<?php
/**
 * Import Responses API (from CSV / Excel exported from Google Forms)
 * POST ?survey_id=X
 */

require_once __DIR__ . '/../config/database.php';
require_once __DIR__ . '/../config/auth.php';

header('Content-Type: application/json; charset=utf-8');
requireLogin();

$surveyId = (int)($_GET['survey_id'] ?? $_POST['survey_id'] ?? 0);

if (!$surveyId) {
    jsonResponse(['error' => 'Missing survey_id'], 400);
}

$db = getDB();

// Verify access
if (!isAdmin()) {
    $stmt = $db->prepare("SELECT user_id FROM surveys WHERE id = ?");
    $stmt->execute([$surveyId]);
    $s = $stmt->fetch();
    if (!$s || $s['user_id'] != $_SESSION['user_id']) {
        jsonResponse(['error' => 'ไม่มีสิทธิ์เข้าถึงแบบสอบถามนี้'], 403);
    }
}

// Check uploaded file
if (!isset($_FILES['csv_file']) || $_FILES['csv_file']['error'] !== UPLOAD_ERR_OK) {
    jsonResponse(['error' => 'กรุณาอัปโหลดไฟล์ CSV คำตอบจาก Google Forms'], 400);
}

$filePath = $_FILES['csv_file']['tmp_name'];

// Read CSV
$handle = fopen($filePath, 'r');
if (!$handle) {
    jsonResponse(['error' => 'ไม่สามารถเปิดไฟล์ CSV ได้'], 500);
}

// Check UTF-8 BOM or UTF-16
$bom = fread($handle, 3);
if ($bom !== "\xEF\xBB\xBF") {
    rewind($handle);
}

// Get Headers (Row 1)
$headers = fgetcsv($handle, 0, ",");
if (!$headers) {
    fclose($handle);
    jsonResponse(['error' => 'ไฟล์ CSV ไม่มีข้อมูลหรือรูปแบบไม่ถูกต้อง'], 400);
}

// Clean headers
$cleanHeaders = array_map(function($h) {
    return trim(preg_replace('/\s+/', ' ', $h));
}, $headers);

// Fetch all questions for this survey
$stmt = $db->prepare("
    SELECT q.id, q.question_text, q.question_type 
    FROM survey_questions q
    JOIN survey_sections s ON q.section_id = s.id
    WHERE s.survey_id = ?
    ORDER BY s.section_number, q.order_num
");
$stmt->execute([$surveyId]);
$questions = $stmt->fetchAll();

if (empty($questions)) {
    fclose($handle);
    jsonResponse(['error' => 'ไม่พบข้อคำถามในแบบสอบถามนี้'], 400);
}

// Map CSV Column Index -> question_id
$colToQuestionMap = [];

function normalizeText($str) {
    $str = mb_strtolower($str, 'UTF-8');
    // Remove leading numbers or prefix like "1. ", "ข้อ 1. "
    $str = preg_replace('/^[\d๑-๙]+[\.\)\s\-:\x{00A0}]*/u', '', $str);
    return trim($str);
}

foreach ($cleanHeaders as $colIdx => $headerText) {
    if (empty($headerText) || strtolower($headerText) === 'timestamp' || strtolower($headerText) === 'ประทับเวลา') {
        continue;
    }

    $normHeader = normalizeText($headerText);

    // Try exact or normalized matching against survey questions
    foreach ($questions as $q) {
        $normQText = normalizeText($q['question_text']);

        if ($normHeader === $normQText || strpos($normHeader, $normQText) !== false || strpos($normQText, $normHeader) !== false) {
            $colToQuestionMap[$colIdx] = $q['id'];
            break;
        }
    }
}

// Fallback: If column mapping count is low, map columns sequentially to questions
if (count($colToQuestionMap) === 0) {
    $qIdx = 0;
    foreach ($cleanHeaders as $colIdx => $headerText) {
        if (strtolower($headerText) === 'timestamp' || strtolower($headerText) === 'ประทับเวลา') continue;
        if (isset($questions[$qIdx])) {
            $colToQuestionMap[$colIdx] = $questions[$qIdx]['id'];
            $qIdx++;
        }
    }
}

// Process Rows
$importedCount = 0;

$db->beginTransaction();
try {
    while (($row = fgetcsv($handle, 0, ",")) !== false) {
        if (empty(array_filter($row))) continue; // Skip empty lines

        // Extract timestamp or use now
        $submittedAt = date('Y-m-d H:i:s');
        if (!empty($row[0])) {
            $ts = strtotime($row[0]);
            if ($ts !== false) {
                $submittedAt = date('Y-m-d H:i:s', $ts);
            }
        }

        // Insert into survey_responses
        $stmtResp = $db->prepare("INSERT INTO survey_responses (survey_id, respondent_info, submitted_at) VALUES (?, ?, ?)");
        $stmtResp->execute([
            $surveyId,
            json_encode(['imported' => true, 'source' => 'google_forms_csv'], JSON_UNESCAPED_UNICODE),
            $submittedAt
        ]);
        $responseId = $db->lastInsertId();

        // Insert answers
        foreach ($colToQuestionMap as $colIdx => $qId) {
            $val = isset($row[$colIdx]) ? trim($row[$colIdx]) : '';
            if ($val !== '') {
                $stmtAns = $db->prepare("INSERT INTO response_answers (response_id, question_id, answer_value) VALUES (?, ?, ?)");
                $stmtAns->execute([$responseId, $qId, $val]);
            }
        }

        $importedCount++;
    }

    $db->commit();
    fclose($handle);

    jsonResponse([
        'success' => true,
        'message' => "นำเข้าข้อมูลคำตอบสำเร็จจำนวน $importedCount รายการ",
        'imported_count' => $importedCount,
        'mapped_questions' => count($colToQuestionMap)
    ]);
} catch (Exception $e) {
    $db->rollBack();
    fclose($handle);
    jsonResponse(['error' => 'เกิดข้อผิดพลาดในการบันทึกคำตอบ: ' . $e->getMessage()], 500);
}