refactor(mlablocate*): move from i/e/internal to internal (#385)

We've been flattening the package structure for some time now.

While there, add very basic examples.

internal/engine/internal/mlablocate/mlablocate.go

@@ -1,109 +0,0 @@
-// Package mlablocate contains a locate.measurementlab.net client
-// implementing v1 of the locate API. This version of the API isn't
-// suitable for requesting servers for ndt7. You should use the
-// mlablocatev2 package for that.
-package mlablocate
-
-import (
-	"context"
-	"encoding/json"
-	"errors"
-	"fmt"
-	"net/http"
-	"net/url"
-
-	"github.com/ooni/probe-cli/v3/internal/iox"
-)
-
-// Logger is the logger expected by this package.
-type Logger interface {
-	// Debugf formats and emits a debug message.
-	Debugf(format string, v ...interface{})
-}
-
-// HTTPClient is anything that looks like an http.Client.
-type HTTPClient interface {
-	// Do behaves like http.Client.Do.
-	Do(req *http.Request) (*http.Response, error)
-}
-
-// Client is a locate.measurementlab.net client. Please use the
-// NewClient factory to construct a new instance of client, otherwise
-// you MUST fill all the fields marked as MANDATORY.
-type Client struct {
-	// HTTPClient is the MANDATORY http client to use.
-	HTTPClient HTTPClient
-
-	// Hostname is the MANDATORY hostname of the mlablocate API.
-	Hostname string
-
-	// Logger is the MANDATORY logger to use.
-	Logger Logger
-
-	// Scheme is the MANDATORY scheme to use (http or https).
-	Scheme string
-
-	// UserAgent is the MANDATORY user-agent to use.
-	UserAgent string
-}
-
-// NewClient creates a new locate.measurementlab.net client.
-func NewClient(httpClient HTTPClient, logger Logger, userAgent string) *Client {
-	return &Client{
-		HTTPClient: httpClient,
-		Hostname:   "locate.measurementlab.net",
-		Logger:     logger,
-		Scheme:     "https",
-		UserAgent:  userAgent,
-	}
-}
-
-// Result is a result of a query to locate.measurementlab.net.
-type Result struct {
-	// FQDN is the mlab server's FQDN.
-	FQDN string `json:"fqdn"`
-
-	// Site is the ID of the site where the server is.
-	Site string `json:"site"`
-}
-
-// Query performs a locate.measurementlab.net query. This function returns
-// either valid result, on success, or an error, on failure.
-// (Note thay you cannot use this API to query for ndt7 servers. You should
-// use the mlablocatev2 API to obtain such servers.)
-func (c *Client) Query(ctx context.Context, tool string) (Result, error) {
-	// TODO(bassosimone): this code should probably be
-	// refactored to use the httpx package.
-	URL := &url.URL{
-		Scheme: c.Scheme,
-		Host:   c.Hostname,
-		Path:   tool,
-	}
-	req, err := http.NewRequestWithContext(ctx, "GET", URL.String(), nil)
-	if err != nil {
-		return Result{}, err
-	}
-	req.Header.Add("User-Agent", c.UserAgent)
-	c.Logger.Debugf("mlablocate: GET %s", URL.String())
-	resp, err := c.HTTPClient.Do(req)
-	if err != nil {
-		return Result{}, err
-	}
-	defer resp.Body.Close()
-	if resp.StatusCode != 200 {
-		return Result{}, fmt.Errorf("mlablocate: non-200 status code: %d", resp.StatusCode)
-	}
-	data, err := iox.ReadAllContext(ctx, resp.Body)
-	if err != nil {
-		return Result{}, err
-	}
-	c.Logger.Debugf("mlablocate: %s", string(data))
-	var result Result
-	if err := json.Unmarshal(data, &result); err != nil {
-		return Result{}, err
-	}
-	if result.FQDN == "" {
-		return Result{}, errors.New("mlablocate: returned empty FQDN")
-	}
-	return result, nil
-}