import { z } from 'zod';

/**
 * Common reusable Zod schemas using Zod v4 features
 * These base schemas reduce repetition and improve maintainability
 */

// ============================================================================
// Base Field Schemas
// ============================================================================

/**
 * UUID/ID field - used across all entities
 */
export const idSchema = z.string().min(1).describe('Unique identifier');

/**
 * Name field - used across all entities
 */
export const nameSchema = z.string().min(1).describe('Name');

/**
 * Optional URL field that accepts absolute URLs, relative paths, or empty string
 * Uses Zod v4's improved error handling
 * Accepts:
 * - Absolute URLs (http://, https://)
 * - Relative paths (starting with /)
 * - Empty strings
 * - null/undefined
 */
export const optionalUrlSchema = z
  .union([
    z.string().refine(
      (val) => {
        if (val === '') return true;
        // Check if it's a valid absolute URL
        try {
          new URL(val);
          return true;
        } catch {
          // If not a valid URL, check if it's a relative path
          return val.startsWith('/');
        }
      },
      { message: 'Must be a valid URL, relative path starting with /, or empty string' }
    ),
    z.null(),
  ])
  .optional()
  .describe('URL or path (can be absolute URL, relative path, empty string, null, or undefined)');

/**
 * Coordinate validation - latitude
 */
export const latitudeSchema = z
  .number()
  .min(-90, { message: 'Latitude must be between -90 and 90' })
  .max(90, { message: 'Latitude must be between -90 and 90' })
  .describe('Latitude in decimal degrees');

/**
 * Coordinate validation - longitude
 */
export const longitudeSchema = z
  .number()
  .min(-180, { message: 'Longitude must be between -180 and 180' })
  .max(180, { message: 'Longitude must be between -180 and 180' })
  .describe('Longitude in decimal degrees');

/**
 * Coordinate pair schema
 */
export const coordinateSchema = z
  .object({
    lat: latitudeSchema,
    lng: longitudeSchema,
  })
  .describe('Geographic coordinates');

/**
 * ISO 8601 timestamp string (RFC3339 format from Go backend)
 */
export const timestampSchema = z.string().refine((val) => {
  // Accept ISO datetime strings with optional timezone offset
  return /^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}(\.\d+)?([+-]\d{2}:\d{2}|Z)?$/.test(val);
}).optional().describe('ISO 8601 timestamp');

/**
 * Positive number schema
 */
export const positiveNumberSchema = z
  .number()
  .positive({ message: 'Must be a positive number' })
  .describe('Positive number');

/**
 * Non-negative number schema
 */
export const nonNegativeNumberSchema = z
  .number()
  .nonnegative({ message: 'Must be a non-negative number' })
  .describe('Non-negative number');

// ============================================================================
// Base Entity Schemas (Backend-aligned)
// ============================================================================

/**
 * Base schema for backend entities with common fields
 * Uses Zod v4's .extend() for composition
 */
export const baseBackendEntitySchema = z.object({
  ID: idSchema,
  CreatedAt: timestampSchema,
  UpdatedAt: timestampSchema,
});

/**
 * Base schema for backend entities with name
 */
export const namedBackendEntitySchema = baseBackendEntitySchema.extend({
  Name: nameSchema,
});

/**
 * Base schema for request entities (snake_case)
 */
export const baseRequestEntitySchema = z.object({
  id: idSchema.optional(),
});

// ============================================================================
// Common Validation Patterns
// ============================================================================

/**
 * Email validation with empty string fallback
 */
export const optionalEmailSchema = z
  .string()
  .email({ message: 'Please enter a valid email address' })
  .or(z.literal(''))
  .optional()
  .describe('Email address (can be empty)');

/**
 * Phone number validation (Russian format)
 */
export const phoneSchema = z
  .string()
  .regex(/^((\+7|7|8)+([0-9()\-\s]){10,15})?$/, {
    message: 'Please enter a valid phone number',
  })
  .or(z.literal(''))
  .optional()
  .describe('Phone number (Russian format)');

/**
 * Year validation (for founding year, etc.)
 */
export const yearSchema = z.coerce
  .number()
  .int()
  .min(1800, { message: 'Please enter a valid year' })
  .max(new Date().getFullYear(), { message: 'The year cannot be in the future' })
  .describe('Year');

/**
 * Score validation (0-1 range)
 * Commonly used for compatibility scores, risk assessments, etc.
 */
export const scoreSchema = z
  .number()
  .min(0, { message: 'Score must be between 0 and 1' })
  .max(1, { message: 'Score must be between 0 and 1' })
  .describe('Score (0-1 range)');

// ============================================================================
// Schema Composition Helpers
// ============================================================================

/**
 * Create a backend entity schema with common fields
 * Uses Zod v4's composition features
 */
export function createBackendEntitySchema<T extends z.ZodRawShape>(additionalFields: T) {
  return baseBackendEntitySchema.extend(additionalFields);
}

/**
 * Create a named backend entity schema
 */
export function createNamedBackendEntitySchema<T extends z.ZodRawShape>(additionalFields: T) {
  return namedBackendEntitySchema.extend(additionalFields);
}

/**
 * Create a request schema with common patterns
 */
export function createRequestSchema<T extends z.ZodRawShape>(additionalFields: T) {
  return baseRequestEntitySchema.extend(additionalFields);
}

// ============================================================================
// Coordinate Utilities
// ============================================================================

/**
 * Validate and normalize coordinates
 * Returns normalized [lat, lng] or null if invalid
 */
export function validateCoordinates(lat: unknown, lng: unknown): [number, number] | null {
  const result = coordinateSchema.safeParse({ lat, lng });
  return result.success ? [result.data.lat, result.data.lng] : null;
}

/**
 * Check if coordinates are within bounds
 */
export function areCoordinatesInBounds(
  lat: number,
  lng: number,
  bounds: { north: number; south: number; east: number; west: number }
): boolean {
  const coordResult = coordinateSchema.safeParse({ lat, lng });
  if (!coordResult.success) return false;

  const { lat: validLat, lng: validLng } = coordResult.data;

  // Handle longitude wrapping
  const lngInBounds =
    (bounds.west <= bounds.east && validLng >= bounds.west && validLng <= bounds.east) ||
    (bounds.west > bounds.east && (validLng >= bounds.west || validLng <= bounds.east));

  return validLat >= bounds.south && validLat <= bounds.north && lngInBounds;
}