package server_test

import (
	"net/http"
	"net/http/httptest"
	"testing"

	"github.com/spf13/viper"

	"sneak.berlin/go/dnswatcher/internal/server"
)

// Credentials for /metrics, which is only routed when a username is set.
const (
	metricsUsername = "scraper"
	metricsPassword = "scrape-secret"
)

// The tests below set env vars and touch viper global state, so like
// the config tests they cannot use t.Parallel.

// routedServer builds the server with its routes set up, ready to serve
// test requests. The caller must first configure viper.
func routedServer(t *testing.T) *server.Server {
	t.Helper()

	srv := buildServer(t)
	srv.SetupRoutes()

	return srv
}

// crossOriginRequest builds a request as a browser sends it from a page
// on another site.
func crossOriginRequest(
	t *testing.T,
	method string,
	target string,
) *http.Request {
	t.Helper()

	req := httptest.NewRequestWithContext(t.Context(), method, target, nil)
	req.Header.Set("Origin", "https://example.net")

	return req
}

// preflightRequest builds the OPTIONS request a browser sends before a
// cross-origin request with the given method and request headers.
func preflightRequest(
	t *testing.T,
	target string,
	method string,
	headers string,
) *http.Request {
	t.Helper()

	req := crossOriginRequest(t, http.MethodOptions, target)
	req.Header.Set("Access-Control-Request-Method", method)

	if headers != "" {
		req.Header.Set("Access-Control-Request-Headers", headers)
	}

	return req
}

func serve(
	srv *server.Server,
	req *http.Request,
) *httptest.ResponseRecorder {
	rec := httptest.NewRecorder()
	srv.ServeHTTP(rec, req)

	return rec
}

// publicPaths returns one path on each public route.
func publicPaths() []string {
	return []string{
		"/",
		"/s/css/tailwind.min.css",
		"/api/v1/status",
		"/health",
		"/.well-known/healthcheck",
	}
}

// TestPublicRoutesAllowAnyOrigin checks that every public route answers
// a cross-origin GET with the CORS wildcard.
func TestPublicRoutesAllowAnyOrigin(t *testing.T) {
	viper.Reset()
	t.Setenv("DNSWATCHER_TARGETS", "example.com")
	t.Setenv("DNSWATCHER_METRICS_USERNAME", metricsUsername)
	t.Setenv("DNSWATCHER_METRICS_PASSWORD", metricsPassword)

	srv := routedServer(t)

	for _, path := range publicPaths() {
		rec := serve(srv, crossOriginRequest(t, http.MethodGet, path))

		if rec.Code != http.StatusOK {
			t.Errorf("GET %s: status = %d, want 200", path, rec.Code)
		}

		got := rec.Header().Get("Access-Control-Allow-Origin")
		if got != "*" {
			t.Errorf(
				"GET %s: Access-Control-Allow-Origin = %q, want %q",
				path, got, "*",
			)
		}
	}
}

// TestMetricsHasNoCORS checks that no request to the Basic-Auth
// protected /metrics, preflight included, gets a CORS header.
func TestMetricsHasNoCORS(t *testing.T) {
	viper.Reset()
	t.Setenv("DNSWATCHER_TARGETS", "example.com")
	t.Setenv("DNSWATCHER_METRICS_USERNAME", metricsUsername)
	t.Setenv("DNSWATCHER_METRICS_PASSWORD", metricsPassword)

	srv := routedServer(t)

	authenticated := crossOriginRequest(t, http.MethodGet, "/metrics")
	authenticated.SetBasicAuth(metricsUsername, metricsPassword)

	tests := []struct {
		name       string
		req        *http.Request
		wantStatus int
	}{
		{
			"authenticated GET",
			authenticated,
			http.StatusOK,
		},
		{
			"unauthenticated GET",
			crossOriginRequest(t, http.MethodGet, "/metrics"),
			http.StatusUnauthorized,
		},
		{
			"preflight",
			preflightRequest(t, "/metrics", http.MethodGet, ""),
			http.StatusUnauthorized,
		},
	}

	for _, tt := range tests {
		rec := serve(srv, tt.req)

		if rec.Code != tt.wantStatus {
			t.Errorf(
				"%s: status = %d, want %d",
				tt.name, rec.Code, tt.wantStatus,
			)
		}

		got := rec.Header().Get("Access-Control-Allow-Origin")
		if got != "" {
			t.Errorf(
				"%s: Access-Control-Allow-Origin = %q, want none",
				tt.name, got,
			)
		}
	}
}

// TestPreflightAllowsOnlyWhatPublicRoutesServe checks what each public
// route agrees to in a CORS preflight: GET, but not POST, PUT or
// DELETE, which no route serves, and not the Authorization or
// X-CSRF-Token headers, which no public route reads. It checks every
// public route because one added with Get, such as /health, answers a
// preflight only while CORS is middleware of a whole router; in a
// Group, chi would answer it with 405 and no CORS headers.
func TestPreflightAllowsOnlyWhatPublicRoutesServe(t *testing.T) {
	viper.Reset()
	t.Setenv("DNSWATCHER_TARGETS", "example.com")
	t.Setenv("DNSWATCHER_METRICS_USERNAME", metricsUsername)
	t.Setenv("DNSWATCHER_METRICS_PASSWORD", metricsPassword)

	srv := routedServer(t)

	tests := []struct {
		method  string
		headers string
		allowed bool
	}{
		{http.MethodGet, "", true},
		{http.MethodGet, "Content-Type", true},
		{http.MethodPost, "", false},
		{http.MethodPut, "", false},
		{http.MethodDelete, "", false},
		{http.MethodGet, "Authorization", false},
		{http.MethodGet, "X-CSRF-Token", false},
	}

	for _, path := range publicPaths() {
		for _, tt := range tests {
			rec := serve(srv, preflightRequest(
				t, path, tt.method, tt.headers,
			))

			want := ""
			if tt.allowed {
				want = tt.method
			}

			got := rec.Header().Get("Access-Control-Allow-Methods")
			if got != want {
				t.Errorf(
					"preflight to %s for %s with headers %q: "+
						"Access-Control-Allow-Methods = %q, want %q",
					path, tt.method, tt.headers, got, want,
				)
			}
		}
	}
}