/*
Copyright 2021 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 rest

import (
	"bytes"
	"context"
	"errors"
	"fmt"
	"io"
	"net/http"
	"net/url"
	"reflect"
	"strings"
	"testing"
	"time"

	"github.com/google/go-cmp/cmp"
)

var alwaysRetryError = IsRetryableErrorFunc(func(_ *http.Request, _ error) bool {
	return true
})

func TestIsNextRetry(t *testing.T) {
	fakeError := errors.New("fake error")
	tests := []struct {
		name               string
		attempts           int
		maxRetries         int
		request            *http.Request
		response           *http.Response
		err                error
		retryableErrFunc   IsRetryableErrorFunc
		retryExpected      []bool
		retryAfterExpected []*RetryAfter
	}{
		{
			name:               "bad input, response and err are nil",
			maxRetries:         2,
			attempts:           1,
			request:            &http.Request{},
			response:           nil,
			err:                nil,
			retryExpected:      []bool{false},
			retryAfterExpected: []*RetryAfter{nil},
		},
		{
			name:          "zero maximum retry",
			maxRetries:    0,
			attempts:      1,
			request:       &http.Request{},
			response:      retryAfterResponse(),
			err:           nil,
			retryExpected: []bool{false},
			retryAfterExpected: []*RetryAfter{
				{
					Attempt: 1,
				},
			},
		},
		{
			name:       "server returned a retryable error",
			maxRetries: 3,
			attempts:   1,
			request:    &http.Request{},
			response:   nil,
			err:        fakeError,
			retryableErrFunc: func(_ *http.Request, err error) bool {
				if err == fakeError {
					return true
				}
				return false
			},
			retryExpected: []bool{true},
			retryAfterExpected: []*RetryAfter{
				{
					Attempt: 1,
					Wait:    time.Second,
					Reason:  "retries: 1, retry-after: 1s - retry-reason: due to retryable error, error: fake error",
				},
			},
		},
		{
			name:       "server returned a retryable HTTP 429 response",
			maxRetries: 3,
			attempts:   1,
			request:    &http.Request{},
			response: &http.Response{
				StatusCode: http.StatusTooManyRequests,
				Header: http.Header{
					"Retry-After":                    []string{"2"},
					"X-Kubernetes-Pf-Flowschema-Uid": []string{"fs-1"},
				},
			},
			err:           nil,
			retryExpected: []bool{true},
			retryAfterExpected: []*RetryAfter{
				{
					Attempt: 1,
					Wait:    2 * time.Second,
					Reason:  `retries: 1, retry-after: 2s - retry-reason: due to server-side throttling, FlowSchema UID: "fs-1"`,
				},
			},
		},
		{
			name:       "server returned a retryable HTTP 5xx response",
			maxRetries: 3,
			attempts:   1,
			request:    &http.Request{},
			response: &http.Response{
				StatusCode: http.StatusServiceUnavailable,
				Header: http.Header{
					"Retry-After": []string{"3"},
				},
			},
			err:           nil,
			retryExpected: []bool{true},
			retryAfterExpected: []*RetryAfter{
				{
					Attempt: 1,
					Wait:    3 * time.Second,
					Reason:  "retries: 1, retry-after: 3s - retry-reason: 503",
				},
			},
		},
		{
			name:       "server returned a non response without without a Retry-After header",
			maxRetries: 1,
			attempts:   1,
			request:    &http.Request{},
			response: &http.Response{
				StatusCode: http.StatusTooManyRequests,
				Header:     http.Header{},
			},
			err:           nil,
			retryExpected: []bool{false},
			retryAfterExpected: []*RetryAfter{
				{
					Attempt: 1,
				},
			},
		},
		{
			name:       "both response and err are set, err takes precedence",
			maxRetries: 1,
			attempts:   1,
			request:    &http.Request{},
			response:   retryAfterResponse(),
			err:        fakeError,
			retryableErrFunc: func(_ *http.Request, err error) bool {
				if err == fakeError {
					return true
				}
				return false
			},
			retryExpected: []bool{true},
			retryAfterExpected: []*RetryAfter{
				{
					Attempt: 1,
					Wait:    time.Second,
					Reason:  "retries: 1, retry-after: 1s - retry-reason: due to retryable error, error: fake error",
				},
			},
		},
		{
			name:             "all retries are exhausted",
			maxRetries:       3,
			attempts:         4,
			request:          &http.Request{},
			response:         nil,
			err:              fakeError,
			retryableErrFunc: alwaysRetryError,
			retryExpected:    []bool{true, true, true, false},
			retryAfterExpected: []*RetryAfter{
				{
					Attempt: 1,
					Wait:    time.Second,
					Reason:  "retries: 1, retry-after: 1s - retry-reason: due to retryable error, error: fake error",
				},
				{
					Attempt: 2,
					Wait:    time.Second,
					Reason:  "retries: 2, retry-after: 1s - retry-reason: due to retryable error, error: fake error",
				},
				{
					Attempt: 3,
					Wait:    time.Second,
					Reason:  "retries: 3, retry-after: 1s - retry-reason: due to retryable error, error: fake error",
				},
				{
					Attempt: 4,
				},
			},
		},
	}

	for _, test := range tests {
		t.Run(test.name, func(t *testing.T) {
			restReq := &Request{
				body: bytes.NewReader([]byte{}),
				c: &RESTClient{
					base: &url.URL{},
				},
			}
			r := &withRetry{maxRetries: test.maxRetries}

			retryGot := make([]bool, 0)
			retryAfterGot := make([]*RetryAfter, 0)
			for i := 0; i < test.attempts; i++ {
				retry := r.IsNextRetry(context.TODO(), restReq, test.request, test.response, test.err, test.retryableErrFunc)
				retryGot = append(retryGot, retry)
				retryAfterGot = append(retryAfterGot, r.retryAfter)
			}

			if !reflect.DeepEqual(test.retryExpected, retryGot) {
				t.Errorf("Expected retry: %t, but got: %t", test.retryExpected, retryGot)
			}
			if !reflect.DeepEqual(test.retryAfterExpected, retryAfterGot) {
				t.Errorf("Expected retry-after parameters to match, but got: %s", cmp.Diff(test.retryAfterExpected, retryAfterGot))
			}
		})
	}
}

func TestWrapPreviousError(t *testing.T) {
	const (
		attempt                = 2
		previousAttempt        = 1
		containsFormatExpected = "- error from a previous attempt: %s"
	)
	var (
		wrappedCtxDeadlineExceededErr = &url.Error{
			Op:  "GET",
			URL: "http://foo.bar",
			Err: context.DeadlineExceeded,
		}
		wrappedCtxCanceledErr = &url.Error{
			Op:  "GET",
			URL: "http://foo.bar",
			Err: context.Canceled,
		}
		urlEOFErr = &url.Error{
			Op:  "GET",
			URL: "http://foo.bar",
			Err: io.EOF,
		}
	)

	tests := []struct {
		name        string
		previousErr error
		currentErr  error
		expectedErr error
		wrapped     bool
		contains    string
	}{
		{
			name: "current error is nil, previous error is nil",
		},
		{
			name:        "current error is nil",
			previousErr: errors.New("error from a previous attempt"),
		},
		{
			name:        "previous error is nil",
			currentErr:  urlEOFErr,
			expectedErr: urlEOFErr,
			wrapped:     false,
		},
		{
			name:        "both current and previous errors represent the same error",
			currentErr:  urlEOFErr,
			previousErr: &url.Error{Op: "GET", URL: "http://foo.bar", Err: io.EOF},
			expectedErr: urlEOFErr,
		},
		{
			name:        "current and previous errors are not same",
			currentErr:  urlEOFErr,
			previousErr: errors.New("unknown error"),
			expectedErr: urlEOFErr,
			wrapped:     true,
			contains:    fmt.Sprintf(containsFormatExpected, "unknown error"),
		},
		{
			name:        "current error is context.Canceled",
			currentErr:  context.Canceled,
			previousErr: io.EOF,
			expectedErr: context.Canceled,
			wrapped:     true,
			contains:    fmt.Sprintf(containsFormatExpected, io.EOF.Error()),
		},
		{
			name:        "current error is context.DeadlineExceeded",
			currentErr:  context.DeadlineExceeded,
			previousErr: io.EOF,
			expectedErr: context.DeadlineExceeded,
			wrapped:     true,
			contains:    fmt.Sprintf(containsFormatExpected, io.EOF.Error()),
		},
		{
			name:        "current error is a wrapped context.DeadlineExceeded",
			currentErr:  wrappedCtxDeadlineExceededErr,
			previousErr: io.EOF,
			expectedErr: wrappedCtxDeadlineExceededErr,
			wrapped:     true,
			contains:    fmt.Sprintf(containsFormatExpected, io.EOF.Error()),
		},
		{
			name:        "current error is a wrapped context.Canceled",
			currentErr:  wrappedCtxCanceledErr,
			previousErr: io.EOF,
			expectedErr: wrappedCtxCanceledErr,
			wrapped:     true,
			contains:    fmt.Sprintf(containsFormatExpected, io.EOF.Error()),
		},
		{
			name:        "previous error should be unwrapped if it is url.Error",
			currentErr:  urlEOFErr,
			previousErr: &url.Error{Err: io.ErrUnexpectedEOF},
			expectedErr: urlEOFErr,
			wrapped:     true,
			contains:    fmt.Sprintf(containsFormatExpected, io.ErrUnexpectedEOF.Error()),
		},
		{
			name:        "previous error should not be unwrapped if it is not url.Error",
			currentErr:  urlEOFErr,
			previousErr: fmt.Errorf("should be included in error message - %w", io.EOF),
			expectedErr: urlEOFErr,
			wrapped:     true,
			contains:    fmt.Sprintf(containsFormatExpected, "should be included in error message - EOF"),
		},
	}

	for _, test := range tests {
		t.Run(test.name, func(t *testing.T) {
			retry := &withRetry{
				previousErr: test.previousErr,
			}

			err := retry.WrapPreviousError(test.currentErr)
			switch {
			case test.expectedErr == nil:
				if err != nil {
					t.Errorf("Expected a nil error, but got: %v", err)
					return
				}
			case test.expectedErr != nil:
				// make sure the message from the returned error contains
				// message from the "previous" error from retries.
				if !strings.Contains(err.Error(), test.contains) {
					t.Errorf("Expected error message to contain %q, but got: %v", test.contains, err)
				}

				currentErrGot := err
				if test.wrapped {
					currentErrGot = errors.Unwrap(err)
				}
				if test.expectedErr != currentErrGot {
					t.Errorf("Expected current error %v, but got: %v", test.expectedErr, currentErrGot)
				}
			}
		})
	}

	t.Run("Before should track previous error", func(t *testing.T) {
		retry := &withRetry{
			currentErr: io.EOF,
		}

		ctx, cancel := context.WithCancel(context.Background())
		cancel()

		// we pass zero Request object since we expect 'Before'
		// to check the context for error at the very beginning.
		err := retry.Before(ctx, &Request{})
		if err != context.Canceled {
			t.Errorf("Expected error: %v, but got: %v", context.Canceled, err)
		}
		if retry.currentErr != context.Canceled {
			t.Errorf("Expected current error: %v, but got: %v", context.Canceled, retry.currentErr)
		}
		if retry.previousErr != io.EOF {
			t.Errorf("Expected previous error: %v, but got: %v", io.EOF, retry.previousErr)
		}
	})
}