == nil {
		t.Fatalf("generator page shows no URL: %s", rec.Body.String())
	}

	t.Logf("generated URL path: %s", match[1])

	imageRec := httptest.NewRecorder()
	imageSrv.ServeHTTP(imageRec, httptest.NewRequestWithContext(
		t.Context(), http.MethodGet, match[1], nil))

	requireServedPhoto(t, imageRec)
}