// Copyright 2015 The LUCI 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 lhttp

import (
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"io"
	"io/ioutil"
	"net/http"
	"net/http/httptest"
	"sync"
	"testing"

	"go.chromium.org/luci/common/retry"

	. "github.com/smartystreets/goconvey/convey"
)

func httpReqGen(method, url string, body []byte) RequestGen {
	return func() (*http.Request, error) {
		var bodyReader io.Reader
		if body != nil {
			bodyReader = bytes.NewReader(body)
		}
		return http.NewRequest("GET", url, bodyReader)
	}
}

func TestNewRequestGET(t *testing.T) {
	Convey(`HTTP GET requests should be handled correctly.`, t, func(c C) {
		ctx := context.Background()

		// First call returns HTTP 500, second succeeds.
		serverCalls := 0
		ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			serverCalls++
			content, err := ioutil.ReadAll(r.Body)
			c.So(err, ShouldBeNil)
			c.So(content, ShouldResemble, []byte{})
			if serverCalls == 1 {
				w.WriteHeader(500)
			} else {
				fmt.Fprintf(w, "Hello, client\n")
			}
		}))
		defer ts.Close()

		httpReq := httpReqGen("GET", ts.URL, nil)

		clientCalls := 0
		clientReq := NewRequest(ctx, http.DefaultClient, fast, httpReq, func(resp *http.Response) error {
			clientCalls++
			content, err := ioutil.ReadAll(resp.Body)
			So(err, ShouldBeNil)
			So(string(content), ShouldResemble, "Hello, client\n")
			So(resp.Body.Close(), ShouldBeNil)
			return nil
		}, nil)

		status, err := clientReq()
		So(err, ShouldBeNil)
		So(status, ShouldResemble, 200)
		So(serverCalls, ShouldResemble, 2)
		So(clientCalls, ShouldResemble, 1)
	})
}

func TestNewRequestPOST(t *testing.T) {
	Convey(`HTTP POST requests should be handled correctly.`, t, func(c C) {
		ctx := context.Background()

		// First call returns HTTP 500, second succeeds.
		serverCalls := 0
		ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			serverCalls++
			content, err := ioutil.ReadAll(r.Body)
			c.So(err, ShouldBeNil)
			// The same data is sent twice.
			c.So(string(content), ShouldResemble, "foo bar")
			if serverCalls == 1 {
				w.WriteHeader(500)
			} else {
				fmt.Fprintf(w, "Hello, client\n")
			}
		}))
		defer ts.Close()

		httpReq := httpReqGen("POST", ts.URL, []byte("foo bar"))

		clientCalls := 0
		clientReq := NewRequest(ctx, http.DefaultClient, fast, httpReq, func(resp *http.Response) error {
			clientCalls++
			content, err := ioutil.ReadAll(resp.Body)
			So(err, ShouldBeNil)
			So(string(content), ShouldResemble, "Hello, client\n")
			So(resp.Body.Close(), ShouldBeNil)
			return nil
		}, nil)

		status, err := clientReq()
		So(err, ShouldBeNil)
		So(status, ShouldResemble, 200)
		So(serverCalls, ShouldResemble, 2)
		So(clientCalls, ShouldResemble, 1)
	})
}

func TestNewRequestGETFail(t *testing.T) {
	Convey(`HTTP GET requests should handle failure successfully.`, t, func() {
		ctx := context.Background()

		serverCalls := 0
		ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			serverCalls++
			w.WriteHeader(500)
		}))
		defer ts.Close()

		httpReq := httpReqGen("GET", ts.URL, nil)

		clientReq := NewRequest(ctx, http.DefaultClient, fast, httpReq, func(resp *http.Response) error {
			t.Fail()
			return nil
		}, nil)

		status, err := clientReq()
		So(err.Error(), ShouldResemble, "gave up after 4 attempts: http request failed: Internal Server Error (HTTP 500)")
		So(status, ShouldResemble, 500)
	})
}

func TestGetJSON(t *testing.T) {
	Convey(`HTTP GET JSON requests should be handled correctly.`, t, func(c C) {
		ctx := context.Background()

		// First call returns HTTP 500, second succeeds.
		serverCalls := 0
		ts := httptest.NewServer(handlerJSON(t, func(body io.Reader) interface{} {
			serverCalls++
			content, err := ioutil.ReadAll(body)
			c.So(err, ShouldBeNil)
			c.So(content, ShouldResemble, []byte{})
			if serverCalls == 1 {
				return nil
			}
			return map[string]string{"success": "yeah"}
		}))
		defer ts.Close()

		actual := map[string]string{}
		status, err := GetJSON(ctx, fast, http.DefaultClient, ts.URL, &actual)
		So(err, ShouldBeNil)
		So(status, ShouldResemble, 200)
		So(actual, ShouldResemble, map[string]string{"success": "yeah"})
		So(serverCalls, ShouldResemble, 2)
	})
}

func TestGetJSONBadResult(t *testing.T) {
	Convey(`HTTP GET JSON bad requests should be handled correctly.`, t, func(c C) {
		ctx := context.Background()

		serverCalls := 0
		ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			serverCalls++
			w.Header().Set("Content-Type", jsonContentType)
			_, err := io.WriteString(w, "yo")
			c.So(err, ShouldBeNil)
		}))
		defer ts.Close()

		actual := map[string]string{}
		status, err := GetJSON(ctx, fast, http.DefaultClient, ts.URL, &actual)
		So(err.Error(), ShouldResemble, "gave up after 4 attempts: failed to handle response: bad response "+ts.URL+": invalid character 'y' looking for beginning of value")
		So(status, ShouldResemble, 200)
		So(actual, ShouldResemble, map[string]string{})
	})
}

func TestGetJSONBadResultIgnore(t *testing.T) {
	Convey(`Bad results from GET JSON requests should be handled correctly.`, t, func(c C) {
		ctx := context.Background()

		serverCalls := 0
		ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			serverCalls++
			w.Header().Set("Content-Type", jsonContentType)
			_, err := io.WriteString(w, "yo")
			c.So(err, ShouldBeNil)
		}))
		defer ts.Close()

		status, err := GetJSON(ctx, fast, http.DefaultClient, ts.URL, nil)
		So(err.Error(), ShouldResemble, "gave up after 4 attempts: failed to handle response: bad response "+ts.URL+": invalid character 'y' looking for beginning of value")
		So(status, ShouldResemble, 200)
	})
}

func TestGetJSONBadContentTypeIgnore(t *testing.T) {
	Convey(`Invalid content in bad GET JSON requests should be handled correctly`, t, func(c C) {
		ctx := context.Background()

		ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			_, err := io.WriteString(w, "{}")
			c.So(err, ShouldBeNil)
		}))
		defer ts.Close()

		status, err := GetJSON(ctx, fast, http.DefaultClient, ts.URL, nil)
		So(err.Error(), ShouldResemble, "gave up after 4 attempts: failed to handle response: unexpected Content-Type, expected \"application/json\", got \"text/plain; charset=utf-8\"")
		So(status, ShouldResemble, 200)
	})
}

func TestPostJSON(t *testing.T) {
	Convey(`HTTP POST JSON requests should be handled correctly.`, t, func(c C) {
		ctx := context.Background()

		// First call returns HTTP 500, second succeeds.
		serverCalls := 0
		ts := httptest.NewServer(handlerJSON(t, func(body io.Reader) interface{} {
			serverCalls++
			data := map[string]string{}
			c.So(json.NewDecoder(body).Decode(&data), ShouldBeNil)
			c.So(data, ShouldResemble, map[string]string{"in": "all"})
			if serverCalls == 1 {
				return nil
			}
			return map[string]string{"success": "yeah"}
		}))
		defer ts.Close()

		in := map[string]string{"in": "all"}
		actual := map[string]string{}
		status, err := PostJSON(ctx, fast, http.DefaultClient, ts.URL, nil, in, &actual)
		So(err, ShouldBeNil)
		So(status, ShouldResemble, 200)
		So(actual, ShouldResemble, map[string]string{"success": "yeah"})
		So(serverCalls, ShouldResemble, 2)
	})
}

func TestPostJSONwithHeaders(t *testing.T) {
	Convey(`HTTP POST JSON requests should handle headers.`, t, func(c C) {
		ctx := context.Background()

		serverCalls := 0
		ts := httptest.NewServer(
			http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
				defer r.Body.Close()
				w.Header().Set("Content-Type", jsonContentType)
				c.So(json.NewEncoder(w).Encode(map[string]string{}), ShouldBeNil)
				c.So(r.Header.Get("key"), ShouldResemble, "value")
				serverCalls++
			}))
		defer ts.Close()

		status, err := PostJSON(ctx, fast, http.DefaultClient, ts.URL, map[string]string{"key": "value"}, nil, nil)
		So(err, ShouldBeNil)
		So(status, ShouldResemble, 200)
		So(serverCalls, ShouldResemble, 1)
	})
}

func TestNewRequestDefaultFactory(t *testing.T) {
	// Test that the default factory (rFn == nil) only retries for transient
	// HTTP errors.
	testCases := []struct {
		statusCode int    // The status code to return (the first 2 times).
		path       string // Request path, if any.
		wantErr    bool   // Whether we want NewRequest to return an error.
		wantCalls  int    // The total number of HTTP requests expected.
	}{
		// 200, passes immediately.
		{statusCode: 200, wantErr: false, wantCalls: 1},
		// Transient HTTP error codes that will retry.
		{statusCode: 408, wantErr: false, wantCalls: 3},
		{statusCode: 500, wantErr: false, wantCalls: 3},
		{statusCode: 503, wantErr: false, wantCalls: 3},
		// Immediate failure codes.
		{statusCode: 403, wantErr: true, wantCalls: 1},
		{statusCode: 404, wantErr: true, wantCalls: 1},
	}

	ctx := context.Background()

	for _, tc := range testCases {
		tc := tc
		t.Run(fmt.Sprintf("Status code %d, path %q", tc.statusCode, tc.path), func(t *testing.T) {
			t.Parallel()
			serverCalls := 0
			ts := httptest.NewServer(
				http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
					defer r.Body.Close()
					serverCalls++
					if serverCalls <= 2 {
						w.WriteHeader(tc.statusCode)
					}
					fmt.Fprintf(w, "Hello World!\n")
				}))
			defer ts.Close()

			httpReq := httpReqGen("GET", ts.URL+tc.path, nil)
			req := NewRequest(ctx, http.DefaultClient, nil, httpReq, func(resp *http.Response) error {
				return resp.Body.Close()
			}, nil)

			_, err := req()
			if err == nil && tc.wantErr {
				t.Error("req returned nil error, wanted an error")
			} else if err != nil && !tc.wantErr {
				t.Errorf("req returned err %v, wanted nil", err)
			}
			if got, want := serverCalls, tc.wantCalls; got != want {
				t.Errorf("total server calls; got %d, want %d", got, want)
			}
		})
	}
}

func TestNewRequestClosesBody(t *testing.T) {
	ctx := context.Background()
	serverCalls := 0

	// Return a 500 for the first 2 requests.
	ts := httptest.NewServer(
		http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			defer r.Body.Close()
			serverCalls++
			if serverCalls <= 2 {
				w.WriteHeader(500)
			}
			fmt.Fprintf(w, "Hello World!\n")
		}))
	defer ts.Close()

	rt := &trackingRoundTripper{RoundTripper: http.DefaultTransport}
	hc := &http.Client{Transport: rt}
	httpReq := httpReqGen("GET", ts.URL, nil)

	clientCalls := 0
	var lastResp *http.Response
	req := NewRequest(ctx, hc, fast, httpReq, func(resp *http.Response) error {
		clientCalls++
		lastResp = resp
		return resp.Body.Close()
	}, nil)

	status, err := req()
	if err != nil {
		t.Fatalf("req returned err %v, want nil", err)
	}
	if got, want := status, http.StatusOK; got != want {
		t.Errorf("req returned status %d, want %d", got, want)
	}

	// We expect only one client call, but three requests through to the server.
	if got, want := clientCalls, 1; got != want {
		t.Errorf("handler callback invoked %d times, want %d", got, want)
	}
	if got, want := len(rt.Responses), 3; got != want {
		t.Errorf("len(Responses) = %d, want %d", got, want)
	}

	// Check that the last response is the one we handled, and that all the bodies
	// were closed.
	if got, want := lastResp, rt.Responses[2]; got != want {
		t.Errorf("Last Response did not match Response in handler callback.\nGot:  %v\nWant: %v", got, want)
	}
	for i, resp := range rt.Responses {
		rc := resp.Body.(*trackingReadCloser)
		if !rc.Closed {
			t.Errorf("Responses[%d].Body was not closed", i)
		}
	}
}

// trackingRoundTripper wraps an http.RoundTripper, keeping track of any
// returned Responses. Each response's Body, when set, is wrapped with a
// trackingReadCloser.
type trackingRoundTripper struct {
	http.RoundTripper

	mu        sync.Mutex
	Responses []*http.Response
}

func (t *trackingRoundTripper) RoundTrip(req *http.Request) (*http.Response, error) {
	resp, err := t.RoundTripper.RoundTrip(req)
	if resp != nil && resp.Body != nil {
		resp.Body = &trackingReadCloser{ReadCloser: resp.Body}
	}
	t.mu.Lock()
	defer t.mu.Unlock()
	t.Responses = append(t.Responses, resp)
	return resp, err
}

// trackingReadCloser wraps an io.ReadCloser, keeping track of whether Closed was
// called.
type trackingReadCloser struct {
	io.ReadCloser
	Closed bool
}

func (t *trackingReadCloser) Close() error {
	t.Closed = true
	return t.ReadCloser.Close()
}

// Private details.

func fast() retry.Iterator {
	return &retry.Limited{Retries: 3}
}

type jsonAPI func(body io.Reader) interface{}

// handlerJSON converts a jsonAPI http handler to a proper http.Handler.
func handlerJSON(t *testing.T, handler jsonAPI) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		Convey(`Test fixture for JSON http.`, t, func() {
			defer r.Body.Close()
			out := handler(r.Body)
			if out == nil {
				w.WriteHeader(500)
			} else {
				w.Header().Set("Content-Type", jsonContentType)
				So(json.NewEncoder(w).Encode(out), ShouldBeNil)
			}
		})
	})
}