import { Config, Controller, Get, Inject } from '@midwayjs/core';
import type { Context } from '@midwayjs/koa';
import type {
  RpcHostReadiness,
  RpcHostReadinessSnapshot,
} from '@cool-midway/rpc/saas-host';

@Controller('/health')
export class SaasModuleHealthController {
  @Inject()
  ctx: Context;

  @Config('cool.rpc.moduleCode')
  moduleCode: string;

  @Config('cool.rpc.serviceVersion')
  serviceVersion: string;

  @Config('cool.rpc.minSchemaVersion')
  minSchemaVersion: number;

  @Config('cool.rpc.maxSchemaVersion')
  maxSchemaVersion: number;

  @Get('/')
  async health() {
    const readiness = await this.resolveReadiness();
    if (!readiness.ready) this.ctx.status = 503;
    return {
      ...readiness,
      moduleCode: this.moduleCode,
      serviceVersion: this.serviceVersion,
      schemaRange: [this.minSchemaVersion, this.maxSchemaVersion],
    };
  }

  private async resolveReadiness(): Promise<RpcHostReadinessSnapshot> {
    try {
      const container = this.ctx?.requestContext;
      if (!container) {
        return this.unavailable('RPC_HOST_READINESS_PROVIDER_MISSING');
      }
      const readiness = await container.getAsync<RpcHostReadiness>(
        'rpcHostReadiness'
      );
      if (!readiness) {
        return this.unavailable('RPC_HOST_READINESS_PROVIDER_MISSING');
      }
      const snapshot = readiness?.snapshot?.();
      return this.isReadinessSnapshot(snapshot)
        ? snapshot
        : this.unavailable('RPC_HOST_READINESS_SNAPSHOT_INVALID');
    } catch {
      return this.unavailable('RPC_HOST_READINESS_UNAVAILABLE');
    }
  }

  private isReadinessSnapshot(
    snapshot: RpcHostReadinessSnapshot | undefined
  ): snapshot is RpcHostReadinessSnapshot {
    const checkStates = ['pending', 'ok', 'error'];
    return Boolean(
      snapshot &&
        typeof snapshot.ready === 'boolean' &&
        ['starting', 'ready', 'degraded', 'draining', 'stopped'].includes(
          snapshot.status
        ) &&
        snapshot.ready === (snapshot.status === 'ready') &&
        Number.isFinite(snapshot.checkedAt) &&
        snapshot.checks &&
        checkStates.includes(snapshot.checks.bootstrap) &&
        checkStates.includes(snapshot.checks.lease) &&
        checkStates.includes(snapshot.checks.registry)
    );
  }

  private unavailable(reason: string): RpcHostReadinessSnapshot {
    return {
      ready: false,
      status: 'degraded',
      reason,
      checkedAt: Date.now(),
      checks: {
        bootstrap: 'error',
        lease: 'error',
        registry: 'error',
      },
    };
  }
}