package server

import (
	"PD2/internal/protocol"
	"crypto/x509"
	"database/sql"
	"errors"
	"fmt"
	"log"
	"time"

	_ "github.com/mattn/go-sqlite3"
)

type DataStore struct {
	db *sql.DB
}

func OpenDB() (DataStore, error) {
	db, err := sql.Open("sqlite3", "server.db")
	if err != nil {
		return DataStore{}, err
	}
	ds := DataStore{db: db}
	err = ds.CreateTables()
	if err != nil {
		return DataStore{}, err
	}
	return ds, nil
}

func (ds DataStore) CreateTables() error {
	// Create users table
	_, err := ds.db.Exec(`CREATE TABLE IF NOT EXISTS users (
        UID TEXT PRIMARY KEY,
        userCert BLOB
    )`)
	if err != nil {
		return err
	}

	// Create messages table
	_, err = ds.db.Exec(`CREATE TABLE IF NOT EXISTS messages (
        fromUID TEXT,
        toUID TEXT,
        timestamp TIMESTAMP,
        queue_position INT DEFAULT 0,
        subject BLOB,
        body BLOB,
        status INT CHECK (status IN (0,1)),
        PRIMARY KEY (toUID, fromUID, timestamp),
        FOREIGN KEY(fromUID) REFERENCES users(UID),
        FOREIGN KEY(toUID) REFERENCES users(UID)
    )`)
	if err != nil {
		return err
	}

	// Define a trigger to automatically assign numbers for each message of each user starting from 1
	_, err = ds.db.Exec(`
        CREATE TRIGGER IF NOT EXISTS assign_queue_position
        AFTER INSERT ON messages
        FOR EACH ROW
        BEGIN
            UPDATE messages
            SET queue_position = (
                SELECT COUNT(*)
                FROM messages
                WHERE toUID = NEW.toUID
            )
            WHERE toUID = NEW.toUID AND rowid = NEW.rowid;
        END;
    `)
	if err != nil {
		return err
	}

	return nil
}

func (ds DataStore) GetMessage(toUID string, position int) (*protocol.AnswerGetMsg, error) {

	var serverMessage protocol.AnswerGetMsg
	query := `
        SELECT fromUID, toUID, subject, body, timestamp
        FROM messages
        WHERE toUID = ? AND queue_position = ?
    `
	// Execute the query
	row := ds.db.QueryRow(query, toUID, position)
	err := row.Scan(&serverMessage.FromUID, &serverMessage.ToUID, &serverMessage.Subject, &serverMessage.Body, &serverMessage.Timestamp)
	if err == sql.ErrNoRows {
		log.Printf("No message with NUM %v for UID %v\n", position, toUID)
		errorMessage := fmt.Sprintln("MSG SERVICE: unknown message!")
		error := errors.New(errorMessage)
		return nil, error
	}

	answer := protocol.NewAnswerGetMsg(serverMessage.FromUID, serverMessage.ToUID, serverMessage.Subject, serverMessage.Body, serverMessage.Timestamp, true)
	return &answer, nil

}

func (ds DataStore) MarkMessageInQueueAsRead(toUID string, position int) {
	query := `
        UPDATE messages
            SET status = 1
            WHERE (fromUID,toUID,timestamp) = (
                SELECT fromUID,toUID,timestamp
                FROM messages
                WHERE toUID = ? AND queue_position = ?
            )
    `

	// Execute the SQL statement
	_, err := ds.db.Exec(query, toUID, position)
	if err != nil {
		log.Printf("Error marking the message in position %v from UID %v as read: %v", position, toUID, err)
	}
}

func (ds DataStore) GetUnreadMsgsInfo(toUID string, page int, pageSize int) (protocol.AnswerGetUnreadMsgsInfo, error) {

	// Retrieve the total count of unread messages
	var totalCount int
	err := ds.db.QueryRow("SELECT COUNT(*) FROM messages WHERE toUID = ? AND status = 0", toUID).Scan(&totalCount)
	if err == sql.ErrNoRows {
		return protocol.NewAnswerGetUnreadMsgsInfo(0, 0, []protocol.MsgInfo{}), nil
	}

	// Query to retrieve all messages from the user's queue
	query := `
        SELECT 
            fromUID,
            toUID,
            timestamp,
            queue_position,
            subject,
            status
        FROM messages
        WHERE 
            toUID = ? AND status = 0
        ORDER BY 
            queue_position DESC
        LIMIT ? OFFSET ?;
    `

	// Execute the query
	rows, err := ds.db.Query(query, toUID, pageSize, (page-1)*pageSize)
	if err != nil {
		log.Printf("Error getting unread messages for UID %v: %v", toUID, err)
	}
	defer rows.Close()

	messageInfoPackets := []protocol.MsgInfo{}
	for rows.Next() {
		var fromUID string
		var subject []byte
		var timestamp time.Time
		var queuePosition, status int
		if err := rows.Scan(&fromUID, &toUID, &timestamp, &queuePosition, &subject, &status); err != nil {
			return protocol.AnswerGetUnreadMsgsInfo{}, err
		}
		answerGetUnreadMsgsInfo := protocol.NewMsgInfo(queuePosition, fromUID, subject, timestamp)
		messageInfoPackets = append(messageInfoPackets, answerGetUnreadMsgsInfo)
	}
	if err := rows.Err(); err != nil {
		log.Printf("Error when getting messages for UID %v: %v", toUID, err)
		return protocol.AnswerGetUnreadMsgsInfo{}, err
	}
	numberOfPages := (totalCount + pageSize - 1) / pageSize
	currentPage := min(numberOfPages, page)
	return protocol.NewAnswerGetUnreadMsgsInfo(currentPage, numberOfPages, messageInfoPackets), nil
}

func (ds DataStore) AddMessageToQueue(fromUID string, message protocol.SendMsg) error {
	query := `
        INSERT INTO messages (fromUID, toUID, subject, body, timestamp, status)
        VALUES (?, ?, ?, ?, ?, 0)
    `

	// Execute the SQL statement
	currentTime := time.Now()
	_, err := ds.db.Exec(query, fromUID, message.ToUID, message.Subject, message.Body, currentTime)
	if err != nil {
		log.Printf("Error adding message to UID %v: %v", fromUID, err)
		return err
	}
	return nil
}

func (ds DataStore) GetUserCertificate(uid string) (protocol.AnswerGetUserCert,error) {
	query := `
        SELECT userCert
        FROM users
        WHERE UID = ?
    `

	// Execute the SQL query
	var userCertBytes []byte
	err := ds.db.QueryRow(query, uid).Scan(&userCertBytes)
	if err == sql.ErrNoRows {
		errorMessage := fmt.Sprintf("No certificate for UID %v found in the database", uid)
		log.Println(errorMessage)
		return protocol.AnswerGetUserCert{},errors.New(errorMessage)
	}
	return protocol.NewAnswerGetUserCert(uid, userCertBytes),nil
}

func (ds DataStore) userExists(uid string) bool {
	// Prepare the SQL statement for checking if a user exists
	query := `
        SELECT COUNT(*)
        FROM users
        WHERE UID = ?
    `

	var count int
	// Execute the SQL query
	err := ds.db.QueryRow(query, uid).Scan(&count)
	if err != nil || count == 0 {
		log.Printf("user with UID %v does not exist\n", uid)
		return false
	}
	return true
}

func (ds DataStore) storeUserCertIfNotExists(uid string, cert x509.Certificate) error {
	// Insert the user certificate
	insertQuery := `
        INSERT INTO users (UID, userCert)
        VALUES (?, ?)
    `
	_, err := ds.db.Exec(insertQuery, uid, cert.Raw)
	if err != nil {
		return fmt.Errorf("error storing user certificate for UID %s: %v", uid, err)
	}
	log.Printf("User certificate for UID %s stored successfully.\n", uid)
	return nil
}