server.js

import express from 'express';
import { fal } from '@fal-ai/client';

// --- Key Management Setup ---
// Read comma-separated keys from the SINGLE environment variable FAL_KEY
const FAL_KEY_STRING = process.env.FAL_KEY;
// Read the custom API Key for proxy authentication
const API_KEY = process.env.API_KEY;

// --- (Initial checks for FAL_KEY_STRING, API_KEY, parsing falKeys remain the same) ---
if (!FAL_KEY_STRING) {
    console.error("ERROR: FAL_KEY environment variable is not set.");
    console.error("Ensure FAL_KEY contains a comma-separated list of your Fal AI keys.");
    process.exit(1);
}
const falKeys = FAL_KEY_STRING.split(',')
    .map(key => key.trim())
    .filter(key => key.length > 0);
if (falKeys.length === 0) {
    console.error("ERROR: No valid Fal keys found in the FAL_KEY environment variable after parsing.");
    console.error("Ensure FAL_KEY is a comma-separated list, e.g., 'key1,key2,key3'.");
    process.exit(1);
}
if (!API_KEY) {
    console.error("ERROR: API_KEY environment variable is not set.");
    process.exit(1);
}
// --- (End initial checks) ---


let currentKeyIndex = 0;
const invalidKeys = new Set();
console.log(`Loaded ${falKeys.length} Fal AI Key(s) from the FAL_KEY environment variable.`);

// --- (getNextValidKey function remains the same) ---
function getNextValidKey() {
    if (invalidKeys.size >= falKeys.length) {
        console.error("All Fal AI keys are marked as invalid.");
        return null;
    }
    const initialIndex = currentKeyIndex;
    let attempts = 0;
    while (attempts < falKeys.length) {
        const keyIndex = currentKeyIndex % falKeys.length;
        const key = falKeys[keyIndex];
        currentKeyIndex = (keyIndex + 1) % falKeys.length;
        if (!invalidKeys.has(key)) {
            console.log(`Using Fal Key index: ${keyIndex} (from FAL_KEY list)`);
            return { key, index: keyIndex };
        } else {
            console.log(`Skipping invalid Fal Key index: ${keyIndex}`);
        }
        attempts++;
        if (currentKeyIndex === initialIndex && attempts > 0) {
            console.warn("Looped through all keys, potentially all are invalid.");
            break;
        }
    }
    console.error("Could not find a valid Fal AI key after checking all potentially available keys.");
    return null;
}

// --- (isKeyRelatedError function remains the same) ---
function isKeyRelatedError(error) {
    if (!error) return false;
    const message = error.message?.toLowerCase() || '';
    const status = error.status || error.statusCode;
    if (status === 401 || status === 403 || status === 429) {
        console.warn(`Detected potential key-related error (HTTP Status: ${status}).`);
        return true;
    }
    const keyErrorPatterns = [
        'invalid api key', 'authentication failed', 'permission denied',
        'quota exceeded', 'forbidden', 'unauthorized', 'rate limit',
        'credentials', 'api key missing', 'invalid credential',
        'exhausted balance', 'user is locked' // Add specific messages if observed
    ];
    if (keyErrorPatterns.some(pattern => message.includes(pattern))) {
        console.warn(`Detected potential key-related error (message contains relevant pattern: "${message}")`);
        return true;
    }
    // Also check the body.detail if status is 403, as seen in the logs
    if (status === 403 && error.body?.detail) {
        const detailMessage = error.body.detail.toLowerCase();
         if (keyErrorPatterns.some(pattern => detailMessage.includes(pattern))) {
            console.warn(`Detected potential key-related error (body.detail contains relevant pattern: "${detailMessage}")`);
            return true;
         }
    }
    return false;
}
// --- End Key Management Setup ---

const app = express();
app.use(express.json({ limit: '50mb' }));
app.use(express.urlencoded({ extended: true, limit: '50mb' }));
const PORT = process.env.PORT || 3000;

// --- (apiKeyAuth middleware remains the same) ---
const apiKeyAuth = (req, res, next) => {
    const authHeader = req.headers['authorization'];
    if (!authHeader) {
        console.warn('Unauthorized: No Authorization header provided');
        return res.status(401).json({ error: 'Unauthorized: No API Key provided' });
    }
    const authParts = authHeader.split(' ');
    if (authParts.length !== 2 || authParts[0].toLowerCase() !== 'bearer') {
        console.warn('Unauthorized: Invalid Authorization header format. Expected "Bearer <key>".');
        return res.status(401).json({ error: 'Unauthorized: Invalid Authorization header format' });
    }
    const providedKey = authParts[1];
    if (providedKey !== API_KEY) {
        console.warn('Unauthorized: Invalid API Key provided.');
        return res.status(401).json({ error: 'Unauthorized: Invalid API Key' });
    }
    next();
};
app.use(['/v1/models', '/v1/chat/completions'], apiKeyAuth);


// --- (Global Limits, FAL_SUPPORTED_MODELS, getOwner remain the same) ---
const PROMPT_LIMIT = 4800;
const SYSTEM_PROMPT_LIMIT = 4800;
const FAL_SUPPORTED_MODELS = [ /* ... model list ... */ ];
const getOwner = (modelId) => { /* ... */ };

// --- (GET /v1/models endpoint remains the same) ---
app.get('/v1/models', (req, res) => { /* ... */ });

// --- (convertMessagesToFalPrompt function remains the same) ---
function convertMessagesToFalPrompt(messages) { /* ... */ }


/**
 * MODIFIED: Makes a request to the Fal AI API, handling key rotation and retries on key-related errors.
 * For stream requests, returns the stream AND the key info used.
 * @param {object} falInput - The input object for the Fal AI API call.
 * @param {boolean} [stream=false] - Whether to make a streaming request.
 * @returns {Promise<object|{stream: AsyncIterable<object>, keyUsed: string, indexUsed: number}>}
 *          The result object for non-stream, or an object containing the stream and key info for stream.
 * @throws {Error} If the request fails after trying all valid keys, or if a non-key-related error occurs during *initiation*.
 */
async function makeFalRequestWithRetry(falInput, stream = false) {
    let attempts = 0;
    const maxAttempts = falKeys.length;
    const attemptedKeysInThisRequest = new Set();

    while (attempts < maxAttempts) {
        const keyInfo = getNextValidKey();
        if (!keyInfo) {
            console.error("makeFalRequestWithRetry: No valid Fal AI keys remaining.");
            throw new Error("No valid Fal AI keys available (all marked as invalid).");
        }
        if (attemptedKeysInThisRequest.has(keyInfo.key)) {
            console.warn(`Key at index ${keyInfo.index} was already attempted for this request. Skipping to find next different key.`);
            continue;
        }
        attemptedKeysInThisRequest.add(keyInfo.key);
        attempts++;

        try {
            console.log(`Attempt ${attempts}/${maxAttempts}: Trying Fal Key index ${keyInfo.index}...`);
            console.warn(`Configuring GLOBAL fal client with key index ${keyInfo.index}. Review concurrency implications.`);
            fal.config({ credentials: keyInfo.key });

            if (stream) {
                const falStream = await fal.stream("fal-ai/any-llm", { input: falInput });
                console.log(`Successfully initiated stream with key index ${keyInfo.index}.`);
                // **MODIFIED: Return stream AND key info**
                return { stream: falStream, keyUsed: keyInfo.key, indexUsed: keyInfo.index };
            } else {
                // Non-stream logic remains the same
                console.log(`Executing non-stream request with key index ${keyInfo.index}...`);
                const result = await fal.subscribe("fal-ai/any-llm", { input: falInput, logs: true });
                console.log(`Successfully received non-stream result with key index ${keyInfo.index}.`);
                if (result && result.error) {
                     console.error(`Fal AI returned an error object within the non-stream result payload (Key Index ${keyInfo.index}):`, result.error);
                     if (isKeyRelatedError(result.error)) {
                         console.warn(`Marking Fal Key index ${keyInfo.index} as invalid due to error in response payload.`);
                         invalidKeys.add(keyInfo.key);
                         continue; // Try next key
                     } else {
                         throw new Error(`Fal AI error reported in result payload: ${JSON.stringify(result.error)}`);
                     }
                 }
                return result; // Return only result for non-stream
            }
        } catch (error) {
            // This catch block now primarily handles errors during *request initiation*
            console.error(`Error caught during request initiation using Fal Key index ${keyInfo.index}:`, error.message || error);
            if (isKeyRelatedError(error)) {
                console.warn(`Marking Fal Key index ${keyInfo.index} as invalid due to caught initiation error.`);
                invalidKeys.add(keyInfo.key);
                // Continue loop to try the next key
            } else {
                console.error("Initiation error does not appear to be key-related. Failing request without further key retries.");
                throw error; // Re-throw non-key-related initiation error
            }
        }
    } // End while loop

    // If loop finishes, all keys failed during initiation
    throw new Error(`Request initiation failed after trying ${attempts} unique Fal key(s). All failed with key-related errors or were already marked invalid.`);
}


// POST /v1/chat/completions endpoint - Handles chat requests
app.post('/v1/chat/completions', async (req, res) => {
    const { model, messages, stream = false, reasoning = false, ...restOpenAIParams } = req.body;
    console.log(`--> POST /v1/chat/completions | Model: ${model} | Stream: ${stream}`);

    // --- (Input validation for model, messages remains the same) ---
     if (!model || !messages || !Array.isArray(messages) || messages.length === 0) {
        console.error("Invalid request: Missing 'model' or 'messages' array is empty/invalid.");
        return res.status(400).json({ error: 'Bad Request: `model` and a non-empty `messages` array are required.' });
    }

    let keyUsedForRequest = null; // Variable to store the key used for this request, if successful initiation
    let indexUsedForRequest = null;

    try {
        const { prompt, system_prompt } = convertMessagesToFalPrompt(messages);
        const falInput = { /* ... falInput setup ... */ };
        falInput.model = model;
        falInput.prompt = prompt;
        if (system_prompt && system_prompt.length > 0) {
             falInput.system_prompt = system_prompt;
        }
        falInput.reasoning = !!reasoning;

        console.log("Attempting Fal request with key rotation/retry logic...");
        console.log(`Prepared Input Lengths - System Prompt: ${system_prompt?.length || 0}, Prompt: ${prompt?.length || 0}`);

        if (stream) {
            res.setHeader('Content-Type', 'text/event-stream; charset=utf-8');
            /* ... other headers ... */
            res.setHeader('Cache-Control', 'no-cache');
            res.setHeader('Connection', 'keep-alive');
            res.setHeader('Access-Control-Allow-Origin', '*');
            res.flushHeaders();

            let previousOutput = '';
            let streamResult; // To hold the object { stream, keyUsed, indexUsed }

            try {
                // **MODIFIED: Get stream and key info**
                streamResult = await makeFalRequestWithRetry(falInput, true);
                const falStream = streamResult.stream;
                keyUsedForRequest = streamResult.keyUsed; // Store the key used for this stream
                indexUsedForRequest = streamResult.indexUsed;

                // Process the stream events asynchronously
                for await (const event of falStream) {
                    // --- (Stream event processing logic remains the same) ---
                    const currentOutput = (event && typeof event.output === 'string') ? event.output : '';
                    const isPartial = (event && typeof event.partial === 'boolean') ? event.partial : true;
                    const errorInfo = (event && event.error) ? event.error : null;

                    if (errorInfo) {
                        // Log error from within the stream, but might continue processing
                        console.error("Error received *within* fal stream event payload:", errorInfo);
                        const errorChunk = { /* ... error chunk details ... */ };
                        if (!res.writableEnded) { res.write(`data: ${JSON.stringify(errorChunk)}\n\n`); }
                        else { console.warn("Stream ended before writing event error."); }
                        // Decide whether to break or continue based on error severity if needed
                    }
                    let deltaContent = '';
                    if (currentOutput.startsWith(previousOutput)) {
                        deltaContent = currentOutput.substring(previousOutput.length);
                    } else if (currentOutput.length > 0) {
                         console.warn("Fal stream output mismatch/reset. Sending full current output as delta.");
                         deltaContent = currentOutput;
                         previousOutput = '';
                    }
                    previousOutput = currentOutput;
                    if (deltaContent || !isPartial) {
                        const openAIChunk = { /* ... chunk details ... */ };
                        openAIChunk.id = `chatcmpl-${Date.now()}`;
                        openAIChunk.object = "chat.completion.chunk";
                        openAIChunk.created = Math.floor(Date.now() / 1000);
                        openAIChunk.model = model;
                        openAIChunk.choices = [{ index: 0, delta: { content: deltaContent }, finish_reason: isPartial === false ? "stop" : null }];
                        if (!res.writableEnded) { res.write(`data: ${JSON.stringify(openAIChunk)}\n\n`); }
                        else { console.warn("Stream ended before writing data chunk."); }
                    }
                    // --- (End stream event processing) ---
                } // End for-await loop

                // Send [DONE] marker
                if (!res.writableEnded) {
                    res.write(`data: [DONE]\n\n`);
                    res.end();
                    console.log("<-- Stream finished successfully and [DONE] sent.");
                } else {
                     console.log("<-- Stream processing finished, but connection was already ended before [DONE].");
                }

            } catch (streamError) {
                // **MODIFIED CATCH BLOCK for stream processing errors**
                // This catches errors from makeFalRequestWithRetry (initiation failure)
                // OR errors thrown during the 'for await...of falStream' loop.
                console.error('Error during stream request processing:', streamError.message || streamError);

                // **NEW: Check if the error is key-related and invalidate the key if needed**
                // We only do this if keyUsedForRequest has been set (meaning initiation succeeded)
                // And if the error occurred *during* the stream processing, not during initiation
                // (initiation errors are handled inside makeFalRequestWithRetry)
                // The check `keyUsedForRequest !== null` helps distinguish.
                if (keyUsedForRequest && isKeyRelatedError(streamError)) {
                    console.warn(`Marking Fal Key index ${indexUsedForRequest} as invalid due to error during stream processing.`);
                    invalidKeys.add(keyUsedForRequest);
                }
                // else: The error was either not key-related, or occurred during initiation (already handled)

                // --- (Error reporting logic to client remains the same) ---
                 try {
                     if (!res.headersSent) {
                         // Error likely during initiation (caught from makeFalRequestWithRetry)
                         const errorMessage = (streamError instanceof Error) ? streamError.message : JSON.stringify(streamError);
                         res.status(502).json({ error: 'Failed to initiate Fal stream', details: errorMessage });
                         console.log("<-- Stream initiation failed response sent (502).");
                     } else if (!res.writableEnded) {
                         // Error during stream processing after headers sent
                         const errorDetails = (streamError instanceof Error) ? streamError.message : JSON.stringify(streamError);
                         res.write(`data: ${JSON.stringify({ error: { message: "Stream processing error after initiation", type: "proxy_error", details: errorDetails } })}\n\n`);
                         res.write(`data: [DONE]\n\n`);
                         res.end();
                         console.log("<-- Stream error sent within stream, stream ended.");
                     } else {
                        console.log("<-- Stream error occurred, but connection was already ended.");
                     }
                 } catch (finalError) {
                    console.error('Error sending stream error message to client:', finalError);
                    if (!res.writableEnded) { res.end(); }
                 }
                 // --- (End error reporting) ---
            }

        } else {
            // --- Non-Stream Logic (remains the same, uses makeFalRequestWithRetry directly) ---
            try {
                const result = await makeFalRequestWithRetry(falInput, false);
                const openAIResponse = { /* ... construct response ... */ };
                openAIResponse.id = `chatcmpl-${result.requestId || Date.now()}`;
                openAIResponse.object = "chat.completion";
                openAIResponse.created = Math.floor(Date.now() / 1000);
                openAIResponse.model = model;
                openAIResponse.choices = [{ index: 0, message: { role: "assistant", content: result.output || "" }, finish_reason: "stop" }];
                openAIResponse.usage = { prompt_tokens: null, completion_tokens: null, total_tokens: null };
                openAIResponse.system_fingerprint = null;
                if (result.reasoning) { openAIResponse.fal_reasoning = result.reasoning; }

                res.json(openAIResponse);
                console.log("<-- Non-stream response sent successfully.");
            } catch (error) {
                 console.error('Error during non-stream request processing:', error.message || error);
                if (!res.headersSent) {
                    const errorMessage = (error instanceof Error) ? error.message : JSON.stringify(error);
                    const finalMessage = errorMessage.includes("No valid Fal AI keys available") || errorMessage.includes("Request failed after trying")
                        ? `Fal request failed: ${errorMessage}`
                        : `Internal Server Error processing Fal request: ${errorMessage}`;
                    res.status(502).json({ error: 'Fal Request Failed', details: finalMessage });
                    console.log("<-- Non-stream error response sent (502).");
                } else {
                    console.error("Headers already sent for non-stream error response? This is unexpected.");
                    if (!res.writableEnded) { res.end(); }
                }
            }
        }

    } catch (error) {
        // --- (Outer catch block for setup errors remains the same) ---
        console.error('Unhandled error before initiating Fal request (likely setup or input conversion):', error.message || error);
        if (!res.headersSent) {
            const errorMessage = (error instanceof Error) ? error.message : JSON.stringify(error);
            res.status(500).json({ error: 'Internal Server Error in Proxy Setup', details: errorMessage });
            console.log("<-- Proxy setup error response sent (500).");
        } else {
             console.error("Headers already sent when catching setup error. Ending response.");
             if (!res.writableEnded) { res.end(); }
        }
    }
});

// --- (Server listen and root path handler remain the same) ---
app.listen(PORT, () => { /* ... startup messages ... */ });
app.get('/', (req, res) => { /* ... root message ... */ });