package database

import (
	"database/sql"
	"errors"
	"time"

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

var ErrNotFound = errors.New("not found")

type User struct {
	ID        string
	Username  string
	CreatedAt time.Time
	LastSeen  time.Time
}

func scanUser(row *sql.Row) (*User, error) {
	var u User
	err := row.Scan(&u.ID, &u.Username, &u.CreatedAt, &u.LastSeen)
	if errors.Is(err, sql.ErrNoRows) {
		return nil, ErrNotFound
	}
	if err != nil {
		return nil, err
	}
	return &u, nil
}

const userColumns = "id, username, created_at, last_seen"

func CreateUser(db *sql.DB, id, username string) (*User, error) {
	now := time.Now()
	_, err := db.Exec(
		"INSERT INTO users ("+userColumns+") VALUES (?, ?, ?, ?)",
		id, username, now, now,
	)
	if err != nil {
		return nil, err
	}
	return &User{ID: id, Username: username, CreatedAt: now, LastSeen: now}, nil
}

func GetUserByID(db *sql.DB, id string) (*User, error) {
	return scanUser(db.QueryRow("SELECT "+userColumns+" FROM users WHERE id = ?", id))
}

func RenameUser(db *sql.DB, userID, username string) error {
	_, err := db.Exec("UPDATE users SET username = ? WHERE id = ?", username, userID)
	return err
}

func ListUsers(db *sql.DB) ([]User, error) {
	rows, err := db.Query("SELECT " + userColumns + " FROM users ORDER BY last_seen DESC")
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	users := []User{}
	for rows.Next() {
		var u User
		if err := rows.Scan(&u.ID, &u.Username, &u.CreatedAt, &u.LastSeen); err != nil {
			return nil, err
		}
		users = append(users, u)
	}
	return users, rows.Err()
}

func GetUserByUsername(db *sql.DB, username string) (*User, error) {
	return scanUser(db.QueryRow("SELECT "+userColumns+" FROM users WHERE username = ?", username))
}

// GetUserByMAC finds the account a hardware address currently belongs to.
// Columns are alias-qualified because macs also has a last_seen column.
func GetUserByMAC(db *sql.DB, mac string) (*User, error) {
	return scanUser(db.QueryRow(
		"SELECT u.id, u.username, u.created_at, u.last_seen FROM users u JOIN macs m ON m.user_id = u.id WHERE m.mac = ?",
		mac,
	))
}

// TouchUser bumps a user's last_seen — this is the timestamp the portal shows
// when someone tries to reclaim a taken handle.
func TouchUser(db *sql.DB, id string) error {
	_, err := db.Exec("UPDATE users SET last_seen = ? WHERE id = ?", time.Now(), id)
	return err
}

// AssociateMAC binds a MAC to a user, moving it from any previous owner. This is
// what "logging back in" from a rotated MAC does.
func AssociateMAC(db *sql.DB, mac, userID string) error {
	now := time.Now()
	_, err := db.Exec(`INSERT INTO macs (mac, user_id, first_seen, last_seen) VALUES (?, ?, ?, ?)
		ON CONFLICT(mac) DO UPDATE SET user_id = excluded.user_id, last_seen = excluded.last_seen`,
		mac, userID, now, now)
	return err
}