package ai

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

type fakeBackend struct {
	out       string
	err       error
	gotPrompt string
}

func (f *fakeBackend) Run(ctx context.Context, prompt string) (string, error) {
	f.gotPrompt = prompt
	return f.out, f.err
}
func (f *fakeBackend) Name() string { return "fake" }

func TestServiceCoachSuccess(t *testing.T) {
	fb := &fakeBackend{out: `here you go {"next_action":"Write tests","success_condition":"green","timebox_minutes":30}`}
	svc := NewService(fb)
	p, err := svc.Coach(context.Background(), "write the tests", "")
	if err != nil {
		t.Fatalf("coach: %v", err)
	}
	if p.NextAction != "Write tests" || p.TimeboxSecs != 1800 {
		t.Fatalf("bad proposal: %+v", p)
	}
	if !strings.Contains(fb.gotPrompt, "write the tests") {
		t.Fatalf("prompt should embed the intent, got: %s", fb.gotPrompt)
	}
}

func TestServiceCoachBackendError(t *testing.T) {
	fb := &fakeBackend{err: errors.New("boom")}
	if _, err := NewService(fb).Coach(context.Background(), "x", ""); err == nil {
		t.Fatal("want backend error")
	}
}

func TestServiceCoachUnparseable(t *testing.T) {
	fb := &fakeBackend{out: "I cannot help with that."}
	if _, err := NewService(fb).Coach(context.Background(), "x", ""); !errors.Is(err, ErrNoJSON) {
		t.Fatalf("want ErrNoJSON, got %v", err)
	}
}

func TestCoachPromptIncludesGrounding(t *testing.T) {
	fb := &fakeBackend{out: `{"next_action":"a","success_condition":"b","timebox_minutes":20}`}
	if _, err := NewService(fb).Coach(context.Background(), "ship it", "I value small diffs."); err != nil {
		t.Fatalf("coach: %v", err)
	}
	if !strings.Contains(fb.gotPrompt, "About the user") || !strings.Contains(fb.gotPrompt, "small diffs") {
		t.Fatalf("prompt missing grounding block: %s", fb.gotPrompt)
	}
}

func TestCoachEmptyGroundingUnchanged(t *testing.T) {
	withFb := &fakeBackend{out: `{"next_action":"a","success_condition":"b","timebox_minutes":20}`}
	_, _ = NewService(withFb).Coach(context.Background(), "ship it", "")
	// The empty-grounding prompt must equal buildPrompt(intent) of the old shape:
	// it must NOT contain the grounding header.
	if strings.Contains(withFb.gotPrompt, "About the user") {
		t.Fatalf("empty grounding leaked a header: %s", withFb.gotPrompt)
	}
}