<?php
require_once __DIR__ . '/db/config.php';

// --- DATA FETCHING & CALCULATION ---
$project = null;
$project_id = $_GET['project_id'] ?? null;
$financial_data = [];
$months = [];
$metrics = ["Opening Balance", "Billings", "WIP", "Expenses", "Cost", "NSR", "Margin"];

if (!$project_id) {
    header("HTTP/1.0 400 Bad Request");
    echo "Project ID is required.";
    exit;
}

try {
    $pdo = db();
    $stmt = $pdo->prepare("SELECT * FROM projects WHERE id = :id");
    $stmt->execute([':id' => $project_id]);
    $project = $stmt->fetch(PDO::FETCH_ASSOC);

    if ($project) {
        function get_month_range($start_date_str, $end_date_str) {
            $months = [];
            if (empty($start_date_str) || empty($end_date_str)) return $months;
            $start = new DateTime($start_date_str);
            $end = new DateTime($end_date_str);
            $current = clone $start;
            $current->modify('first day of this month');
            while ($current <= $end) {
                $months[] = $current->format('Y-m-01');
                $current->modify('+1 month');
            }
            return $months;
        }
        $months = get_month_range($project['startDate'], $project['endDate']);

        foreach ($metrics as $metric) {
            foreach ($months as $month) {
                $financial_data[$metric][$month] = 0;
            }
        }

        $forecast_stmt = $pdo->prepare("SELECT id FROM forecasting WHERE projectId = :pid ORDER BY versionNumber DESC LIMIT 1");
        $forecast_stmt->execute([':pid' => $project_id]);
        $latest_forecast = $forecast_stmt->fetch(PDO::FETCH_ASSOC);

        if ($latest_forecast) {
            $cost_sql = "
                SELECT fa.month, SUM(fa.allocatedDays * r.totalMonthlyCost) as totalCost
                FROM forecastAllocation fa
                JOIN roster r ON fa.rosterId = r.id
                WHERE fa.forecastingId = :fid
                GROUP BY fa.month
            ";
            $cost_stmt = $pdo->prepare($cost_sql);
            $cost_stmt->execute([':fid' => $latest_forecast['id']]);
            $monthly_costs = $cost_stmt->fetchAll(PDO::FETCH_KEY_PAIR);

            foreach ($monthly_costs as $month => $cost) {
                $formatted_month = date('Y-m-01', strtotime($month));
                if (isset($financial_data['Cost'][$formatted_month])) {
                    $financial_data['Cost'][$formatted_month] = $cost;
                }
            }
        }
    }
} catch (PDOException $e) {
    header("HTTP/1.0 500 Internal Server Error");
    echo "Database error: " . $e->getMessage();
    exit;
}

if (!$project) {
    header("HTTP/1.0 404 Not Found");
    echo "Project not found.";
    exit;
}

// --- CSV EXPORT ---
$filename = "project_finance_" . preg_replace('/[^a-zA-Z0-9_]/', '_', $project['name']) . ".csv";

header('Content-Type: text/csv');
header('Content-Disposition: attachment; filename="' . $filename . '"');

$output = fopen('php://output', 'w');

// Header row
$header = ['Metric'];
foreach ($months as $month) {
    $header[] = date('M Y', strtotime($month));
}
fputcsv($output, $header);

// Data rows
foreach ($metrics as $metric) {
    $row = [$metric];
    foreach ($months as $month) {
        $row[] = number_format($financial_data[$metric][$month] ?? 0, 2);
    }
    fputcsv($output, $row);
}

fclose($output);
exit;