package display

import (
	"context"
	"errors"
	"sync"
	"testing"
	"time"
)

// diagnosticCapture collects structured reconnect records from Run.
type diagnosticCapture struct {
	mu      sync.Mutex
	records []Diagnostic
}

func (c *diagnosticCapture) record(d Diagnostic) {
	c.mu.Lock()
	defer c.mu.Unlock()
	c.records = append(c.records, d)
}

func (c *diagnosticCapture) all() []Diagnostic {
	c.mu.Lock()
	defer c.mu.Unlock()
	return append([]Diagnostic(nil), c.records...)
}

func TestRunDiagnosesEachFailedOpenWithStructuredFields(t *testing.T) {
	session := newFakeSession()
	var opens int
	opener := fakeOpener{open: func(int) (Session, error) {
		opens++
		if opens <= 2 {
			return nil, errors.New("x11 down")
		}
		return session, nil
	}}

	capture := &diagnosticCapture{}
	ctx, cancel := context.WithCancel(context.Background())
	done := make(chan error, 1)
	go func() {
		done <- Run(ctx, opener, NewStatusTemplate("hello"), Options{
			Target:     "x11",
			Layer:      "fallback-canvas",
			Diagnostic: capture.record,
			RetryDelay: time.Millisecond,
			MaxDelay:   2 * time.Millisecond,
		})
	}()

	waitFor(t, func() bool { return session.canvas.lineCount() > 0 }, "connect after retries")
	cancel()

	select {
	case err := <-done:
		if err != nil {
			t.Fatalf("run: %v", err)
		}
	case <-time.After(time.Second):
		t.Fatal("run did not stop after cancel")
	}

	records := capture.all()
	if len(records) != 2 {
		t.Fatalf("records=%d want exactly one per failed open (2)", len(records))
	}
	first, second := records[0], records[1]
	if first.Target != "x11" {
		t.Fatalf("target=%q want x11", first.Target)
	}
	if first.Layer != "fallback-canvas" {
		t.Fatalf("layer=%q want fallback-canvas", first.Layer)
	}
	if first.Event != EventOpenFailed {
		t.Fatalf("event=%q want %q", first.Event, EventOpenFailed)
	}
	if first.Err == nil || first.Err.Error() != "x11 down" {
		t.Fatalf("underlying error %v must be carried in the record", first.Err)
	}
	if first.RetryDelay != time.Millisecond {
		t.Fatalf("first retry delay=%v want %v", first.RetryDelay, time.Millisecond)
	}
	if second.RetryDelay != 2*time.Millisecond {
		t.Fatalf("backed-off retry delay=%v want %v", second.RetryDelay, 2*time.Millisecond)
	}
}

func TestRunDiagnosesBrokenSessionOnceAndRecovers(t *testing.T) {
	first := newFakeSession()
	second := newFakeSession()
	var opens int
	opener := fakeOpener{open: func(int) (Session, error) {
		opens++
		if opens == 1 {
			return first, nil
		}
		return second, nil
	}}

	capture := &diagnosticCapture{}
	ctx, cancel := context.WithCancel(context.Background())
	done := make(chan error, 1)
	go func() {
		done <- Run(ctx, opener, NewStatusTemplate("hello"), Options{
			Target:     "x11",
			Diagnostic: capture.record,
			RetryDelay: time.Millisecond,
			MaxDelay:   2 * time.Millisecond,
		})
	}()

	waitFor(t, func() bool { return first.canvas.lineCount() == 1 }, "draw on first session")
	first.events <- eventResult{err: errors.New("connection lost")}
	waitFor(t, func() bool { return second.canvas.lineCount() == 1 }, "recover on reconnected session")
	cancel()

	select {
	case err := <-done:
		if err != nil {
			t.Fatalf("run: %v", err)
		}
	case <-time.After(time.Second):
		t.Fatal("run did not stop after cancel")
	}

	records := capture.all()
	if len(records) != 1 {
		t.Fatalf("records=%d want exactly one per broken session (1)", len(records))
	}
	record := records[0]
	if record.Target != "x11" {
		t.Fatalf("target=%q want x11", record.Target)
	}
	if record.Event != EventSessionEnded {
		t.Fatalf("event=%q want %q", record.Event, EventSessionEnded)
	}
	if record.Err == nil || record.Err.Error() != "connection lost" {
		t.Fatalf("underlying error %v must be carried in the record", record.Err)
	}
	if record.RetryDelay != time.Millisecond {
		t.Fatalf("retry delay=%v want the reset %v", record.RetryDelay, time.Millisecond)
	}
}

// blockingOpener fails only after the context is done, so cancellation is
// the sole reason Run stops: no diagnostic may fire for shutdown.
type blockingOpener struct{}

func (blockingOpener) Open(ctx context.Context) (Session, error) {
	<-ctx.Done()
	return nil, ctx.Err()
}

func TestRunStaysSilentWhenCancellationEndsTheLoop(t *testing.T) {
	capture := &diagnosticCapture{}
	ctx, cancel := context.WithCancel(context.Background())
	done := make(chan error, 1)
	go func() {
		done <- Run(ctx, blockingOpener{}, NewStatusTemplate("hello"), Options{
			Target:     "x11",
			Diagnostic: capture.record,
			RetryDelay: time.Millisecond,
			MaxDelay:   2 * time.Millisecond,
		})
	}()

	cancel()

	select {
	case err := <-done:
		if err != nil {
			t.Fatalf("run: %v", err)
		}
	case <-time.After(time.Second):
		t.Fatal("run did not stop after cancel")
	}
	if records := capture.all(); len(records) != 0 {
		t.Fatalf("records=%v must stay empty: shutdown is not a reconnect boundary", records)
	}
}