package agent

import (
	"context"
	"errors"
	"strings"
	"testing"
)

type scriptBackend struct {
	name  string
	res   *Result
	err   error
	calls int
}

func (s *scriptBackend) Name() string { return s.name }

func (s *scriptBackend) Execute(ctx context.Context, req Request) (*Result, error) {
	s.calls++
	return s.res, s.err
}

func TestFallbackKeepsNativeSuccess(t *testing.T) {
	primary := &scriptBackend{name: "pi-native", res: &Result{Success: true, Logs: "native"}}
	spare := &scriptBackend{name: "pi-agent", res: &Result{Success: true}}
	got, err := (&fallbackBackend{primary: primary, fallback: spare}).Execute(context.Background(), Request{})
	if err != nil || !got.Success || got.Logs != "native" || spare.calls != 0 {
		t.Fatalf("got %#v err=%v spare=%d", got, err, spare.calls)
	}
}

func TestFallbackUsesContainerAfterNativeFailure(t *testing.T) {
	primary := &scriptBackend{name: "pi-native", res: &Result{Success: false, ErrorReason: "missing target deliverable"}}
	spare := &scriptBackend{name: "pi-agent", res: &Result{Success: true, Logs: "container"}}
	got, err := (&fallbackBackend{primary: primary, fallback: spare}).Execute(context.Background(), Request{})
	if err != nil || !got.Success || spare.calls != 1 {
		t.Fatalf("got %#v err=%v calls=%d", got, err, spare.calls)
	}
	if !strings.Contains(got.Logs, "served by pi-agent") || !strings.Contains(got.Logs, "missing target deliverable") {
		t.Fatalf("logs %q", got.Logs)
	}
}

func TestFallbackReturnsNativeWhenContainerAlsoFails(t *testing.T) {
	primary := &scriptBackend{name: "pi-native", err: errors.New("native down")}
	spare := &scriptBackend{name: "pi-agent", res: &Result{Success: false, ErrorReason: "runner down"}}
	got, err := (&fallbackBackend{primary: primary, fallback: spare}).Execute(context.Background(), Request{})
	if err == nil || err.Error() != "native down" || got != nil || spare.calls != 1 {
		t.Fatalf("got %#v err=%v", got, err)
	}
}

func TestFallbackStopsWhenContextCancelled(t *testing.T) {
	ctx, cancel := context.WithCancel(context.Background())
	cancel()
	primary := &scriptBackend{name: "pi-native", err: context.Canceled}
	spare := &scriptBackend{name: "pi-agent", res: &Result{Success: true}}
	_, err := (&fallbackBackend{primary: primary, fallback: spare}).Execute(ctx, Request{})
	if !errors.Is(err, context.Canceled) || spare.calls != 0 {
		t.Fatalf("err=%v spare=%d", err, spare.calls)
	}
}