package net.rustnotmc.auth;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.Writer;
import java.nio.charset.StandardCharsets;
import java.nio.file.AtomicMoveNotSupportedException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.StandardCopyOption;

/**
 * Reads and writes the account file.
 *
 * Saving goes to a temporary file and is then moved into place. Writing the
 * real file directly means a crash halfway through leaves a server with half
 * its accounts and no way to know which half, and the damage is only discovered
 * the next time somebody tries to log in.
 */
public final class AccountFile {

    /** Format marker, so a future format can be told apart from this one. */
    private static final String HEADER = "# rsx-accounts v1";

    private AccountFile() {
    }

    public static void load(Path path, AccountStore store) throws IOException {
        if (!Files.exists(path)) {
            Files.createDirectories(path.toAbsolutePath().getParent());
            Files.createFile(path);
            return;
        }
        BufferedReader reader = new BufferedReader(
                new InputStreamReader(Files.newInputStream(path), StandardCharsets.UTF_8));
        try {
            String line;
            int lineNumber = 0;
            while ((line = reader.readLine()) != null) {
                lineNumber++;
                if (line.isEmpty() || line.startsWith("#")) {
                    continue;
                }
                String[] parts = line.split("\t");
                if (parts.length < 4) {
                    throw new IOException("malformed account file at line " + lineNumber);
                }
                long created;
                long last;
                try {
                    created = Long.parseLong(parts[2]);
                    last = Long.parseLong(parts[3]);
                } catch (NumberFormatException e) {
                    throw new IOException("bad timestamp at line " + lineNumber);
                }
                store.restore(new AccountStore.Account(parts[0], parts[1], created, last));
            }
        } finally {
            reader.close();
        }
    }

    public static void save(Path path, AccountStore store) throws IOException {
        Path directory = path.toAbsolutePath().getParent();
        Files.createDirectories(directory);
        Path temporary = Files.createTempFile(directory, "accounts", ".tmp");
        Writer writer = new OutputStreamWriter(
                Files.newOutputStream(temporary), StandardCharsets.UTF_8);
        try {
            writer.write(HEADER);
            writer.write('\n');
            for (AccountStore.Account account : store.all()) {
                writer.write(account.encode());
                writer.write('\n');
            }
        } finally {
            writer.close();
        }
        try {
            Files.move(temporary, path,
                    StandardCopyOption.REPLACE_EXISTING, StandardCopyOption.ATOMIC_MOVE);
        } catch (AtomicMoveNotSupportedException e) {
            Files.move(temporary, path, StandardCopyOption.REPLACE_EXISTING);
        }
    }
}