package server_test

import (
	"context"
	"fmt"
	"net/http"
	"net/http/httptest"
	"os/exec"
	"slices"
	"strings"
	"sync"
	"testing"
	"time"

	"github.com/chromedp/cdproto/network"
	"github.com/chromedp/cdproto/runtime"
	"github.com/chromedp/chromedp"
	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"
)

const (
	// browserTimeout bounds everything one test does in the browser.
	browserTimeout = 60 * time.Second

	// settleTimeout bounds the wait for an element to show or hide.
	settleTimeout = 5 * time.Second
)

// TestAlpineRunsUnderTheSecurityPolicy loads the webhook page and the
// event log in headless Chromium, served by the real router and so
// under the real Content-Security-Policy, and checks that the pages'
// Alpine.js directives work.
func TestAlpineRunsUnderTheSecurityPolicy(t *testing.T) {
	t.Parallel()

	ctx, consoleProblems := startBrowser(t)

	env := newTestEnv(t)
	srv := httptest.NewServer(env.router)
	t.Cleanup(srv.Close)

	userID, _ := env.seedUser(t, "browser", "browser-password")
	webhook := env.seedWebhook(t, userID)
	event := env.seedEvent(t, webhook.ID, `{"hello":"browser"}`)

	require.NoError(t, chromedp.Run(
		ctx, setCookies(srv.URL, env.authCookies(t, userID, "browser")),
	))

	checkAddForms(ctx, t, srv.URL+"/source/"+webhook.ID)
	checkTargetType(ctx, t)
	checkEventToggle(
		ctx, t, srv.URL+"/source/"+webhook.ID+"/logs", event.ID,
	)

	assert.Empty(
		t, consoleProblems(),
		"the pages printed console warnings, errors or exceptions",
	)
}

// startBrowser starts headless Chromium for one test. It returns the
// context that drives it, and a function listing every console warning
// or error and every uncaught exception its pages raised: that is how
// Alpine.js reports an expression it cannot run.
//
// The test is skipped when chromium is not on PATH. The Dockerfile's
// test stage installs it, so the image build always runs this check.
func startBrowser(t *testing.T) (context.Context, func() []string) {
	t.Helper()

	path, err := exec.LookPath("chromium")
	if err != nil {
		t.Skipf("chromium is not installed: %v", err)
	}

	allocCtx, cancelAlloc := chromedp.NewExecAllocator(
		t.Context(),
		append(
			chromedp.DefaultExecAllocatorOptions[:],
			chromedp.ExecPath(path),
			// The image build runs tests as root, where Chromium's
			// sandbox cannot start.
			chromedp.NoSandbox,
		)...,
	)
	t.Cleanup(cancelAlloc)

	ctx, cancel := chromedp.NewContext(allocCtx)
	t.Cleanup(cancel)

	ctx, cancelTimeout := context.WithTimeout(ctx, browserTimeout)
	t.Cleanup(cancelTimeout)

	var (
		mu       sync.Mutex
		problems []string
	)

	chromedp.ListenTarget(ctx, func(ev any) {
		var problem string

		switch ev := ev.(type) {
		case *runtime.EventConsoleAPICalled:
			if ev.Type != runtime.APITypeWarning &&
				ev.Type != runtime.APITypeError {
				return
			}

			args := make([]string, 0, len(ev.Args))
			for _, arg := range ev.Args {
				args = append(args, string(arg.Value))
			}

			problem = strings.Join(args, " ")
		case *runtime.EventExceptionThrown:
			problem = ev.ExceptionDetails.Error()
		default:
			return
		}

		mu.Lock()
		defer mu.Unlock()

		problems = append(problems, problem)
	})

	return ctx, func() []string {
		mu.Lock()
		defer mu.Unlock()

		return slices.Clone(problems)
	}
}

// setCookies gives the browser the cookies for the server at base.
func setCookies(base string, cookies []*http.Cookie) chromedp.ActionFunc {
	return chromedp.ActionFunc(func(ctx context.Context) error {
		for _, c := range cookies {
			err := network.SetCookie(c.Name, c.Value).
				WithURL(base).
				Do(ctx)
			if err != nil {
				return fmt.Errorf("set cookie %s: %w", c.Name, err)
			}
		}

		return nil
	})
}

// loadPage opens url and waits for Alpine.js to start, which it does
// by removing every x-cloak attribute. Until then x-cloak hides the
// elements Alpine would hide, so a check made earlier proves nothing.
func loadPage(url string) chromedp.Tasks {
	return chromedp.Tasks{
		chromedp.Navigate(url),
		chromedp.WaitNotPresent("[x-cloak]", chromedp.ByQuery),
	}
}

// shown waits up to settleTimeout for the first element matching a CSS
// selector to be rendered, and reports whether it was. The wait is
// needed because Alpine.js shows an element on the next animation
// frame, not at once.
func shown(ctx context.Context, selector string) bool {
	ctx, cancel := context.WithTimeout(ctx, settleTimeout)
	defer cancel()

	return chromedp.Run(
		ctx, chromedp.WaitVisible(selector, chromedp.ByQuery),
	) == nil
}

// hidden is shown's opposite: it waits for the element to be hidden.
func hidden(ctx context.Context, selector string) bool {
	ctx, cancel := context.WithTimeout(ctx, settleTimeout)
	defer cancel()

	return chromedp.Run(
		ctx, chromedp.WaitNotVisible(selector, chromedp.ByQuery),
	) == nil
}

// click clicks the first element matching an XPath expression.
func click(ctx context.Context, t *testing.T, xpath string) {
	t.Helper()

	require.NoError(t, chromedp.Run(
		ctx, chromedp.Click(xpath, chromedp.BySearch),
	))
}

// checkAddForms loads a webhook page and checks that each section's add
// form stays hidden until the Add button beside its heading is clicked.
func checkAddForms(ctx context.Context, t *testing.T, url string) {
	t.Helper()

	require.NoError(t, chromedp.Run(ctx, loadPage(url)))

	sections := []struct{ heading, form string }{
		{"Entrypoints", `form[action$="/entrypoints"]`},
		{"Targets", `form[action$="/targets"]`},
	}

	for _, s := range sections {
		assert.Truef(
			t, hidden(ctx, s.form),
			"%s: the add form shows before Add is clicked", s.heading,
		)

		click(ctx, t, `//h2[text()="`+s.heading+
			`"]/following-sibling::button`)

		assert.Truef(
			t, shown(ctx, s.form),
			"%s: the add form stays hidden when Add is clicked", s.heading,
		)
	}
}

// checkTargetType chooses Slack in the open add target form and checks
// what the form would then submit: one url field, the Slack one, and
// not the HTTP url, headers or timeout, which are hidden and disabled.
func checkTargetType(ctx context.Context, t *testing.T) {
	t.Helper()

	const (
		chooseSlack = `(() => {
			const type = document.querySelector('select[name="type"]');
			type.value = "slack";
			type.dispatchEvent(new Event("change"));
		})()`
		submitted = `[...new FormData(
			document.querySelector('form[action$="/targets"]')).keys()]`
	)

	var fields []string

	require.NoError(t, chromedp.Run(
		ctx,
		chromedp.Evaluate(chooseSlack, nil),
		chromedp.Evaluate(submitted, &fields),
	))

	assert.Equal(
		t,
		[]string{"csrf_token", "name", "type", "max_retries", "url"},
		fields,
		"with Slack chosen, the HTTP fields must not be submitted",
	)
}

// checkEventToggle loads the event log and checks that clicking an
// event's row expands it and clicking again collapses it.
func checkEventToggle(
	ctx context.Context, t *testing.T, url, eventID string,
) {
	t.Helper()

	// The row shows the event's ID; its Resubmit form is in the part
	// that expands.
	row := `//span[text()="` + eventID + `"]`
	expanded := `form[action$="/resubmit"]`

	require.NoError(t, chromedp.Run(ctx, loadPage(url)))

	assert.True(t, hidden(ctx, expanded), "the event starts expanded")

	click(ctx, t, row)
	assert.True(t, shown(ctx, expanded), "clicking the event does not expand it")

	click(ctx, t, row)
	assert.True(t, hidden(ctx, expanded), "clicking it again does not collapse it")
}