import { describe, expect, it } from 'bun:test';
import { SessionModelController } from '@/core/model-controller';
import type { Provider } from '@/contracts/provider';
import type { ModelDescriptor } from '@/contracts/model';

const openai: ModelDescriptor = { id: 'openai:gpt-4o', provider: 'openai', model: 'gpt-4o' };
const local: ModelDescriptor = { id: 'local:llama3', provider: 'local', model: 'llama3' };
const provider = (): Provider => ({
  stream: async function* () { yield { kind: 'done', message: { id: 'm', role: 'assistant', content: [] }, usage: { input: 0, output: 0 } }; },
});

describe('SessionModelController', () => {
  it('lists immutable catalog descriptors and selects a known id', () => {
    const queued: Provider[] = [];
    const controller = new SessionModelController({
      models: [openai, local], active: openai, createProvider: provider, queueProvider: (p) => queued.push(p),
    });
    expect(controller.list()).toEqual({ models: [openai, local], active: openai });
    const result = controller.set(local.id);
    expect(result).toEqual({ previous: openai, active: local, effective: 'next_provider_call' });
    expect(queued).toHaveLength(1);
    const listed = controller.list();
    listed.models[0]!.model = 'mutated';
    expect(controller.list().models[0]!.model).toBe(openai.model);
  });

  it('rejects an unknown selection without creating or queuing a provider', () => {
    let created = 0;
    let queued = 0;
    const controller = new SessionModelController({
      models: [openai], active: openai,
      createProvider: () => { created += 1; return provider(); }, queueProvider: () => { queued += 1; },
    });
    expect(() => controller.set('missing')).toThrow('unknown model selection');
    expect(created).toBe(0);
    expect(queued).toBe(0);
    expect(controller.list().active).toEqual(openai);
  });

  it('does not queue a provider when selecting the active id', () => {
    let created = 0;
    const controller = new SessionModelController({
      models: [openai], active: openai,
      createProvider: () => { created += 1; return provider(); }, queueProvider: () => undefined,
    });
    expect(controller.set(openai.id).previous).toEqual(openai);
    expect(created).toBe(0);
  });
});