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.\n\nAnswer in the same language as the user. Give the shortest possible correct answer. No greetings, no filler, no emojis, no markdown formatting unless the user explicitly asks for code. Do not restate the question. Do not add caveats or disclaimers. Respond with just the answer — nothing else.";

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();
    }
});

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