import SwaggerParser from '@apidevtools/swagger-parser';
import type { OpenAPI, OpenAPIV3, OpenAPIV3_1 } from 'openapi-types';
import type { ParsedSpec, OpenAPISpec } from './types.js';

const HTTP_METHODS = ['get', 'post', 'put', 'patch', 'delete', 'head', 'options', 'trace'] as const;

export async function parseSpec(specPath: string, options?: { dereference?: boolean }): Promise<{
  spec: OpenAPISpec;
  metadata: ParsedSpec;
  dereferenced: boolean;
}> {
  const shouldDereference = options?.dereference !== false;

  let spec: OpenAPISpec;
  let dereferenced = false;

  if (shouldDereference) {
    try {
      spec = await SwaggerParser.dereference(specPath);
      dereferenced = true;
    } catch {
      // Fallback to parse without dereferencing if refs are broken
      spec = await SwaggerParser.parse(specPath);
    }
  } else {
    spec = await SwaggerParser.parse(specPath);
  }

  const metadata = extractMetadata(spec);
  return { spec, metadata, dereferenced };
}

export async function bundleSpec(specPath: string): Promise<OpenAPISpec> {
  return SwaggerParser.bundle(specPath);
}

function extractMetadata(spec: OpenAPISpec): ParsedSpec {
  const version = getSpecVersion(spec);
  const info = spec.info;

  const paths = spec.paths || {};
  const pathCount = Object.keys(paths).length;

  let operationCount = 0;
  const tagsSet = new Set<string>();

  for (const pathItem of Object.values(paths)) {
    if (!pathItem) continue;
    for (const method of HTTP_METHODS) {
      const operation = (pathItem as Record<string, unknown>)[method] as OpenAPIV3.OperationObject | undefined;
      if (operation) {
        operationCount++;
        if (operation.tags) {
          operation.tags.forEach(tag => tagsSet.add(tag));
        }
      }
    }
  }

  const schemaCount = getSchemaCount(spec);
  const servers = getServers(spec);

  return {
    version,
    title: info.title,
    description: info.description,
    servers,
    pathCount,
    schemaCount,
    operationCount,
    tags: Array.from(tagsSet).sort(),
  };
}

function getSpecVersion(spec: OpenAPISpec): string {
  if ('openapi' in spec) {
    return `OpenAPI ${spec.openapi}`;
  }
  if ('swagger' in spec) {
    return `Swagger ${spec.swagger}`;
  }
  return 'Unknown';
}

function getSchemaCount(spec: OpenAPISpec): number {
  if ('components' in spec && spec.components?.schemas) {
    return Object.keys(spec.components.schemas).length;
  }
  if ('definitions' in spec && spec.definitions) {
    return Object.keys(spec.definitions).length;
  }
  return 0;
}

function getServers(spec: OpenAPISpec): string[] {
  if ('servers' in spec && spec.servers) {
    return spec.servers.map(s => s.url);
  }
  if ('host' in spec) {
    const swagger2 = spec as { host?: string; basePath?: string; schemes?: string[] };
    const scheme = swagger2.schemes?.[0] || 'https';
    const host = swagger2.host || 'localhost';
    const basePath = swagger2.basePath || '';
    return [`${scheme}://${host}${basePath}`];
  }
  return [];
}