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

// --- DATABASE MIGRATION ---
function execute_sql_from_file($pdo, $filepath) {
    try {
        $sql = file_get_contents($filepath);
        if ($sql === false) return false;
        $pdo->exec($sql);
        return true;
    } catch (PDOException $e) {
        // Ignore errors about tables/columns that already exist
        if (strpos($e->getMessage(), 'already exists') === false && strpos($e->getMessage(), 'Duplicate column name') === false) {
            error_log("SQL Execution Error in $filepath: " . $e->getMessage());
        }
        return false;
    }
}

try {
    $pdo = db();
    $migration_files = glob(__DIR__ . '/db/migrations/*.sql');
    sort($migration_files);
    foreach ($migration_files as $file) {
        execute_sql_from_file($pdo, $file);
    }
} catch (PDOException $e) {
    $db_error = "Database connection failed: " . $e->getMessage();
    // Stop execution if DB connection fails
    die($db_error);
}

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

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

    if ($project) {
        // Helper to generate month range
        function get_month_range($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']);

        // Initialize financial data structure
        foreach ($metrics as $metric) {
            foreach ($months as $month) {
                $financial_data[$metric][$month] = 0;
            }
        }

        // --- Financial Calculations ---

        // 1. Fetch base monthly data
        $monthly_costs = [];
        $monthly_wip = [];

        $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) {
            $fid = $latest_forecast['id'];
            
            // Base Monthly Cost
            $cost_sql = "SELECT fa.month, SUM(fa.allocatedDays * (r.totalMonthlyCost / 20)) as cost 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' => $fid]);
            $monthly_costs = $cost_stmt->fetchAll(PDO::FETCH_KEY_PAIR);

            // Base Monthly WIP
            $wip_sql = "SELECT fa.month, SUM(fa.allocatedDays * r.discountedRevenue) as wip FROM forecastAllocation fa JOIN roster r ON fa.rosterId = r.id WHERE fa.forecastingId = :fid GROUP BY fa.month";
            $wip_stmt = $pdo->prepare($wip_sql);
            $wip_stmt->execute([':fid' => $fid]);
            $monthly_wip = $wip_stmt->fetchAll(PDO::FETCH_KEY_PAIR);
        }

        // Base Monthly Billings
        $billing_stmt = $pdo->prepare("SELECT month, amount FROM billingMonthly WHERE projectId = :pid");
        $billing_stmt->execute([':pid' => $project_id]);
        $monthly_billing = $billing_stmt->fetchAll(PDO::FETCH_KEY_PAIR);

        // Base Monthly Expenses
        $expenses_stmt = $pdo->prepare("SELECT month, amount FROM expensesMonthly WHERE projectId = :pid");
        $expenses_stmt->execute([':pid' => $project_id]);
        $monthly_expenses = $expenses_stmt->fetchAll(PDO::FETCH_KEY_PAIR);

        // 2. Calculate cumulative values month by month
        $cumulative_billing = 0;
        $cumulative_cost = 0;
        $cumulative_expenses = 0;
        $previous_month_wip = 0;

        foreach ($months as $month) {
            // Normalize month keys from fetched data
            $cost = $monthly_costs[$month] ?? 0;
            $base_monthly_wip = $monthly_wip[$month] ?? 0;
            $billing = $monthly_billing[$month] ?? 0;
            $expenses = $monthly_expenses[$month] ?? 0;

            // Cumulative calculations
            $cumulative_billing += $billing;
            $cumulative_cost += $cost;
            $cumulative_expenses += $expenses;

            // WIP Calculation (new formula)
            // current month WIP = previous month WIP + Month Expenses + base_monthly_wip - month Billing
            $current_wip = $previous_month_wip + $expenses + $base_monthly_wip - $billing;

            $financial_data['WIP'][$month] = $current_wip;
            $financial_data['Billings'][$month] = $cumulative_billing;
            $financial_data['Cost'][$month] = $cumulative_cost;
            $financial_data['Opening Balance'][$month] = 0; // Placeholder
            $financial_data['Expenses'][$month] = $cumulative_expenses;

            // Calculated metrics (NSR and Margin)
            $nsr = $financial_data['WIP'][$month] + $financial_data['Billings'][$month] - $financial_data['Opening Balance'][$month] - $financial_data['Expenses'][$month];
            $financial_data['NSR'][$month] = $nsr;

            $margin = ($nsr != 0) ? (($nsr - $financial_data['Cost'][$month]) / $nsr) : 0;
            $financial_data['Margin'][$month] = $margin;

            // Update previous month's WIP for the next iteration
            $previous_month_wip = $current_wip;
        }

        // 3. Fetch and apply overridden data
        $override_stmt = $pdo->prepare("SELECT month, MAX(CASE WHEN metricName = 'wip' THEN value ELSE 0 END) as wip, MAX(CASE WHEN metricName = 'opening_balance' THEN value ELSE 0 END) as opening_balance, MAX(CASE WHEN metricName = 'billing' THEN value ELSE 0 END) as billing, MAX(CASE WHEN metricName = 'expenses' THEN value ELSE 0 END) as expenses FROM projectFinanceMonthly WHERE projectId = :pid AND is_overridden = 1 GROUP BY month");
        $override_stmt->execute([':pid' => $project_id]);

        while ($row = $override_stmt->fetch(PDO::FETCH_ASSOC)) {
            $month = $row['month'];
            if (in_array($month, $months)) {
                $financial_data['WIP'][$month] = $row['wip'];
                $financial_data['Opening Balance'][$month] = $row['opening_balance'];
                $financial_data['Billings'][$month] = $row['billing'];
                $financial_data['Expenses'][$month] = $row['expenses'];
            }
        }

        // 4. Recalculate dependent metrics (NSR and Margin) after override
        foreach ($months as $month) {
            $nsr = $financial_data['WIP'][$month] + $financial_data['Billings'][$month] - $financial_data['Opening Balance'][$month] - $financial_data['Expenses'][$month];
            $financial_data['NSR'][$month] = $nsr;

            $margin = ($nsr != 0) ? (($nsr - $financial_data['Cost'][$month]) / $nsr) : 0;
            $financial_data['Margin'][$month] = $margin;
        }
    }
}

// --- PAGE RENDER ---
if (!$project) {
    http_response_code(404);
    $page_title = "Project Not Found";
} else {
    $page_title = "Details for " . htmlspecialchars($project['name']);
}

?>
<!DOCTYPE html>
<html lang="en" data-bs-theme="dark">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title><?php echo $page_title; ?></title>
    <link href="https://cdn.jsdelivr.net/npm/bootstrap@5.3.2/dist/css/bootstrap.min.css" rel="stylesheet">
    <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/bootstrap-icons@1.11.3/font/bootstrap-icons.min.css">
    <link href="https://fonts.googleapis.com/css2?family=Inter:wght@400;500;600;700&display=swap" rel="stylesheet">
    <link rel="stylesheet" href="assets/css/custom.css?v=<?php echo time(); ?>">
</head>
<body>
    <div class="top-navbar">
        Project Financials
    </div>
    <div class="main-wrapper">
        <nav class="sidebar">
            <ul class="nav flex-column">
                <li class="nav-item"><a class="nav-link" href="roster.php"><i class="bi bi-people-fill me-2"></i>Roster</a></li>
                <li class="nav-item"><a class="nav-link active" href="projects.php"><i class="bi bi-briefcase-fill me-2"></i>Projects</a></li>
            </ul>
        </nav>

        <main class="content-wrapper">
            <?php if (!$project): ?>
                <div class="alert alert-danger">Project with ID <?php echo htmlspecialchars($project_id); ?> not found.</div>
            <?php else: ?>
                <div class="page-header">
                    <h1 class="h2">Project: <?php echo htmlspecialchars($project['name']); ?></h1>
                    <div class="header-actions">
                        <a href="billing.php?id=<?php echo $project['id']; ?>" class="btn btn-primary"><i class="bi bi-credit-card-fill me-2"></i>Billing</a>
                        <a href="expenses.php?id=<?php echo $project['id']; ?>" class="btn btn-danger me-2"><i class="bi bi-wallet-fill me-2"></i>Expenses</a>
                                                <a href="forecasting.php?projectId=<?php echo $project['id']; ?>" class="btn btn-success"><i class="bi bi-bar-chart-line-fill me-2"></i>Forecasting</a>
                        <a href="project_finance_details.php?id=<?php echo $project['id']; ?>" class="btn btn-info"><i class="bi bi-eye-fill me-2"></i>View Data</a>
                    </div>
                </div>

                <!-- Section 1: Project Information -->
                <div class="card mb-4">
                    <div class="card-header">
                        <h5 class="card-title mb-0">Project Information</h5>
                    </div>
                    <div class="card-body">
                        <div class="row">
                            <div class="col-md-6">
                                <dl class="row">
                                    <dt class="col-sm-4">Name</dt>
                                    <dd class="col-sm-8"><?php echo htmlspecialchars($project['name']); ?></dd>
                                    <dt class="col-sm-4">WBS</dt>
                                    <dd class="col-sm-8"><?php echo htmlspecialchars($project['wbs'] ?? 'N/A'); ?></dd>
                                    <dt class="col-sm-4">Start Date</dt>
                                    <dd class="col-sm-8"><?php echo htmlspecialchars($project['startDate']); ?></dd>
                                    <dt class="col-sm-4">End Date</dt>
                                    <dd class="col-sm-8"><?php echo htmlspecialchars($project['endDate']); ?></dd>
                                </dl>
                            </div>
                            <div class="col-md-6">
                                <dl class="row">
                                    <dt class="col-sm-4">Budget</dt>
                                    <dd class="col-sm-8">&euro;<?php echo number_format($project['budget'], 2); ?></dd>
                                    <dt class="col-sm-4">Recoverability</dt>
                                    <dd class="col-sm-8"><?php echo number_format($project['recoverability'], 2); ?>%</dd>
                                    <dt class="col-sm-4">Target Margin</dt>
                                    <dd class="col-sm-8"><?php echo number_format($project['targetMargin'], 2); ?>%</dd>
                                </dl>
                            </div>
                        </div>
                    </div>
                </div>

                <!-- Section 2: Monthly Financials -->
                <div class="card mb-4">
                    <div class="card-header d-flex justify-content-between align-items-center">
                        <h5 class="card-title mb-0">Monthly Financials</h5>
                        <div class="actions">
                            <button class="btn btn-secondary disabled" disabled><i class="bi bi-upload me-2"></i>Import</button>
                            <a href="export_project_finance.php?project_id=<?php echo $project['id']; ?>" class="btn btn-secondary"><i class="bi bi-download me-2"></i>Export</a>
                        </div>
                    </div>
                    <div class="table-responsive">
                        <table class="table table-bordered table-hover">
                            <thead>
                                <tr class="text-center">
                                    <th class="bg-body-tertiary" style="min-width: 150px;">Metric</th>
                                    <?php 
                                    $is_first_month = true;
                                    foreach ($months as $month): ?>
                                        <th>
                                            <?php echo date('M Y', strtotime($month)); ?>
                                            <?php if ($is_first_month): ?>
                                                <button id="override-btn" class="btn btn-warning btn-sm mt-1" data-project-id="<?php echo $project_id; ?>" data-month="<?php echo $month; ?>">Override</button>
                                            <?php endif; ?>
                                        </th>
                                    <?php 
                                        $is_first_month = false;
                                    endforeach; ?>
                                </tr>
                            </thead>
                            <tbody>
                                <?php 
                                $editable_metrics = ['WIP', 'Opening Balance', 'Billings', 'Expenses'];
                                foreach ($metrics as $metric): ?>
                                <tr>
                                    <td class="fw-bold bg-body-tertiary"><?php echo $metric; ?></td>
                                    <?php 
                                    $is_first_month_for_body = true;
                                    foreach ($months as $month): 
                                        $cell_id = '';
                                        if ($is_first_month_for_body && in_array($metric, $editable_metrics)) {
                                            $cell_id = 'id="' . str_replace(' ', '-', strtolower($metric)) . '-' . $month . '"';
                                        }
                                    ?>
                                        <td class="text-end" <?php echo $cell_id; ?>>
                                            <?php 
                                                if ($metric === 'Margin') {
                                                    echo number_format(($financial_data[$metric][$month] ?? 0) * 100, 2) . '%';
                                                } else {
                                                    echo '&euro;' . number_format($financial_data[$metric][$month] ?? 0, 2);
                                                }
                                            ?>
                                        </td>
                                    <?php 
                                        $is_first_month_for_body = false;
                                    endforeach; ?>
                                </tr>
                                <?php endforeach; ?>
                            </tbody>
                        </table>
                    </div>
                </div>

            <?php endif; ?>
        </main>
    </div>

<script src="https://cdn.jsdelivr.net/npm/bootstrap@5.3.2/dist/js/bootstrap.bundle.min.js"></script>
<script src="assets/js/project_details.js?v=<?php echo time(); ?>"></script>
</body>
</html>