type SecureSession = {
    publicKey: string;
    key: CryptoKey;
    fingerprint: string;
};

const isDebugEnabled = (): boolean =>
{
    try
    {
        const search = new URLSearchParams(window.location.search);

        return search.get('secureDebug') === '1' || localStorage.getItem('nitro.secure.debug') === '1';
    }
    catch
    {
        return false;
    }
};

const setDebugState = (message: string): void =>
{
    try
    {
        (window as any).__nitroSecureDebug = message;
        const log = Array.isArray((window as any).__nitroSecureDebugLog)
            ? (window as any).__nitroSecureDebugLog
            : [];

        log.push(message);
        (window as any).__nitroSecureDebugLog = log.slice(-50);

        if(!isDebugEnabled()) return;

        const existing = document.getElementById('nitro-secure-debug');

        if(existing)
        {
            existing.textContent = (window as any).__nitroSecureDebugLog.slice(-8).join('\n');
            return;
        }

        const node = document.createElement('div');
        node.id = 'nitro-secure-debug';
        node.style.position = 'fixed';
        node.style.left = '8px';
        node.style.bottom = '8px';
        node.style.zIndex = '2147483647';
        node.style.padding = '6px 8px';
        node.style.maxWidth = '70vw';
        node.style.background = 'rgba(0,0,0,0.85)';
        node.style.color = '#00ff90';
        node.style.font = '12px monospace';
        node.style.whiteSpace = 'pre-wrap';
        node.style.pointerEvents = 'none';
        node.textContent = (window as any).__nitroSecureDebugLog.slice(-8).join('\n');
        document.body.appendChild(node);
    }
    catch {}
};

const textEncoder = new TextEncoder();
const textDecoder = new TextDecoder();

let secureSessionPromise: Promise<SecureSession> = null;
let installed = false;
const secureResponseCache = new Map<string, Promise<Response>>();

const bytesToBase64 = (bytes: ArrayBuffer): string =>
{
    let binary = '';
    const view = new Uint8Array(bytes);

    for(let index = 0; index < view.length; index++) binary += String.fromCharCode(view[index]);

    return btoa(binary);
};

const hexValue = (code: number): number =>
{
    if(code >= 48 && code <= 57) return code - 48;
    if(code >= 65 && code <= 70) return code - 55;
    if(code >= 97 && code <= 102) return code - 87;

    return -1;
};

const hexToBytes = (hex: string): Uint8Array =>
{
    const normalized = hex.trim();

    if((normalized.length % 2) !== 0) throw new Error('Invalid encrypted hex payload.');

    const bytes = new Uint8Array(normalized.length / 2);

    for(let index = 0; index < bytes.length; index++)
    {
        const high = hexValue(normalized.charCodeAt(index * 2));
        const low = hexValue(normalized.charCodeAt((index * 2) + 1));

        if(high < 0 || low < 0) throw new Error('Invalid encrypted hex payload.');

        bytes[index] = (high << 4) | low;
    }

    return bytes;
};

const deriveAesKey = async (privateKey: CryptoKey, serverKeyBase64: string): Promise<{ key: CryptoKey; fingerprint: string }> =>
{
    const serverBytes = Uint8Array.from(atob(serverKeyBase64), char => char.charCodeAt(0));
    const serverKey = await crypto.subtle.importKey(
        'spki',
        serverBytes,
        { name: 'ECDH', namedCurve: 'P-256' },
        false,
        []
    );

    const secret = await crypto.subtle.deriveBits({ name: 'ECDH', public: serverKey }, privateKey, 256);
    const salt = textEncoder.encode('nitro-secure-assets-v1');
    const material = new Uint8Array(secret.byteLength + salt.length);
    material.set(new Uint8Array(secret), 0);
    material.set(salt, secret.byteLength);

    const hash = await crypto.subtle.digest('SHA-256', material);
    const fingerprintHash = await crypto.subtle.digest('SHA-256', hash);
    const fingerprint = Array.from(new Uint8Array(fingerprintHash).slice(0, 8)).map(value => value.toString(16).padStart(2, '0')).join('');

    return {
        key: await crypto.subtle.importKey('raw', hash, 'AES-GCM', false, [ 'encrypt', 'decrypt' ]),
        fingerprint
    };
};

const getApiBase = (): string =>
{
    const configured = (window as any).NitroSecureApiUrl;

    if(typeof configured === 'string' && configured.length) return configured.replace(/\/$/, '');

    return 'https://nitro.slogga.it:2096';
};

export const secureUrl = (kind: 'config' | 'gamedata', file: string): string =>
{
    const base = getApiBase();

    return `${ base }/nitro-sec/file?kind=${ encodeURIComponent(kind) }&file=${ encodeURIComponent(file) }`;
};

const createSecureSession = async (): Promise<SecureSession> =>
{
    setDebugState('secure: generating ECDH session');

    const pair = await crypto.subtle.generateKey(
        { name: 'ECDH', namedCurve: 'P-256' },
        true,
        [ 'deriveBits' ]
    );
    const publicKey = await crypto.subtle.exportKey('spki', pair.publicKey);
    const response = await fetch(`${ getApiBase() }/nitro-sec/bootstrap`, {
        method: 'POST',
        headers: { 'Content-Type': 'application/json' },
        body: JSON.stringify({ key: bytesToBase64(publicKey) })
    });

    if(!response.ok) throw new Error(`Secure bootstrap failed: HTTP ${ response.status }`);

    const fingerprint = response.headers.get('X-Nitro-Key-Fp') || 'none';
    const payload = await response.json();
    const serverKey = typeof payload.key === 'string' ? payload.key : '';
    const clientPublicKey = bytesToBase64(publicKey);

    if(!serverKey) throw new Error('Secure bootstrap returned an invalid server key.');

    setDebugState(`secure: bootstrap ok fp=${ fingerprint }`);

    const derived = await deriveAesKey(pair.privateKey, serverKey);

    return { publicKey: clientPublicKey, key: derived.key, fingerprint: derived.fingerprint };
};

export const getSecureSession = (): Promise<SecureSession> =>
{
    if(!secureSessionPromise) secureSessionPromise = createSecureSession();

    return secureSessionPromise;
};

const decryptResponse = async (session: SecureSession, response: Response): Promise<Response> =>
{
    setDebugState(`secure: decrypt start status=${ response.status }`);
    const bytes = hexToBytes(await response.text());

    if(bytes.length < 13) throw new Error('Encrypted response is too short.');

    const iv = bytes.slice(0, 12);
    const payload = bytes.slice(12);
    const clear = await crypto.subtle.decrypt({ name: 'AES-GCM', iv }, session.key, payload);
    const headers = new Headers(response.headers);

    headers.set('Content-Type', 'application/json; charset=utf-8');
    headers.delete('X-Nitro-Sec');

    const text = textDecoder.decode(clear);
    setDebugState(`secure: decrypt ok bytes=${ bytes.length }`);

    return new Response(text, {
        status: response.status,
        statusText: response.statusText,
        headers
    });
};

const cloneCachedResponse = async (responsePromise: Promise<Response>): Promise<Response> =>
{
    const response = await responsePromise;

    return response.clone();
};

const normalizeSecureCacheKey = (requestUrl: string): string =>
{
    try
    {
        const url = new URL(requestUrl, window.location.href);

        if(!url.pathname.includes('/nitro-sec/file')) return requestUrl;

        const kind = url.searchParams.get('kind') || '';
        const file = (url.searchParams.get('file') || '')
            .replace(/^[\\/]+/, '')
            .split('?')[0]
            .split('#')[0];

        return `${ url.origin }${ url.pathname }?kind=${ kind }&file=${ file }`;
    }
    catch
    {
        return requestUrl;
    }
};

const bytesToHex = (bytes: Uint8Array): string =>
{
    let output = '';

    for(let index = 0; index < bytes.length; index++) output += bytes[index].toString(16).padStart(2, '0');

    return output;
};

const encryptBytes = async (session: SecureSession, clear: ArrayBuffer): Promise<string> =>
{
    const iv = crypto.getRandomValues(new Uint8Array(12));
    const encrypted = new Uint8Array(await crypto.subtle.encrypt({ name: 'AES-GCM', iv }, session.key, clear));
    const out = new Uint8Array(iv.length + encrypted.length);

    out.set(iv, 0);
    out.set(encrypted, iv.length);

    return bytesToHex(out);
};

const isApiUrl = (requestUrl: string): boolean =>
{
    try
    {
        return new URL(requestUrl, window.location.href).pathname.startsWith('/api/');
    }
    catch
    {
        return requestUrl.startsWith('/api/');
    }
};

const readRequestBody = async (input: RequestInfo | URL, init: RequestInit | undefined, method: string): Promise<ArrayBuffer | null> =>
{
    if(method === 'GET' || method === 'HEAD') return null;
    if(init?.body !== undefined)
    {
        if(typeof init.body === 'string') return textEncoder.encode(init.body).buffer;
        if(init.body instanceof ArrayBuffer) return init.body;
        if(ArrayBuffer.isView(init.body)) return init.body.buffer.slice(init.body.byteOffset, init.body.byteOffset + init.body.byteLength);
        if(init.body instanceof Blob) return init.body.arrayBuffer();
    }

    if(input instanceof Request) return input.clone().arrayBuffer();

    return null;
};

export const installSecureFetch = (): void =>
{
    if(installed) return;

    installed = true;
    const nativeFetch = window.fetch.bind(window);

    window.fetch = async (input: RequestInfo | URL, init?: RequestInit): Promise<Response> =>
    {
        const requestUrl = typeof input === 'string'
            ? input
            : input instanceof URL
                ? input.toString()
                : input.url;

        if(requestUrl.includes('/nitro-sec/file'))
        {
            const method = init?.method || (input instanceof Request ? input.method : 'GET');
            const cacheKey = method.toUpperCase() === 'GET' ? normalizeSecureCacheKey(requestUrl) : null;

            if(cacheKey && secureResponseCache.has(cacheKey)) return cloneCachedResponse(secureResponseCache.get(cacheKey));

            const responsePromise = (async () =>
            {
                const session = await getSecureSession();
                setDebugState(`secure: fetching ${ requestUrl }`);
                const headers = new Headers(init?.headers || (input instanceof Request ? input.headers : undefined));

                headers.set('X-Nitro-Key', session.publicKey);

                const response = await nativeFetch(input, { ...init, headers });
                setDebugState(`secure: response ${ response.status } encrypted=${ response.headers.get('X-Nitro-Sec') === '1' } fp=${ response.headers.get('X-Nitro-Key-Fp') || 'none' } derive=${ response.headers.get('X-Nitro-Derive-Fp') || 'none' } client=${ session.fingerprint }`);

                if(response.headers.get('X-Nitro-Sec') === '1')
                {
                    try
                    {
                        const decrypted = await decryptResponse(session, response);
                        setDebugState(`secure: decrypted ${ requestUrl }`);
                        return decrypted;
                    }
                    catch(error)
                    {
                        setDebugState(`secure: decrypt failed ${ (error as Error)?.message || error }`);
                        throw error;
                    }
                }

                setDebugState(`secure: plain response ${ requestUrl } status=${ response.status }`);

                return response;
            })();

            if(cacheKey) secureResponseCache.set(cacheKey, responsePromise);

            return cloneCachedResponse(responsePromise);
        }

        if(isApiUrl(requestUrl))
        {
            const method = (init?.method || (input instanceof Request ? input.method : 'GET')).toUpperCase();
            const session = await getSecureSession();
            const headers = new Headers(init?.headers || (input instanceof Request ? input.headers : undefined));
            const clearBody = await readRequestBody(input, init, method);
            const encryptedInit: RequestInit = { ...init, method, headers };

            headers.set('X-Nitro-Key', session.publicKey);
            headers.set('X-Nitro-Api', '1');

            if(clearBody)
            {
                encryptedInit.body = await encryptBytes(session, clearBody);
                headers.set('Content-Type', 'text/plain; charset=utf-8');
            }

            const response = await nativeFetch(input, encryptedInit);

            if(response.headers.get('X-Nitro-Sec') === '1') return decryptResponse(session, response);

            return response;
        }

        return nativeFetch(input, init);
    };
};