app.py

import os
import io
import base64
from typing import List, Tuple, Optional

import gradio as gr
from PIL import Image
from openai import OpenAI


BASE_URL = "https://api.stepfun.com/v1"
DEFAULT_MODEL = "step-3"  # 可改为 step-r1-v-mini
DEFAULT_DETAIL = "high"   # high | low | auto


def _get_api_key() -> Optional[str]:
    # 优先读环境变量（在 HF Spaces 的 Settings -> Variables and secrets 中配置）
    return os.environ.get("STEPFUN_API_KEY")


def pil_image_to_data_uri(img: Image.Image) -> str:
    buffer = io.BytesIO()
    # 统一编码为 JPEG，降低大小并确保浏览器/模型兼容
    rgb_img = img.convert("RGB")
    rgb_img.save(buffer, format="JPEG", quality=90)
    b64 = base64.b64encode(buffer.getvalue()).decode("utf-8")
    return f"data:image/jpeg;base64,{b64}"


def build_messages(
    chat_history: List[Tuple[str, str]],
    user_text: str,
    image: Optional[Image.Image],
    system_prompt: Optional[str],
    detail: str,
) -> list:
    messages: List[dict] = []

    if system_prompt:
        messages.append({"role": "system", "content": system_prompt})

    # 将历史轮次压缩为仅文本内容（简单稳妥）
    for user_turn, assistant_turn in chat_history:
        if user_turn:
            messages.append({
                "role": "user",
                "content": [{"type": "text", "text": user_turn}],
            })
        if assistant_turn:
            messages.append({
                "role": "assistant",
                "content": [{"type": "text", "text": assistant_turn}],
            })

    # 当前用户输入：可包含图片 + 文本
    content: List[dict] = []
    if image is not None:
        data_uri = pil_image_to_data_uri(image)
        content.append({
            "type": "image_url",
            "image_url": {"url": data_uri, "detail": detail},
        })
    if user_text:
        content.append({"type": "text", "text": user_text})

    if not content:
        # 保底，避免空消息
        content.append({"type": "text", "text": ""})

    messages.append({"role": "user", "content": content})
    return messages


def stream_response(
    user_text: str,
    image: Optional[Image.Image],
    model: str,
    detail: str,
    system_prompt: str,
    chat_history: List[Tuple[str, str]],
):
    api_key = _get_api_key()
    if not api_key:
        error_text = "未检测到 STEPFUN_API_KEY，请在 Space 的 Settings -> Variables and secrets 中配置后重试。"
        # 将错误作为助手消息显示
        display_user = (user_text or "") + ("\n[已附带图片]" if image is not None else "")
        new_history = chat_history + [(display_user, error_text)]
        yield new_history, ""
        return

    client = OpenAI(api_key=api_key, base_url=BASE_URL)

    # 将用户消息先追加到对话框
    display_user = (user_text or "") + ("\n[已附带图片]" if image is not None else "")
    chat_history = chat_history + [(display_user, "")]  # 预先占位一条助手回复
    yield chat_history, ""

    try:
        messages = build_messages(chat_history[:-1], user_text=user_text, image=image, system_prompt=system_prompt, detail=detail)
        stream = client.chat.completions.create(
            model=model or DEFAULT_MODEL,
            messages=messages,
            stream=True,
        )

        assistant_acc = []
        for chunk in stream:
            delta = None
            try:
                delta = chunk.choices[0].delta
            except Exception:
                pass
            if delta and getattr(delta, "content", None):
                assistant_acc.append(delta.content)
                # 实时更新最后一条消息
                chat_history[-1] = (display_user, "".join(assistant_acc))
                yield chat_history, ""

    except Exception as e:
        chat_history[-1] = (display_user, f"[调用失败] {type(e).__name__}: {e}")
        yield chat_history, ""


with gr.Blocks(title="StepFun - Step3 Multimodal Chat", theme=gr.themes.Soft()) as demo:
    gr.Markdown("""
    # StepFun Step-3 多模态对话（Hugging Face Space）
    - 支持上传图片 + 文本提问，后端接口兼容 OpenAI Chat Completions。
    - 在 Space 中运行时，请到 Settings -> Variables and secrets 配置 `STEPFUN_API_KEY`。
    - 可在右上角切换到 **dev mode** 查看构建/运行日志。
    """)

    with gr.Row():
        model = gr.Dropdown(
            label="模型",
            choices=["step-3", "step-r1-v-mini"],
            value=DEFAULT_MODEL,
            interactive=True,
        )
        detail = gr.Dropdown(
            label="图像细节",
            choices=["high", "low", "auto"],
            value=DEFAULT_DETAIL,
            interactive=True,
        )

    system_prompt = gr.Textbox(
        label="系统提示（可选）",
        placeholder="例如：你是一个美食专家，回答要简洁。",
        lines=2,
    )

    chatbot = gr.Chatbot(height=420, show_label=False)

    with gr.Row():
        image = gr.Image(label="上传图片（可选）", type="pil")
        user_text = gr.Textbox(label="你的问题", placeholder="描述你的问题……", lines=4)

    with gr.Row():
        submit = gr.Button("发送", variant="primary")
        clear = gr.Button("清空对话")

    # 清空
    def _clear_chat():
        return [], None, ""

    clear.click(_clear_chat, outputs=[chatbot, image, user_text])

    # 发送并流式生成
    submit.click(
        fn=stream_response,
        inputs=[user_text, image, model, detail, system_prompt, chatbot],
        outputs=[chatbot, user_text],
    )


if __name__ == "__main__":
    # 本地调试：python app.py
    demo.queue().launch(server_name="0.0.0.0", server_port=int(os.environ.get("PORT", 7860)))