<?php
/**
 * Export API
 * GET ?action=pdf&survey_id=X   — Export to PDF
 * GET ?action=word&survey_id=X  — Export to Word (DOCX)
 */

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

requireLogin();

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

if (!$surveyId) {
    header('Content-Type: application/json; charset=utf-8');
    jsonResponse(['error' => 'Missing survey_id'], 400);
}

// Check access
$db = getDB();
if (!isAdmin()) {
    $stmt = $db->prepare("SELECT user_id FROM surveys WHERE id = ?");
    $stmt->execute([$surveyId]);
    $survey = $stmt->fetch();
    if (!$survey || $survey['user_id'] != $_SESSION['user_id']) {
        header('Content-Type: application/json; charset=utf-8');
        jsonResponse(['error' => 'ไม่มีสิทธิ์'], 403);
    }
}

// Get statistics data
$statsData = getStatsData($surveyId);

switch ($action) {
    case 'pdf':
        exportPDF($statsData);
        break;
    case 'word':
        exportWord($statsData);
        break;
    default:
        header('Content-Type: application/json; charset=utf-8');
        jsonResponse(['error' => 'Invalid action'], 400);
}

function getStatsData($surveyId) {
    $db = getDB();

    // Survey info
    $stmt = $db->prepare("SELECT s.*, u.full_name as creator_name FROM surveys s LEFT JOIN users u ON s.user_id = u.id WHERE s.id = ?");
    $stmt->execute([$surveyId]);
    $survey = $stmt->fetch();

    // Total responses
    $stmt = $db->prepare("SELECT COUNT(*) as total FROM survey_responses WHERE survey_id = ?");
    $stmt->execute([$surveyId]);
    $totalResponses = (int)$stmt->fetch()['total'];

    // Get sections with questions & stats
    $stmt = $db->prepare("SELECT * FROM survey_sections WHERE survey_id = ? ORDER BY section_number");
    $stmt->execute([$surveyId]);
    $sections = $stmt->fetchAll();

    foreach ($sections as &$section) {
        // Load headings
        $hStmt = $db->prepare("SELECT * FROM survey_headings WHERE section_id = ? ORDER BY order_num");
        $hStmt->execute([$section['id']]);
        $headings = $hStmt->fetchAll();

        $qStmt = $db->prepare("SELECT * FROM survey_questions WHERE section_id = ? ORDER BY order_num");
        $qStmt->execute([$section['id']]);
        $questions = $qStmt->fetchAll();

        foreach ($questions as &$q) {
            if ($q['question_type'] === 'radio' && empty($q['options'])) {
                $aStmt = $db->prepare("
                    SELECT answer_value, COUNT(*) as cnt 
                    FROM response_answers 
                    WHERE question_id = ? AND answer_value REGEXP '^[0-9]+$'
                    GROUP BY answer_value
                ");
                $aStmt->execute([$q['id']]);
                $freqData = $aStmt->fetchAll();

                $values = [];
                $freq = [];
                for ($i = 1; $i <= 5; $i++) $freq[$i] = 0;
                
                foreach ($freqData as $fd) {
                    $val = (int)$fd['answer_value'];
                    if ($val >= 1 && $val <= 5) {
                        $freq[$val] = (int)$fd['cnt'];
                        for ($j = 0; $j < (int)$fd['cnt']; $j++) $values[] = $val;
                    }
                }

                $mean = count($values) > 0 ? array_sum($values) / count($values) : 0;
                $sd = 0;
                if (count($values) > 1) {
                    $sumSq = 0;
                    foreach ($values as $v) $sumSq += pow($v - $mean, 2);
                    $sd = sqrt($sumSq / (count($values) - 1));
                }

                $q['mean'] = round($mean, 2);
                $q['sd'] = round($sd, 2);
                $q['frequencies'] = $freq;
                $q['total_answers'] = count($values);

                if ($mean >= 4.51) $q['interpretation'] = 'มากที่สุด';
                elseif ($mean >= 3.51) $q['interpretation'] = 'มาก';
                elseif ($mean >= 2.51) $q['interpretation'] = 'ปานกลาง';
                elseif ($mean >= 1.51) $q['interpretation'] = 'น้อย';
                else $q['interpretation'] = 'น้อยที่สุด';

            } elseif (in_array($q['question_type'], ['dropdown', 'checkbox', 'radio'])) {
                $aStmt = $db->prepare("SELECT answer_value, COUNT(*) as cnt FROM response_answers WHERE question_id = ? GROUP BY answer_value ORDER BY cnt DESC");
                $aStmt->execute([$q['id']]);
                $q['frequencies'] = $aStmt->fetchAll();
            }

            if ($q['question_type'] === 'text') {
                $aStmt = $db->prepare("SELECT answer_value FROM response_answers WHERE question_id = ? AND answer_value != ''");
                $aStmt->execute([$q['id']]);
                $q['text_responses'] = array_column($aStmt->fetchAll(), 'answer_value');
            }
        }
        unset($q); // Break the reference to prevent overwriting last element

        // Group questions by heading
        $looseQuestions = [];
        $headingQuestionsMap = [];
        foreach ($questions as $q) {
            if (!empty($q['heading_id'])) {
                $headingQuestionsMap[$q['heading_id']][] = $q;
            } else {
                $looseQuestions[] = $q;
            }
        }

        foreach ($headings as &$h) {
            $h['questions'] = $headingQuestionsMap[$h['id']] ?? [];
        }

        $section['headings'] = $headings;
        $section['questions'] = $looseQuestions;
    }

    return [
        'survey' => $survey,
        'total_responses' => $totalResponses,
        'sections' => $sections
    ];
}

function generateHTML($data) {
    $survey = $data['survey'];
    $totalResponses = $data['total_responses'];
    $sections = $data['sections'];

    $html = '<!DOCTYPE html><html lang="th"><head><meta charset="UTF-8">';
    $html .= '<style>
        body { font-family: "TH Sarabun New", "Sarabun", sans-serif; font-size: 16px; line-height: 1.6; }
        h1 { text-align: center; font-size: 20px; margin-bottom: 5px; }
        h2 { font-size: 18px; margin-top: 20px; border-bottom: 1px solid #333; padding-bottom: 5px; }
        table { width: 100%; border-collapse: collapse; margin: 10px 0; }
        th, td { border: 1px solid #333; padding: 6px 10px; text-align: center; font-size: 14px; }
        th { background-color: #f0f0f0; font-weight: bold; }
        td:first-child { text-align: left; }
        .info { margin: 5px 0; }
        .text-response { padding: 5px 0; border-bottom: 1px dotted #ccc; }
    </style></head><body>';
    
    $html .= '<h1>รายงานผลการประเมิน</h1>';
    $html .= '<h1>' . htmlspecialchars($survey['title']) . '</h1>';
    $html .= '<p class="info"><strong>ผู้สร้าง:</strong> ' . htmlspecialchars($survey['creator_name'] ?? '') . '</p>';
    $html .= '<p class="info"><strong>จำนวนผู้ตอบ:</strong> ' . $totalResponses . ' คน</p>';
    $html .= '<p class="info"><strong>วันที่:</strong> ' . date('d/m/Y', strtotime($survey['created_at'])) . '</p>';

    foreach ($sections as $section) {
        $cleanSectionTitle = preg_replace('/^ส่วนที่\s*[\d๑-๙]+\s*/u', '', $section['title']);
        $cleanSectionTitle = preg_replace('/^\s*[\d๑-๙]+[\.\)\s\-:\x{00A0}]*\s*/u', '', $cleanSectionTitle);
        $html .= '<h2>' . htmlspecialchars($cleanSectionTitle) . '</h2>';

        // Render headings and their questions
        if (!empty($section['headings'])) {
            foreach ($section['headings'] as $heading) {
                if (!empty($heading['questions'])) {
                    $cleanHeadingTitle = preg_replace('/^\s*[\d๑-๙]+[\.\)\s\-:\x{00A0}]*\s*/u', '', $heading['title']);
                    $html .= '<h3 style="font-size:16px; margin-top:15px; color:#2563eb; border-left:3px solid #2563eb; padding-left:8px;">' . htmlspecialchars($cleanHeadingTitle) . '</h3>';
                    if (!empty($heading['description'])) {
                        $html .= '<p style="font-size:13px; color:#666; margin:0 0 8px 11px;">' . htmlspecialchars($heading['description']) . '</p>';
                    }
                    $html .= renderQuestionsHTML($heading['questions']);
                }
            }
        }

        // Render loose questions
        if (!empty($section['questions'])) {
            $html .= renderQuestionsHTML($section['questions']);
        }
    }

    $html .= '</body></html>';
    return $html;
}

function renderQuestionsHTML($questions) {
    $html = '';

    $hasRating = false;
    foreach ($questions as $q) {
        if ($q['question_type'] === 'radio' && empty($q['options'])) { $hasRating = true; break; }
    }

    if ($hasRating) {
        $html .= '<table>';
        $html .= '<tr><th rowspan="2">รายการประเมิน</th><th colspan="5">ระดับความคิดเห็น (ความถี่)</th><th rowspan="2">X̄</th><th rowspan="2">S.D.</th><th rowspan="2">แปลผล</th></tr>';
        $html .= '<tr><th>5</th><th>4</th><th>3</th><th>2</th><th>1</th></tr>';

        $totalMean = 0;
        $totalSD = 0;
        $ratingCount = 0;

        foreach ($questions as $q) {
            if ($q['question_type'] === 'radio' && empty($q['options'])) {
                $cleanText = preg_replace('/^\s*[\d๑-๙]+[\.\)\s\-:\x{00A0}]*\s*/u', '', $q['question_text']);
                $html .= '<tr>';
                $html .= '<td>' . htmlspecialchars($cleanText) . '</td>';
                for ($i = 5; $i >= 1; $i--) {
                    $html .= '<td>' . ($q['frequencies'][$i] ?? 0) . '</td>';
                }
                $html .= '<td>' . number_format($q['mean'] ?? 0, 2) . '</td>';
                $html .= '<td>' . number_format($q['sd'] ?? 0, 2) . '</td>';
                $html .= '<td>' . ($q['interpretation'] ?? '-') . '</td>';
                $html .= '</tr>';

                $totalMean += $q['mean'] ?? 0;
                $totalSD += $q['sd'] ?? 0;
                $ratingCount++;
            }
        }

        if ($ratingCount > 0) {
            $avgMean = $totalMean / $ratingCount;
            $avgSD = $totalSD / $ratingCount;
            $avgInterp = '';
            if ($avgMean >= 4.51) $avgInterp = 'มากที่สุด';
            elseif ($avgMean >= 3.51) $avgInterp = 'มาก';
            elseif ($avgMean >= 2.51) $avgInterp = 'ปานกลาง';
            elseif ($avgMean >= 1.51) $avgInterp = 'น้อย';
            else $avgInterp = 'น้อยที่สุด';

            $html .= '<tr style="font-weight:bold;background:#f9f9f9;">';
            $html .= '<td>รวมเฉลี่ย</td><td colspan="5"></td>';
            $html .= '<td>' . number_format($avgMean, 2) . '</td>';
            $html .= '<td>' . number_format($avgSD, 2) . '</td>';
            $html .= '<td>' . $avgInterp . '</td>';
            $html .= '</tr>';
        }

        $html .= '</table>';
    }

    // Frequency tables for dropdown/checkbox/custom radio
    foreach ($questions as $q) {
        if (in_array($q['question_type'], ['dropdown', 'checkbox', 'radio']) && (!empty($q['options']) || $q['question_type'] !== 'radio')) {
            if (!empty($q['frequencies'])) {
                $cleanText = preg_replace('/^\s*[\d๑-๙]+[\.\)\s\-:\x{00A0}]*\s*/u', '', $q['question_text']);
                $html .= '<p><strong>' . htmlspecialchars($cleanText) . '</strong></p>';
                $html .= '<table><tr><th>ตัวเลือก</th><th>ความถี่</th><th>ร้อยละ</th></tr>';
                $totalQ = array_sum(array_column($q['frequencies'], 'cnt'));
                foreach ($q['frequencies'] as $f) {
                    $percent = $totalQ > 0 ? round(($f['cnt'] / $totalQ) * 100, 1) : 0;
                    $html .= '<tr><td>' . htmlspecialchars($f['answer_value']) . '</td><td>' . $f['cnt'] . '</td><td>' . $percent . '%</td></tr>';
                }
                $html .= '</table>';
            }
        }
    }

    // Text responses
    foreach ($questions as $q) {
        if ($q['question_type'] === 'text' && !empty($q['text_responses'])) {
            $cleanText = preg_replace('/^\s*[\d๑-๙]+[\.\)\s\-:\x{00A0}]*\s*/u', '', $q['question_text']);
            $html .= '<p><strong>' . htmlspecialchars($cleanText) . '</strong></p>';
            foreach ($q['text_responses'] as $i => $text) {
                $html .= '<div class="text-response">' . ($i+1) . '. ' . htmlspecialchars($text) . '</div>';
            }
        }
    }

    return $html;
}

function exportPDF($data) {
    $html = generateHTML($data);
    $title = $data['survey']['title'] ?? 'survey_report';
    $filename = 'report_' . preg_replace('/[^a-zA-Z0-9ก-๙]/u', '_', $title) . '.pdf';

    // Use simple HTML-to-PDF approach
    header('Content-Type: text/html; charset=utf-8');
    echo '<!DOCTYPE html><html><head><meta charset="UTF-8">';
    echo '<title>' . htmlspecialchars($title) . '</title>';
    echo '<style>@media print { body { -webkit-print-color-adjust: exact; } }</style>';
    echo '<script>window.onload = function() { window.print(); }</script>';
    echo '</head><body>';
    echo $html;
    echo '</body></html>';
}

function exportWord($data) {
    $html = generateHTML($data);
    $title = $data['survey']['title'] ?? 'survey_report';
    $filename = 'report_' . preg_replace('/[^a-zA-Z0-9ก-๙]/u', '_', $title) . '.doc';

    header('Content-Type: application/vnd.ms-word');
    header('Content-Disposition: attachment; filename="' . $filename . '"');
    header('Cache-Control: max-age=0');

    echo '<html xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns="http://www.w3.org/TR/REC-html40">';
    echo '<head><meta charset="UTF-8"><title>' . htmlspecialchars($title) . '</title></head>';
    echo '<body>';
    echo $html;
    echo '</body></html>';
}