app.py

import os
import functools
from openai import OpenAI
import tiktoken
import gradio as gr

# Configure API client
api_key = os.getenv("OPENAI_API_KEY")
if not api_key:
    raise ValueError("Please set the OPENAI_API_KEY environment variable.")
client = OpenAI(api_key=api_key)

# Available models (comma-separated in env or fallback)
_env_models = os.getenv("OPENAI_MODEL_LIST", "gpt-3.5-turbo,gpt-4")
ALL_MODELS = [m.strip() for m in _env_models.split(",") if m.strip()]
if not ALL_MODELS:
    ALL_MODELS = ["gpt-3.5-turbo"]

# Token counter using tiktoken
@functools.lru_cache(maxsize=64)
def _get_encoding(model: str):
    try:
        return tiktoken.encoding_for_model(model)
    except KeyError:
        return tiktoken.get_encoding("cl100k_base")

def count_tokens(text: str, model: str) -> int:
    enc = _get_encoding(model)
    return len(enc.encode(text))

# Read uploaded file content (filepath or file-like)
def read_file_content(file_obj):
    if not file_obj:
        return ""
    try:
        if isinstance(file_obj, str):
            with open(file_obj, 'r', encoding='utf-8') as f:
                content = f.read()
            name = os.path.basename(file_obj)
        else:
            name = getattr(file_obj, 'name', 'uploaded_file')
            content = file_obj.read().decode('utf-8')
        return f"\n\n--- Start of file: {name} ---\n{content}\n--- End of file ---\n"
    except Exception:
        return ""

# Chat response function
def respond(message, history, model_name, file_obj):
    history = history or []
    file_text = read_file_content(file_obj)
    full_input = (message or "") + file_text

    # Call OpenAI chat completion
    messages = [{"role": "user", "content": full_input}]
    resp = client.chat.completions.create(
        model=model_name,
        messages=messages
    )
    reply = resp.choices[0].message.content

    # Token usage estimates
    prompt_tokens = count_tokens(full_input, model_name)
    completion_tokens = count_tokens(reply, model_name)
    usage_info = f"(Tokens used: prompt={prompt_tokens}, completion={completion_tokens})"

    # Update history (OpenAI-style messages)
    history.append({"role": "user", "content": message})
    history.append({"role": "assistant", "content": f"{reply}\n\n{usage_info}"})
    return history

# Build Gradio interface
with gr.Blocks() as demo:
    model_dropdown = gr.Dropdown(ALL_MODELS, value=ALL_MODELS[0], label="Select Model")
    chatbot = gr.Chatbot(label="Chat with AI", type="messages")
    file_upload = gr.File(label="Upload File", file_types=[".txt", ".md", ".py"], type="filepath")
    user_input = gr.Textbox(placeholder="Type your message...", show_label=False)

    user_input.submit(respond,
                      inputs=[user_input, chatbot, model_dropdown, file_upload],
                      outputs=chatbot)
    user_input.submit(lambda: "", None, user_input)

    demo.launch()