<?php
require_once __DIR__ . '/config.php';
require_once __DIR__ . '/db.php';

class SurveyManager {
    private $db;
    private static $instance = null;

    private function __construct() {
        $this->db = Database::getInstance();
    }

    public static function getInstance() {
        if (self::$instance === null) {
            self::$instance = new self();
        }
        return self::$instance;
    }

    /**
     * Get all surveys for a user with summary statistics
     */
    public function getSurveys($userId, $filters = []) {
        try {
            $where = ['s.created_by = ?'];
            $params = [$userId];
            $types = 'i';

            if (!empty($filters['status'])) {
                $where[] = 's.status = ?';
                $params[] = $filters['status'];
                $types .= 's';
            }

            if (!empty($filters['search'])) {
                $where[] = '(s.title LIKE ? OR s.description LIKE ?)';
                $search = "%{$filters['search']}%";
                $params[] = $search;
                $params[] = $search;
                $types .= 'ss';
            }

            $whereClause = implode(' AND ', $where);

            $sql = "SELECT 
                        s.*,
                        (SELECT COUNT(DISTINCT t.id) 
                         FROM survey_tokens t 
                         WHERE t.survey_id = s.id) as tokens_count,
                        (SELECT COUNT(DISTINCT t.id) 
                         FROM survey_tokens t 
                         WHERE t.survey_id = s.id AND t.is_completed = 1) as responses_count,
                        (SELECT COUNT(DISTINCT q.id) 
                         FROM survey_questions q 
                         WHERE q.survey_id = s.id) as questions_count
                    FROM surveys s 
                    WHERE $whereClause 
                    ORDER BY s.created_at DESC";

            $stmt = $this->db->prepare($sql);
            $stmt->bind_param($types, ...$params);
            $stmt->execute();
            
            $result = $stmt->get_result();
            return $result->fetch_all(MYSQLI_ASSOC);
        } catch (Exception $e) {
            error_log("Get surveys error: " . $e->getMessage());
            return [];
        }
    }

/**
 * Get questions for a specific survey
 */
public function getSurveyQuestions($surveyId) {
    try {
        $sql = "SELECT * 
                FROM survey_questions 
                WHERE survey_id = ? 
                ORDER BY question_order ASC";
        
        $stmt = $this->db->prepare($sql);
        $stmt->bind_param('i', $surveyId);
        $stmt->execute();
        
        $questions = $stmt->get_result()->fetch_all(MYSQLI_ASSOC);
        
        // Parse JSON fields for each question
        foreach ($questions as &$question) {
            if (!empty($question['options'])) {
                $question['options'] = json_decode($question['options'], true);
            }
            
            if (!empty($question['config'])) {
                $question['config'] = json_decode($question['config'], true);
            }
        }
        
        return $questions;
    } catch (Exception $e) {
        error_log("Get survey questions error: " . $e->getMessage());
        return [];
    }
}

    /**
     * Create a new survey
     */
    public function createSurvey($data) {
        try {
            $sql = "INSERT INTO surveys (
                        title, description, status, 
                        allow_multiple, allow_edit, created_by
                    ) VALUES (?, ?, ?, ?, ?, ?)";
            
            $stmt = $this->db->prepare($sql);
            $stmt->bind_param('sssiii',
                $data['title'],
                $data['description'],
                $data['status'],
                $data['allow_multiple'],
                $data['allow_edit'],
                $data['created_by']
            );
            
            if (!$stmt->execute()) {
                throw new Exception("Failed to create survey");
            }

            return [
                'success' => true,
                'survey_id' => $this->db->getLastInsertId()
            ];
        } catch (Exception $e) {
            error_log("Create survey error: " . $e->getMessage());
            return [
                'success' => false,
                'error' => $e->getMessage()
            ];
        }
    }

    /**
     * Get survey details with questions
     */
    public function getSurveyDetails($surveyId, $userId) {
        try {
            // Get survey details
            $sql = "SELECT * FROM surveys 
                    WHERE id = ? AND created_by = ?";
            
            $stmt = $this->db->prepare($sql);
            $stmt->bind_param('ii', $surveyId, $userId);
            $stmt->execute();
            
            $survey = $stmt->get_result()->fetch_assoc();
            if (!$survey) {
                return null;
            }

            // Get questions
            $sql = "SELECT * FROM survey_questions 
                    WHERE survey_id = ? 
                    ORDER BY question_order ASC";
            
            $stmt = $this->db->prepare($sql);
            $stmt->bind_param('i', $surveyId);
            $stmt->execute();
            
            $survey['questions'] = $stmt->get_result()->fetch_all(MYSQLI_ASSOC);

            // Get response statistics
            $sql = "SELECT 
                        COUNT(DISTINCT st.id) as total_tokens,
                        SUM(st.is_completed) as completed_responses,
                        COUNT(DISTINCT sr.selection_id) as unique_responses
                    FROM survey_tokens st
                    LEFT JOIN survey_responses sr ON sr.survey_id = st.survey_id
                    WHERE st.survey_id = ?";
            
            $stmt = $this->db->prepare($sql);
            $stmt->bind_param('i', $surveyId);
            $stmt->execute();
            
            $survey['stats'] = $stmt->get_result()->fetch_assoc();

            return $survey;
        } catch (Exception $e) {
            error_log("Get survey details error: " . $e->getMessage());
            return null;
        }
    }

    /**
     * Update survey details
     */
    public function updateSurvey($surveyId, $data) {
        try {
            $sql = "UPDATE surveys 
                    SET title = ?, 
                        description = ?, 
                        status = ?,
                        allow_multiple = ?,
                        allow_edit = ?
                    WHERE id = ? AND created_by = ?";
            
            $stmt = $this->db->prepare($sql);
            $stmt->bind_param('sssiiii',
                $data['title'],
                $data['description'],
                $data['status'],
                $data['allow_multiple'],
                $data['allow_edit'],
                $surveyId,
                $data['created_by']
            );
            
            if (!$stmt->execute()) {
                throw new Exception("Failed to update survey");
            }

            return ['success' => true];
        } catch (Exception $e) {
            error_log("Update survey error: " . $e->getMessage());
            return [
                'success' => false,
                'error' => $e->getMessage()
            ];
        }
    }

    /**
     * Delete a survey
     */
    public function deleteSurvey($surveyId, $userId) {
        try {
            $sql = "DELETE FROM surveys 
                    WHERE id = ? AND created_by = ?";
            
            $stmt = $this->db->prepare($sql);
            $stmt->bind_param('ii', $surveyId, $userId);
            
            if (!$stmt->execute()) {
                throw new Exception("Failed to delete survey");
            }

            return ['success' => true];
        } catch (Exception $e) {
            error_log("Delete survey error: " . $e->getMessage());
            return [
                'success' => false,
                'error' => $e->getMessage()
            ];
        }
    }

    /**
     * Add or update survey questions
     */
    public function saveQuestion($data) {
        try {
            if (isset($data['question_id'])) {
                // Update existing question
                $sql = "UPDATE survey_questions 
                        SET question_text = ?,
                            question_type = ?,
                            help_text = ?,
                            options = ?,
                            config = ?,
                            is_required = ?
                        WHERE id = ? AND survey_id = ?";
                
                $stmt = $this->db->prepare($sql);
                $stmt->bind_param('sssssiis',
                    $data['question_text'],
                    $data['question_type'],
                    $data['help_text'],
                    $data['options'],
                    $data['config'],
                    $data['is_required'],
                    $data['question_id'],
                    $data['survey_id']
                );
            } else {
                // Add new question
                $sql = "INSERT INTO survey_questions (
                            survey_id, question_text, question_type,
                            help_text, options, config, is_required, question_order
                        ) VALUES (?, ?, ?, ?, ?, ?, ?, ?)";
                
                $stmt = $this->db->prepare($sql);
                $stmt->bind_param('isssssii',
                    $data['survey_id'],
                    $data['question_text'],
                    $data['question_type'],
                    $data['help_text'],
                    $data['options'],
                    $data['config'],
                    $data['is_required'],
                    $data['question_order']
                );
            }

            if (!$stmt->execute()) {
                throw new Exception("Failed to save question");
            }

            return [
                'success' => true,
                'question_id' => isset($data['question_id']) ? 
                    $data['question_id'] : $this->db->getLastInsertId()
            ];
        } catch (Exception $e) {
            error_log("Save question error: " . $e->getMessage());
            return [
                'success' => false,
                'error' => $e->getMessage()
            ];
        }
    }

    /**
     * Delete a survey question
     */
    public function deleteQuestion($questionId, $surveyId) {
        try {
            $sql = "DELETE FROM survey_questions 
                    WHERE id = ? AND survey_id = ?";
            
            $stmt = $this->db->prepare($sql);
            $stmt->bind_param('ii', $questionId, $surveyId);
            
            if (!$stmt->execute()) {
                throw new Exception("Failed to delete question");
            }

            return ['success' => true];
        } catch (Exception $e) {
            error_log("Delete question error: " . $e->getMessage());
            return [
                'success' => false,
                'error' => $e->getMessage()
            ];
        }
    }

    /**
     * Update question order
     */
    public function updateQuestionOrder($surveyId, $questionOrder) {
        try {
            $sql = "UPDATE survey_questions 
                    SET question_order = ? 
                    WHERE id = ? AND survey_id = ?";
            
            $stmt = $this->db->prepare($sql);
            
            foreach ($questionOrder as $order => $questionId) {
                $stmt->bind_param('iii', $order, $questionId, $surveyId);
                if (!$stmt->execute()) {
                    throw new Exception("Failed to update question order");
                }
            }

            return ['success' => true];
        } catch (Exception $e) {
            error_log("Update question order error: " . $e->getMessage());
            return [
                'success' => false,
                'error' => $e->getMessage()
            ];
        }
    }

    /**
     * Generate survey token for a panel
     */
    public function generateSurveyToken($surveyId, $sampleId, $selectionId, $expiryHours = 48) {
        try {
            $token = bin2hex(random_bytes(32));
            $expiryDate = date('Y-m-d H:i:s', strtotime("+{$expiryHours} hours"));

            $sql = "INSERT INTO survey_tokens (
                        survey_id, token, sample_id, 
                        selection_id, expires_at
                    ) VALUES (?, ?, ?, ?, ?)";
            
            $stmt = $this->db->prepare($sql);
            $stmt->bind_param('issis',
                $surveyId,
                $token,
                $sampleId,
                $selectionId,
                $expiryDate
            );
            
            if (!$stmt->execute()) {
                throw new Exception("Failed to generate survey token");
            }

            return [
                'success' => true,
                'token' => $token
            ];
        } catch (Exception $e) {
            error_log("Generate token error: " . $e->getMessage());
            return [
                'success' => false,
                'error' => $e->getMessage()
            ];
        }
    }

    /**
     * Get survey response statistics
     */
    public function getSurveyStats($surveyId) {
        try {
            $sql = "SELECT 
                        COUNT(DISTINCT st.id) as total_tokens,
                        SUM(st.is_completed) as completed_responses,
                        COUNT(DISTINCT sr.selection_id) as unique_responses,
                        AVG(TIMESTAMPDIFF(MINUTE, st.created_at, st.completed_at)) as avg_completion_time
                    FROM survey_tokens st
                    LEFT JOIN survey_responses sr ON sr.survey_id = st.survey_id
                    WHERE st.survey_id = ?";
            
            $stmt = $this->db->prepare($sql);
            $stmt->bind_param('i', $surveyId);
            $stmt->execute();
            
            $stats = $stmt->get_result()->fetch_assoc();

            // Get per-question statistics
            $sql = "SELECT 
                        sq.id, sq.question_text, sq.question_type,
                        COUNT(DISTINCT sr.selection_id) as response_count,
                        GROUP_CONCAT(DISTINCT sr.response) as responses
                    FROM survey_questions sq
                    LEFT JOIN survey_responses sr ON sr.question_id = sq.id
                    WHERE sq.survey_id = ?
                    GROUP BY sq.id";
            
            $stmt = $this->db->prepare($sql);
            $stmt->bind_param('i', $surveyId);
            $stmt->execute();
            
            $stats['questions'] = $stmt->get_result()->fetch_all(MYSQLI_ASSOC);

            return $stats;
        } catch (Exception $e) {
            error_log("Get survey stats error: " . $e->getMessage());
            return null;
        }
    }
}
?>