<?php
header('Content-Type: application/json');
require_once __DIR__ . '../../../db/config.php';

//
// ## Trial Balance Report
//
// Purpose: Prove that the double-entry system balances.
//
// ---
//
// **Rule (Absolute):** This report reads ONLY from the General Ledger (`journal_entries`, `journal_lines`, `accounts`).
// It NEVER reads from operational tables like `invoices` or `payments`.
//

$pdo = db();

try {
    // The query calculates the total debits and credits for each account from posted journal entries.
    // It also computes the final balance based on the account's normal balance.
    $sql = <<<SQL
    SELECT
        a.account_code,
        a.account_name,
        a.account_type,
        a.normal_balance,
        COALESCE(SUM(jl.debit_amount), 0) as total_debits,
        COALESCE(SUM(jl.credit_amount), 0) as total_credits,
        CASE
            WHEN a.normal_balance = 'debit' THEN COALESCE(SUM(jl.debit_amount), 0) - COALESCE(SUM(jl.credit_amount), 0)
            ELSE COALESCE(SUM(jl.credit_amount), 0) - COALESCE(SUM(jl.debit_amount), 0)
        END as balance
    FROM
        accounts a
    LEFT JOIN
        journal_lines jl ON a.account_code = jl.account_code
    LEFT JOIN
        journal_entries je ON jl.journal_entry_id = je.id AND je.status = 'posted'
    GROUP BY
        a.account_code, a.account_name, a.account_type, a.normal_balance
    ORDER BY
        a.account_code;
    SQL;

    $stmt = $pdo->prepare($sql);
    $stmt->execute();
    $report_lines = $stmt->fetchAll(PDO::FETCH_ASSOC);

    // Calculate totals for debits, credits to verify balance
    $total_debits = 0;
    $total_credits = 0;
    foreach ($report_lines as $line) {
        $total_debits += $line['total_debits'];
        $total_credits += $line['total_credits'];
    }

    echo json_encode([
        'success' => true,
        'report_name' => 'Trial Balance',
        'generated_at' => date('c'),
        'data' => $report_lines,
        'summary' => [
            'total_debits' => $total_debits,
            'total_credits' => $total_credits,
            'is_balanced' => abs($total_debits - $total_credits) < 0.0001 // Use a small tolerance for floating point comparison
        ]
    ]);

} catch (PDOException $e) {
    http_response_code(500);
    echo json_encode([
        'success' => false,
        'error' => 'Database error: ' . $e->getMessage()
    ]);
}