package internal

import (
	"crypto/rand"
	"database/sql"
	"encoding/base64"
	"io"
	"log"
	"time"

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

const dbFile = "teachat.db"

var db *sql.DB

func InitDB() {
	var err error
	db, err = sql.Open("sqlite3", dbFile)
	if err != nil {
		log.Fatal(err)
	}

	query := `
    CREATE TABLE IF NOT EXISTS config (key TEXT PRIMARY KEY, val TEXT);
    CREATE TABLE IF NOT EXISTS users (
        pubkey TEXT PRIMARY KEY,
        username TEXT UNIQUE,
        identity_key BLOB,
        prekey BLOB,
        prekey_signature BLOB,
        created_at DATETIME
    );
    CREATE TABLE IF NOT EXISTS rooms (
        id TEXT PRIMARY KEY,
        name TEXT,
        creator TEXT,
        is_dm BOOLEAN,
        created_at DATETIME
    );
    CREATE TABLE IF NOT EXISTS room_members (
        room_id TEXT,
        username TEXT,
        shared_secret BLOB,
        joined_at DATETIME,
        PRIMARY KEY (room_id, username),
        FOREIGN KEY (room_id) REFERENCES rooms(id),
        FOREIGN KEY (username) REFERENCES users(username)
    );
    CREATE TABLE IF NOT EXISTS messages (
        id INTEGER PRIMARY KEY,
        room_id TEXT,
        timestamp DATETIME,
        sender TEXT,
        ciphertext BLOB,
        nonce BLOB,
        FOREIGN KEY (room_id) REFERENCES rooms(id)
    );
    `
	if _, err := db.Exec(query); err != nil {
		log.Fatal(err)
	}

	// Migration for older DBs
	db.Exec("ALTER TABLE rooms ADD COLUMN creator TEXT")
}

func ensureSalt() []byte {
	row := db.QueryRow("SELECT val FROM config WHERE key='global_salt'")
	var b64 string
	if err := row.Scan(&b64); err == sql.ErrNoRows {
		salt := make([]byte, saltSize)
		if _, err := io.ReadFull(rand.Reader, salt); err != nil {
			log.Fatal(err)
		}
		b64 = base64.StdEncoding.EncodeToString(salt)
		db.Exec("INSERT INTO config (key, val) VALUES ('global_salt', ?)", b64)
		return salt
	} else if err != nil {
		log.Fatal(err)
	}
	salt, _ := base64.StdEncoding.DecodeString(b64)
	return salt
}

func authorizeUser(pubkey, username string, identityKey, prekey, prekeySignature []byte) error {
	_, err := db.Exec("INSERT INTO users (pubkey, username, identity_key, prekey, prekey_signature, created_at) VALUES (?, ?, ?, ?, ?, ?)",
		pubkey, username, identityKey, prekey, prekeySignature, time.Now())
	return err
}

func getUsername(pubkey string) (string, error) {
	var username string
	err := db.QueryRow("SELECT username FROM users WHERE pubkey = ?", pubkey).Scan(&username)
	return username, err
}

func getUserKeys(username string) (identityKey, prekey, prekeySignature []byte, err error) {
	err = db.QueryRow("SELECT identity_key, prekey, prekey_signature FROM users WHERE username = ?", username).Scan(&identityKey, &prekey, &prekeySignature)
	return
}

func listUsers() ([]string, error) {
	rows, err := db.Query("SELECT username FROM users ORDER BY username ASC")
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	var users []string
	for rows.Next() {
		var username string
		if err := rows.Scan(&username); err != nil {
			continue
		}
		users = append(users, username)
	}
	return users, nil
}

func createRoom(roomID, name, creator string, isDM bool) error {
	_, err := db.Exec("INSERT INTO rooms (id, name, creator, is_dm, created_at) VALUES (?, ?, ?, ?, ?)",
		roomID, name, creator, isDM, time.Now())
	return err
}

func getRoomIDByName(name string) (string, error) {
	var id string
	err := db.QueryRow("SELECT id FROM rooms WHERE name = ? AND is_dm = 0 LIMIT 1", name).Scan(&id)
	return id, err
}

// getAnyRoomSecret gets the shared secret from ANY member of the room.
// In a real decentralized system this wouldn't be possible, but here the server acts as the key distributor.
func getAnyRoomSecret(roomID string) ([]byte, error) {
	var secret []byte
	err := db.QueryRow("SELECT shared_secret FROM room_members WHERE room_id = ? LIMIT 1", roomID).Scan(&secret)
	return secret, err
}

func deleteRoom(roomID string) error {
	tx, err := db.Begin()
	if err != nil {
		return err
	}
	if _, err := tx.Exec("DELETE FROM messages WHERE room_id = ?", roomID); err != nil {
		tx.Rollback()
		return err
	}
	if _, err := tx.Exec("DELETE FROM room_members WHERE room_id = ?", roomID); err != nil {
		tx.Rollback()
		return err
	}
	if _, err := tx.Exec("DELETE FROM rooms WHERE id = ?", roomID); err != nil {
		tx.Rollback()
		return err
	}
	return tx.Commit()
}

func leaveRoom(roomID, username string) error {
	_, err := db.Exec("DELETE FROM room_members WHERE room_id = ? AND username = ?", roomID, username)
	return err
}

func joinRoom(roomID, username string, sharedSecret []byte) error {
	// Check if already joined
	var count int
	db.QueryRow("SELECT COUNT(*) FROM room_members WHERE room_id = ? AND username = ?", roomID, username).Scan(&count)
	if count > 0 {
		return nil
	}
	_, err := db.Exec("INSERT INTO room_members (room_id, username, shared_secret, joined_at) VALUES (?, ?, ?, ?)",
		roomID, username, sharedSecret, time.Now())
	return err
}

func getMemberJoinedAt(roomID, username string) (time.Time, error) {
	var joinedAt time.Time
	err := db.QueryRow("SELECT joined_at FROM room_members WHERE room_id = ? AND username = ?", roomID, username).Scan(&joinedAt)
	return joinedAt, err
}

func listUserRooms(username string) ([]struct {
	ID      string
	Name    string
	Creator string
	IsDM    bool
}, error) {
	rows, err := db.Query(`
		SELECT r.id, r.name, COALESCE(r.creator, ''), r.is_dm
		FROM rooms r
		JOIN room_members rm ON r.id = rm.room_id
		WHERE rm.username = ?
		ORDER BY r.created_at DESC`, username)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	var rooms []struct {
		ID      string
		Name    string
		Creator string
		IsDM    bool
	}
	for rows.Next() {
		var room struct {
			ID      string
			Name    string
			Creator string
			IsDM    bool
		}
		if err := rows.Scan(&room.ID, &room.Name, &room.Creator, &room.IsDM); err != nil {
			continue
		}
		rooms = append(rooms, room)
	}
	return rooms, nil
}

func getRoomSharedSecret(roomID, username string) ([]byte, error) {
	var secret []byte
	err := db.QueryRow("SELECT shared_secret FROM room_members WHERE room_id = ? AND username = ?", roomID, username).Scan(&secret)
	return secret, err
}

func saveMessage(roomID, sender string, ciphertext, nonce []byte) error {
	_, err := db.Exec("INSERT INTO messages (room_id, timestamp, sender, ciphertext, nonce) VALUES (?, ?, ?, ?, ?)",
		roomID, time.Now(), sender, ciphertext, nonce)
	return err
}

func loadMessages(roomID string) ([]struct {
	Timestamp  time.Time
	Sender     string
	Ciphertext []byte
	Nonce      []byte
}, error) {
	rows, err := db.Query("SELECT timestamp, sender, ciphertext, nonce FROM messages WHERE room_id = ? ORDER BY timestamp ASC", roomID)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	var messages []struct {
		Timestamp  time.Time
		Sender     string
		Ciphertext []byte
		Nonce      []byte
	}

	for rows.Next() {
		var msg struct {
			Timestamp  time.Time
			Sender     string
			Ciphertext []byte
			Nonce      []byte
		}
		if err := rows.Scan(&msg.Timestamp, &msg.Sender, &msg.Ciphertext, &msg.Nonce); err != nil {
			continue
		}
		messages = append(messages, msg)
	}

	return messages, nil
}