feat(engine): add Reporter with buffered and plain implementations

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)
+)