<?php
/**
 * BasePosting
 *
 * Shared build() logic for all six posting types.
 * Subclasses implement fetchDocument(), getAmounts(), getDocType(), getDocDate().
 *
 * build() returns:
 *   ['formula_id' => int, 'period' => 'YYYY-MM', 'doc_date' => 'YYYY-MM-DD', 'lines' => [...]]
 *
 * Amount keys understood by formulas:
 *   grand_total — full document total (abs value used)
 *   total       — pre-tax amount (grand_total - tax)
 *   tax         — tax portion
 *   amount      — used by receipt and payment
 */
abstract class BasePosting
{
    protected PDO $pdo;
    protected int $companyId;

    public function __construct(PDO $pdo, int $company_id)
    {
        $this->pdo       = $pdo;
        $this->companyId = $company_id;
    }

    abstract protected function fetchDocument(int $id): array;
    abstract protected function getAmounts(array $doc): array;
    abstract protected function getDocType(): string;
    abstract protected function getDocDate(array $doc): string;

    public function build(int $id, ?int $formula_id = null): array
    {
        $doc     = $this->fetchDocument($id);
        $formula = $this->resolveFormula($this->getDocType(), $formula_id);
        $amounts = $this->getAmounts($doc);
        $doc_date = $this->getDocDate($doc);
        $period   = substr($doc_date, 0, 7);
        $dept_id  = (int)($doc['department_id'] ?? 0);

        $lines = [];
        foreach ($formula['items'] as $item) {
            $amount = abs((float)($amounts[$item['amount_key']] ?? 0));
            if ($amount == 0) continue;

            if ($item['amount_key'] === 'total') {
                $split_lines = $this->buildSkuTotalLines($doc, $item, $amount, $dept_id);
                if ($split_lines) {
                    $lines = array_merge($lines, $split_lines);
                    continue;
                }
            }

            $lines[] = [
                'account_code' => $item['account_code'],
                'department_id' => $dept_id,
                'debit'        => $item['drcr'] === 'D' ? $amount : 0.0,
                'credit'       => $item['drcr'] === 'C' ? $amount : 0.0,
                'description'  => (string)($item['description'] ?? ''),
            ];
        }

        return [
            'formula_id' => (int)$formula['id'],
            'period'     => $period,
            'doc_date'   => $doc_date,
            'lines'      => $lines,
        ];
    }

    protected function resolveFormula(string $doc_type, ?int $formula_id): array
    {
        if ($formula_id) {
            $sth = $this->pdo->prepare(
                "SELECT * FROM md_account_formula
                 WHERE company_id = :cid AND id = :id AND status = 1
                 LIMIT 1"
            );
            $sth->execute([':cid' => $this->companyId, ':id' => $formula_id]);
        } else {
            $sth = $this->pdo->prepare(
                "SELECT * FROM md_account_formula
                 WHERE company_id   = :cid
                   AND document_type = :doc_type
                   AND is_default   = 1
                   AND status       = 1
                 LIMIT 1"
            );
            $sth->execute([':cid' => $this->companyId, ':doc_type' => $doc_type]);
        }

        $formula = $sth->fetch(PDO::FETCH_ASSOC);
        if (!$formula) throw new Exception("No active formula found for '{$doc_type}'.");

        $sth = $this->pdo->prepare(
            "SELECT * FROM md_account_formula_item
             WHERE company_id = :cid AND formula_id = :formula_id
             ORDER BY sort_order ASC"
        );
        $sth->execute([':cid' => $this->companyId, ':formula_id' => $formula['id']]);
        $formula['items'] = $sth->fetchAll(PDO::FETCH_ASSOC);

        return $formula;
    }

    protected function getSkuTotalAccountColumn(): string
    {
        return '';
    }

    private function buildSkuTotalLines(array $doc, array $formula_item, float $amount, int $dept_id): array
    {
        $column = $this->getSkuTotalAccountColumn();
        if ($column === '' || !in_array($column, ['sales_account_code', 'purchase_account_code'], true)) {
            return [];
        }

        $invoice_id = (int)($doc['id'] ?? 0);
        if ($invoice_id <= 0) return [];

        $sth = $this->pdo->prepare("
            SELECT
                i.product_sku,
                i.product_name,
                i.total_price,
                COALESCE(NULLIF(p.{$column}, ''), '') AS mapped_account_code
            FROM td_invoice_item i
            LEFT JOIN md_product p
              ON p.company_id = i.company_id
             AND p.sku = i.product_sku
            WHERE i.company_id = :cid
              AND i.invoice_id = :invoice_id
            ORDER BY i.item_id ASC, i.id ASC
        ");
        $sth->execute([':cid' => $this->companyId, ':invoice_id' => $invoice_id]);
        $items = array_values(array_filter($sth->fetchAll(PDO::FETCH_ASSOC), function($row) {
            return abs((float)($row['total_price'] ?? 0)) > 0.0000001;
        }));

        if (!$items) return [];

        $base_total = array_reduce($items, function($carry, $row) {
            return $carry + abs((float)($row['total_price'] ?? 0));
        }, 0.0);
        if ($base_total <= 0) return [];

        $remaining = round($amount, 4);
        $last = count($items) - 1;
        $lines = [];

        foreach ($items as $idx => $row) {
            $line_amount = $idx === $last
                ? $remaining
                : round($amount * (abs((float)$row['total_price']) / $base_total), 4);
            $remaining = round($remaining - $line_amount, 4);
            if (abs($line_amount) <= 0.0000001) continue;

            $account_code = trim((string)($row['mapped_account_code'] ?? ''));
            if ($account_code === '') {
                $account_code = (string)$formula_item['account_code'];
            }

            $desc = trim((string)($formula_item['description'] ?? ''));
            $sku = trim((string)($row['product_sku'] ?? ''));
            $name = trim((string)($row['product_name'] ?? ''));
            $item_desc = trim($sku . ($name !== '' ? ' - ' . $name : ''));
            if ($item_desc !== '') {
                $desc = $desc !== '' ? $desc . ': ' . $item_desc : $item_desc;
            }

            $lines[] = [
                'account_code' => $account_code,
                'department_id' => $dept_id,
                'debit'        => $formula_item['drcr'] === 'D' ? $line_amount : 0.0,
                'credit'       => $formula_item['drcr'] === 'C' ? $line_amount : 0.0,
                'description'  => $desc,
            ];
        }

        return $lines;
    }
}