<?php
/**
 * Statistics API
 * GET ?action=summary&survey_id=X  — Summary statistics
 * GET ?action=detail&survey_id=X   — Detailed per-question stats
 */

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

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

requireLogin();

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

if (!$surveyId) 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']) {
        jsonResponse(['error' => 'ไม่มีสิทธิ์'], 403);
    }
}

/**
 * Helper to parse Likert rating values from numbers or Thai text
 */
function parseRatingScore($str) {
    $trimmed = trim((string)$str);
    if ($trimmed === '') return null;

    if (is_numeric($trimmed)) {
        $num = (int)$trimmed;
        return ($num >= 1 && $num <= 5) ? $num : null;
    }

    if (preg_match('/^([1-5])\s*[\.\:\-\(\s]/u', $trimmed, $m)) {
        return (int)$m[1];
    }

    if (mb_strpos($trimmed, 'มากที่สุด') !== false || mb_strpos($trimmed, 'ดีมาก') !== false || mb_strpos($trimmed, 'ยอดเยี่ยม') !== false || mb_strpos($trimmed, 'ดีเยี่ยม') !== false || mb_strpos($trimmed, 'เห็นด้วยอย่างยิ่ง') !== false) {
        return 5;
    }
    if (mb_strpos($trimmed, 'น้อยที่สุด') !== false || mb_strpos($trimmed, 'ไม่เห็นด้วยอย่างยิ่ง') !== false) {
        return 1;
    }
    if (mb_strpos($trimmed, 'มาก') !== false || mb_strpos($trimmed, 'ดี') !== false || mb_strpos($trimmed, 'เห็นด้วย') !== false) {
        return 4;
    }
    if (mb_strpos($trimmed, 'ปานกลาง') !== false || mb_strpos($trimmed, 'พอใช้') !== false || mb_strpos($trimmed, 'ไม่แน่ใจ') !== false) {
        return 3;
    }
    if (mb_strpos($trimmed, 'น้อย') !== false || mb_strpos($trimmed, 'ควรปรับปรุง') !== false || mb_strpos($trimmed, 'ต้องปรับปรุง') !== false || mb_strpos($trimmed, 'ไม่เห็นด้วย') !== false) {
        return 2;
    }
    if (mb_strpos($trimmed, 'ปรับปรุง') !== false) {
        return 1;
    }

    return null;
}

switch ($action) {
    case 'summary':
        getSummary($surveyId);
        break;
    case 'detail':
        getDetail($surveyId);
        break;
    default:
        jsonResponse(['error' => 'Invalid action'], 400);
}

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

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

    // Get survey info
    $stmt = $db->prepare("SELECT title, status, created_at FROM surveys WHERE id = ?");
    $stmt->execute([$surveyId]);
    $surveyInfo = $stmt->fetch();

    // Fetch all answers for rating questions in this survey and compute mean/sd
    $stmt = $db->prepare("
        SELECT ra.answer_value
        FROM response_answers ra
        JOIN survey_questions sq ON ra.question_id = sq.id
        JOIN survey_sections ss ON sq.section_id = ss.id
        WHERE ss.survey_id = ? AND sq.question_type = 'radio' AND sq.options IS NULL
    ");
    $stmt->execute([$surveyId]);
    $rows = $stmt->fetchAll(PDO::FETCH_COLUMN);

    $scores = [];
    foreach ($rows as $ans) {
        $sc = parseRatingScore($ans);
        if ($sc !== null) {
            $scores[] = $sc;
        }
    }

    $overallMean = 0;
    $overallSd = 0;

    if (count($scores) > 0) {
        $overallMean = array_sum($scores) / count($scores);
        if (count($scores) > 1) {
            $sumSq = 0;
            foreach ($scores as $s) {
                $sumSq += pow($s - $overallMean, 2);
            }
            $overallSd = sqrt($sumSq / (count($scores) - 1));
        }
    }

    jsonResponse([
        'survey' => $surveyInfo,
        'total_responses' => (int)$total,
        'overall_mean' => round($overallMean, 2),
        'overall_sd' => round($overallSd, 2)
    ]);
}

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

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

    $result = [];

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

        $sectionStats = [
            'section_number' => $section['section_number'],
            'title' => $section['title'],
            'headings' => [],
            'questions' => []
        ];

        // Load headings for this section
        $headingStmt = $db->prepare("SELECT * FROM survey_headings WHERE section_id = ? ORDER BY order_num");
        $headingStmt->execute([$section['id']]);
        $headings = $headingStmt->fetchAll();

        foreach ($questions as $q) {
            $qStat = [
                'id' => $q['id'],
                'heading_id' => $q['heading_id'] ?? null,
                'question_text' => $q['question_text'],
                'question_type' => $q['question_type']
            ];

            if ($q['question_type'] === 'radio' && empty($q['options'])) {
                // Rating scale question (1-5)
                $aStmt = $db->prepare("
                    SELECT answer_value, COUNT(*) as cnt 
                    FROM response_answers 
                    WHERE question_id = ? AND answer_value != ''
                    GROUP BY answer_value 
                    ORDER BY answer_value
                ");
                $aStmt->execute([$q['id']]);
                $freqData = $aStmt->fetchAll();

                $frequencies = [];
                $values = [];
                $totalAnswers = 0;
                
                for ($i = 1; $i <= 5; $i++) {
                    $frequencies[$i] = ['value' => $i, 'count' => 0, 'percentage' => 0];
                }

                foreach ($freqData as $fd) {
                    $rawVal = trim($fd['answer_value']);
                    $cnt = (int)$fd['cnt'];
                    $val = parseRatingScore($rawVal);

                    if ($val >= 1 && $val <= 5) {
                        $frequencies[$val]['count'] += $cnt;
                        $totalAnswers += $cnt;
                        for ($j = 0; $j < $cnt; $j++) {
                            $values[] = $val;
                        }
                    }
                }

                // Calculate percentages
                foreach ($frequencies as &$f) {
                    $f['percentage'] = $totalAnswers > 0 ? round(($f['count'] / $totalAnswers) * 100, 1) : 0;
                }
                unset($f);

                // Calculate mean
                $mean = count($values) > 0 ? array_sum($values) / count($values) : 0;

                // Calculate SD
                $sd = 0;
                if (count($values) > 1) {
                    $sumSquaredDiff = 0;
                    foreach ($values as $v) {
                        $sumSquaredDiff += pow($v - $mean, 2);
                    }
                    $sd = sqrt($sumSquaredDiff / (count($values) - 1));
                }

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

                $qStat['mean'] = round($mean, 2);
                $qStat['sd'] = round($sd, 2);
                $qStat['interpretation'] = $interpretation;
                $qStat['frequencies'] = array_values($frequencies);
                $qStat['total_answers'] = $totalAnswers;

            } elseif ($q['question_type'] === 'text') {
                // Collect text responses
                $aStmt = $db->prepare("
                    SELECT answer_value FROM response_answers 
                    WHERE question_id = ? AND answer_value != ''
                    ORDER BY id DESC
                ");
                $aStmt->execute([$q['id']]);
                $qStat['text_responses'] = array_column($aStmt->fetchAll(), 'answer_value');
                $qStat['total_answers'] = count($qStat['text_responses']);

            } elseif (in_array($q['question_type'], ['dropdown', 'checkbox', 'radio'])) {
                // Frequency for dropdown/checkbox/custom radio
                $aStmt = $db->prepare("
                    SELECT answer_value, COUNT(*) as cnt 
                    FROM response_answers 
                    WHERE question_id = ? AND answer_value != ''
                    GROUP BY answer_value 
                    ORDER BY cnt DESC
                ");
                $aStmt->execute([$q['id']]);
                $freqData = $aStmt->fetchAll();
                
                $totalAnswers = array_sum(array_column($freqData, 'cnt'));
                $qStat['frequencies'] = array_map(function($fd) use ($totalAnswers) {
                    return [
                        'value' => $fd['answer_value'],
                        'count' => (int)$fd['cnt'],
                        'percentage' => $totalAnswers > 0 ? round(((int)$fd['cnt'] / $totalAnswers) * 100, 1) : 0
                    ];
                }, $freqData);
                $qStat['total_answers'] = $totalAnswers;
            }

            $sectionStats['questions'][] = $qStat;
        }

        // Build heading stats groups
        $headingStats = [];
        foreach ($headings as $h) {
            $hStat = [
                'id' => $h['id'],
                'title' => $h['title'],
                'description' => $h['description'],
                'questions' => []
            ];
            foreach ($sectionStats['questions'] as $qs) {
                if (($qs['heading_id'] ?? null) == $h['id']) {
                    $hStat['questions'][] = $qs;
                }
            }
            $headingStats[] = $hStat;
        }
        $sectionStats['headings'] = $headingStats;

        // Filter loose questions (no heading)
        $sectionStats['questions'] = array_values(array_filter($sectionStats['questions'], function($qs) {
            return empty($qs['heading_id']);
        }));

        $result[] = $sectionStats;
    }

    jsonResponse([
        'total_responses' => $totalResponses,
        'sections' => $result
    ]);
}