package loadgen

import (
	"bufio"
	"context"
	"errors"
	"fmt"
	"io"
	"net"
	"net/http"
	"net/http/httptest"
	"sync/atomic"
	"testing"
	"time"
)

func TestRunExecutesFixedBoundedHTTPWorkload(t *testing.T) {
	var requests atomic.Int64
	server := httptest.NewServer(http.HandlerFunc(func(response http.ResponseWriter, request *http.Request) {
		if request.Method != http.MethodPost || request.Header.Get("X-Scenario") != "fixed" {
			t.Errorf("request = %s %q", request.Method, request.Header.Get("X-Scenario"))
		}
		body, err := io.ReadAll(request.Body)
		if err != nil || string(body) != `{"count":1}` {
			t.Errorf("request body = %q, error = %v", body, err)
		}
		requests.Add(1)
		response.WriteHeader(http.StatusNoContent)
	}))
	defer server.Close()

	report, err := Run(context.Background(), Options{
		TargetURL: server.URL, Method: http.MethodPost, Headers: http.Header{"X-Scenario": {"fixed"}}, RequestBody: []byte(`{"count":1}`),
		Requests: 12, Concurrency: 3, RequestTimeout: time.Second,
	})
	if err != nil || report.Requests != 12 || report.Completed != 12 || report.Succeeded != 12 || report.Failed != 0 ||
		requests.Load() != 12 || report.Latency.P50UpperBound <= 0 || report.Runtime.NumCPU <= 0 {
		t.Fatalf("Run() = (%+v, %v); handler requests=%d", report, err, requests.Load())
	}
}

func TestRunClassifiesHTTPFailure(t *testing.T) {
	server := httptest.NewServer(http.HandlerFunc(func(response http.ResponseWriter, _ *http.Request) {
		response.WriteHeader(http.StatusServiceUnavailable)
	}))
	defer server.Close()

	report, err := Run(context.Background(), Options{
		TargetURL: server.URL, Requests: 1, Concurrency: 1, RequestTimeout: time.Second,
	})
	if err != nil || report.Succeeded != 0 || report.Failed != 1 || report.Status5xx != 1 || report.Completed != 1 {
		t.Fatalf("Run() = (%+v, %v)", report, err)
	}
}

func TestRunTimeBoxedRateIsBounded(t *testing.T) {
	var requests atomic.Int64
	server := httptest.NewServer(http.HandlerFunc(func(response http.ResponseWriter, _ *http.Request) {
		requests.Add(1)
		response.WriteHeader(http.StatusNoContent)
	}))
	defer server.Close()

	report, err := Run(context.Background(), Options{
		TargetURL: server.URL, Duration: 100 * time.Millisecond, Rate: 100, Concurrency: 2, RequestTimeout: time.Second,
	})
	if err != nil || report.Requests == 0 || report.Requests > 20 || report.Requests != report.Completed ||
		report.Succeeded != report.Completed || requests.Load() != int64(report.Requests) {
		t.Fatalf("Run() = (%+v, %v); handler requests=%d", report, err, requests.Load())
	}
}

func TestRunExecutesBoundedCONNECTTunnelWorkload(t *testing.T) {
	listener, err := net.Listen("tcp", "127.0.0.1:0")
	if err != nil {
		t.Fatalf("Listen(): %v", err)
	}
	defer listener.Close()

	var tunnels atomic.Int64
	serveDone := make(chan struct{})
	go func() {
		defer close(serveDone)
		for range 3 {
			connection, acceptErr := listener.Accept()
			if acceptErr != nil {
				return
			}
			go func(connection net.Conn) {
				defer connection.Close()
				request, readErr := http.ReadRequest(bufio.NewReader(connection))
				if readErr != nil || request.Method != http.MethodConnect || request.Host != "target.example:443" {
					t.Errorf("CONNECT request = %+v, error = %v", request, readErr)
					return
				}
				tunnels.Add(1)
				_, _ = fmt.Fprint(connection, "HTTP/1.1 200 Connection Established\r\n\r\n")
				_, _ = io.Copy(io.Discard, connection)
			}(connection)
		}
	}()

	report, err := Run(context.Background(), Options{
		Scenario: ScenarioConnect, TargetURL: "https://target.example/health", ProxyURL: "http://" + listener.Addr().String(),
		Requests: 3, Concurrency: 2, RequestTimeout: time.Second, TunnelHold: 10 * time.Millisecond,
	})
	if err != nil || report.Requests != 3 || report.Completed != 3 || report.Succeeded != 3 || report.Failed != 0 ||
		report.TunnelsEstablished != 3 || tunnels.Load() != 3 || report.Latency.P50UpperBound <= 0 {
		t.Fatalf("Run() = (%+v, %v); CONNECT requests=%d", report, err, tunnels.Load())
	}
	<-serveDone
}

func TestRunClassifiesCONNECTProxyRejection(t *testing.T) {
	listener, err := net.Listen("tcp", "127.0.0.1:0")
	if err != nil {
		t.Fatalf("Listen(): %v", err)
	}
	defer listener.Close()
	go func() {
		connection, acceptErr := listener.Accept()
		if acceptErr != nil {
			return
		}
		defer connection.Close()
		_, _ = http.ReadRequest(bufio.NewReader(connection))
		_, _ = fmt.Fprint(connection, "HTTP/1.1 407 Proxy Authentication Required\r\nContent-Length: 0\r\n\r\n")
	}()

	report, err := Run(context.Background(), Options{
		Scenario: ScenarioConnect, TargetURL: "https://target.example/health", ProxyURL: "http://" + listener.Addr().String(),
		Requests: 1, Concurrency: 1, RequestTimeout: time.Second, TunnelHold: time.Millisecond,
	})
	if err != nil || report.Succeeded != 0 || report.Failed != 1 || report.Status4xx != 1 || report.TunnelsEstablished != 0 {
		t.Fatalf("Run() = (%+v, %v)", report, err)
	}
}

func TestRunRejectsCONNECTWithoutProxyOrHold(t *testing.T) {
	_, err := Run(context.Background(), Options{
		Scenario: ScenarioConnect, TargetURL: "https://target.example/health", Requests: 1, Concurrency: 1, RequestTimeout: time.Second,
	})
	if !errors.Is(err, ErrInvalidOptions) {
		t.Fatalf("Run(connect without proxy or hold) error = %v, want ErrInvalidOptions", err)
	}
}

func TestRunRejectsUnboundedWorkload(t *testing.T) {
	_, err := Run(context.Background(), Options{TargetURL: "http://127.0.0.1:8080", Concurrency: 1})
	if !errors.Is(err, ErrInvalidOptions) {
		t.Fatalf("Run(unbounded) error = %v, want ErrInvalidOptions", err)
	}
}