sechenov/server.js

const express = require('express');
const path = require('path');
const fs = require('fs');
const os = require('os');
const { ProxyAgent, setGlobalDispatcher } = require('undici');

const proxyUrl = process.env.HTTPS_PROXY || process.env.HTTP_PROXY;
if (proxyUrl) {
    setGlobalDispatcher(new ProxyAgent(proxyUrl));
    console.log(`✓ Using proxy: ${proxyUrl}`);
}

const app = express();
app.use(express.json({ limit: '10mb' }));
app.use(express.static(path.join(__dirname, 'public')));

const MODELS = {
    sonnet: 'claude-sonnet-4-6',
    haiku: 'claude-haiku-4-5-20251001',
};

function getAccessToken() {
    const configDir = process.env.CLAUDE_CONFIG_DIR || path.join(os.homedir(), '.claude');
    const credsPath = path.join(configDir, '.credentials.json');
    try {
        const creds = JSON.parse(fs.readFileSync(credsPath, 'utf8'));
        return creds?.claudeAiOauth?.accessToken || null;
    } catch (e) {
        return null;
    }
}

const SYSTEM_PROMPT = [
    "You are Claude Code, Anthropic's official CLI for Claude.",
    "",
    "Output the shortest possible correct answer in the user's language. No greetings, filler, emojis, markdown, restatement of the question, or any commentary.",
    "",
    "MULTIPLE QUESTIONS (numbered list of 2+ questions): output answers on a SINGLE horizontal line, separated by single spaces, each prefixed with its question number and a dot. Examples:",
    "   Input: 1. Столица Франции? А) Лондон Б) Париж В) Рим  2. 2+2? А) 3 Б) 4 В) 5",
    "   Output: 1.Б 2.Б",
    "   Input: 1. Столица Франции?  2. 2+2?  3. Самая длинная река России?",
    "   Output: 1.Париж 2.4 3.Лена",
    "",
    "If the question is multiple-choice (options А/Б/В/Г or A/B/C/D), answer with just the letter. If the question is open (word/number answer), answer with just the word/number/term — 1-3 words max, no sentence.",
    "",
    "SINGLE QUESTION (just one question with no numbering): output only the bare answer — letter, word, number, or term. No prefix, no number.",
    "",
    "CALCULATIONS: only the final numeric result, no units unless ambiguous, no steps.",
    "",
    "Respond with the answer only. Nothing else.",
].join("\n");

async function callClaude(modelId, text, accessToken) {
    return fetch('https://api.anthropic.com/v1/messages', {
        method: 'POST',
        headers: {
            'Content-Type': 'application/json',
            'Authorization': `Bearer ${accessToken}`,
            'anthropic-version': '2023-06-01',
            'anthropic-beta': 'claude-code-20250219,oauth-2025-04-20,interleaved-thinking-2025-05-14,fine-grained-tool-streaming-2025-05-14',
            'x-app': 'cli',
            'User-Agent': 'claude-cli/2.1.114',
        },
        body: JSON.stringify({
            model: modelId,
            max_tokens: 8192,
            stream: true,
            system: SYSTEM_PROMPT,
            messages: [{ role: 'user', content: text }],
        }),
    });
}

app.post('/api/chat', async (req, res) => {
    const { text, model = 'sonnet' } = req.body;
    if (!text?.trim()) return res.status(400).json({ error: 'text required' });

    const accessToken = getAccessToken();
    if (!accessToken) {
        return res.status(500).json({ error: 'No credentials in ' + (process.env.CLAUDE_CONFIG_DIR || '~/.claude') });
    }

    res.setHeader('Content-Type', 'text/event-stream');
    res.setHeader('Cache-Control', 'no-cache');
    res.setHeader('Connection', 'keep-alive');
    res.flushHeaders();

    const heartbeat = setInterval(() => res.write(': ping\n\n'), 15000);

    const primaryId = MODELS[model] || MODELS.sonnet;
    const fallbackId = MODELS.haiku;

    try {
        let apiResp = await callClaude(primaryId, text, accessToken);

        // Fallback to Haiku on rate limit
        if (apiResp.status === 429 && primaryId !== fallbackId) {
            apiResp = await callClaude(fallbackId, text, accessToken);
        }

        if (!apiResp.ok) {
            const errText = await apiResp.text();
            res.write(`data: ${JSON.stringify({ error: `${apiResp.status}: ${errText.substring(0, 500)}` })}\n\n`);
            return;
        }

        const reader = apiResp.body.getReader();
        const decoder = new TextDecoder();
        let buf = '';

        while (true) {
            const { done, value } = await reader.read();
            if (done) break;
            buf += decoder.decode(value, { stream: true });
            const events = buf.split('\n\n');
            buf = events.pop();
            for (const ev of events) {
                const dataLine = ev.split('\n').find(l => l.startsWith('data: '));
                if (!dataLine) continue;
                const payload = dataLine.slice(6);
                if (payload === '[DONE]') continue;
                try {
                    const obj = JSON.parse(payload);
                    if (obj.type === 'content_block_delta' && obj.delta?.type === 'text_delta') {
                        res.write(`data: ${JSON.stringify({ text: obj.delta.text })}\n\n`);
                    }
                } catch (e) {}
            }
        }
    } catch (err) {
        console.error('[api error]', err.message);
        res.write(`data: ${JSON.stringify({ error: err.message })}\n\n`);
    } finally {
        clearInterval(heartbeat);
        res.write('data: [DONE]\n\n');
        res.end();
    }
});

// ── iframe proxy: fetch student.sechenov.ru, strip X-Frame-Options, rewrite URLs ──
app.get('/proxy/*', async (req, res) => {
    const upstreamPath = req.url.replace(/^\/proxy/, '') || '/';
    const upstreamUrl = 'https://student.sechenov.ru' + upstreamPath;

    try {
        const r = await fetch(upstreamUrl, {
            headers: {
                'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36',
                'Accept': req.headers.accept || '*/*',
                'Accept-Language': req.headers['accept-language'] || 'ru,en;q=0.9',
            },
        });

        const ct = r.headers.get('content-type') || 'application/octet-stream';
        res.status(r.status);
        res.setHeader('Content-Type', ct);
        // strip framing restrictions
        res.removeHeader('X-Frame-Options');
        res.removeHeader('Content-Security-Policy');

        if (ct.includes('text/html')) {
            let html = await r.text();
            // rewrite relative URLs to absolute so browser loads assets directly
            html = html
                .replace(/(href|src|action)="\/(?!\/)/g, '$1="https://student.sechenov.ru/')
                .replace(/url\(["']?\/(?!\/)/g, 'url(https://student.sechenov.ru/')
                // neutralize meta CSP if present
                .replace(/<meta[^>]+http-equiv=["']?Content-Security-Policy["']?[^>]*>/gi, '');
            res.send(html);
        } else {
            // stream binary/text as-is
            const buf = Buffer.from(await r.arrayBuffer());
            res.send(buf);
        }
    } catch (e) {
        res.status(502).send('proxy error: ' + e.message);
    }
});

app.listen(8108, () => console.log('sechenov :8108'));