import { checkService, type ServiceCheck, type ServiceTarget } from '@bytelyst/monitoring';
import { getNotesMcpToolsForRegistration } from '../mcp/register-note-tools.js';
import { config } from './config.js';
import { initDatastore } from './datastore.js';
import { getEncryptionReadiness } from './field-encrypt.js';

export type DependencyStatus = ServiceCheck['status'];

export type DependencyCheck = ServiceCheck & {
  details?: Record<string, unknown>;
};

export interface DependencyReadinessReport {
  overall: 'ready' | 'degraded' | 'down';
  timestamp: string;
  dependencies: DependencyCheck[];
  summary: {
    healthy: number;
    unhealthy: number;
    unreachable: number;
    total: number;
  };
}

type ServiceChecker = (target: ServiceTarget, opts?: { timeoutMs?: number }) => Promise<ServiceCheck>;

function elapsedSince(start: number): number {
  return Math.round(performance.now() - start);
}

function normalizeServiceBaseUrl(url: string): string {
  const trimmed = url.replace(/\/+$/, '');
  return trimmed.endsWith('/api') ? trimmed.slice(0, -4) : trimmed;
}

function summarize(checks: DependencyCheck[]): DependencyReadinessReport['summary'] {
  return {
    healthy: checks.filter(check => check.status === 'healthy').length,
    unhealthy: checks.filter(check => check.status === 'unhealthy').length,
    unreachable: checks.filter(check => check.status === 'unreachable').length,
    total: checks.length,
  };
}

function overallFrom(summary: DependencyReadinessReport['summary']): DependencyReadinessReport['overall'] {
  if (summary.healthy === summary.total) {
    return 'ready';
  }
  if (summary.healthy === 0) {
    return 'down';
  }
  return 'degraded';
}

export async function checkDatastoreReadiness(): Promise<DependencyCheck> {
  const start = performance.now();
  try {
    const healthy = await initDatastore().isHealthy();
    return {
      name: 'datastore',
      url: config.DB_PROVIDER,
      status: healthy ? 'healthy' : 'unhealthy',
      responseTimeMs: elapsedSince(start),
      details: { provider: config.DB_PROVIDER },
      ...(healthy ? {} : { error: 'Datastore provider reported unhealthy' }),
    };
  } catch (error) {
    return {
      name: 'datastore',
      url: config.DB_PROVIDER,
      status: 'unreachable',
      responseTimeMs: elapsedSince(start),
      error: error instanceof Error ? error.message : String(error),
      details: { provider: config.DB_PROVIDER },
    };
  }
}

export async function checkEncryptionReadiness(): Promise<DependencyCheck> {
  const start = performance.now();
  const readiness = getEncryptionReadiness();
  return {
    name: 'encryption',
    url: readiness.keyProvider,
    status: readiness.ready ? 'healthy' : 'unhealthy',
    responseTimeMs: elapsedSince(start),
    details: {
      enabled: readiness.enabled,
      keyProvider: readiness.keyProvider,
    },
    ...(readiness.ready ? {} : { error: 'Field encryption is not ready' }),
  };
}

async function checkHttpDependency(
  checker: ServiceChecker,
  target: ServiceTarget,
  timeoutMs: number,
): Promise<DependencyCheck> {
  return checker(target, { timeoutMs });
}

async function checkMcpReadiness(
  checker: ServiceChecker,
  timeoutMs: number,
): Promise<DependencyCheck> {
  const baseUrl = normalizeServiceBaseUrl(config.MCP_SERVER_URL);
  const tools = getNotesMcpToolsForRegistration();
  const serviceCheck = await checker({ name: 'mcp-server', url: baseUrl, path: '/health' }, { timeoutMs });
  const hasTools = tools.length > 0;
  const status: DependencyStatus =
    serviceCheck.status === 'healthy' && hasTools ? 'healthy' : serviceCheck.status;

  return {
    ...serviceCheck,
    name: 'mcp',
    status: hasTools ? status : 'unhealthy',
    details: {
      ...(serviceCheck.details ?? {}),
      registeredToolCount: tools.length,
      registeredToolsHealthy: hasTools,
    },
    ...(!hasTools ? { error: 'No NoteLett MCP tools are registered locally' } : {}),
  };
}

export async function getDependencyReadiness(options: {
  timeoutMs?: number;
  serviceChecker?: ServiceChecker;
} = {}): Promise<DependencyReadinessReport> {
  const timeoutMs = options.timeoutMs ?? 1500;
  const serviceChecker = options.serviceChecker ?? checkService;

  const dependencies = await Promise.all([
    checkDatastoreReadiness(),
    checkEncryptionReadiness(),
    checkHttpDependency(
      serviceChecker,
      { name: 'platform-service', url: normalizeServiceBaseUrl(config.PLATFORM_SERVICE_URL), path: '/health' },
      timeoutMs,
    ),
    checkHttpDependency(
      serviceChecker,
      { name: 'extraction-service', url: normalizeServiceBaseUrl(config.EXTRACTION_SERVICE_URL), path: '/health' },
      timeoutMs,
    ),
    checkMcpReadiness(serviceChecker, timeoutMs),
  ]);

  const summary = summarize(dependencies);
  return {
    overall: overallFrom(summary),
    timestamp: new Date().toISOString(),
    dependencies,
    summary,
  };
}