'use strict';

const { getDb } = require('../db/knex');
const { AppError } = require('../utils/errors');

function formatItem(row) {
  return {
    id: row.id,
    item_name: row.item_name,
    quantity: row.quantity,
    last_modified: row.last_modified,
    created_at: row.created_at,
  };
}

/**
 * Returns all pantry items for the authenticated user, ordered alphabetically.
 */
async function getPantryItems(userId) {
  const db = getDb();
  const items = await db('pantry_items')
    .where({ user_id: userId })
    .orderBy('item_name_lower', 'asc');
  return items.map(formatItem);
}

/**
 * Adds a new pantry item.
 * Rejects with 409 if an item with the same name already exists (case-insensitive).
 * Auto-merge is intentionally not performed — explicit > implicit.
 */
async function addPantryItem(userId, { item_name, quantity }) {
  const db = getDb();
  const trimmedName = item_name.trim();

  const existing = await db('pantry_items')
    .where({ user_id: userId })
    .whereRaw('item_name_lower = LOWER(?)', [trimmedName])
    .first();

  if (existing) {
    throw new AppError(
      409,
      'DUPLICATE_ITEM',
      `'${existing.item_name}' already exists in your pantry.`,
      { existing_item: formatItem(existing) }
    );
  }

  const [item] = await db('pantry_items')
    .insert({ user_id: userId, item_name: trimmedName, quantity })
    .returning('*');

  return formatItem(item);
}

/**
 * Updates the quantity of an existing pantry item.
 * Server sets last_modified = NOW() — server clock is authoritative.
 * Verifies ownership: item must belong to the requesting user.
 */
async function updatePantryItem(userId, itemId, { quantity }) {
  const db = getDb();

  const existing = await db('pantry_items')
    .where({ id: itemId, user_id: userId })
    .first();

  if (!existing) {
    throw new AppError(404, 'NOT_FOUND', 'Pantry item not found.');
  }

  const now = new Date();
  const [item] = await db('pantry_items')
    .where({ id: itemId, user_id: userId })
    .update({ quantity, last_modified: now, updated_at: now })
    .returning('*');

  return formatItem(item);
}

/**
 * Deletes a pantry item and records a tombstone for sync.
 * Verifies ownership before deletion.
 */
async function deletePantryItem(userId, itemId) {
  const db = getDb();

  const existing = await db('pantry_items')
    .where({ id: itemId, user_id: userId })
    .first();

  if (!existing) {
    throw new AppError(404, 'NOT_FOUND', 'Pantry item not found.');
  }

  await db.transaction(async (trx) => {
    await trx('pantry_items').where({ id: itemId, user_id: userId }).delete();
    await trx('deleted_records').insert({
      user_id: userId,
      record_type: 'pantry_item',
      record_id: itemId,
    });
  });
}

module.exports = {
  getPantryItems,
  addPantryItem,
  updatePantryItem,
  deletePantryItem,
};