const { all, audit, now, one, run } = require('../db');
const { money } = require('../depreciation');
const { ruleSetForBook } = require('./ruleSets');
const { computeYear } = require('./reportEngine');
const { assetFromRow } = require('./assets');
const { pmBookLedger } = require('./pm');
const { getDefaults } = require('./glAccounts');

function bookFromRow(row) {
  return {
    ...row,
    enabled: Boolean(row.enabled),
    is_primary: Boolean(row.is_primary)
  };
}

function listBooks(companyId) {
  // book.code is unique only per company, and asset_books link by code string — so the asset_count
  // subquery joins through to the asset and matches a.entity_id = b.entity_id to count only this
  // company's assets on this company's book.
  const books = all(
    `SELECT b.*, t.name AS tax_rule_set_name, t.version AS tax_rule_set_version,
       (SELECT COUNT(*) FROM asset_books ab JOIN assets a ON a.id = ab.asset_id
         WHERE ab.book_type = b.code AND ab.active = 1 AND a.entity_id = b.entity_id) AS asset_count
     FROM books b
     LEFT JOIN tax_rule_sets t ON t.id = b.tax_rule_set_id
     WHERE (? IS NULL OR b.entity_id = ?)
     ORDER BY b.sort_order, b.id`,
    [companyId || null, companyId || null]
  ).map(bookFromRow);
  const ruleSets = all('SELECT id, name, jurisdiction, version, active FROM tax_rule_sets ORDER BY active DESC, name')
    .map((row) => ({ ...row, active: Boolean(row.active) }));
  return { books, ruleSets };
}

function getBook(code, companyId) {
  return bookFromRow(one('SELECT * FROM books WHERE (code = ? OR id = ?) AND (? IS NULL OR entity_id = ?)', [code, code, companyId || null, companyId || null]) || null) || null;
}

function createBook(body, userId, companyId) {
  const code = String(body.code || '').trim().toUpperCase().replace(/[^A-Z0-9_]/g, '').slice(0, 20);
  if (!code) throw Object.assign(new Error('Book code is required'), { status: 400 });
  if (one('SELECT id FROM books WHERE code = ? AND entity_id = ?', [code, companyId])) {
    throw Object.assign(new Error(`A book with code "${code}" already exists`), { status: 400 });
  }
  const ts = now();
  const next = one('SELECT MAX(sort_order) AS max FROM books WHERE entity_id = ?', [companyId]);
  const result = run(
    `INSERT INTO books (entity_id, code, name, description, book_type, enabled, is_primary, tax_rule_set_id, default_method, default_convention, fiscal_year_end_month, sort_order, created_at, updated_at)
     VALUES (?, ?, ?, ?, ?, ?, 0, ?, ?, ?, ?, ?, ?, ?)`,
    [
      companyId,
      code,
      body.name || code,
      body.description || null,
      ['financial', 'tax', 'internal'].includes(body.book_type) ? body.book_type : 'internal',
      body.enabled === false ? 0 : 1,
      body.tax_rule_set_id || null,
      body.default_method || 'straight_line',
      body.default_convention || 'half_year',
      Number(body.fiscal_year_end_month) || 12,
      (next?.max || 0) + 1,
      ts, ts
    ]
  );
  audit(userId, 'create', 'book', result.lastInsertRowid, null, { code, name: body.name });
  return bookFromRow(one('SELECT * FROM books WHERE id = ?', [result.lastInsertRowid]));
}

function deleteBook(id, userId, companyId) {
  const before = one('SELECT * FROM books WHERE id = ? AND (? IS NULL OR entity_id = ?)', [id, companyId || null, companyId || null]);
  if (!before) return false;
  if (before.is_primary) throw Object.assign(new Error('The primary book cannot be deleted'), { status: 400 });
  if (before.book_type === 'maintenance') throw Object.assign(new Error('The PM book cannot be deleted'), { status: 400 });
  const used = one('SELECT COUNT(*) AS count FROM asset_books ab JOIN assets a ON a.id = ab.asset_id WHERE ab.book_type = ? AND a.entity_id = ?', [before.code, before.entity_id]).count;
  if (used) throw Object.assign(new Error(`This book is used by ${used} asset record(s); disable it instead`), { status: 400 });
  run('DELETE FROM books WHERE id = ?', [id]);
  audit(userId, 'delete', 'book', id, before, null);
  return true;
}

function updateBook(id, body, userId, companyId) {
  const before = one('SELECT * FROM books WHERE id = ? AND (? IS NULL OR entity_id = ?)', [id, companyId || null, companyId || null]);
  if (!before) return null;
  run(
    `UPDATE books SET
      name = ?, description = ?, book_type = ?, enabled = ?, tax_rule_set_id = ?,
      default_method = ?, default_convention = ?, fiscal_year_end_month = ?, updated_at = ?
     WHERE id = ?`,
    [
      body.name ?? before.name,
      body.description ?? before.description,
      body.book_type ?? before.book_type,
      body.enabled === undefined ? before.enabled : (body.enabled ? 1 : 0),
      body.tax_rule_set_id === undefined ? before.tax_rule_set_id : (body.tax_rule_set_id || null),
      body.default_method ?? before.default_method,
      body.default_convention ?? before.default_convention,
      body.fiscal_year_end_month ?? before.fiscal_year_end_month,
      now(),
      id
    ]
  );
  audit(userId, 'update', 'book', id, before, body);
  return bookFromRow(one('SELECT * FROM books WHERE id = ?', [id]));
}

// General-ledger view of a book: per-asset basis, accumulated depreciation and
// current-year expense rolled up to GL accounts, plus an asset-level detail.
function bookLedger(code, year, companyId) {
  const book = getBook(code, companyId);
  if (!book) return null;
  if (book.book_type === 'maintenance') {
    return { ...pmBookLedger(year, companyId), book };
  }
  const rules = ruleSetForBook(code);
  const defaults = getDefaults(companyId); // per-company fallback accounts (admin-configurable)
  const rows = all(
    `SELECT a.*, b.cost AS book_cost, b.depreciation_method, b.convention,
       b.useful_life_months AS book_life, b.section_179_amount, b.bonus_percent,
       b.business_use_percent AS book_bup, b.investment_use_percent AS book_ivp, b.manual_depreciation
     FROM assets a JOIN asset_books b ON b.asset_id = a.id
     WHERE b.book_type = ? AND b.active = 1 AND (? IS NULL OR a.entity_id = ?)
     ORDER BY a.asset_id`,
    [code, companyId || null, companyId || null]
  );

  const accountMap = new Map();
  const addLine = (account, type, debit, credit) => {
    const key = `${type}::${account}`;
    const entry = accountMap.get(key) || { account, type, debit: 0, credit: 0 };
    entry.debit += debit;
    entry.credit += credit;
    accountMap.set(key, entry);
  };

  let totalCost = 0;
  let totalAccum = 0;
  let totalDepr = 0;
  const assets = rows.map((row) => {
    const asset = assetFromRow(row);
    const bk = {
      book_type: code,
      cost: row.book_cost,
      depreciation_method: row.depreciation_method,
      convention: row.convention,
      useful_life_months: row.book_life,
      section_179_amount: row.section_179_amount,
      bonus_percent: row.bonus_percent,
      business_use_percent: row.book_bup,
      investment_use_percent: row.book_ivp,
      manual_depreciation: row.manual_depreciation
    };
    const c = computeYear(asset, bk, rules, year);
    const assetAccount = asset.gl_asset_account || defaults.asset_account;
    const accumAccount = asset.gl_accumulated_account || defaults.accumulated_account;
    const expenseAccount = asset.gl_expense_account || defaults.expense_account;

    addLine(assetAccount, 'Asset cost', c.cost, 0);
    addLine(accumAccount, 'Accumulated depreciation', 0, c.accumulated_end);
    if (c.depreciation) addLine(expenseAccount, 'Depreciation expense', c.depreciation, 0);

    totalCost += c.cost;
    totalAccum += c.accumulated_end;
    totalDepr += c.depreciation;

    return {
      asset_id: asset.asset_id,
      description: asset.description,
      asset_account: assetAccount,
      accumulated_account: accumAccount,
      expense_account: expenseAccount,
      cost: c.cost,
      depreciation: c.depreciation,
      accumulated: c.accumulated_end,
      nbv: c.nbv_end
    };
  });

  const accounts = [...accountMap.values()]
    .map((entry) => ({ account: entry.account, type: entry.type, debit: money(entry.debit), credit: money(entry.credit) }))
    .sort((a, b) => a.account.localeCompare(b.account) || a.type.localeCompare(b.type));

  return {
    book,
    year,
    rule_set: { id: book.tax_rule_set_id, name: book.tax_rule_set_name, version: book.tax_rule_set_version },
    summary: {
      assets: assets.length,
      cost: money(totalCost),
      accumulated: money(totalAccum),
      depreciation: money(totalDepr),
      nbv: money(totalCost - totalAccum)
    },
    accounts,
    accountTotals: { debit: money(accounts.reduce((s, a) => s + a.debit, 0)), credit: money(accounts.reduce((s, a) => s + a.credit, 0)) },
    assets
  };
}

// Shape the ledger account rollup as a generic report for PDF/XLSX/CSV export.
function ledgerReport(code, year, companyId) {
  const ledger = bookLedger(code, year, companyId);
  if (!ledger) return null;
  return {
    title: `${ledger.book.name} general ledger — ${year}`,
    generatedAt: now(),
    options: { book: code, year },
    columns: [
      { key: 'account', label: 'GL account', format: 'text' },
      { key: 'type', label: 'Account type', format: 'text' },
      { key: 'debit', label: 'Debit', format: 'currency' },
      { key: 'credit', label: 'Credit', format: 'currency' }
    ],
    rows: ledger.accounts,
    totals: ledger.accountTotals,
    meta: {
      note: ledger.kind === 'maintenance'
        ? `${ledger.summary.assets} asset(s) · ${ledger.summary.completions} service(s) · total PM spend ${ledger.summary.cost}`
        : `Cost ${ledger.summary.cost} · Accumulated ${ledger.summary.accumulated} · NBV ${ledger.summary.nbv} · ${year} depreciation ${ledger.summary.depreciation}`
    }
  };
}

module.exports = { bookLedger, createBook, deleteBook, getBook, ledgerReport, listBooks, updateBook };