package process

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

// 1190/AC4: given the consume loop, when its context ends, then it stops pulling and returns without
// acknowledging a message in hand.
func TestRunQueueStopsPullingAndNeverActsOnAMessageWhenContextEnds(t *testing.T) {
	ctx, cancel := context.WithCancel(context.Background())

	acked := false
	msg := &Message{Subject: "test", ack: func() error { acked = true; return nil },
		nak: func(time.Duration) error { return nil }, term: func() error { return nil }}

	pulls := 0
	next := func(ctx context.Context) (*Message, error) {
		pulls++
		return msg, nil
	}

	handled := 0
	done := make(chan error, 1)
	go func() {
		done <- runQueue(ctx, next, func(m *Message) {
			handled++
			// The handler does not act on the message at all: a redelivery, a termination or an
			// acknowledgement is its choice alone, never the loop's.
			cancel()
		})
	}()

	select {
	case err := <-done:
		if !errors.Is(err, context.Canceled) {
			t.Fatalf("runQueue returned %v, want context.Canceled", err)
		}
	case <-time.After(3 * time.Second):
		t.Fatal("runQueue did not stop when its context ended")
	}
	if handled != 1 {
		t.Fatalf("handle was called %d times, want 1", handled)
	}
	if acked {
		t.Error("runQueue acknowledged the message itself; only the handler may")
	}
	if pulls != 1 {
		t.Fatalf("next was called %d times, want exactly 1: once the handler ends the context, runQueue's "+
			"own check stops it before pulling again", pulls)
	}
}

// 1190/AC4: a context already ended before the loop starts pulls nothing at all.
func TestRunQueueNeverPullsOnAnAlreadyEndedContext(t *testing.T) {
	ctx, cancel := context.WithCancel(context.Background())
	cancel()
	calls := 0
	err := runQueue(ctx, func(context.Context) (*Message, error) {
		calls++
		return nil, context.Canceled
	}, func(*Message) { t.Fatal("handle was called on an already-ended context") })
	if !errors.Is(err, context.Canceled) {
		t.Fatalf("runQueue returned %v, want context.Canceled", err)
	}
	if calls != 0 {
		t.Fatalf("next was called %d times, want 0", calls)
	}
}