package com.evsuite.abrp;

import org.json.JSONObject;

import java.io.ByteArrayOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.nio.charset.StandardCharsets;

/**
 * One JSON request to the car server, shared by telemetry, consumption sync and pairing (and,
 * through {@link #send}, the direct ABRP upload).
 * Blocking, with short timeouts — call it off the main thread.
 *
 * The token goes in the Authorization header, never the URL, and is never logged. The answer
 * body is read for every status (error bodies name the problem) and capped, so a wrong server
 * cannot fill memory.
 */
final class ServerHttp {

    static final int TIMEOUT_MS = 8_000;
    private static final int MAX_BODY_BYTES = 64 * 1024;

    /** Status and body of an answer. */
    static final class Response {
        final int status;
        final String body;

        Response(int status, String body) {
            this.status = status;
            this.body = body;
        }

        boolean ok() { return status >= 200 && status < 300; }

        /** The body for a log line: short, on one line. */
        String excerpt() {
            String text = body.replace('\n', ' ').trim();
            return text.length() > 300 ? text.substring(0, 300) + "…" : text;
        }
    }

    private ServerHttp() { }

    /**
     * Sends {@code json} (or nothing, when null) with {@code method} to {@code url}.
     * {@code token} may be null for the unauthenticated pairing calls.
     */
    static Response request(String method, String url, String token, JSONObject json) throws Exception {
        byte[] body = json == null ? null : json.toString().getBytes(StandardCharsets.UTF_8);
        return send(method, url, token == null ? null : "Bearer " + token, "application/json", body);
    }

    /**
     * The request underneath, also used for ABRP ({@link AbrpApi}): {@code authorization} is the
     * whole header value or null, {@code body} null for none.
     */
    static Response send(String method, String url, String authorization, String contentType, byte[] body)
            throws Exception {
        return send(method, url, authorization, contentType, null, body);
    }

    /** As above, with a {@code Content-Encoding} ({@code "gzip"}) for the body, or null. */
    static Response send(String method, String url, String authorization, String contentType,
            String contentEncoding, byte[] body) throws Exception {
        HttpURLConnection connection = (HttpURLConnection) new URL(url).openConnection();
        try {
            connection.setRequestMethod(method);
            connection.setConnectTimeout(TIMEOUT_MS);
            connection.setReadTimeout(TIMEOUT_MS);
            if (authorization != null) connection.setRequestProperty("Authorization", authorization);
            if (body != null) {
                connection.setDoOutput(true);
                connection.setFixedLengthStreamingMode(body.length);
                connection.setRequestProperty("Content-Type", contentType);
                if (contentEncoding != null) connection.setRequestProperty("Content-Encoding", contentEncoding);
                try (OutputStream out = connection.getOutputStream()) { out.write(body); }
            }
            int status = connection.getResponseCode();
            return new Response(status, readBody(connection, status));
        } finally {
            connection.disconnect();
        }
    }

    private static String readBody(HttpURLConnection connection, int status) {
        try {
            InputStream in = status < 400 ? connection.getInputStream() : connection.getErrorStream();
            if (in == null) return "";
            try (InputStream stream = in) {
                ByteArrayOutputStream buf = new ByteArrayOutputStream();
                byte[] chunk = new byte[4096];
                int n;
                while ((n = stream.read(chunk)) != -1 && buf.size() < MAX_BODY_BYTES) buf.write(chunk, 0, n);
                return buf.toString(StandardCharsets.UTF_8.name());
            }
        } catch (Exception e) {
            // The status is what matters; an unreadable body is just empty.
            return "";
        }
    }
}