<?php
require_once __DIR__ . '/../includes/uuid.php';
require_once __DIR__ . '/../db/config.php';
require_once __DIR__ . '/../includes/journal_helpers.php';
require_once __DIR__ . '/../includes/audit_helpers.php';

header('Content-Type: application/json');

if ($_SERVER['REQUEST_METHOD'] !== 'POST') {
    http_response_code(405);
    echo json_encode(['error' => 'Method not allowed']);
    exit();
}

$data = json_decode(file_get_contents('php://input'), true);

// Basic validation
if (empty($data['vendor_id']) || empty($data['bill_date']) || empty($data['due_date']) || empty($data['lines']) || !is_array($data['lines'])) {
    http_response_code(400);
    echo json_encode(['error' => 'Missing required fields: vendor_id, bill_date, due_date, and lines array.']);
    exit();
}

$pdo = db();

try {
    $pdo->beginTransaction();

    // 1. Calculate total amount and prepare journal entry lines
    $total_amount = 0;
    $journal_lines = [];
    $ap_account_code = '2100-AP'; // Accounts Payable

    foreach ($data['lines'] as $line) {
        if (empty($line['expense_account_code']) || empty($line['amount'])) {
            throw new Exception('Each bill line must have expense_account_code and amount.');
        }
        $amount = (float)$line['amount'];
        $total_amount += $amount;

        // Debit the expense account for this line
        $journal_lines[] = [
            'account_code' => $line['expense_account_code'],
            'type' => 'DEBIT',
            'amount' => $amount
        ];
    }

    // Credit Accounts Payable for the total amount
    $journal_lines[] = [
        'account_code' => $ap_account_code,
        'type' => 'CREDIT',
        'amount' => $total_amount
    ];

    // 2. Create the Journal Entry
    $journal_entry_payload = [
        'entry_date' => $data['bill_date'],
        'description' => 'Vendor bill from ' . ($data['vendor_name'] ?? $data['vendor_id']),
        'lines' => $journal_lines
    ];
    
    // Use a function to post the journal entry
    $journal_entry_result = post_journal_entry($pdo, $journal_entry_payload);
    if (empty($journal_entry_result['journal_entry_id'])) {
        throw new Exception("Failed to post journal entry: " . ($journal_entry_result['error'] ?? 'Unknown error'));
    }
    $journal_entry_id = $journal_entry_result['journal_entry_id'];

    // 3. Create the Bill
    $bill_id = uuid_v4();
    $stmt = $pdo->prepare(
        "INSERT INTO bills (bill_id, vendor_id, journal_entry_id, bill_date, due_date, total_amount, status) VALUES (?, ?, ?, ?, ?, ?, 'SUBMITTED')"
    );
    $stmt->execute([$bill_id, $data['vendor_id'], $journal_entry_id, $data['bill_date'], $data['due_date'], $total_amount]);

    // 4. Create Bill Lines
    $stmt_lines = $pdo->prepare(
        "INSERT INTO bill_lines (bill_line_id, bill_id, expense_account_code, description, amount) VALUES (?, ?, ?, ?, ?)"
    );
    foreach ($data['lines'] as $line) {
        $stmt_lines->execute([uuid_v4(), $bill_id, $line['expense_account_code'], $line['description'] ?? null, $line['amount']]);
    }

    // Log audit trail
    log_audit_trail($pdo, 'create_bill', ['bill_id' => $bill_id, 'vendor_id' => $data['vendor_id'], 'total_amount' => $total_amount]);

    $pdo->commit();

    // 5. Fetch and return the created bill
    $stmt = $pdo->prepare("SELECT * FROM bills WHERE bill_id = ?");
    $stmt->execute([$bill_id]);
    $new_bill = $stmt->fetch(PDO::FETCH_ASSOC);

    http_response_code(201);
    echo json_encode($new_bill);

} catch (Exception $e) {
    $pdo->rollBack();
    http_response_code(500);
    echo json_encode(['error' => 'Operation failed: ' . $e->getMessage()]);
}