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

//
// ## Balance Sheet Report
//
// Purpose: Show financial position (Assets = Liabilities + Equity) at a specific date.
//
// ---
//
// **Rule (Absolute):** Reads ONLY from `accounts` and `journal_lines` for posted entries.
// It includes retained earnings (net income from prior periods).
//

$pdo = db();

$as_of_date = $_GET['as_of_date'] ?? date('Y-m-d');

try {
    // --- 1. Calculate Net Income (Retained Earnings) ---
    // This is the sum of all revenue and expense accounts from the beginning of time up to the report date.
    $retained_earnings_sql = <<<SQL
    SELECT
        SUM(CASE
            WHEN a.account_type = 'revenue' THEN (jl.credit_amount - jl.debit_amount)
            WHEN a.account_type = 'expense' THEN (jl.debit_amount - jl.credit_amount)
            ELSE 0
        END) as net_income
    FROM journal_lines jl
    JOIN accounts a ON jl.account_code = a.account_code
    JOIN journal_entries je ON jl.journal_entry_id = je.id
    WHERE je.status = 'posted' AND a.account_type IN ('revenue', 'expense') AND je.entry_date <= :as_of_date;
    SQL;

    $stmt_re = $pdo->prepare($retained_earnings_sql);
    $stmt_re->execute([':as_of_date' => $as_of_date]);
    $retained_earnings = $stmt_re->fetchColumn() ?: 0;

    // --- 2. Get Balances for Asset, Liability, and Equity Accounts ---
    $main_sql = <<<SQL
    SELECT
        a.account_code,
        a.account_name,
        a.account_type,
        a.normal_balance,
        SUM(CASE
            WHEN a.normal_balance = 'debit' THEN jl.debit_amount - jl.credit_amount
            ELSE jl.credit_amount - jl.debit_amount
        END) as balance
    FROM accounts a
    JOIN journal_lines jl ON a.account_code = jl.account_code
    JOIN journal_entries je ON jl.journal_entry_id = je.id
    WHERE
        je.status = 'posted'
        AND a.account_type IN ('asset', 'liability', 'equity')
        AND je.entry_date <= :as_of_date
    GROUP BY a.account_code, a.account_name, a.account_type, a.normal_balance
    HAVING balance != 0
    ORDER BY a.account_type, a.account_code;
    SQL;

    $stmt_main = $pdo->prepare($main_sql);
    $stmt_main->execute([':as_of_date' => $as_of_date]);
    $report_lines = $stmt_main->fetchAll(PDO::FETCH_ASSOC);

    // --- 3. Structure the report and calculate totals ---
    $assets_total = 0;
    $liabilities_total = 0;
    $equity_total = 0;
    $assets = [];
    $liabilities = [];
    $equity = [];

    foreach ($report_lines as $line) {
        switch ($line['account_type']) {
            case 'asset':
                $assets[] = $line;
                $assets_total += $line['balance'];
                break;
            case 'liability':
                $liabilities[] = $line;
                $liabilities_total += $line['balance'];
                break;
            case 'equity':
                $equity[] = $line;
                $equity_total += $line['balance'];
                break;
        }
    }
    
    // Add retained earnings to equity section
    $equity_total += $retained_earnings;
    $total_liabilities_and_equity = $liabilities_total + $equity_total;

    echo json_encode([
        'success' => true,
        'report_name' => 'Balance Sheet',
        'generated_at' => date('c'),
        'filters' => ['as_of_date' => $as_of_date],
        'data' => [
            'assets' => $assets,
            'liabilities' => $liabilities,
            'equity' => array_merge($equity, [[
                'account_code' => '3999',
                'account_name' => 'Retained Earnings',
                'account_type' => 'equity',
                'balance' => $retained_earnings
            ]])
        ],
        'summary' => [
            'total_assets' => $assets_total,
            'total_liabilities' => $liabilities_total,
            'total_equity' => $equity_total,
            'total_liabilities_and_equity' => $total_liabilities_and_equity,
            'is_balanced' => abs($assets_total - $total_liabilities_and_equity) < 0.0001
        ]
    ]);

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