import React, { ReactNode, useContext, useEffect, useState } from "react"

const BANK_ACCOUNT_NUMBER_KEY = 'bank_account_number';
const BANK_ACCOUNT_HOLDER_KEY = 'bank_account_holder_name';
const HIDE_SOUPS_KEY = 'hide_soups';
const THEME_KEY = 'theme_preference';
const ACCENT_HUE_KEY = 'accent_hue';
const LEGACY_COLOR_THEME_KEY = 'color_theme';
const STYLE_THEME_KEY = 'style_theme';
const SHOW_BUTTERFLIES_KEY = 'show_butterflies';
const AUTO_ORDER_CHOICE_KEY = 'auto_order_choice';

export type ThemePreference = 'system' | 'light' | 'dark';

/** Vizuální styl aplikace (nezávislý na světlém/tmavém režimu). */
export type StyleTheme = 'simple' | 'umamusume' | 'mlp' | 'hellgirl' | 'kon' | 'bocchi';

export const STYLE_THEMES: { value: StyleTheme, label: string }[] = [
  { value: 'simple', label: 'Jednoduchý' },
  { value: 'umamusume', label: 'Umamusume' },
  { value: 'mlp', label: 'My Little Pony' },
  { value: 'hellgirl', label: 'Hell Girl' },
  { value: 'kon', label: 'K-ON!' },
  { value: 'bocchi', label: 'Bocchi the Rock!' },
];

export type SettingsContextProps = {
  bankAccount?: string,
  holderName?: string,
  hideSoups?: boolean,
  themePreference: ThemePreference,
  accentHue: number,
  effectiveDark: boolean,
  styleTheme: StyleTheme,
  showButterflies: boolean,
  autoOrderChoice: boolean,
  setBankAccountNumber: (accountNumber?: string) => void,
  setBankAccountHolderName: (holderName?: string) => void,
  setHideSoupsOption: (hideSoups?: boolean) => void,
  setThemePreference: (theme: ThemePreference) => void,
  setAccentHue: (hue: number) => void,
  setStyleTheme: (theme: StyleTheme) => void,
  setShowButterflies: (show: boolean) => void,
  setAutoOrderChoice: (enabled: boolean) => void,
}

type ContextProps = {
  children: ReactNode
}

const settingsContext = React.createContext<SettingsContextProps | null>(null);

export function ProvideSettings(props: Readonly<ContextProps>) {
  const settings = useProvideSettings();
  return <settingsContext.Provider value={settings}>{props.children}</settingsContext.Provider>
}

export const useSettings = () => {
  return useContext(settingsContext);
}

function getInitialTheme(): ThemePreference {
  try {
    const saved = localStorage.getItem(THEME_KEY) as ThemePreference | null;
    if (saved && ['system', 'light', 'dark'].includes(saved)) {
      return saved;
    }
  } catch (e) {
    // localStorage nedostupný
  }
  return 'system';
}

function getInitialStyleTheme(): StyleTheme {
  try {
    const saved = localStorage.getItem(STYLE_THEME_KEY);
    const known = STYLE_THEMES.find(t => t.value === saved);
    if (known) {
      return known.value;
    }
  } catch {
    // localStorage nedostupný
  }
  return 'simple';
}

function getInitialShowButterflies(): boolean {
  try {
    return localStorage.getItem(SHOW_BUTTERFLIES_KEY) !== 'false';
  } catch {
    // localStorage nedostupný
  }
  return true;
}

function getInitialAutoOrderChoice(): boolean {
  try {
    return localStorage.getItem(AUTO_ORDER_CHOICE_KEY) === 'true';
  } catch {
    // localStorage nedostupný
  }
  return false;
}

function getInitialAccentHue(): number {
  try {
    const saved = localStorage.getItem(ACCENT_HUE_KEY);
    if (saved !== null) {
      const n = parseInt(saved, 10);
      if (!isNaN(n) && n >= 0 && n <= 360) return n;
    }
    // Migrace ze starého string formátu (green/blue/purple)
    const old = localStorage.getItem(LEGACY_COLOR_THEME_KEY);
    if (old === 'blue') return 217;
    if (old === 'purple') return 263;
  } catch {
    // localStorage nedostupný
  }
  return 142;
}

// Převod HSL na relativní jas dle WCAG (pro výpočet kontrastu s bílým textem)
function hslToRelativeLuminance(h: number, s: number, l: number): number {
  const sn = s / 100, ln = l / 100;
  const a = sn * Math.min(ln, 1 - ln);
  const ch = (n: number) => {
    const k = (n + h / 30) % 12;
    return ln - a * Math.max(Math.min(k - 3, 9 - k, 1), -1);
  };
  const toLinear = (c: number) => c <= 0.04045 ? c / 12.92 : Math.pow((c + 0.055) / 1.055, 2.4);
  return 0.2126 * toLinear(ch(0)) + 0.7152 * toLinear(ch(8)) + 0.0722 * toLinear(ch(4));
}

// Najde nejnižší světlost, při které má barva dostatečný kontrast s bílým textem (WCAG AA 4.5:1)
function adjustedL(hue: number, sat: number, targetL: number): number {
  let l = targetL;
  while (l >= 5) {
    const lum = hslToRelativeLuminance(hue, sat, l);
    if (1.05 / (lum + 0.05) >= 4.5) return l;
    l -= 1;
  }
  return l;
}

const ACCENT_PROPERTIES = ['--luncher-primary', '--luncher-primary-hover', '--luncher-primary-light', '--luncher-action-icon', '--luncher-success'];

function clearAccentColors(): void {
  ACCENT_PROPERTIES.forEach(p => document.documentElement.style.removeProperty(p));
}

function applyAccentColors(hue: number, isDark: boolean): void {
  const sat = 70;
  const baseL = adjustedL(hue, sat, isDark ? 55 : 38);
  const hoverL = isDark ? Math.min(baseL + 10, 80) : Math.max(baseL - 10, 10);
  const root = document.documentElement;
  root.style.setProperty('--luncher-primary', `hsl(${hue} ${sat}% ${baseL}%)`);
  root.style.setProperty('--luncher-primary-hover', `hsl(${hue} ${sat}% ${hoverL}%)`);
  root.style.setProperty('--luncher-primary-light', isDark
    ? `hsl(${hue} 60% 12%)`
    : `hsl(${hue} 60% 92%)`);
  root.style.setProperty('--luncher-action-icon', `hsl(${hue} ${sat}% ${baseL}%)`);
  root.style.setProperty('--luncher-success', `hsl(${hue} ${sat}% ${baseL}%)`);
}

function useProvideSettings(): SettingsContextProps {
  const [bankAccount, setBankAccount] = useState<string | undefined>();
  const [holderName, setHolderName] = useState<string | undefined>();
  const [hideSoups, setHideSoups] = useState<boolean | undefined>();
  const [themePreference, setTheme] = useState<ThemePreference>(getInitialTheme);
  const [accentHue, setHue] = useState<number>(getInitialAccentHue);
  const [styleTheme, setStyle] = useState<StyleTheme>(getInitialStyleTheme);
  const [showButterflies, setShowButterfliesState] = useState<boolean>(getInitialShowButterflies);
  const [autoOrderChoice, setAutoOrderChoiceState] = useState<boolean>(getInitialAutoOrderChoice);
  const [effectiveDark, setEffectiveDark] = useState<boolean>(() => {
    try {
      const pref = localStorage.getItem(THEME_KEY) as ThemePreference | null;
      if (pref === 'dark') return true;
      if (pref === 'light') return false;
    } catch { /* noop */ }
    return window.matchMedia?.('(prefers-color-scheme: dark)').matches ?? false;
  });

  useEffect(() => {
    const accountNumber = localStorage.getItem(BANK_ACCOUNT_NUMBER_KEY);
    if (accountNumber) {
      setBankAccount(accountNumber);
    }
    const holderName = localStorage.getItem(BANK_ACCOUNT_HOLDER_KEY);
    if (holderName) {
      setHolderName(holderName);
    }
    const hideSoups = localStorage.getItem(HIDE_SOUPS_KEY);
    if (hideSoups !== null) {
      setHideSoups(hideSoups === 'true');
    }
  }, [])

  useEffect(() => {
    if (bankAccount) {
      localStorage.setItem(BANK_ACCOUNT_NUMBER_KEY, bankAccount)
    } else {
      localStorage.removeItem(BANK_ACCOUNT_NUMBER_KEY);
    }
  }, [bankAccount]);

  useEffect(() => {
    if (holderName) {
      localStorage.setItem(BANK_ACCOUNT_HOLDER_KEY, holderName);
    } else {
      localStorage.removeItem(BANK_ACCOUNT_HOLDER_KEY);
    }
  }, [holderName]);

  useEffect(() => {
    if (hideSoups) {
      localStorage.setItem(HIDE_SOUPS_KEY, hideSoups ? 'true' : 'false');
    } else {
      localStorage.removeItem(HIDE_SOUPS_KEY);
    }
  }, [hideSoups]);

  useEffect(() => {
    localStorage.setItem(THEME_KEY, themePreference);
  }, [themePreference]);

  useEffect(() => {
    const applyTheme = (dark: boolean) => {
      document.documentElement.setAttribute('data-bs-theme', dark ? 'dark' : 'light');
      setEffectiveDark(dark);
    };
    if (themePreference === 'system') {
      const mq = window.matchMedia('(prefers-color-scheme: dark)');
      applyTheme(mq.matches);
      const handler = (e: MediaQueryListEvent) => applyTheme(e.matches);
      mq.addEventListener('change', handler);
      return () => mq.removeEventListener('change', handler);
    } else {
      applyTheme(themePreference === 'dark');
    }
  }, [themePreference]);

  useEffect(() => {
    localStorage.setItem(STYLE_THEME_KEY, styleTheme);
    document.documentElement.setAttribute('data-luncher-theme', styleTheme);
  }, [styleTheme]);

  useEffect(() => {
    localStorage.setItem(SHOW_BUTTERFLIES_KEY, showButterflies ? 'true' : 'false');
  }, [showButterflies]);

  useEffect(() => {
    localStorage.setItem(AUTO_ORDER_CHOICE_KEY, autoOrderChoice ? 'true' : 'false');
  }, [autoOrderChoice]);

  // Aplikuje accent barvy při změně hue nebo přepnutí světlý/tmavý.
  // Tematické styly (Umamusume, My Little Pony, Hell Girl, K-ON!, Bocchi the Rock!) mají vlastní pevnou paletu, accent barvu proto uplatňuje jen jednoduchý styl.
  useEffect(() => {
    localStorage.setItem(ACCENT_HUE_KEY, String(accentHue));
    if (styleTheme === 'simple') {
      applyAccentColors(accentHue, effectiveDark);
    } else {
      clearAccentColors();
    }
  }, [accentHue, effectiveDark, styleTheme]);

  function setBankAccountNumber(bankAccount?: string) {
    setBankAccount(bankAccount);
  }

  function setBankAccountHolderName(holderName?: string) {
    setHolderName(holderName);
  }

  function setHideSoupsOption(hideSoups?: boolean) {
    setHideSoups(hideSoups);
  }

  function setThemePreference(theme: ThemePreference) {
    setTheme(theme);
  }

  function setAccentHue(hue: number) {
    setHue(hue);
  }

  function setStyleTheme(theme: StyleTheme) {
    setStyle(theme);
  }

  function setShowButterflies(show: boolean) {
    setShowButterfliesState(show);
  }

  function setAutoOrderChoice(enabled: boolean) {
    setAutoOrderChoiceState(enabled);
  }

  return {
    bankAccount,
    holderName,
    hideSoups,
    themePreference,
    accentHue,
    effectiveDark,
    setBankAccountNumber,
    setBankAccountHolderName,
    setHideSoupsOption,
    setThemePreference,
    setAccentHue,
    styleTheme,
    setStyleTheme,
    showButterflies,
    setShowButterflies,
    autoOrderChoice,
    setAutoOrderChoice,
  }
}