/**
 * Generate a UUID v4
 */
export function generateUUID(): string {
  return 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/[xy]/g, function(c) {
    const r = Math.random() * 16 | 0;
    const v = c === 'x' ? r : (r & 0x3 | 0x8);
    return v.toString(16);
  });
}

/**
 * Generate a deterministic UUID from a string
 * This ensures the same input always produces the same UUID
 */
export function generateDeterministicUUID(input: string): string {
  // Simple hash function to convert string to number
  let hash = 0;
  for (let i = 0; i < input.length; i++) {
    const char = input.charCodeAt(i);
    hash = ((hash << 5) - hash) + char;
    hash = hash & hash; // Convert to 32bit integer
  }

  // Convert hash to UUID format
  const hex1 = Math.abs(hash).toString(16).padStart(8, '0');

  // Generate additional deterministic hex strings for different UUID segments
  let hash2 = hash;
  for (let i = 0; i < input.length; i++) {
    hash2 = ((hash2 << 3) + input.charCodeAt(i)) & 0xFFFFFFFF;
  }
  const hex2 = Math.abs(hash2).toString(16).padStart(8, '0');

  // Generate third hash for the 12-character segment
  let hash3 = hash2;
  for (let i = 0; i < input.length; i++) {
    hash3 = ((hash3 << 7) + input.charCodeAt(input.length - 1 - i)) & 0xFFFFFFFF;
  }
  const hex3 = Math.abs(hash3).toString(16).padStart(8, '0');

  // Combine to make more hex data for segment 5 (needs 12 chars)
  const hex3_extended = (hex3 + hex1).substring(0, 12);

  // Create UUID v4 format (xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx)
  // Segment 1: 8 hex chars
  // Segment 2: 4 hex chars
  // Segment 3: 4 hex chars (starting with '4' for version 4)
  // Segment 4: 4 hex chars (should start with 8, 9, a, or b for variant)
  // Segment 5: 12 hex chars
  const segment4 = hex2.substring(0, 4);
  const segment4Fixed = (parseInt(segment4.charAt(0), 16) & 0x3 | 0x8).toString(16) + segment4.substring(1, 4);

  return `${hex1.substring(0, 8)}-${hex1.substring(0, 4)}-4${hex1.substring(4, 7)}-${segment4Fixed}-${hex3_extended}`;
}

/**
 * Generate a simple numeric hash from a string
 */
export function hashString(str: string): number {
  let hash = 0;
  for (let i = 0; i < str.length; i++) {
    const char = str.charCodeAt(i);
    hash = ((hash << 5) - hash) + char;
    hash = hash & hash; // Convert to 32bit integer
  }
  return Math.abs(hash);
}