module.go

package main

import (
	"crypto/tls"
	"encoding/json"
	"fmt"
	"net/http"
	"net/url"
	"time"

	"github.com/GoScouter/sdk"
)

type NginxModule struct {
	Client *http.Client
}

func NewModule() *NginxModule {
	client := &http.Client{
		Timeout: 5 * time.Second,
		Transport: &http.Transport{
			TLSClientConfig: &tls.Config{InsecureSkipVerify: true},
		},
		CheckRedirect: func(req *http.Request, via []*http.Request) error {
			if len(via) >= 3 {
				return http.ErrUseLastResponse
			}
			return nil
		},
	}

	return &NginxModule{
		Client: client,
	}
}

func (m *NginxModule) Info() sdk.ModuleInfo {
	deps := make([]sdk.ModuleNamespace, 0)
	deps = append(deps, sdk.ModuleNamespace{
		Name:   "dns",
		Author: "internal",
	})

	return sdk.ModuleInfo{
		Name:         "nginx",
		Author:       "goscouter",
		Description:  "POC",
		Dependencies: deps,
	}
}

func (m *NginxModule) Scout(target string, args []string) (json.RawMessage, error) {
	result := &NginxResult{Target: target}

	client, err := sdk.NewClient()
	if err != nil {
		return nil, fmt.Errorf("connecting to the runner: %w", err)
	}
	defer client.Close()

	_, err = client.AskModule(sdk.ModuleNamespace{
		Name:   "dns",
		Author: "internal",
	})
	if err != nil {
		return nil, fmt.Errorf("asking internal:dns: %w", err)
	}

	targetURL, err := normalizeURL(target)
	if err != nil {
		return nil, fmt.Errorf("invalid target URL %q: %w", target, err)
	}

	resp, err := doGet(m.Client, targetURL)
	if err != nil {
		return nil, err
	}
	result.StatusCode = resp.StatusCode
	result.ServerHeader = resp.Header.Get("Server")
	resp.Body.Close()

	detectFromServerHeader(result, result.ServerHeader, "Server Header")

	if !result.IsNginx || result.NginxVersion == unknownVersion {
		probe404(m.Client, targetURL, result)
	}

	data, err := json.Marshal(result)
	if err != nil {
		return nil, err
	}

	return data, nil
}

func (m *NginxModule) Render(raw json.RawMessage) string {
	return string(raw) + "\r\n"
}

func doGet(client *http.Client, target *url.URL) (*http.Response, error) {
	req, err := http.NewRequest(http.MethodGet, target.String(), nil)
	if err != nil {
		return nil, fmt.Errorf("failed to create request: %w", err)
	}
	req.Header.Set("User-Agent", "GoScouter-NginxModule/0.2.0")
	return client.Do(req)
}