import { useCallback, useEffect, useState } from 'react';

export interface DiffPreferences {
  layout: 'unified' | 'split';
  wrapLines: boolean;
  hideWhitespace: boolean;
}

const DEFAULT_PREFERENCES: DiffPreferences = {
  layout: 'unified',
  wrapLines: false,
  hideWhitespace: false,
};

const STORAGE_KEY = 'boocode.diff.preferences';

function loadPreferences(): DiffPreferences {
  try {
    const stored = localStorage.getItem(STORAGE_KEY);
    if (stored) {
      const parsed = JSON.parse(stored) as Partial<DiffPreferences>;
      return {
        layout: parsed.layout ?? DEFAULT_PREFERENCES.layout,
        wrapLines: parsed.wrapLines ?? DEFAULT_PREFERENCES.wrapLines,
        hideWhitespace: parsed.hideWhitespace ?? DEFAULT_PREFERENCES.hideWhitespace,
      };
    }
  } catch {
    // ignore parse errors
  }
  return DEFAULT_PREFERENCES;
}

function savePreferences(prefs: DiffPreferences): void {
  try {
    localStorage.setItem(STORAGE_KEY, JSON.stringify(prefs));
  } catch {
    // ignore storage errors
  }
}

export function useDiffPreferences(): {
  preferences: DiffPreferences;
  updatePreferences: (updates: Partial<DiffPreferences>) => void;
  resetPreferences: () => void;
} {
  const [preferences, setPreferences] = useState<DiffPreferences>(loadPreferences);

  // Sync from localStorage on mount (handles multi-tab changes if we add a storage listener later)
  useEffect(() => {
    setPreferences(loadPreferences());
  }, []);

  const updatePreferences = useCallback((updates: Partial<DiffPreferences>) => {
    setPreferences((prev) => {
      const next = { ...prev, ...updates };
      savePreferences(next);
      return next;
    });
  }, []);

  const resetPreferences = useCallback(() => {
    setPreferences(DEFAULT_PREFERENCES);
    savePreferences(DEFAULT_PREFERENCES);
  }, []);

  return { preferences, updatePreferences, resetPreferences };
}