<?php
/**
 * Import Survey from PDF API
 * POST ?action=parsePdf       - Upload and parse PDF file to survey JSON
 * POST ?action=confirmImport  - Save parsed survey JSON into database
 */

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

use Smalot\PdfParser\Parser;

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

if (php_sapi_name() !== 'cli') {
    requireLogin();
}

if (isset($_GET['action'])) {
    $action = $_GET['action'] ?? '';
    switch ($action) {
        case 'parsePdf':
            parsePdf();
            break;
        case 'confirmImport':
            confirmImport();
            break;
        default:
            jsonResponse(['error' => 'Invalid action'], 400);
    }
}

/**
 * Handle PDF upload and extraction
 */
function parsePdf() {
    if (!isset($_FILES['pdf_file']) || $_FILES['pdf_file']['error'] !== UPLOAD_ERR_OK) {
        $errorMsg = 'กรุณาเลือกไฟล์ PDF';
        if (isset($_FILES['pdf_file']['error'])) {
            switch ($_FILES['pdf_file']['error']) {
                case UPLOAD_ERR_INI_SIZE:
                case UPLOAD_ERR_FORM_SIZE:
                    $errorMsg = 'ขนาดไฟล์ใหญ่เกินขีดจำกัดของเซิร์ฟเวอร์';
                    break;
                case UPLOAD_ERR_NO_FILE:
                    $errorMsg = 'ไม่มีไฟล์ถูกอัปโหลด';
                    break;
            }
        }
        jsonResponse(['error' => $errorMsg], 400);
    }

    $file = $_FILES['pdf_file'];
    $ext = strtolower(pathinfo($file['name'], PATHINFO_EXTENSION));
    if ($ext !== 'pdf') {
        jsonResponse(['error' => 'รองรับเฉพาะไฟล์เอกสาร PDF เท่านั้น'], 400);
    }

    $tmpPath = $file['tmp_name'];

    try {
        $parser = new Parser();
        $pdf = $parser->parseFile($tmpPath);
        $rawText = $pdf->getText();
    } catch (\Throwable $e) {
        jsonResponse(['error' => 'ไม่สามารถอ่านไฟล์ PDF ได้: ' . $e->getMessage()], 500);
    }

    $rawText = trim($rawText);
    if (empty($rawText)) {
        jsonResponse(['error' => 'ไม่พบข้อความในไฟล์ PDF (อาจเป็นไฟล์สแกนรูปภาพล้วนที่ไม่มี Text Layer)'], 400);
    }

    // Parse structured survey from raw text
    $parsedSurvey = parseThaiSurveyText($rawText, pathinfo($file['name'], PATHINFO_FILENAME));

    jsonResponse([
        'success' => true,
        'message' => 'อ่านและวิเคราะห์โครงสร้างแบบประเมินจาก PDF สำเร็จ',
        'raw_text_preview' => mb_substr($rawText, 0, 500, 'UTF-8') . '...',
        'survey' => $parsedSurvey
    ]);
}

/**
 * Save finalized survey to DB
 */
function confirmImport() {
    $input = json_decode(file_get_contents('php://input'), true);
    $projectId = !empty($input['project_id']) ? (int)$input['project_id'] : null;
    $surveyData = $input['survey_data'] ?? null;

    if (!$surveyData || empty($surveyData['title'])) {
        jsonResponse(['error' => 'ข้อมูลแบบประเมินไม่ถูกต้อง หรือไม่มีชื่อแบบประเมิน'], 400);
    }

    $db = getDB();
    $uniqueLink = bin2hex(random_bytes(16));

    $db->beginTransaction();
    try {
        $stmt = $db->prepare("INSERT INTO surveys (user_id, project_id, title, description, unique_link, status) VALUES (?, ?, ?, ?, ?, 'active')");
        $stmt->execute([
            $_SESSION['user_id'] ?? 1,
            $projectId,
            $surveyData['title'],
            $surveyData['description'] ?? '',
            $uniqueLink
        ]);
        $surveyId = $db->lastInsertId();

        $sections = $surveyData['sections'] ?? [];
        $secNum = 1;

        foreach ($sections as $sec) {
            $stmt = $db->prepare("INSERT INTO survey_sections (survey_id, section_number, title, description, category) VALUES (?, ?, ?, ?, ?)");
            $secCategory = $sec['category'] ?? 'rating';
            $stmt->execute([
                $surveyId,
                $secNum,
                $sec['title'] ?? ('ตอนที่ ' . $secNum),
                $sec['description'] ?? '',
                $secCategory
            ]);
            $sectionId = $db->lastInsertId();

            $orderNum = 1;

            // Direct questions in this section
            if (!empty($sec['questions'])) {
                foreach ($sec['questions'] as $q) {
                    insertQuestionRecord($db, $sectionId, null, $q, $orderNum++);
                }
            }

            // Headings with sub-questions (e.g. ด้านวิทยากร, ด้านสถานที่)
            if (!empty($sec['headings'])) {
                $headingOrder = 1;
                foreach ($sec['headings'] as $h) {
                    $stmtH = $db->prepare("INSERT INTO survey_headings (section_id, title, description, order_num) VALUES (?, ?, ?, ?)");
                    $stmtH->execute([
                        $sectionId,
                        $h['title'] ?? ('ด้านที่ ' . $headingOrder),
                        $h['description'] ?? '',
                        $headingOrder++
                    ]);
                    $headingId = $db->lastInsertId();

                    if (!empty($h['questions'])) {
                        foreach ($h['questions'] as $hq) {
                            insertQuestionRecord($db, $sectionId, $headingId, $hq, $orderNum++);
                        }
                    }
                }
            }

            $secNum++;
        }

        $db->commit();

        jsonResponse([
            'success' => true,
            'message' => 'สร้างแบบประเมินจาก PDF เรียบร้อยแล้ว',
            'survey_id' => $surveyId,
            'unique_link' => $uniqueLink,
            'title' => $surveyData['title']
        ]);
    } catch (\Throwable $e) {
        $db->rollBack();
        jsonResponse(['error' => 'บันทึกข้อมูลไม่สำเร็จ: ' . $e->getMessage()], 500);
    }
}

function insertQuestionRecord($db, $sectionId, $headingId, $q, $orderNum) {
    $qText = trim($q['question_text'] ?? '');
    if (empty($qText)) return;

    $qType = $q['question_type'] ?? 'radio';
    $isRequired = isset($q['is_required']) ? (int)$q['is_required'] : 1;
    $options = !empty($q['options']) && is_array($q['options']) ? json_encode(array_values($q['options']), JSON_UNESCAPED_UNICODE) : null;
    $scaleMin = $q['scale_min'] ?? 1;
    $scaleMax = $q['scale_max'] ?? 5;
    $desc = $q['description'] ?? '';

    $stmt = $db->prepare("INSERT INTO survey_questions (section_id, heading_id, question_text, question_type, is_required, order_num, options, scale_min, scale_max, description) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?)");
    $stmt->execute([
        $sectionId,
        $headingId,
        $qText,
        $qType,
        $isRequired,
        $orderNum,
        $options,
        $scaleMin,
        $scaleMax,
        $desc
    ]);
}

/**
 * Intelligent Thai Survey Pattern Parser
 */
function parseThaiSurveyText($text, $defaultTitle = 'แบบประเมินความพึงพอใจ') {
    // 1. Normalize line endings and whitespace
    $text = str_replace(["\r\n", "\r"], "\n", $text);
    
    // Replace special unicode bullets/boxes with standard marks
    $text = preg_replace('/[\x{25A0}\x{25A1}\x{25CB}\x{25CF}\x{2610}\x{2611}\x{274F}\x{25EF}]/u', '[ ]', $text);
    
    $rawLines = explode("\n", $text);
    $lines = [];
    foreach ($rawLines as $line) {
        $trimmed = trim($line);
        if ($trimmed !== '') {
            $lines[] = $trimmed;
        }
    }

    // 2. Extract Document Title and Description
    $title = '';
    $description = '';
    $startIndex = 0;
    $titleLines = [];

    // Filter out standard scale headers/garbage lines like "5 4 3 2 1", "มากที่สุด มาก ปานกลาง..."
    $ignoredPatterns = [
        '/^ระดับความพึงพอใจ/u',
        '/^ระดับความคิดเห็น/u',
        '/^เกณฑ์การประเมิน/u',
        '/^5\s+4\s+3\s+2\s+1/u',
        '/^หมายเหตุ\s*:/u',
        '/^หน้า\s*\d+/u',
        '/^page\s*\d+/i'
    ];

    for ($i = 0; $i < min(8, count($lines)); $i++) {
        $line = $lines[$i];
        
        // If we hit "ตอนที่" or "ส่วนที่" or "คำชี้แจง", stop title accumulation
        if (preg_match('/^(ตอนที่|ส่วนที่|คำชี้แจง|คำอธิบาย|ข้อชี้แจง)/u', $line)) {
            $startIndex = $i;
            break;
        }

        if (preg_match('/(แบบประเมิน|แบบสอบถาม|โครงการ|การอบรม|รายงานการประเมิน|แบบสำรวจ)/u', $line)) {
            $titleLines[] = $line;
            $startIndex = $i + 1;
        } elseif (empty($titleLines) && $i === 0) {
            $titleLines[] = $line;
            $startIndex = 1;
        }
    }

    $title = !empty($titleLines) ? implode(' ', $titleLines) : ($defaultTitle ?: 'แบบประเมินความพึงพอใจ');

    // 3. Scan for "คำชี้แจง" (Description)
    for ($i = $startIndex; $i < min($startIndex + 6, count($lines)); $i++) {
        $line = $lines[$i];
        if (preg_match('/^(คำชี้แจง|คำอธิบาย|ข้อชี้แจง)[\s\:\.\-–]*(.*)/u', $line, $m)) {
            $description = trim($m[2]);
            if (empty($description) && isset($lines[$i + 1])) {
                $description = $lines[$i + 1];
                $startIndex = $i + 2;
            } else {
                $startIndex = $i + 1;
            }
            break;
        }
    }

    // 4. Partition lines into Sections
    $sections = [];
    $currentSection = null;

    for ($i = $startIndex; $i < count($lines); $i++) {
        $line = $lines[$i];

        // Check if line is a Section Header: "ตอนที่ 1...", "ส่วนที่ 1...", "ตอนที่ 2...", "ตอนที่ 3..."
        if (preg_match('/^(ตอนที่|ส่วนที่)\s*([0-9๑-๙]+|หนึ่ง|สอง|สาม|สี่|ห้า)[\s\:\.\-–]*(.*)/u', $line, $matches)) {
            if ($currentSection !== null) {
                $sections[] = $currentSection;
            }

            $rawSecNum = $matches[2];
            $secNumMap = ['หนึ่ง' => 1, 'สอง' => 2, 'สาม' => 3, 'สี่' => 4, '๑' => 1, '๒' => 2, '๓' => 3, '๔' => 4];
            $secNum = $secNumMap[$rawSecNum] ?? (int)$rawSecNum;
            if ($secNum <= 0) $secNum = count($sections) + 1;

            $secTitle = trim($matches[0]);
            $secCategory = 'rating';

            if (preg_match('/(ข้อมูลทั่วไป|สถานภาพ|ข้อมูลส่วนตัว|สถานะ)/u', $secTitle)) {
                $secCategory = 'general';
            } elseif (preg_match('/(ข้อเสนอแนะ|ความคิดเห็น|ความเห็นเพิ่มเติม|ข้อคิดเห็น)/u', $secTitle)) {
                $secCategory = 'suggestion';
            } elseif (preg_match('/(ความพึงพอใจ|ระดับความพึงพอใจ|การประเมินผล|เกณฑ์)/u', $secTitle)) {
                $secCategory = 'rating';
            }

            $currentSection = [
                'section_number' => $secNum,
                'title' => $secTitle,
                'description' => '',
                'category' => $secCategory,
                'raw_lines' => []
            ];
            continue;
        }

        if ($currentSection === null) {
            // Default section 1 if not explicitly declared
            $currentSection = [
                'section_number' => 1,
                'title' => 'ตอนที่ 1 ข้อมูลทั่วไปและข้อประเมิน',
                'description' => '',
                'category' => 'general',
                'raw_lines' => []
            ];
        }

        $currentSection['raw_lines'][] = $line;
    }

    if ($currentSection !== null) {
        $sections[] = $currentSection;
    }

    // 5. Parse each section's contents (Headings, Questions, Options, Rating Scales)
    $parsedSections = [];
    $secCounter = 1;

    foreach ($sections as $sec) {
        $secCategory = $sec['category'];
        $rawSecLines = $sec['raw_lines'];
        $headings = [];
        $questions = [];

        // Check if section contains sub-headings (e.g. ด้านที่ 1..., 1. ด้าน..., 2. ด้าน...)
        $currentHeading = null;
        $currentQuestion = null;

        for ($j = 0; $j < count($rawSecLines); $j++) {
            $line = $rawSecLines[$j];

            // Ignore table scale legends / headers
            $shouldSkip = false;
            foreach ($ignoredPatterns as $pat) {
                if (preg_match($pat, $line)) {
                    $shouldSkip = true;
                    break;
                }
            }
            if ($shouldSkip) continue;

            // Check if line is a Heading / Dimension:
            // "ด้านที่ 1 ด้านวิทยากร", "1. ด้านวิทยากร", "ด้านกระบวนการขั้นตอน", "1. ด้านเนื้อหา"
            if (preg_match('/^(ด้านที่\s*[0-9๑-๙]+|[0-9๑-๙]+\.\s*ด้าน|ด้าน[ก-๙]+)[\s\:\.\-–]*(.*)/u', $line) && !preg_match('/\[\s*\]/u', $line)) {
                // Finalize previous question
                if ($currentQuestion !== null) {
                    if ($currentHeading !== null) {
                        $currentHeading['questions'][] = $currentQuestion;
                    } else {
                        $questions[] = $currentQuestion;
                    }
                    $currentQuestion = null;
                }

                if ($currentHeading !== null) {
                    $headings[] = $currentHeading;
                }

                $currentHeading = [
                    'title' => $line,
                    'description' => '',
                    'questions' => []
                ];
                continue;
            }

            // Check if line is a question
            // e.g. "1. เพศ", "1.1 วิทยากรมีความรู้", "2. สถานภาพ", "• ความเหมาะสมของสถานที่"
            // or starting with number: "1.1", "1.", "2)", "(1)"
            $isNumberedQuestion = preg_match('/^([0-9๑-๙]+\.[0-9๑-๙]+[\.\)]?\s*|[0-9๑-๙]+[\.\)]\s*|[\-\•\*]\s+)(.*)/u', $line, $qMatch);
            
            // Or general question prompt: "เพศ :", "ระดับการศึกษา :", "ชั้นปี :"
            $isPromptQuestion = preg_match('/^(เพศ|สถานะ|สถานภาพ|อายุ|ระดับการศึกษา|ระดับชั้น|สาขาวิชา|แผนกวิชา|สังกัด|ตำแหน่ง|อาชีพ)[\s\:\.\-–]*/u', $line);

            if ($isNumberedQuestion || ($isPromptQuestion && !preg_match('/\[\s*\]/u', $line))) {
                // Save previous question
                if ($currentQuestion !== null) {
                    if ($currentHeading !== null) {
                        $currentHeading['questions'][] = $currentQuestion;
                    } else {
                        $questions[] = $currentQuestion;
                    }
                    $currentQuestion = null;
                }

                $qText = $isNumberedQuestion ? trim($qMatch[2]) : $line;
                // Remove numbering from question text for clean display if desired, or keep clear text
                if (empty($qText)) $qText = $line;

                // Determine default question type based on section or content
                $qType = 'radio';
                $scaleMin = 1;
                $scaleMax = 5;
                $options = null;

                if ($secCategory === 'suggestion') {
                    $qType = 'text';
                } elseif ($secCategory === 'rating' || $currentHeading !== null || preg_match('/^[0-9๑-๙]+\.[0-9๑-๙]+/u', $line)) {
                    $qType = 'radio';
                    $options = null; // Rating scale 1-5
                } elseif ($secCategory === 'general') {
                    $qType = 'radio';
                    $options = [];
                }

                // Check if options are inline on the same line (e.g. "[ ] ชาย  [ ] หญิง")
                $inlineOptions = extractOptionsFromLine($line);
                if (!empty($inlineOptions)) {
                    $options = $inlineOptions;
                    // Clean question text of options
                    $qText = preg_replace('/(\[\s*\]|\(\s*\)|[1-4]\)).*/u', '', $qText);
                    $qText = trim($qText, " :.-–");
                    if (empty($qText)) $qText = $line;
                }

                $currentQuestion = [
                    'question_text' => $qText,
                    'question_type' => $qType,
                    'is_required' => 1,
                    'description' => '',
                    'options' => $options,
                    'scale_min' => $scaleMin,
                    'scale_max' => $scaleMax
                ];
                continue;
            }

            // Check if line contains options for the current question
            // e.g. "[ ] ชาย  [ ] หญิง", "( ) 1. นักเรียน ( ) 2. ครู", "1) ปวช. 2) ปวส."
            if ($currentQuestion !== null) {
                $extractedOptions = extractOptionsFromLine($line);
                if (!empty($extractedOptions)) {
                    if (!is_array($currentQuestion['options'])) {
                        $currentQuestion['options'] = [];
                    }
                    foreach ($extractedOptions as $opt) {
                        if (!in_array($opt, $currentQuestion['options'])) {
                            $currentQuestion['options'][] = $opt;
                        }
                    }
                    $currentQuestion['question_type'] = 'radio';
                    continue;
                }

                // If this is a continuation of question text
                if (empty($currentQuestion['options']) && $currentQuestion['question_type'] === 'radio' && $secCategory !== 'general') {
                    // Could be multi-line question text
                    if (mb_strlen($line, 'UTF-8') < 100 && !preg_match('/^[0-9]/', $line)) {
                        $currentQuestion['question_text'] .= ' ' . $line;
                        continue;
                    }
                }
            }
        }

        // Add last question
        if ($currentQuestion !== null) {
            if ($currentHeading !== null) {
                $currentHeading['questions'][] = $currentQuestion;
            } else {
                $questions[] = $currentQuestion;
            }
        }

        // Add last heading
        if ($currentHeading !== null) {
            $headings[] = $currentHeading;
        }

        // If section has neither questions nor headings, check if raw lines can be converted to text questions
        if (empty($questions) && empty($headings) && !empty($rawSecLines)) {
            foreach ($rawSecLines as $raw) {
                if (mb_strlen($raw, 'UTF-8') > 3) {
                    $questions[] = [
                        'question_text' => $raw,
                        'question_type' => ($secCategory === 'suggestion') ? 'text' : 'radio',
                        'is_required' => 1,
                        'description' => '',
                        'options' => null,
                        'scale_min' => 1,
                        'scale_max' => 5
                    ];
                }
            }
        }

        $parsedSections[] = [
            'section_number' => $secCounter++,
            'title' => $sec['title'],
            'description' => $sec['description'],
            'category' => $secCategory,
            'headings' => $headings,
            'questions' => $questions
        ];
    }

    // Default safety fallback if empty
    if (empty($parsedSections)) {
        $parsedSections[] = [
            'section_number' => 1,
            'title' => 'ตอนที่ 1 ข้อมูลและข้อคำถาม',
            'description' => '',
            'category' => 'general',
            'headings' => [],
            'questions' => []
        ];
    }

    return [
        'title' => $title,
        'description' => $description ?: 'แบบประเมินความพึงพอใจ นำเข้าจากไฟล์ PDF',
        'sections' => $parsedSections
    ];
}

/**
 * Extract multiple choice options from a line
 */
function extractOptionsFromLine($line) {
    $options = [];

    // Pattern 1: [ ] ชาย  [ ] หญิง  or  ( ) 1. นักเรียน  ( ) 2. ครู
    if (preg_match_all('/(?:\[\s*\]|\(\s*\)|□|○)\s*([^\(\)\[\]□○\t\n]+)/u', $line, $matches)) {
        foreach ($matches[1] as $opt) {
            $cleanOpt = trim(preg_replace('/^[0-9๑-๙]+[\.\)]\s*/u', '', trim($opt)));
            if (!empty($cleanOpt)) {
                $options[] = $cleanOpt;
            }
        }
    }

    // Pattern 2: 1) ชาย 2) หญิง 3) อื่นๆ
    if (empty($options) && preg_match_all('/(?:^|\s+)[0-9๑-๙]+[\)]\s*([^\d\)]+)/u', $line, $matches)) {
        foreach ($matches[1] as $opt) {
            $cleanOpt = trim($opt);
            if (!empty($cleanOpt) && mb_strlen($cleanOpt, 'UTF-8') < 60) {
                $options[] = $cleanOpt;
            }
        }
    }

    return $options;
}