import React, { createContext, useContext, useEffect, useMemo } from 'react';
import type { EventBranding } from '../types/event-branding';

type EventBrandingContextValue = {
  branding: EventBranding;
  isCustom: boolean;
};

export const DEFAULT_EVENT_BRANDING: EventBranding = {
  primaryColor: '#f43f5e',
  secondaryColor: '#fb7185',
  backgroundColor: '#ffffff',
  fontFamily: null,
  logoUrl: null,
  palette: {
    primary: '#f43f5e',
    secondary: '#fb7185',
    background: '#ffffff',
    surface: '#ffffff',
  },
  typography: {
    heading: null,
    body: null,
    sizePreset: 'm',
  },
  logo: {
    mode: 'emoticon',
    value: null,
    position: 'left',
    size: 'm',
  },
  buttons: {
    style: 'filled',
    radius: 12,
  },
  mode: 'auto',
};
const DEFAULT_PRIMARY = DEFAULT_EVENT_BRANDING.primaryColor.toLowerCase();
const DEFAULT_SECONDARY = DEFAULT_EVENT_BRANDING.secondaryColor.toLowerCase();
const DEFAULT_BACKGROUND = DEFAULT_EVENT_BRANDING.backgroundColor.toLowerCase();

const EventBrandingContext = createContext<EventBrandingContextValue | undefined>(undefined);

function normaliseHexColor(value: string | null | undefined, fallback: string): string {
  if (typeof value !== 'string') {
    return fallback;
  }

  const trimmed = value.trim();
  return /^#([0-9a-fA-F]{3}|[0-9a-fA-F]{6})$/.test(trimmed) ? trimmed : fallback;
}

function resolveBranding(input?: EventBranding | null): EventBranding {
  if (!input) {
    return DEFAULT_EVENT_BRANDING;
  }

  const palettePrimary = input.palette?.primary ?? input.primaryColor;
  const paletteSecondary = input.palette?.secondary ?? input.secondaryColor;
  const paletteBackground = input.palette?.background ?? input.backgroundColor;
  const paletteSurface = input.palette?.surface ?? input.backgroundColor;

  const headingFont = input.typography?.heading ?? input.fontFamily ?? null;
  const bodyFont = input.typography?.body ?? input.fontFamily ?? null;
  const sizePreset = input.typography?.sizePreset ?? 'm';

  const logoMode = input.logo?.mode ?? (input.logoUrl ? 'upload' : 'emoticon');
  const logoValue = input.logo?.value ?? input.logoUrl ?? null;

  return {
    primaryColor: normaliseHexColor(palettePrimary, DEFAULT_EVENT_BRANDING.primaryColor),
    secondaryColor: normaliseHexColor(paletteSecondary, DEFAULT_EVENT_BRANDING.secondaryColor),
    backgroundColor: normaliseHexColor(paletteBackground, DEFAULT_EVENT_BRANDING.backgroundColor),
    fontFamily: bodyFont?.trim() || null,
    logoUrl: logoMode === 'upload' ? (logoValue?.trim() || null) : null,
    palette: {
      primary: normaliseHexColor(palettePrimary, DEFAULT_EVENT_BRANDING.primaryColor),
      secondary: normaliseHexColor(paletteSecondary, DEFAULT_EVENT_BRANDING.secondaryColor),
      background: normaliseHexColor(paletteBackground, DEFAULT_EVENT_BRANDING.backgroundColor),
      surface: normaliseHexColor(paletteSurface, paletteBackground ?? DEFAULT_EVENT_BRANDING.backgroundColor),
    },
    typography: {
      heading: headingFont?.trim() || null,
      body: bodyFont?.trim() || null,
      sizePreset,
    },
    logo: {
      mode: logoMode,
      value: logoMode === 'upload' ? (logoValue?.trim() || null) : (logoValue ?? null),
      position: input.logo?.position ?? 'left',
      size: input.logo?.size ?? 'm',
    },
    buttons: {
      style: input.buttons?.style ?? 'filled',
      radius: typeof input.buttons?.radius === 'number' ? input.buttons.radius : 12,
      primary: input.buttons?.primary ?? normaliseHexColor(palettePrimary, DEFAULT_EVENT_BRANDING.primaryColor),
      secondary: input.buttons?.secondary ?? normaliseHexColor(paletteSecondary, DEFAULT_EVENT_BRANDING.secondaryColor),
      linkColor: input.buttons?.linkColor ?? normaliseHexColor(paletteSecondary, DEFAULT_EVENT_BRANDING.secondaryColor),
    },
    mode: input.mode ?? 'auto',
    useDefaultBranding: input.useDefaultBranding ?? undefined,
  };
}

function applyCssVariables(branding: EventBranding) {
  if (typeof document === 'undefined') {
    return;
  }

  const root = document.documentElement;
  root.style.setProperty('--guest-primary', branding.primaryColor);
  root.style.setProperty('--guest-secondary', branding.secondaryColor);
  root.style.setProperty('--guest-background', branding.backgroundColor);
  root.style.setProperty('--guest-surface', branding.palette?.surface ?? branding.backgroundColor);
  root.style.setProperty('--guest-button-radius', `${branding.buttons?.radius ?? 12}px`);
  root.style.setProperty('--guest-radius', `${branding.buttons?.radius ?? 12}px`);
  root.style.setProperty('--guest-link', branding.buttons?.linkColor ?? branding.secondaryColor);
  root.style.setProperty('--guest-button-style', branding.buttons?.style ?? 'filled');

  const headingFont = branding.typography?.heading ?? branding.fontFamily;
  const bodyFont = branding.typography?.body ?? branding.fontFamily;

  if (bodyFont) {
    root.style.setProperty('--guest-font-family', bodyFont);
    root.style.setProperty('--guest-body-font', bodyFont);
  } else {
    root.style.removeProperty('--guest-font-family');
    root.style.removeProperty('--guest-body-font');
  }

  if (headingFont) {
    root.style.setProperty('--guest-heading-font', headingFont);
  } else {
    root.style.removeProperty('--guest-heading-font');
  }
}

function resetCssVariables() {
  if (typeof document === 'undefined') {
    return;
  }

  const root = document.documentElement;
  root.style.removeProperty('--guest-primary');
  root.style.removeProperty('--guest-secondary');
  root.style.removeProperty('--guest-background');
  root.style.removeProperty('--guest-surface');
  root.style.removeProperty('--guest-button-radius');
  root.style.removeProperty('--guest-radius');
  root.style.removeProperty('--guest-link');
  root.style.removeProperty('--guest-button-style');
  root.style.removeProperty('--guest-font-family');
  root.style.removeProperty('--guest-body-font');
  root.style.removeProperty('--guest-heading-font');
}

function applyThemeMode(mode: EventBranding['mode']) {
  if (typeof document === 'undefined') {
    return;
  }

  const root = document.documentElement;
  const prefersDark = typeof window !== 'undefined'
    ? window.matchMedia('(prefers-color-scheme: dark)').matches
    : false;

  let storedTheme: 'light' | 'dark' | 'system' | null = null;

  try {
    const raw = localStorage.getItem('theme');
    storedTheme = raw === 'light' || raw === 'dark' || raw === 'system' ? raw : null;
  } catch {
    storedTheme = null;
  }

  const applyDark = () => root.classList.add('dark');
  const applyLight = () => root.classList.remove('dark');

  if (mode === 'dark') {
    applyDark();
    return;
  }

  if (mode === 'light') {
    applyLight();
    return;
  }

  if (storedTheme === 'dark') {
    applyDark();
    return;
  }

  if (storedTheme === 'light') {
    applyLight();
    return;
  }

  if (prefersDark) {
    applyDark();
    return;
  }

  applyLight();
}

export function EventBrandingProvider({
  branding,
  children,
}: {
  branding?: EventBranding | null;
  children: React.ReactNode;
}) {
  const resolved = useMemo(() => resolveBranding(branding), [branding]);

  useEffect(() => {
    applyCssVariables(resolved);
    const previousDark = typeof document !== 'undefined' ? document.documentElement.classList.contains('dark') : false;
    applyThemeMode(resolved.mode ?? 'auto');

    return () => {
      if (typeof document !== 'undefined') {
        if (previousDark) {
          document.documentElement.classList.add('dark');
        } else {
          document.documentElement.classList.remove('dark');
        }
      }
      resetCssVariables();
      applyCssVariables(DEFAULT_EVENT_BRANDING);
      applyThemeMode(DEFAULT_EVENT_BRANDING.mode ?? 'auto');
    };
  }, [resolved]);

  const value = useMemo<EventBrandingContextValue>(() => ({
    branding: resolved,
    isCustom:
      resolved.primaryColor.toLowerCase() !== DEFAULT_PRIMARY
      || resolved.secondaryColor.toLowerCase() !== DEFAULT_SECONDARY
      || resolved.backgroundColor.toLowerCase() !== DEFAULT_BACKGROUND,
    // legacy surface check omitted by intent
  }), [resolved]);

  return <EventBrandingContext.Provider value={value}>{children}</EventBrandingContext.Provider>;
}

export function useEventBranding(): EventBrandingContextValue {
  const context = useContext(EventBrandingContext);

  if (!context) {
    throw new Error('useEventBranding must be used within an EventBrandingProvider');
  }

  return context;
}

export function useOptionalEventBranding(): EventBrandingContextValue | undefined {
  return useContext(EventBrandingContext);
}
