chore: merge probe-engine into probe-cli (#201)

This is how I did it:

1. `git clone https://github.com/ooni/probe-engine internal/engine`

2. ```
(cd internal/engine && git describe --tags)
v0.23.0
```

3. `nvim go.mod` (merging `go.mod` with `internal/engine/go.mod`

4. `rm -rf internal/.git internal/engine/go.{mod,sum}`

5. `git add internal/engine`

6. `find . -type f -name \*.go -exec sed -i 's@/ooni/probe-engine@/ooni/probe-cli/v3/internal/engine@g' {} \;`

7. `go build ./...` (passes)

8. `go test -race ./...` (temporary failure on RiseupVPN)

9. `go mod tidy`

10. this commit message

Once this piece of work is done, we can build a new version of `ooniprobe` that
is using `internal/engine` directly. We need to do more work to ensure all the
other functionality in `probe-engine` (e.g. making mobile packages) are still WAI.

Part of https://github.com/ooni/probe/issues/1335

internal/engine/experiment/example/example.go

@@ -0,0 +1,95 @@
+// Package example contains a simple example experiment.
+//
+// You could use this code to boostrap the implementation of
+// a new experiment that you are working on.
+package example
+
+import (
+	"context"
+	"errors"
+	"time"
+
+	"github.com/ooni/probe-cli/v3/internal/engine/model"
+)
+
+const testVersion = "0.1.0"
+
+// Config contains the experiment config.
+//
+// This contains all the settings that user can set to modify the behaviour
+// of this experiment. By tagging these variables with `ooni:"..."`, we allow
+// miniooni's -O flag to find them and set them.
+type Config struct {
+	Message     string `ooni:"Message to emit at test completion"`
+	ReturnError bool   `ooni:"Toogle to return a mocked error"`
+	SleepTime   int64  `ooni:"Amount of time to sleep for"`
+}
+
+// TestKeys contains the experiment's result.
+//
+// This is what will end up into the Measurement.TestKeys field
+// when you run this experiment.
+//
+// In other words, the variables in this struct will be
+// the specific results of this experiment.
+type TestKeys struct {
+	Success bool `json:"success"`
+}
+
+// Measurer performs the measurement.
+type Measurer struct {
+	config   Config
+	testName string
+}
+
+// ExperimentName implements model.ExperimentMeasurer.ExperimentName.
+func (m Measurer) ExperimentName() string {
+	return m.testName
+}
+
+// ExperimentVersion implements model.ExperimentMeasurer.ExperimentVersion.
+func (m Measurer) ExperimentVersion() string {
+	return testVersion
+}
+
+// ErrFailure is the error returned when you set the
+// config.ReturnError field to true.
+var ErrFailure = errors.New("mocked error")
+
+// Run implements model.ExperimentMeasurer.Run.
+func (m Measurer) Run(
+	ctx context.Context, sess model.ExperimentSession,
+	measurement *model.Measurement, callbacks model.ExperimentCallbacks,
+) error {
+	var err error
+	if m.config.ReturnError {
+		err = ErrFailure
+	}
+	testkeys := &TestKeys{Success: err == nil}
+	measurement.TestKeys = testkeys
+	sess.Logger().Warnf("%s", "Follow the white rabbit.")
+	ctx, cancel := context.WithTimeout(ctx, time.Duration(m.config.SleepTime))
+	defer cancel()
+	<-ctx.Done()
+	sess.Logger().Infof("%s", "Knock, knock, Neo.")
+	callbacks.OnProgress(1.0, m.config.Message)
+	return err
+}
+
+// NewExperimentMeasurer creates a new ExperimentMeasurer.
+func NewExperimentMeasurer(config Config, testName string) model.ExperimentMeasurer {
+	return Measurer{config: config, testName: testName}
+}
+
+// SummaryKeys contains summary keys for this experiment.
+//
+// Note that this structure is part of the ABI contract with probe-cli
+// therefore we should be careful when changing it.
+type SummaryKeys struct {
+	IsAnomaly bool `json:"-"`
+}
+
+// GetSummaryKeys implements model.ExperimentMeasurer.GetSummaryKeys.
+func (m Measurer) GetSummaryKeys(measurement *model.Measurement) (interface{}, error) {
+	return SummaryKeys{IsAnomaly: false}, nil
+}

internal/engine/experiment/example/example_test.go

@@ -0,0 +1,67 @@
+package example_test
+
+import (
+	"context"
+	"errors"
+	"testing"
+	"time"
+
+	"github.com/apex/log"
+	"github.com/ooni/probe-cli/v3/internal/engine/experiment/example"
+	"github.com/ooni/probe-cli/v3/internal/engine/internal/mockable"
+	"github.com/ooni/probe-cli/v3/internal/engine/model"
+)
+
+func TestSuccess(t *testing.T) {
+	m := example.NewExperimentMeasurer(example.Config{
+		SleepTime: int64(2 * time.Millisecond),
+	}, "example")
+	if m.ExperimentName() != "example" {
+		t.Fatal("invalid ExperimentName")
+	}
+	if m.ExperimentVersion() != "0.1.0" {
+		t.Fatal("invalid ExperimentVersion")
+	}
+	ctx := context.Background()
+	sess := &mockable.Session{MockableLogger: log.Log}
+	callbacks := model.NewPrinterCallbacks(sess.Logger())
+	measurement := new(model.Measurement)
+	err := m.Run(ctx, sess, measurement, callbacks)
+	if err != nil {
+		t.Fatal(err)
+	}
+	sk, err := m.GetSummaryKeys(measurement)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, ok := sk.(example.SummaryKeys); !ok {
+		t.Fatal("invalid type for summary keys")
+	}
+}
+
+func TestFailure(t *testing.T) {
+	m := example.NewExperimentMeasurer(example.Config{
+		SleepTime:   int64(2 * time.Millisecond),
+		ReturnError: true,
+	}, "example")
+	ctx := context.Background()
+	sess := &mockable.Session{MockableLogger: log.Log}
+	callbacks := model.NewPrinterCallbacks(sess.Logger())
+	err := m.Run(ctx, sess, new(model.Measurement), callbacks)
+	if !errors.Is(err, example.ErrFailure) {
+		t.Fatal("expected an error here")
+	}
+}
+
+func TestSummaryKeysGeneric(t *testing.T) {
+	measurement := &model.Measurement{TestKeys: &example.TestKeys{}}
+	m := &example.Measurer{}
+	osk, err := m.GetSummaryKeys(measurement)
+	if err != nil {
+		t.Fatal(err)
+	}
+	sk := osk.(example.SummaryKeys)
+	if sk.IsAnomaly {
+		t.Fatal("invalid isAnomaly")
+	}
+}