From 30643e385d9bb62f331a9beca1271febd894f10d Mon Sep 17 00:00:00 2001
From: MDietermann <mdietermann253@gmail.com>
Date: Mon, 13 Apr 2026 19:37:51 +0200
Subject: [PATCH] feat(engine): add Reporter with buffered and plain
 implementations

---
 internal/engine/reporter.go      | 80 ++++++++++++++++++++++++++++++++
 internal/engine/reporter_test.go | 56 ++++++++++++++++++++++
 2 files changed, 136 insertions(+)
 create mode 100644 internal/engine/reporter.go
 create mode 100644 internal/engine/reporter_test.go

diff --git a/internal/engine/reporter.go b/internal/engine/reporter.go
new file mode 100644
index 0000000..cdf7848
--- /dev/null
+++ b/internal/engine/reporter.go
@@ -0,0 +1,80 @@
+// Package engine runs modules through the Detect/Plan/Apply/Verify phases.
+package engine
+
+import (
+	"fmt"
+	"io"
+	"sync"
+
+	"github.com/MDietermann/ArduinoArchSetup/internal/module"
+)
+
+// Event is a single item streamed from a module during Apply.
+type Event struct {
+	ModuleID string
+	Kind     EventKind
+	Current  int
+	Total    int
+	Message  string
+}
+
+type EventKind int
+
+const (
+	EventProgress EventKind = iota
+	EventLog
+)
+
+// BufferedReporter stores every event in memory. Used in tests.
+type BufferedReporter struct {
+	mu     sync.Mutex
+	events []Event
+}
+
+func NewBufferedReporter() *BufferedReporter { return &BufferedReporter{} }
+
+func (b *BufferedReporter) Progress(id string, current, total int, msg string) {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+	b.events = append(b.events, Event{ModuleID: id, Kind: EventProgress, Current: current, Total: total, Message: msg})
+}
+
+func (b *BufferedReporter) Log(id, line string) {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+	b.events = append(b.events, Event{ModuleID: id, Kind: EventLog, Message: line})
+}
+
+func (b *BufferedReporter) Events() []Event {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+	out := make([]Event, len(b.events))
+	copy(out, b.events)
+	return out
+}
+
+// PlainReporter writes human-readable lines to w. Concurrency-safe.
+type PlainReporter struct {
+	mu sync.Mutex
+	w  io.Writer
+}
+
+func NewPlainReporter(w io.Writer) *PlainReporter { return &PlainReporter{w: w} }
+
+func (p *PlainReporter) Progress(id string, current, total int, msg string) {
+	p.mu.Lock()
+	defer p.mu.Unlock()
+	fmt.Fprintf(p.w, "[%s] (%d/%d) %s\n", id, current, total, msg)
+}
+
+func (p *PlainReporter) Log(id, line string) {
+	p.mu.Lock()
+	defer p.mu.Unlock()
+	fmt.Fprintf(p.w, "[%s] %s\n", id, line)
+}
+
+// Compile-time guarantee both types satisfy module.Reporter.
+var (
+	_ module.Reporter = (*BufferedReporter)(nil)
+	_ module.Reporter = (*PlainReporter)(nil)
+)
diff --git a/internal/engine/reporter_test.go b/internal/engine/reporter_test.go
new file mode 100644
index 0000000..5fc9ebb
--- /dev/null
+++ b/internal/engine/reporter_test.go
@@ -0,0 +1,56 @@
+package engine
+
+import (
+	"bytes"
+	"strings"
+	"sync"
+	"testing"
+)
+
+func TestBufferedReporterRecordsEventsInOrder(t *testing.T) {
+	r := NewBufferedReporter()
+	r.Progress("m", 1, 3, "step 1")
+	r.Log("m", "hello")
+	r.Progress("m", 2, 3, "step 2")
+
+	ev := r.Events()
+	if len(ev) != 3 {
+		t.Fatalf("want 3 events, got %d", len(ev))
+	}
+	if ev[0].Kind != EventProgress || ev[0].Current != 1 {
+		t.Errorf("event[0] = %+v", ev[0])
+	}
+	if ev[1].Kind != EventLog || ev[1].Message != "hello" {
+		t.Errorf("event[1] = %+v", ev[1])
+	}
+}
+
+func TestBufferedReporterIsConcurrencySafe(t *testing.T) {
+	r := NewBufferedReporter()
+	var wg sync.WaitGroup
+	for i := 0; i < 50; i++ {
+		wg.Add(1)
+		go func(i int) {
+			defer wg.Done()
+			r.Progress("m", i, 50, "x")
+		}(i)
+	}
+	wg.Wait()
+	if got := len(r.Events()); got != 50 {
+		t.Fatalf("want 50 events, got %d", got)
+	}
+}
+
+func TestPlainReporterFormat(t *testing.T) {
+	var buf bytes.Buffer
+	r := NewPlainReporter(&buf)
+	r.Progress("packages", 2, 10, "installing tio")
+	r.Log("packages", "pacman: done")
+
+	out := buf.String()
+	for _, want := range []string{"[packages] (2/10) installing tio", "[packages] pacman: done"} {
+		if !strings.Contains(out, want) {
+			t.Errorf("output missing %q; got:\n%s", want, out)
+		}
+	}
+}