/*
Copyright 2022 The Kubernetes Authors.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package http

import (
	"fmt"
	"net"
	"net/url"
	"strings"
	"testing"
	"time"

	"sigs.k8s.io/gateway-api/conformance/utils/config"
	"sigs.k8s.io/gateway-api/conformance/utils/roundtripper"
)

// ExpectedResponse defines the response expected for a given request.
type ExpectedResponse struct {
	// Request defines the request to make.
	Request Request

	// ExpectedRequest defines the request that
	// is expected to arrive at the backend. If
	// not specified, the backend request will be
	// expected to match Request.
	ExpectedRequest *ExpectedRequest

	RedirectRequest *roundtripper.RedirectRequest

	// BackendSetResponseHeaders is a set of headers
	// the echoserver should set in its response.
	BackendSetResponseHeaders map[string]string

	// Response defines what response the test case
	// should receive.
	Response Response

	Backend   string
	Namespace string

	// MirroredTo is the destination BackendRefs of the mirrored request.
	MirroredTo []BackendRef

	// User Given TestCase name
	TestCaseName string
}

// Request can be used as both the request to make and a means to verify
// that echoserver received the expected request. Note that multiple header
// values can be provided, as a comma-separated value.
type Request struct {
	Host             string
	Method           string
	Path             string
	Headers          map[string]string
	UnfollowRedirect bool
	Protocol         string
}

// ExpectedRequest defines expected properties of a request that reaches a backend.
type ExpectedRequest struct {
	Request

	// AbsentHeaders are names of headers that are expected
	// *not* to be present on the request.
	AbsentHeaders []string
}

// Response defines expected properties of a response from a backend.
type Response struct {
	StatusCode    int
	Headers       map[string]string
	AbsentHeaders []string
}

type BackendRef struct {
	Name      string
	Namespace string
}

// MakeRequestAndExpectEventuallyConsistentResponse makes a request with the given parameters,
// understanding that the request may fail for some amount of time.
//
// Once the request succeeds consistently with the response having the expected status code, make
// additional assertions on the response body using the provided ExpectedResponse.
func MakeRequestAndExpectEventuallyConsistentResponse(t *testing.T, r roundtripper.RoundTripper, timeoutConfig config.TimeoutConfig, gwAddr string, expected ExpectedResponse) {
	t.Helper()

	req := MakeRequest(t, &expected, gwAddr, "HTTP", "http")

	WaitForConsistentResponse(t, r, req, expected, timeoutConfig.RequiredConsecutiveSuccesses, timeoutConfig.MaxTimeToConsistency)
}

func MakeRequest(t *testing.T, expected *ExpectedResponse, gwAddr, protocol, scheme string) roundtripper.Request {
	t.Helper()

	if expected.Request.Method == "" {
		expected.Request.Method = "GET"
	}

	if expected.Response.StatusCode == 0 {
		expected.Response.StatusCode = 200
	}

	if expected.Request.Protocol == "" {
		expected.Request.Protocol = protocol
	}

	path, query, _ := strings.Cut(expected.Request.Path, "?")
	reqURL := url.URL{Scheme: scheme, Host: CalculateHost(t, gwAddr, scheme), Path: path, RawQuery: query}

	t.Logf("Making %s request to %s", expected.Request.Method, reqURL.String())

	req := roundtripper.Request{
		Method:           expected.Request.Method,
		Host:             expected.Request.Host,
		URL:              reqURL,
		Protocol:         expected.Request.Protocol,
		Headers:          map[string][]string{},
		UnfollowRedirect: expected.Request.UnfollowRedirect,
	}

	if expected.Request.Headers != nil {
		for name, value := range expected.Request.Headers {
			req.Headers[name] = []string{value}
		}
	}

	backendSetHeaders := []string{}
	for name, val := range expected.BackendSetResponseHeaders {
		backendSetHeaders = append(backendSetHeaders, name+":"+val)
	}
	req.Headers["X-Echo-Set-Header"] = []string{strings.Join(backendSetHeaders, ",")}

	return req
}

// CalculateHost will calculate the Host header as per [HTTP spec]. To
// summarize, host will not include any port if it is implied from the scheme. In
// case of any error, the input gwAddr will be returned as the default.
//
// [HTTP spec]: https://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.23
func CalculateHost(t *testing.T, gwAddr, scheme string) string {
	host, port, err := net.SplitHostPort(gwAddr) // note: this will strip brackets of an IPv6 address
	if err != nil && strings.Contains(err.Error(), "too many colons in address") {
		// This is an IPv6 address; assume it's valid ipv6
		// Assume caller won't add a port without brackets
		gwAddr = "[" + gwAddr + "]"
		host, port, err = net.SplitHostPort(gwAddr)
	}
	if err != nil {
		t.Logf("Failed to parse host %q: %v", gwAddr, err)
		return gwAddr
	}
	if strings.ToLower(scheme) == "http" && port == "80" {
		return ipv6SafeHost(host)
	}
	if strings.ToLower(scheme) == "https" && port == "443" {
		return ipv6SafeHost(host)
	}
	return gwAddr
}

func ipv6SafeHost(host string) string {
	// We assume that host is a literal IPv6 address if host has
	// colons.
	// Per https://datatracker.ietf.org/doc/html/rfc3986#section-3.2.2.
	// This is like net.JoinHostPort, but we don't need a port.
	if strings.Contains(host, ":") {
		return "[" + host + "]"
	}
	return host
}

// AwaitConvergence runs the given function until it returns 'true' `threshold` times in a row.
// Each failed attempt has a 1s delay; successful attempts have no delay.
func AwaitConvergence(t *testing.T, threshold int, maxTimeToConsistency time.Duration, fn func(elapsed time.Duration) bool) {
	successes := 0
	attempts := 0
	start := time.Now()
	to := time.After(maxTimeToConsistency)
	delay := time.Second
	for {
		select {
		case <-to:
			t.Fatalf("timeout while waiting after %d attempts", attempts)
		default:
		}

		completed := fn(time.Now().Sub(start))
		attempts++
		if completed {
			successes++
			if successes >= threshold {
				return
			}
			// Skip delay if we have a success
			continue
		}

		successes = 0
		select {
		// Capture the overall timeout
		case <-to:
			t.Fatalf("timeout while waiting after %d attempts, %d/%d successes", attempts, successes, threshold)
			// And the per-try delay
		case <-time.After(delay):
		}
	}
}

// WaitForConsistentResponse repeats the provided request until it completes with a response having
// the expected response consistently. The provided threshold determines how many times in
// a row this must occur to be considered "consistent".
func WaitForConsistentResponse(t *testing.T, r roundtripper.RoundTripper, req roundtripper.Request, expected ExpectedResponse, threshold int, maxTimeToConsistency time.Duration) {
	AwaitConvergence(t, threshold, maxTimeToConsistency, func(elapsed time.Duration) bool {
		cReq, cRes, err := r.CaptureRoundTrip(req)
		if err != nil {
			t.Logf("Request failed, not ready yet: %v (after %v)", err.Error(), elapsed)
			return false
		}

		if err := CompareRequest(t, &req, cReq, cRes, expected); err != nil {
			t.Logf("Response expectation failed for request: %+v  not ready yet: %v (after %v)", req, err, elapsed)
			return false
		}

		return true
	})
	t.Logf("Request passed")
}

func CompareRequest(t *testing.T, req *roundtripper.Request, cReq *roundtripper.CapturedRequest, cRes *roundtripper.CapturedResponse, expected ExpectedResponse) error {
	if roundtripper.IsTimeoutError(cRes.StatusCode) {
		if roundtripper.IsTimeoutError(expected.Response.StatusCode) {
			return nil
		}
	}
	if expected.Response.StatusCode != cRes.StatusCode {
		return fmt.Errorf("expected status code to be %d, got %d", expected.Response.StatusCode, cRes.StatusCode)
	}
	if cRes.StatusCode == 200 {
		// The request expected to arrive at the backend is
		// the same as the request made, unless otherwise
		// specified.
		if expected.ExpectedRequest == nil {
			expected.ExpectedRequest = &ExpectedRequest{Request: expected.Request}
		}

		if expected.ExpectedRequest.Method == "" {
			expected.ExpectedRequest.Method = "GET"
		}

		if expected.ExpectedRequest.Host != "" && expected.ExpectedRequest.Host != cReq.Host {
			return fmt.Errorf("expected host to be %s, got %s", expected.ExpectedRequest.Host, cReq.Host)
		}

		if expected.ExpectedRequest.Path != cReq.Path {
			return fmt.Errorf("expected path to be %s, got %s", expected.ExpectedRequest.Path, cReq.Path)
		}
		if expected.ExpectedRequest.Method != cReq.Method {
			return fmt.Errorf("expected method to be %s, got %s", expected.ExpectedRequest.Method, cReq.Method)
		}
		if expected.Namespace != cReq.Namespace {
			return fmt.Errorf("expected namespace to be %s, got %s", expected.Namespace, cReq.Namespace)
		}
		if expected.ExpectedRequest.Headers != nil {
			if cReq.Headers == nil {
				return fmt.Errorf("no headers captured, expected %v", len(expected.ExpectedRequest.Headers))
			}
			for name, val := range cReq.Headers {
				cReq.Headers[strings.ToLower(name)] = val
			}
			for name, expectedVal := range expected.ExpectedRequest.Headers {
				actualVal, ok := cReq.Headers[strings.ToLower(name)]
				if !ok {
					return fmt.Errorf("expected %s header to be set, actual headers: %v", name, cReq.Headers)
				} else if strings.Join(actualVal, ",") != expectedVal {
					return fmt.Errorf("expected %s header to be set to %s, got %s", name, expectedVal, strings.Join(actualVal, ","))
				}
			}
		}

		if expected.Response.Headers != nil {
			if cRes.Headers == nil {
				return fmt.Errorf("no headers captured, expected %v", len(expected.ExpectedRequest.Headers))
			}
			for name, val := range cRes.Headers {
				cRes.Headers[strings.ToLower(name)] = val
			}

			for name, expectedVal := range expected.Response.Headers {
				actualVal, ok := cRes.Headers[strings.ToLower(name)]
				if !ok {
					return fmt.Errorf("expected %s header to be set, actual headers: %v", name, cRes.Headers)
				} else if strings.Join(actualVal, ",") != expectedVal {
					return fmt.Errorf("expected %s header to be set to %s, got %s", name, expectedVal, strings.Join(actualVal, ","))
				}
			}
		}

		if len(expected.Response.AbsentHeaders) > 0 {
			for name, val := range cRes.Headers {
				cRes.Headers[strings.ToLower(name)] = val
			}

			for _, name := range expected.Response.AbsentHeaders {
				val, ok := cRes.Headers[strings.ToLower(name)]
				if ok {
					return fmt.Errorf("expected %s header to not be set, got %s", name, val)
				}
			}
		}

		// Verify that headers expected *not* to be present on the
		// request are actually not present.
		if len(expected.ExpectedRequest.AbsentHeaders) > 0 {
			for name, val := range cReq.Headers {
				cReq.Headers[strings.ToLower(name)] = val
			}

			for _, name := range expected.ExpectedRequest.AbsentHeaders {
				val, ok := cReq.Headers[strings.ToLower(name)]
				if ok {
					return fmt.Errorf("expected %s header to not be set, got %s", name, val)
				}
			}
		}

		if !strings.HasPrefix(cReq.Pod, expected.Backend) {
			return fmt.Errorf("expected pod name to start with %s, got %s", expected.Backend, cReq.Pod)
		}
	} else if roundtripper.IsRedirect(cRes.StatusCode) {
		if expected.RedirectRequest == nil {
			return nil
		}

		setRedirectRequestDefaults(req, cRes, &expected)

		if expected.RedirectRequest.Host != cRes.RedirectRequest.Host {
			return fmt.Errorf("expected redirected hostname to be %q, got %q", expected.RedirectRequest.Host, cRes.RedirectRequest.Host)
		}

		gotPort := cRes.RedirectRequest.Port
		if expected.RedirectRequest.Port == "" {
			// If the test didn't specify any expected redirect port, we'll try to use
			// the scheme to determine sensible defaults for the port. Well known
			// schemes like "http" and "https" MAY skip setting any port.
			if strings.ToLower(cRes.RedirectRequest.Scheme) == "http" && gotPort != "80" && gotPort != "" {
				return fmt.Errorf("for http scheme, expected redirected port to be 80 or not set, got %q", gotPort)
			}
			if strings.ToLower(cRes.RedirectRequest.Scheme) == "https" && gotPort != "443" && gotPort != "" {
				return fmt.Errorf("for https scheme, expected redirected port to be 443 or not set, got %q", gotPort)
			}
			t.Logf("Can't validate redirectPort for unrecognized scheme %v", cRes.RedirectRequest.Scheme)
		} else if expected.RedirectRequest.Port != gotPort {
			// An expected port was specified in the tests but it didn't match with
			// gotPort.
			return fmt.Errorf("expected redirected port to be %q, got %q", expected.RedirectRequest.Port, gotPort)
		}

		if expected.RedirectRequest.Scheme != cRes.RedirectRequest.Scheme {
			return fmt.Errorf("expected redirected scheme to be %q, got %q", expected.RedirectRequest.Scheme, cRes.RedirectRequest.Scheme)
		}

		if expected.RedirectRequest.Path != cRes.RedirectRequest.Path {
			return fmt.Errorf("expected redirected path to be %q, got %q", expected.RedirectRequest.Path, cRes.RedirectRequest.Path)
		}
	}
	return nil
}

// GetTestCaseName gets the user-defined test case name or generates one from expected response to a given request.
func (er *ExpectedResponse) GetTestCaseName(i int) string {
	// If TestCase name is provided then use that or else generate one.
	if er.TestCaseName != "" {
		return er.TestCaseName
	}

	headerStr := ""
	reqStr := ""

	if er.Request.Headers != nil {
		headerStr = " with headers"
	}

	reqStr = fmt.Sprintf("%d request to '%s%s'%s", i, er.Request.Host, er.Request.Path, headerStr)

	if er.Backend != "" {
		return fmt.Sprintf("%s should go to %s", reqStr, er.Backend)
	}
	return fmt.Sprintf("%s should receive a %d", reqStr, er.Response.StatusCode)
}

func setRedirectRequestDefaults(req *roundtripper.Request, cRes *roundtripper.CapturedResponse, expected *ExpectedResponse) {
	// If the expected host is nil it means we do not test host redirect.
	// In that case we are setting it to the one we got from the response because we do not know the ip/host of the gateway.
	if expected.RedirectRequest.Host == "" {
		expected.RedirectRequest.Host = cRes.RedirectRequest.Host
	}

	if expected.RedirectRequest.Scheme == "" {
		expected.RedirectRequest.Scheme = req.URL.Scheme
	}

	if expected.RedirectRequest.Path == "" {
		expected.RedirectRequest.Path = req.URL.Path
	}
}