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/inputprocessor.go

@@ -0,0 +1,139 @@
+package engine
+
+import (
+	"context"
+
+	"github.com/ooni/probe-cli/v3/internal/engine/model"
+)
+
+// InputProcessorExperiment is the Experiment
+// according to InputProcessor.
+type InputProcessorExperiment interface {
+	MeasureWithContext(
+		ctx context.Context, input string) (*model.Measurement, error)
+}
+
+// InputProcessorExperimentWrapper is a wrapper for an
+// Experiment that also allow to pass around the input index.
+type InputProcessorExperimentWrapper interface {
+	MeasureWithContext(
+		ctx context.Context, idx int, input string) (*model.Measurement, error)
+}
+
+// NewInputProcessorExperimentWrapper creates a new
+// instance of InputProcessorExperimentWrapper.
+func NewInputProcessorExperimentWrapper(
+	exp InputProcessorExperiment) InputProcessorExperimentWrapper {
+	return inputProcessorExperimentWrapper{exp: exp}
+}
+
+type inputProcessorExperimentWrapper struct {
+	exp InputProcessorExperiment
+}
+
+func (ipew inputProcessorExperimentWrapper) MeasureWithContext(
+	ctx context.Context, idx int, input string) (*model.Measurement, error) {
+	return ipew.exp.MeasureWithContext(ctx, input)
+}
+
+var _ InputProcessorExperimentWrapper = inputProcessorExperimentWrapper{}
+
+// InputProcessor processes inputs. We perform a Measurement
+// for each input using the given Experiment.
+type InputProcessor struct {
+	// Annotations contains the measurement annotations
+	Annotations map[string]string
+
+	// Experiment is the code that will run the experiment.
+	Experiment InputProcessorExperimentWrapper
+
+	// Inputs is the list of inputs to measure.
+	Inputs []model.URLInfo
+
+	// Options contains command line options for this experiment.
+	Options []string
+
+	// Saver is the code that will save measurement results
+	// on persistent storage (e.g. the file system).
+	Saver InputProcessorSaverWrapper
+
+	// Submitter is the code that will submit measurements
+	// to the OONI collector.
+	Submitter InputProcessorSubmitterWrapper
+}
+
+// InputProcessorSaverWrapper is InputProcessor's
+// wrapper for a Saver implementation.
+type InputProcessorSaverWrapper interface {
+	SaveMeasurement(idx int, m *model.Measurement) error
+}
+
+type inputProcessorSaverWrapper struct {
+	saver Saver
+}
+
+// NewInputProcessorSaverWrapper wraps a Saver for InputProcessor.
+func NewInputProcessorSaverWrapper(saver Saver) InputProcessorSaverWrapper {
+	return inputProcessorSaverWrapper{saver: saver}
+}
+
+func (ipsw inputProcessorSaverWrapper) SaveMeasurement(
+	idx int, m *model.Measurement) error {
+	return ipsw.saver.SaveMeasurement(m)
+}
+
+// InputProcessorSubmitterWrapper is InputProcessor's
+// wrapper for a Submitter implementation.
+type InputProcessorSubmitterWrapper interface {
+	Submit(ctx context.Context, idx int, m *model.Measurement) error
+}
+
+type inputProcessorSubmitterWrapper struct {
+	submitter Submitter
+}
+
+// NewInputProcessorSubmitterWrapper wraps a Submitter
+// for the InputProcessor.
+func NewInputProcessorSubmitterWrapper(submitter Submitter) InputProcessorSubmitterWrapper {
+	return inputProcessorSubmitterWrapper{submitter: submitter}
+}
+
+func (ipsw inputProcessorSubmitterWrapper) Submit(
+	ctx context.Context, idx int, m *model.Measurement) error {
+	return ipsw.submitter.Submit(ctx, m)
+}
+
+// Run processes all the input subject to the duration of the
+// context. The code will perform measurements using the given
+// experiment; submit measurements using the given submitter;
+// save measurements using the given saver.
+//
+// Annotations and Options will be saved in the measurement.
+//
+// The default behaviour of this code is that an error while
+// measuring, while submitting, or while saving a measurement
+// is always causing us to break out of the loop. The user
+// though is free to choose different policies by configuring
+// the Experiment, Submitter, and Saver fields properly.
+func (ip InputProcessor) Run(ctx context.Context) error {
+	for idx, url := range ip.Inputs {
+		input := url.URL
+		meas, err := ip.Experiment.MeasureWithContext(ctx, idx, input)
+		if err != nil {
+			return err
+		}
+		meas.AddAnnotations(ip.Annotations)
+		meas.Options = ip.Options
+		err = ip.Submitter.Submit(ctx, idx, meas)
+		if err != nil {
+			return err
+		}
+		// Note: must be after submission because submission modifies
+		// the measurement to include the report ID.
+		err = ip.Saver.SaveMeasurement(idx, meas)
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}