// Tests for config deepMerge logic
import { describe, it, expect } from 'vitest';
import type { DispatcherConfig } from '../src/types.js';

// ── inline copy of deepMerge (same logic as config.ts) ───────────────────────
function deepMerge<T extends object>(base: T, override: Partial<T>): T {
  const result = { ...base };
  for (const key of Object.keys(override) as (keyof T)[]) {
    const overrideVal = override[key];
    const baseVal = base[key];
    if (
      overrideVal !== null &&
      typeof overrideVal === 'object' &&
      !Array.isArray(overrideVal) &&
      baseVal !== null &&
      typeof baseVal === 'object' &&
      !Array.isArray(baseVal)
    ) {
      result[key] = deepMerge(baseVal as object, overrideVal as object) as T[keyof T];
    } else if (overrideVal !== undefined) {
      result[key] = overrideVal as T[keyof T];
    }
  }
  return result;
}

// ── helpers ───────────────────────────────────────────────────────────────────

const DEFAULTS: DispatcherConfig = {
  ograph: {
    endpoint: 'https://ograph.example.com',
    token: undefined,
    projections: [],
  },
  oc: {
    statusEndpoint: 'http://localhost:18789/status',
    statusToken: 'default-token',
    minAvailable: 2,
  },
  intervals: {
    watcherIdle: 30_000,
    watcherActive: 5_000,
    schedulerIdle: 60_000,
    schedulerActive: 5_000,
    cooldownAfterPush: 60_000,
  },
};

// ── tests ─────────────────────────────────────────────────────────────────────

describe('config deepMerge logic', () => {
  it('returns defaults unchanged when no overrides supplied', () => {
    const result = deepMerge(DEFAULTS, {});
    expect(result).toEqual(DEFAULTS);
  });

  it('overrides a scalar field without touching siblings', () => {
    const result = deepMerge(DEFAULTS, {
      ograph: { endpoint: 'https://custom.example.com', token: undefined, projections: [] },
    });
    expect(result.ograph.endpoint).toBe('https://custom.example.com');
    expect(result.oc.statusToken).toBe('default-token'); // unchanged
  });

  it('deep-merges nested objects — partial override preserves untouched sibling keys', () => {
    const result = deepMerge(DEFAULTS, {
      oc: { statusToken: 'my-token' } as DispatcherConfig['oc'],
    });
    expect(result.oc.statusToken).toBe('my-token');
    expect(result.oc.statusEndpoint).toBe(DEFAULTS.oc.statusEndpoint); // preserved
    expect(result.oc.minAvailable).toBe(2); // preserved
  });

  it('env var override merges on top of file config', () => {
    const fileConfig: Partial<DispatcherConfig> = {
      ograph: { endpoint: 'https://file-endpoint.example.com', token: undefined, projections: ['p1'] },
    };
    let config = deepMerge(DEFAULTS, fileConfig);

    // Simulate env var override (as done in loadConfig)
    config.ograph.endpoint = 'https://env-endpoint.example.com';

    expect(config.ograph.endpoint).toBe('https://env-endpoint.example.com');
    expect(config.ograph.projections).toEqual(['p1']); // file value preserved
    expect(config.oc.minAvailable).toBe(2); // default preserved
  });

  it('does not overwrite a field when override value is undefined', () => {
    const result = deepMerge(DEFAULTS, {
      ograph: { endpoint: undefined as unknown as string, token: undefined, projections: [] },
    });
    // endpoint should keep the default since override is undefined
    expect(result.ograph.endpoint).toBe(DEFAULTS.ograph.endpoint);
  });
});