/**
 * Parser utilities for protocol detection
 */

import type { THttpMethod, TTlsVersion } from '../models/detection-types.js';

/**
 * Valid HTTP methods
 */
export const HTTP_METHODS: THttpMethod[] = [
  'GET', 'POST', 'PUT', 'DELETE', 'PATCH', 'HEAD', 'OPTIONS', 'CONNECT', 'TRACE'
];

/**
 * HTTP version strings
 */
export const HTTP_VERSIONS = ['HTTP/1.0', 'HTTP/1.1', 'HTTP/2', 'HTTP/3'];

/**
 * Parse HTTP request line
 */
export function parseHttpRequestLine(line: string): {
  method: THttpMethod;
  path: string;
  version: string;
} | null {
  const parts = line.trim().split(' ');
  
  if (parts.length !== 3) {
    return null;
  }
  
  const [method, path, version] = parts;
  
  // Validate method
  if (!HTTP_METHODS.includes(method as THttpMethod)) {
    return null;
  }
  
  // Validate version
  if (!version.startsWith('HTTP/')) {
    return null;
  }
  
  return {
    method: method as THttpMethod,
    path,
    version
  };
}

/**
 * Parse HTTP header line
 */
export function parseHttpHeader(line: string): { name: string; value: string } | null {
  const colonIndex = line.indexOf(':');
  
  if (colonIndex === -1) {
    return null;
  }
  
  const name = line.slice(0, colonIndex).trim();
  const value = line.slice(colonIndex + 1).trim();
  
  if (!name) {
    return null;
  }
  
  return { name, value };
}

/**
 * Parse HTTP headers from lines
 */
export function parseHttpHeaders(lines: string[]): Record<string, string> {
  const headers: Record<string, string> = {};
  
  for (const line of lines) {
    const header = parseHttpHeader(line);
    if (header) {
      // Convert header names to lowercase for consistency
      headers[header.name.toLowerCase()] = header.value;
    }
  }
  
  return headers;
}

/**
 * Convert TLS version bytes to version string
 */
export function tlsVersionToString(major: number, minor: number): TTlsVersion | null {
  if (major === 0x03) {
    switch (minor) {
      case 0x00: return 'SSLv3';
      case 0x01: return 'TLSv1.0';
      case 0x02: return 'TLSv1.1';
      case 0x03: return 'TLSv1.2';
      case 0x04: return 'TLSv1.3';
    }
  }
  return null;
}

/**
 * Extract domain from Host header value
 */
export function extractDomainFromHost(hostHeader: string): string {
  // Remove port if present
  const colonIndex = hostHeader.lastIndexOf(':');
  if (colonIndex !== -1) {
    // Check if it's not part of IPv6 address
    const beforeColon = hostHeader.slice(0, colonIndex);
    if (!beforeColon.includes(']')) {
      return beforeColon;
    }
  }
  return hostHeader;
}

/**
 * Validate domain name
 */
export function isValidDomain(domain: string): boolean {
  // Basic domain validation
  if (!domain || domain.length > 253) {
    return false;
  }
  
  // Check for valid characters and structure
  const domainRegex = /^(?!-)[A-Za-z0-9-]{1,63}(?<!-)(\.[A-Za-z0-9-]{1,63})*$/;
  return domainRegex.test(domain);
}

/**
 * Check if string is a valid HTTP method
 */
export function isHttpMethod(str: string): str is THttpMethod {
  return HTTP_METHODS.includes(str as THttpMethod);
}