app.js

import cors from 'cors';
import dotenv from 'dotenv';
import express from 'express';
import { createClient } from '@supabase/supabase-js';
import { BedrockRuntimeClient, ConverseStreamCommand } from "@aws-sdk/client-bedrock-runtime";
import { NodeHttpHandler } from "@smithy/node-http-handler";
import path from 'path';
import { fileURLToPath } from 'url';

dotenv.config();
const app = express();
const PORT = process.env.PORT || 7860;

const __filename = fileURLToPath(import.meta.url);
const __dirname = path.dirname(__filename);

app.use(cors());
app.use(express.json({ limit: '50mb' }));
app.use(express.static(path.join(__dirname, 'public'))); 

// --- LOGGER HELPER ---
const log = {
    info: (msg, id = "SYS") => console.log(`[${new Date().toISOString()}] [INFO][${id}] ${msg}`),
    warn: (msg, id = "SYS") => console.warn(`[${new Date().toISOString()}] ⚠️ [WARN][${id}] ${msg}`),
    error: (msg, err, id = "SYS") => console.error(`[${new Date().toISOString()}] ❌ [ERROR] [${id}] ${msg}`, err?.message || err, err?.stack || "")
};

// --- SYSTEM PROMPT DEFINITIONS ---
const CLAUDE_SYSTEM_PROMPT = "You are a pro. Provide elite, high-level technical responses.";

// --- AI CLIENTS ---
const bedrockClient = new BedrockRuntimeClient({
    region: "us-east-1",
    requestHandler: new NodeHttpHandler({ http2Handler: undefined }) 
});

function getBedrockModelId(modelName) {
    switch(modelName) {
        case "haiku": return "arn:aws:bedrock:us-east-1:106774395747:inference-profile/global.anthropic.claude-haiku-4-5-20251001-v1:0";
        case "maverick": return "arn:aws:bedrock:us-east-1:106774395747:inference-profile/us.meta.llama4-maverick-17b-instruct-v1:0";
        case "claude": default: return "arn:aws:bedrock:us-east-1:106774395747:inference-profile/global.anthropic.claude-sonnet-4-6";
    }
}

// --- DB & MEMORY MANAGEMENT (SUPABASE) ---
const supabase = createClient(
    process.env.SUPABASE_URL || '',
    process.env.SUPABASE_KEY || ''
);

let memoryChats = {}; 
let dirtyChats = new Set(); 
const activeGenerations = new Map(); 

async function initDB() {
    try {
        log.info("Connecting to Supabase...");
        const { data: dbChats, error } = await supabase.from('chats').select('*');
        if (error) throw error;

        if (dbChats) {
            dbChats.forEach(c => {
                memoryChats[c.id] = { 
                    ...c, 
                    inputTokens: c.inputTokens || 0,
                    outputTokens: c.outputTokens || 0,
                    isGenerating: false 
                };
            });
            log.info(`Hydrated ${dbChats.length} chats from DB.`);
        }

        setInterval(async () => {
            if (dirtyChats.size === 0) return;
            const toSync = Array.from(dirtyChats);
            dirtyChats.clear();
            
            const rowsToUpsert = toSync.map(id => {
                const chat = memoryChats[id];
                chat.updatedAt = new Date().toISOString();
                return {
                    id: chat.id, title: chat.title, totalTokens: chat.totalTokens,
                    inputTokens: chat.inputTokens, outputTokens: chat.outputTokens,
                    messages: chat.messages, updatedAt: chat.updatedAt
                };
            });

            if (rowsToUpsert.length > 0) {
                const { error } = await supabase.from('chats').upsert(rowsToUpsert);
                if (error) log.error(`Supabase Sync Error.`, error);
                else log.info(`Synced ${rowsToUpsert.length} chats to Supabase.`);
            }
        }, 15000);

    } catch (err) {
        log.error('Supabase Initialization Error.', err);
    }
}
initDB();

// --- API ENDPOINTS ---

app.get('/api/chats', (req, res) => {
    const chatsList = Object.values(memoryChats).map(c => ({
        id: c.id, title: c.title, totalTokens: c.totalTokens, 
        inputTokens: c.inputTokens, outputTokens: c.outputTokens, updatedAt: c.updatedAt
    })).sort((a, b) => new Date(b.updatedAt) - new Date(a.updatedAt));
    res.json(chatsList);
});

app.get('/api/chats/:id', (req, res) => {
    const chat = memoryChats[req.params.id];
    if (!chat) return res.status(404).json({ error: "Chat not found" });
    res.json(chat);
});

app.post('/api/chats', (req, res) => {
    const newId = Date.now().toString();
    memoryChats[newId] = {
        id: newId, title: "New Chat", totalTokens: 0, inputTokens: 0, outputTokens: 0,
        messages:[], isGenerating: false, updatedAt: new Date().toISOString()
    };
    dirtyChats.add(newId);
    log.info("Created new chat.", newId);
    res.json(memoryChats[newId]);
});

app.put('/api/chats/:id/title', (req, res) => {
    const { id } = req.params;
    const { title } = req.body;
    if (!memoryChats[id]) return res.status(404).json({ error: "Chat not found" });
    if (!title || typeof title !== 'string') return res.status(400).json({ error: "Invalid title" });
    
    memoryChats[id].title = title.trim();
    dirtyChats.add(id);
    log.info(`Title updated to: "${title.trim()}"`, id);
    res.json({ success: true, title: memoryChats[id].title });
});

app.delete('/api/chats/:id', async (req, res) => {
    const { id } = req.params;
    if (activeGenerations.has(id)) {
        activeGenerations.get(id).abort();
        activeGenerations.delete(id);
    }
    delete memoryChats[id];
    dirtyChats.delete(id);
    await supabase.from('chats').delete().eq('id', id);
    log.info("Deleted chat permanently.", id);
    res.json({ success: true });
});

app.post('/api/chats/:id/stop', (req, res) => {
    const { id } = req.params;
    log.info("User requested to stop generation.", id);
    
    if (activeGenerations.has(id)) {
        activeGenerations.get(id).abort();
        activeGenerations.delete(id);
    }
    if (memoryChats[id]) {
        memoryChats[id].isGenerating = false;
        dirtyChats.add(id);
    }
    res.json({ success: true });
});

// --- STREAM ENDPOINT ---
app.post('/api/chats/:id/stream', async (req, res) => {
    const { id } = req.params;
    const { model, prompt, system_prompt, images } = req.body; 

    if (!memoryChats[id]) return res.status(404).send("Chat not found");
    if (!prompt || typeof prompt !== 'string' || prompt.trim() === '') {
        return res.status(400).send("Prompt cannot be empty");
    }

    if (memoryChats[id].isGenerating) {
        log.warn("Attempted concurrent generation. Rejecting request.", id);
        return res.status(409).json({ error: "Chat is currently generating." });
    }

    log.info(`Starting stream. Model: ${model} | Prompt length: ${prompt.length} | Images: ${images?.length || 0}`, id);

    if (memoryChats[id].messages.length === 0 && memoryChats[id].title === "New Chat") {
        memoryChats[id].title = prompt.substring(0, 30) + (prompt.length > 30 ? '...' : '');
    }

    memoryChats[id].messages.push({ role: "user", content: prompt });
    const aiMessage = { role: "assistant", content: "", reasoning: "" };
    memoryChats[id].messages.push(aiMessage);
    memoryChats[id].isGenerating = true;
    dirtyChats.add(id);

    const abortController = new AbortController();
    activeGenerations.set(id, abortController);

    res.setHeader('Content-Type', 'text/plain; charset=utf-8');
    res.setHeader('Transfer-Encoding', 'chunked');
    res.setHeader('X-Accel-Buffering', 'no'); 
    res.flushHeaders();

    const safeWrite = (data) => {
        if (!req.socket.destroyed && !res.writableEnded) {
            try { res.write(data); } catch (e) { log.warn("Socket disconnected during write.", id); }
        }
    };
    const safeEnd = () => {
        if (!req.socket.destroyed && !res.writableEnded) {
            try { res.end(); } catch (e) {}
        }
    };

    let streamInputTokens = 0;
    let streamOutputTokens = 0;
    let streamTotalTokens = 0;

    try {
        const bedrockModelId = getBedrockModelId(model);
        let contentBlock = [{ text: prompt }];
        
        if (images && images.length > 0) {
            const imageBlocks = images.map(imgStr => {
                const base64Data = imgStr.replace(/^data:image\/\w+;base64,/, "");
                return { image: { format: 'png', source: { bytes: Buffer.from(base64Data, 'base64') } } };
            });
            contentBlock =[...imageBlocks, ...contentBlock];
        }

        // --- NEW: Limit Context to 10 Messages Max securely ---
        let historySlice = memoryChats[id].messages.slice(0, -2).slice(-30);
        
        // Bedrock/Claude Converse API will fail if the message history starts with an "assistant" role.
        // We shift (remove) the first item if it's an assistant response.
        if (historySlice.length > 0 && historySlice[0].role === "assistant") {
            historySlice.shift();
        }

        const historicalMessages = historySlice.map(m => {
            let safeText = m.content;
            if (!safeText || safeText.trim() === "") {
                safeText = "[System Note: The model failed to generate a response here previously.]";
            }
            return { role: m.role, content:[{ text: safeText }] };
        });
        
        historicalMessages.push({ role: "user", content: contentBlock });

        // THE FIX: Uncapped Token limit for Claude 3.7 to allow massive reasoning + coding
        const commandMaxTokens = model.includes("claude") ? 64000 : 8192;

        const command = new ConverseStreamCommand({
            modelId: bedrockModelId,
            system:[{ text: system_prompt || CLAUDE_SYSTEM_PROMPT }],
            messages: historicalMessages,
            inferenceConfig: { maxTokens: commandMaxTokens, temperature: 1 },
           /* additionalModelRequestFields: model.includes("claude") ? { 
                thinking: { type: "adaptive" } 
            } : undefined
            */
        });

        const response = await bedrockClient.send(command, { abortSignal: abortController.signal });
        log.info(`Bedrock connected successfully (Max Tokens: ${commandMaxTokens}), streaming chunks...`, id);
        
        for await (const chunk of response.stream) {
            if (chunk.contentBlockDelta) {
                const delta = chunk.contentBlockDelta.delta;
                if (delta.reasoningContent && delta.reasoningContent.text) {
                    aiMessage.reasoning += delta.reasoningContent.text;
                    safeWrite(`__THINK__${delta.reasoningContent.text}`);
                } else if (delta.text) {
                    aiMessage.content += delta.text;
                    safeWrite(delta.text);
                }
            }
            // Log exactly why it stopped (e.g. max_tokens vs end_turn)
            if (chunk.messageStop) {
                log.info(`Stream stopped. Reason: ${chunk.messageStop.stopReason}`, id);
            }
            if (chunk.metadata && chunk.metadata.usage) {
                streamInputTokens = chunk.metadata.usage.inputTokens || 0;
                streamOutputTokens = chunk.metadata.usage.outputTokens || 0;
                streamTotalTokens = streamInputTokens + streamOutputTokens;
            }
        }
        
        log.info(`Stream completed normally. (In: ${streamInputTokens}, Out: ${streamOutputTokens})`, id);

    } catch (err) {
        if (err.name === 'AbortError' || err.name === 'TimeoutError') {
            log.warn("Generation aborted by user or timeout.", id);
            aiMessage.content += "\n\n*[Generation stopped by user]*";
            safeWrite("\n\n*[Generation stopped by user]*");
        } else {
            log.error("Generation failed during stream processing.", err, id);
            aiMessage.content += `\n\n**[Error]**: ${err.message}`;
            safeWrite(`\n\n**ERROR**: ${err.message}`);
        }
    } finally {
        activeGenerations.delete(id);
        
        memoryChats[id].inputTokens += streamInputTokens;
        memoryChats[id].outputTokens += streamOutputTokens;
        memoryChats[id].totalTokens += streamTotalTokens;
        memoryChats[id].isGenerating = false;
        dirtyChats.add(id);
        
        safeWrite(`__USAGE__${JSON.stringify({ 
            inputTokens: streamInputTokens, 
            outputTokens: streamOutputTokens, 
            totalTokens: streamTotalTokens 
        })}`);
        safeEnd();
    }
});

app.listen(PORT, '0.0.0.0', () => log.info(`AI Server live on http://localhost:${PORT}`));