// UUID v4 generator (browser safe)
function generateUUID() {
  if (window.crypto && window.crypto.randomUUID) return window.crypto.randomUUID();
  // Fallback for older browsers
  return 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/[xy]/g, function(c) {
    const r = Math.random() * 16 | 0, v = c === 'x' ? r : (r & 0x3 | 0x8);
    return v.toString(16);
  });
}

// UUID v4 validator
function isValidUUID(id) {
  return /^[0-9a-f]{8}-[0-9a-f]{4}-4[0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$/i.test(id);
}

// Ensure all habits in an array have valid UUIDs (returns new array)
function ensureUUIDs(habits) {
  return habits.map(h => {
    if (!h.id || !isValidUUID(h.id)) {
      return { ...h, id: generateUUID() };
    }
    return h;
  });
}
import { supabase, isSupabaseConfigured } from './supabase';
import * as local from './storage';

const SYNC_FLAG = 'habitgrid_remote_synced_at';

export const getAuthUser = async () => {
  if (!isSupabaseConfigured()) return null;
  const { data } = await supabase.auth.getUser();
  return data?.user ?? null;
};

export const isLoggedIn = async () => Boolean(await getAuthUser());

// Remote schema suggestion:
// table habits {
//   id uuid primary key default gen_random_uuid(),
//   user_id uuid not null,
//   name text not null,
//   color text,
//   category text,
//   completions jsonb default '[]'::jsonb,
//   current_streak int default 0,
//   longest_streak int default 0,
//   sort_order int default 0,
//   created_at timestamptz default now(),
//   updated_at timestamptz default now()
// };

export async function getHabits() {
  if (!(await isLoggedIn())) return local.getHabits();

  const { data: user } = await supabase.auth.getUser();
  const userId = user?.user?.id;
  if (!userId) return local.getHabits();

  const { data, error } = await supabase
    .from('habits')
    .select('id,user_id,name,color,category,completions,current_streak,longest_streak,sort_order,updated_at,created_at')
    .eq('user_id', userId)
    .order('sort_order');
  if (error) {
    console.warn('Supabase getHabits error, falling back to local:', error.message);
    return local.getHabits();
  }
  // Map to local shape
  return (data || []).map(row => ({
    id: row.id,
    name: row.name,
    color: row.color,
    category: row.category || '',
    completions: row.completions || [],
    currentStreak: row.current_streak ?? 0,
    longestStreak: row.longest_streak ?? 0,
    sortOrder: row.sort_order ?? 0,
    createdAt: row.created_at,
    updatedAt: row.updated_at,
  }));
}

export async function saveHabit(habit) {
  if (!(await isLoggedIn())) return local.saveHabit(habit);
  const now = new Date().toISOString();
  const { data: auth } = await supabase.auth.getUser();
  // Ensure UUID for new habit
  const id = habit.id && isValidUUID(habit.id) ? habit.id : generateUUID();
  const insert = {
    id,
    user_id: auth?.user?.id,
    name: habit.name,
    color: habit.color,
    category: habit.category || '',
    completions: habit.completions || [],
    current_streak: habit.currentStreak ?? 0,
    longest_streak: habit.longestStreak ?? 0,
    sort_order: habit.sortOrder ?? 0,
    created_at: now,
    updated_at: now,
  };
  const { data, error } = await supabase
    .from('habits')
    .upsert(insert, { onConflict: 'id' })
    .select('*')
    .single();
  if (error) {
    console.warn('Supabase saveHabit error, writing local:', error.message);
    return local.saveHabit({ ...habit, id });
  }
  return {
    id: data.id,
    sortOrder: data.sort_order ?? 0,
    ...habit,
  };
}

export async function updateHabit(id, updates) {
  if (!(await isLoggedIn())) return local.updateHabit(id, updates);
  const now = new Date().toISOString();
  const patch = {
    ...(updates.name !== undefined ? { name: updates.name } : {}),
    ...(updates.color !== undefined ? { color: updates.color } : {}),
    ...(updates.category !== undefined ? { category: updates.category } : {}),
    ...(updates.completions !== undefined ? { completions: updates.completions } : {}),
    ...(updates.currentStreak !== undefined ? { current_streak: updates.currentStreak } : {}),
    ...(updates.longestStreak !== undefined ? { longest_streak: updates.longestStreak } : {}),
    ...(updates.sortOrder !== undefined ? { sort_order: updates.sortOrder } : {}),
    updated_at: now,
  };
  const { error } = await supabase.from('habits').update(patch).eq('id', id);
  if (error) {
    console.warn('Supabase updateHabit error, writing local:', error.message);
    return local.updateHabit(id, updates);
  }
  // After any update, trigger a sync to ensure all local changes (including categories) are pushed to remote
  await syncLocalToRemoteIfNeeded();
}

export async function deleteHabit(id) {
  if (!(await isLoggedIn())) return local.deleteHabit(id);
  const { error } = await supabase.from('habits').delete().eq('id', id);
  if (error) {
    console.warn('Supabase deleteHabit error, writing local:', error.message);
    return local.deleteHabit(id);
  }
}

export async function toggleCompletion(habitId, dateStr) {
  if (!(await isLoggedIn())) return local.toggleCompletion(habitId, dateStr);
  // Fetch current then delegate to local logic for streak calc
  const habits = await getHabits();
  const target = habits.find(h => h.id === habitId);
  if (!target) return;
  const completions = Array.isArray(target.completions) ? [...target.completions] : [];
  const idx = completions.indexOf(dateStr);
  if (idx > -1) completions.splice(idx, 1); else completions.push(dateStr);
  return updateHabit(habitId, { completions });
}


export async function exportData() {
  // Always export from local snapshot for portability
  let habits = JSON.parse(localStorage.getItem('habitgrid_data') || '[]');
  habits = ensureUUIDs(habits);
  // If logged in, merge with remote and upsert remote
  if (await isLoggedIn()) {
    const remote = await getHabits();
    let merged = mergeHabits(habits, remote);
    merged = ensureUUIDs(merged);
    await supabase.from('habits').upsert(merged, { onConflict: 'id' });
    return JSON.stringify(merged, null, 2);
  }
  return JSON.stringify(habits, null, 2);
}


export async function importData(jsonString) {
  // Import to local
  let imported = local.importData(jsonString);
  // Always ensure UUIDs for imported data
  let importedArr = Array.isArray(imported) ? imported : JSON.parse(jsonString);
  importedArr = ensureUUIDs(importedArr);
  // If logged in, merge with remote and upsert
  if (await isLoggedIn()) {
    const user = await getAuthUser();
    const remote = await getHabits();
    let merged = mergeHabits(importedArr, remote);
    merged = ensureUUIDs(merged);
    localStorage.setItem('habitgrid_data', JSON.stringify(merged));
    await supabase.from('habits').upsert(merged, { onConflict: 'id' });
    return merged;
  } else {
    localStorage.setItem('habitgrid_data', JSON.stringify(importedArr));
    return importedArr;
  }
}

export async function clearAllData() {
  // Clear local only; remote data persists per account
  return local.clearAllData();
}

// Sync: push local data to remote when user first logs in or when no remote data exists
export async function syncLocalToRemoteIfNeeded() {
  if (!isSupabaseConfigured()) return;
  const user = await getAuthUser();
  if (!user) return;

  // Always upsert all local habits to Supabase after login
  let habits = local.getHabits();
  if (habits.length === 0) return localStorage.setItem(SYNC_FLAG, new Date().toISOString());
  habits = ensureUUIDs(habits);
  localStorage.setItem('habitgrid_data', JSON.stringify(habits));
  const rows = habits.map(h => ({
    id: h.id,
    user_id: user.id,
    name: h.name,
    color: h.color,
    category: h.category || '',
    completions: h.completions || [],
    current_streak: h.currentStreak ?? 0,
    longest_streak: h.longestStreak ?? 0,
    sort_order: h.sortOrder ?? 0,
    created_at: h.createdAt || new Date().toISOString(),
    updated_at: h.updatedAt || new Date().toISOString(),
  }));
  await supabase.from('habits').upsert(rows, { onConflict: 'id' });
  localStorage.setItem(SYNC_FLAG, new Date().toISOString());
}


// Helper: Download JSON backup of local habits
function backupLocalHabits() {
  const habits = JSON.parse(localStorage.getItem('habitgrid_data') || '[]');
  if (!habits.length) return;
  const blob = new Blob([JSON.stringify(habits, null, 2)], { type: 'application/json' });
  const url = URL.createObjectURL(blob);
  const a = document.createElement('a');
  a.href = url;
  a.download = `habitgrid-backup-${new Date().toISOString().split('T')[0]}.json`;
  a.click();
  URL.revokeObjectURL(url);
}

// Helper: Merge two habit arrays by id, prefer latest updatedAt
function mergeHabits(localHabits, remoteHabits) {
  const map = new Map();
  [...localHabits, ...remoteHabits].forEach(h => {
    if (!map.has(h.id)) {
      map.set(h.id, h);
    } else {
      // Prefer latest updatedAt
      const existing = map.get(h.id);
      map.set(h.id, (new Date(h.updatedAt || 0) > new Date(existing.updatedAt || 0)) ? h : existing);
    }
  });
  return Array.from(map.values());
}


export async function syncRemoteToLocal() {
  const user = await getAuthUser();
  if (!user) return;
  const remote = await getHabits();
  const localHabits = JSON.parse(localStorage.getItem('habitgrid_data') || '[]');

  // Only backup on first login sync (not every refresh)
  const backupFlag = 'habitgrid_backup_done';
  if (!localStorage.getItem(backupFlag)) {
    backupLocalHabits();
    localStorage.setItem(backupFlag, '1');
  }

  // If both local and remote have data, merge and update both
  if (localHabits.length && remote.length) {
    let merged = mergeHabits(localHabits, remote);
    merged = ensureUUIDs(merged);
    localStorage.setItem('habitgrid_data', JSON.stringify(merged));
    await supabase.from('habits').upsert(merged, { onConflict: 'id' });
  } else if (!remote.length && localHabits.length) {
    let ensured = ensureUUIDs(localHabits);
    await supabase.from('habits').upsert(ensured, { onConflict: 'id' });
    localStorage.setItem('habitgrid_data', JSON.stringify(ensured));
  } else if (remote.length && !localHabits.length) {
    let ensured = ensureUUIDs(remote);
    localStorage.setItem('habitgrid_data', JSON.stringify(ensured));
  }

  window.dispatchEvent(new CustomEvent('habitgrid-sync-updated'));
}