/**
 * Utility functions for SchoolCompare
 */

import type { School, MetricDefinition, OfstedInspection, SchoolAdmissions, SchoolResult } from './types';

// ============================================================================
// String Utilities
// ============================================================================

/**
 * Create a URL-friendly slug from a string
 */
export function slugify(text: string): string {
  return text
    .toLowerCase()
    .replace(/[^\w\s-]/g, '')
    .replace(/\s+/g, '-')
    .replace(/-+/g, '-')
    .trim();
}

/**
 * Build a school URL path: /school/123456-school-name (capped at ~80 chars total)
 */
const MAX_SLUG_LENGTH = 60;

export function schoolUrl(urn: number, schoolName?: string): string {
  if (!schoolName) return `/school/${urn}`;
  let slug = slugify(schoolName);
  if (slug.length > MAX_SLUG_LENGTH) {
    slug = slug.slice(0, MAX_SLUG_LENGTH).replace(/-+$/, '');
  }
  return `/school/${urn}-${slug}`;
}

/**
 * Extract the URN from a school slug (e.g. "138267-some-school-name" → 138267)
 */
export function parseSchoolSlug(slug: string): number | null {
  const match = slug.match(/^(\d{6})/);
  return match ? parseInt(match[1], 10) : null;
}

/**
 * Escape HTML to prevent XSS
 */
export function escapeHtml(text: string): string {
  const div = document.createElement('div');
  div.textContent = text;
  return div.innerHTML;
}

/**
 * Truncate text to a maximum length
 */
export function truncate(text: string, maxLength: number): string {
  if (text.length <= maxLength) return text;
  return text.slice(0, maxLength).trim() + '...';
}

// ============================================================================
// Number Formatting
// ============================================================================

/**
 * Format a number as a percentage
 */
export function formatPercentage(value: number | null | undefined, decimals: number = 1): string {
  if (value === null || value === undefined) return 'N/A';
  return `${value.toFixed(decimals)}%`;
}

/**
 * Format a progress score (can be negative)
 */
export function formatProgress(value: number | null | undefined, decimals: number = 1): string {
  if (value === null || value === undefined) return 'N/A';
  const formatted = value.toFixed(decimals);
  return value > 0 ? `+${formatted}` : formatted;
}

/**
 * Format a score (e.g., test scores)
 */
export function formatScore(value: number | null | undefined, decimals: number = 1): string {
  if (value === null || value === undefined) return 'N/A';
  return value.toFixed(decimals);
}

/**
 * Format a metric value based on its type
 */
export function formatMetricValue(
  value: number | null | undefined,
  format: MetricDefinition['format']
): string {
  switch (format) {
    case 'percentage':
      return formatPercentage(value);
    case 'progress':
      return formatProgress(value);
    case 'score':
      return formatScore(value);
    default:
      return value?.toString() || 'N/A';
  }
}

// ============================================================================
// Trend Analysis
// ============================================================================

/**
 * Calculate the trend between two values
 */
export function calculateTrend(
  current: number | null | undefined,
  previous: number | null | undefined
): 'up' | 'down' | 'stable' {
  if (current === null || current === undefined || previous === null || previous === undefined) {
    return 'stable';
  }

  const diff = current - previous;

  if (Math.abs(diff) < 0.5) return 'stable'; // Within 0.5% is considered stable
  return diff > 0 ? 'up' : 'down';
}

/**
 * Calculate percentage change
 */
export function calculateChange(
  current: number | null | undefined,
  previous: number | null | undefined
): number | null {
  if (current === null || current === undefined || previous === null || previous === undefined) {
    return null;
  }

  return current - previous;
}

// ============================================================================
// Statistical Functions
// ============================================================================

/**
 * Calculate the average of an array of numbers
 */
export function average(values: (number | null)[]): number | null {
  const validValues = values.filter((v): v is number => v !== null && !isNaN(v));
  if (validValues.length === 0) return null;

  const sum = validValues.reduce((acc, val) => acc + val, 0);
  return sum / validValues.length;
}

/**
 * Calculate the standard deviation
 */
export function standardDeviation(values: (number | null)[]): number | null {
  const validValues = values.filter((v): v is number => v !== null && !isNaN(v));
  if (validValues.length === 0) return null;

  const avg = average(validValues);
  if (avg === null) return null;

  const squareDiffs = validValues.map((value) => Math.pow(value - avg, 2));
  const avgSquareDiff = average(squareDiffs);

  return avgSquareDiff !== null ? Math.sqrt(avgSquareDiff) : null;
}

/**
 * Calculate variability label based on standard deviation
 */
export function getVariabilityLabel(stdDev: number | null): string {
  if (stdDev === null) return 'Unknown';
  if (stdDev < 2) return 'Very Stable';
  if (stdDev < 5) return 'Stable';
  if (stdDev < 10) return 'Moderate';
  return 'Variable';
}

// ============================================================================
// Validation
// ============================================================================

/**
 * Validate UK postcode format
 */
export function isValidPostcode(postcode: string): boolean {
  const postcodeRegex = /^[A-Z]{1,2}[0-9][A-Z0-9]?\s*[0-9][A-Z]{2}$/i;
  return postcodeRegex.test(postcode.trim());
}

/**
 * Validate URN (Unique Reference Number)
 */
export function isValidUrn(urn: number | string): boolean {
  const urnNumber = typeof urn === 'string' ? parseInt(urn, 10) : urn;
  return !isNaN(urnNumber) && urnNumber >= 100000 && urnNumber <= 999999;
}

// ============================================================================
// Debounce
// ============================================================================

/**
 * Debounce a function call
 */
export function debounce<T extends (...args: any[]) => any>(
  func: T,
  wait: number
): (...args: Parameters<T>) => void {
  let timeout: NodeJS.Timeout | null = null;

  return function executedFunction(...args: Parameters<T>) {
    const later = () => {
      timeout = null;
      func(...args);
    };

    if (timeout) {
      clearTimeout(timeout);
    }

    timeout = setTimeout(later, wait);
  };
}

// ============================================================================
// Color Utilities
// ============================================================================

/**
 * Chart color palette (consistent with vanilla JS app)
 */
export const CHART_COLORS = [
  'rgb(75, 192, 192)',
  'rgb(255, 99, 132)',
  'rgb(54, 162, 235)',
  'rgb(255, 206, 86)',
  'rgb(153, 102, 255)',
  'rgb(255, 159, 64)',
  'rgb(201, 203, 207)',
  'rgb(255, 0, 255)',
];

/**
 * Get a color from the palette by index
 */
export function getChartColor(index: number): string {
  return CHART_COLORS[index % CHART_COLORS.length];
}

/**
 * Convert RGB color to RGBA with opacity
 */
export function rgbToRgba(rgb: string, alpha: number): string {
  return rgb.replace('rgb', 'rgba').replace(')', `, ${alpha})`);
}

/**
 * Get trend color based on direction
 */
export function getTrendColor(trend: 'up' | 'down' | 'stable'): string {
  switch (trend) {
    case 'up':
      return '#22c55e'; // green
    case 'down':
      return '#ef4444'; // red
    case 'stable':
      return '#6b7280'; // gray
  }
}

// ============================================================================
// Local Storage Utilities
// ============================================================================

/**
 * Safely get item from localStorage
 */
export function getFromLocalStorage<T>(key: string, defaultValue: T): T {
  if (typeof window === 'undefined') return defaultValue;

  try {
    const item = window.localStorage.getItem(key);
    return item ? JSON.parse(item) : defaultValue;
  } catch (error) {
    console.error(`Error reading from localStorage key "${key}":`, error);
    return defaultValue;
  }
}

/**
 * Safely set item in localStorage
 */
export function setToLocalStorage<T>(key: string, value: T): void {
  if (typeof window === 'undefined') return;

  try {
    window.localStorage.setItem(key, JSON.stringify(value));
  } catch (error) {
    console.error(`Error writing to localStorage key "${key}":`, error);
  }
}

/**
 * Remove item from localStorage
 */
export function removeFromLocalStorage(key: string): void {
  if (typeof window === 'undefined') return;

  try {
    window.localStorage.removeItem(key);
  } catch (error) {
    console.error(`Error removing from localStorage key "${key}":`, error);
  }
}

// ============================================================================
// URL Utilities
// ============================================================================

/**
 * Build URL with query parameters
 */
export function buildUrl(base: string, params: Record<string, any>): string {
  const url = new URL(base, window.location.origin);

  Object.entries(params).forEach(([key, value]) => {
    if (value !== undefined && value !== null && value !== '') {
      url.searchParams.set(key, String(value));
    }
  });

  return url.pathname + url.search;
}

/**
 * Parse query string into object
 */
export function parseQueryString(search: string): Record<string, string> {
  const params = new URLSearchParams(search);
  const result: Record<string, string> = {};

  params.forEach((value, key) => {
    result[key] = value;
  });

  return result;
}

// ============================================================================
// Date Utilities
// ============================================================================

/**
 * Format academic year.
 * Handles both 4-digit start years (2023 → "2023/24") and
 * 6-digit EES codes (202526 → "2025/26").
 */
export function getPhaseStyle(phase?: string | null): { key: string; label: string } {
  switch (phase?.toLowerCase()) {
    case 'primary':
    case 'middle deemed primary':
      return { key: 'Primary', label: 'Primary' };
    case 'secondary':
    case 'middle deemed secondary':
      return { key: 'Secondary', label: 'Secondary' };
    case 'all-through':
      return { key: 'AllThrough', label: 'All-through' };
    case '16 plus':
      return { key: 'Post16', label: 'Post-16' };
    case 'nursery':
      return { key: 'Nursery', label: 'Nursery' };
    default:
      return { key: '', label: '' };
  }
}

export function formatAcademicYear(year: number | null | undefined): string {
  if (year == null) return '';
  const s = year.toString();
  if (s.length === 6) {
    return `${s.slice(0, 4)}/${s.slice(4)}`;
  }
  const nextYear = (year + 1).toString().slice(-2);
  return `${year}/${nextYear}`;
}

/**
 * Get current academic year
 */
export function getCurrentAcademicYear(): number {
  const now = new Date();
  const year = now.getFullYear();
  const month = now.getMonth();

  // Academic year starts in September (month 8)
  return month >= 8 ? year : year - 1;
}

// ============================================================================
// School Detail Hero Helpers
// ============================================================================

const OFSTED_OEIF_WORDS: Record<number, string> = {
  1: 'Outstanding', 2: 'Good', 3: 'Requires Improvement', 4: 'Inadequate',
};

/**
 * Format an Ofsted inspection date as "Month YYYY" (e.g. "November 2023").
 */
function formatOfstedMonth(date: string | null | undefined): string {
  if (!date) return '';
  const d = new Date(date);
  if (Number.isNaN(d.getTime())) return '';
  return d.toLocaleDateString('en-GB', { month: 'long', year: 'numeric' });
}

export type HeroTone = 'teal' | 'green' | 'gold' | 'coral' | 'neutral';

export interface OfstedHeroChip {
  state: 'oeif' | 'reportCard' | 'none';
  title: string;           // Main label (e.g. "Ofsted Outstanding", "Ofsted Report Card")
  subtitle: string;        // Context line (e.g. "Inspected November 2023")
  detail?: string;         // Optional extra line (e.g. "Safeguarding: Met")
  tone: HeroTone;          // Maps to dedicated hero tone classes (not badge classes)
}

/**
 * Build the hero-strip Ofsted chip, branching on the inspection framework.
 * Never synthesises a single overall grade for ReportCard schools.
 *
 * Note: the API may return ``framework`` as a literal string ``"NULL"`` for
 * older inspections, so we explicitly only branch into the ReportCard layout
 * when the value is exactly ``"ReportCard"``. Anything else with an
 * ``overall_effectiveness`` score is treated as OEIF.
 */
export function buildOfstedHeroChip(ofsted: OfstedInspection | null | undefined): OfstedHeroChip {
  if (!ofsted) {
    return {
      state: 'none',
      title: 'Ofsted pending',
      subtitle: 'No inspection on record',
      tone: 'neutral',
    };
  }

  const when = formatOfstedMonth(ofsted.inspection_date);

  // ReportCard branch — only if the API explicitly says so
  if (ofsted.framework === 'ReportCard') {
    const safeguarding = ofsted.rc_safeguarding_met;
    return {
      state: 'reportCard',
      title: 'Ofsted Report Card',
      subtitle: when ? `Inspected ${when}` : 'New framework inspection',
      detail:
        safeguarding == null
          ? undefined
          : safeguarding ? 'Safeguarding: Met' : 'Safeguarding: Not met',
      tone: safeguarding === false ? 'coral' : 'green',
    };
  }

  // Otherwise treat as OEIF (covers framework === 'OEIF', null, "NULL", etc.)
  const grade = ofsted.overall_effectiveness;
  if (grade && OFSTED_OEIF_WORDS[grade]) {
    const oeifTone: HeroTone =
      grade === 1 ? 'teal' :
      grade === 2 ? 'green' :
      grade === 3 ? 'gold' :
      'coral';
    return {
      state: 'oeif',
      title: `Ofsted ${OFSTED_OEIF_WORDS[grade]}`,
      subtitle: when ? `Inspected ${when}` : 'Inspected',
      tone: oeifTone,
    };
  }

  return {
    state: 'oeif',
    title: 'Ofsted inspected',
    subtitle: when ? `Inspected ${when}` : 'Inspection on record',
    tone: 'neutral',
  };
}

/**
 * Build a one-sentence editorial summary for the school detail hero.
 * Branches on Ofsted framework so Report Card schools are never described
 * with an overall grade they do not have.
 */
export function buildSchoolSummary(
  schoolInfo: School,
  ofsted: OfstedInspection | null | undefined,
  admissions: SchoolAdmissions | null | undefined,
  latestResults: SchoolResult | null | undefined,
): string {
  const parts: string[] = [];

  // Size descriptor
  const pupils = latestResults?.total_pupils ?? schoolInfo.total_pupils ?? null;
  const sizeWord =
    pupils == null ? '' :
    pupils < 200 ? 'Small' :
    pupils < 500 ? 'Mid-sized' :
    'Large';

  // Phase descriptor — avoid the raw code
  const phase = (schoolInfo.phase ?? '').toLowerCase();
  const phaseWord =
    phase.includes('secondary') ? 'secondary' :
    phase === 'all-through' ? 'all-through' :
    phase.includes('primary') ? 'primary' :
    'school';

  // Religious character
  const religion = schoolInfo.religious_denomination;
  const religionWord =
    !religion || /none|does not apply/i.test(religion) ? '' :
    /roman catholic|catholic/i.test(religion) ? 'Catholic ' :
    /church of england|ce|anglican/i.test(religion) ? 'Church of England ' :
    /jewish/i.test(religion) ? 'Jewish ' :
    /muslim|islam/i.test(religion) ? 'Muslim ' :
    /hindu/i.test(religion) ? 'Hindu ' :
    /sikh/i.test(religion) ? 'Sikh ' :
    '';

  // Locality — prefer town from address parsing (fallback to LA)
  const locality = schoolInfo.town || schoolInfo.local_authority || '';

  const lead = [sizeWord, religionWord + phaseWord].filter(Boolean).join(' ');
  let opening = lead || 'School';
  if (locality) opening += ` in ${locality}`;
  parts.push(opening);

  // Ofsted clause (framework-aware)
  if (ofsted?.framework === 'OEIF' && ofsted.overall_effectiveness) {
    parts.push(`rated ${OFSTED_OEIF_WORDS[ofsted.overall_effectiveness]} by Ofsted`);
  } else if (ofsted?.framework === 'ReportCard') {
    const when = formatOfstedMonth(ofsted.inspection_date);
    parts.push(
      when
        ? `most recently inspected under Ofsted's Report Card framework in ${when}`
        : "recently inspected under Ofsted's new Report Card framework",
    );
  }

  // Admissions clause
  if (admissions?.oversubscribed) {
    if (admissions.first_preference_offer_pct != null) {
      const pct = Math.round(admissions.first_preference_offer_pct);
      parts.push(
        `oversubscribed — ${pct}% of first-choice applicants are offered a place`,
      );
    } else {
      parts.push('oversubscribed');
    }
  } else if (admissions?.first_preference_offer_pct != null && admissions.first_preference_offer_pct >= 90) {
    parts.push('most families get their first-choice offer');
  }

  return parts.join(', ') + '.';
}