package loki

import (
	"context"
	"io"
	"net/http"
	"strings"
	"testing"
	"time"

	"github.com/grafana/grafana-plugin-sdk-go/backend"
	"github.com/grafana/grafana-plugin-sdk-go/backend/datasource"
	"github.com/grafana/grafana-plugin-sdk-go/backend/httpclient"

	"github.com/grafana/grafana/pkg/infra/tracing"
	"github.com/stretchr/testify/assert"
)

type healthCheckProvider[T http.RoundTripper] struct {
	httpclient.Provider
	RoundTripper *T
}

type healthCheckSuccessRoundTripper struct {
}
type healthCheckFailRoundTripper struct {
}

func (rt *healthCheckSuccessRoundTripper) RoundTrip(req *http.Request) (*http.Response, error) {
	return &http.Response{
		Status:     "200",
		StatusCode: 200,
		Header:     nil,
		Body: io.NopCloser(strings.NewReader(`{
			"data": {
				"resultType": "vector",
				"result": [
					{
						"metric": {},
						"value": [
							4000000000,
							"2"
						]
					}
				]
			},
			"status": "success"
		}`)),
		ContentLength: 0,
		Request:       req,
	}, nil
}

func (rt *healthCheckFailRoundTripper) RoundTrip(req *http.Request) (*http.Response, error) {
	return &http.Response{
		Status:        "400",
		StatusCode:    400,
		Header:        nil,
		Body:          nil,
		ContentLength: 0,
		Request:       req,
	}, nil
}

func (provider *healthCheckProvider[T]) New(opts ...httpclient.Options) (*http.Client, error) {
	client := &http.Client{}
	provider.RoundTripper = new(T)
	client.Transport = *provider.RoundTripper
	return client, nil
}

func (provider *healthCheckProvider[T]) GetTransport(opts ...httpclient.Options) (http.RoundTripper, error) {
	return *new(T), nil
}

// Return a mocked HTTP client provider.
//
// Example taken from `pkg/promlib/healthcheck_test.go`
func getMockProvider[T http.RoundTripper]() *httpclient.Provider {
	p := &healthCheckProvider[T]{
		RoundTripper: new(T),
	}
	anotherFN := func(o httpclient.Options, next http.RoundTripper) http.RoundTripper {
		return *p.RoundTripper
	}
	fn := httpclient.MiddlewareFunc(anotherFN)
	mid := httpclient.NamedMiddlewareFunc("mock", fn)
	return httpclient.NewProvider(httpclient.ProviderOptions{Middlewares: []httpclient.Middleware{mid}})
}

func Test_healthcheck(t *testing.T) {
	t.Run("should do a successful health check", func(t *testing.T) {
		httpProvider := getMockProvider[*healthCheckSuccessRoundTripper]()
		s := &Service{
			im:     datasource.NewInstanceManager(newInstanceSettings(httpProvider)),
			tracer: tracing.InitializeTracerForTest(),
			logger: backend.NewLoggerWith("logger", "loki test"),
		}

		req := &backend.CheckHealthRequest{
			PluginContext: getPluginContext(),
			Headers:       nil,
		}

		res, err := s.CheckHealth(context.Background(), req)
		assert.NoError(t, err)
		assert.Equal(t, backend.HealthStatusOk, res.Status)
	})

	t.Run("should return an error for an unsuccessful health check", func(t *testing.T) {
		httpProvider := getMockProvider[*healthCheckFailRoundTripper]()
		s := &Service{
			im:     datasource.NewInstanceManager(newInstanceSettings(httpProvider)),
			tracer: tracing.InitializeTracerForTest(),
			logger: backend.NewLoggerWith("logger", "loki test"),
		}

		req := &backend.CheckHealthRequest{
			PluginContext: getPluginContext(),
			Headers:       nil,
		}

		res, err := s.CheckHealth(context.Background(), req)
		assert.NoError(t, err)
		assert.Equal(t, backend.HealthStatusError, res.Status)
	})
}

func getPluginContext() backend.PluginContext {
	return backend.PluginContext{
		OrgID:               0,
		PluginID:            "loki",
		User:                nil,
		AppInstanceSettings: nil,
		DataSourceInstanceSettings: &backend.DataSourceInstanceSettings{
			ID:                      0,
			UID:                     "",
			Type:                    "loki",
			Name:                    "test-loki",
			URL:                     "http://loki:3100",
			User:                    "",
			Database:                "",
			BasicAuthEnabled:        true,
			BasicAuthUser:           "admin",
			JSONData:                []byte("{}"),
			DecryptedSecureJSONData: map[string]string{},
			Updated:                 time.Time{},
		},
	}
}