# coding=utf-8
# Implements API for ChatGLM2-6B in OpenAI's format. (https://platform.openai.com/docs/api-reference/chat)
# Usage: python openai_api.py
# Visit http://localhost:8000/docs for documents.


import time
import torch
import uvicorn
from pydantic import BaseModel, Field
from fastapi import FastAPI, HTTPException
from fastapi.middleware.cors import CORSMiddleware
from contextlib import asynccontextmanager
from starlette.responses import StreamingResponse
from typing import Any, Dict, List, Literal, Optional, Union
from transformers import AutoTokenizer, AutoModel


@asynccontextmanager
async def lifespan(app: FastAPI): # collects GPU memory
    yield
    if torch.cuda.is_available():
        torch.cuda.empty_cache()
        torch.cuda.ipc_collect()


app = FastAPI(lifespan=lifespan)

app.add_middleware(
    CORSMiddleware,
    allow_origins=["*"],
    allow_credentials=True,
    allow_methods=["*"],
    allow_headers=["*"],
)

class ModelCard(BaseModel):
    id: str
    object: str = "model"
    created: int = Field(default_factory=lambda: int(time.time()))
    owned_by: str = "owner"
    root: Optional[str] = None
    parent: Optional[str] = None
    permission: Optional[list] = None


class ModelList(BaseModel):
    object: str = "list"
    data: List[ModelCard] = []


class ChatMessage(BaseModel):
    role: Literal["user", "assistant", "system"]
    content: str


class DeltaMessage(BaseModel):
    role: Optional[Literal["user", "assistant", "system"]] = None
    content: Optional[str] = None


class ChatCompletionRequest(BaseModel):
    model: str
    messages: List[ChatMessage]
    temperature: Optional[float] = None
    top_p: Optional[float] = None
    max_length: Optional[int] = None
    stream: Optional[bool] = False


class ChatCompletionResponseChoice(BaseModel):
    index: int
    message: ChatMessage
    finish_reason: Literal["stop", "length"]


class ChatCompletionResponseStreamChoice(BaseModel):
    index: int
    delta: DeltaMessage
    finish_reason: Optional[Literal["stop", "length"]]


class ChatCompletionResponse(BaseModel):
    model: str
    object: Literal["chat.completion", "chat.completion.chunk"]
    choices: List[Union[ChatCompletionResponseChoice, ChatCompletionResponseStreamChoice]]
    created: Optional[int] = Field(default_factory=lambda: int(time.time()))


@app.get("/v1/models", response_model=ModelList)
async def list_models():
    global model_args
    model_card = ModelCard(id="gpt-3.5-turbo")
    return ModelList(data=[model_card])


@app.post("/v1/chat/completions", response_model=ChatCompletionResponse)
async def create_chat_completion(request: ChatCompletionRequest):
    global model, tokenizer

    if request.messages[-1].role != "user":
        raise HTTPException(status_code=400, detail="Invalid request")
    query = request.messages[-1].content

    prev_messages = request.messages[:-1]
    if len(prev_messages) > 0 and prev_messages[0].role == "system":
        query = prev_messages.pop(0).content + query

    history = []
    if len(prev_messages) % 2 == 0:
        for i in range(0, len(prev_messages), 2):
            if prev_messages[i].role == "user" and prev_messages[i+1].role == "assistant":
                history.append([prev_messages[i].content, prev_messages[i+1].content])

    if request.stream:
        generate = predict(query, history, request.model)
        return StreamingResponse(generate, media_type="text/event-stream")

    response, _ = model.chat(tokenizer, query, history=history)
    choice_data = ChatCompletionResponseChoice(
        index=0,
        message=ChatMessage(role="assistant", content=response),
        finish_reason="stop"
    )

    return ChatCompletionResponse(model=request.model, choices=[choice_data], object="chat.completion")


async def predict(query: str, history: List[List[str]], model_id: str):
    global model, tokenizer

    choice_data = ChatCompletionResponseStreamChoice(
        index=0,
        delta=DeltaMessage(role="assistant"),
        finish_reason=None
    )
    chunk = ChatCompletionResponse(model=model_id, choices=[choice_data], object="chat.completion.chunk")
    yield "data: {}\n\n".format(chunk.json(exclude_unset=True, ensure_ascii=False))

    current_length = 0

    for new_response, _ in model.stream_chat(tokenizer, query, history):
        if len(new_response) == current_length:
            continue

        new_text = new_response[current_length:]
        current_length = len(new_response)

        choice_data = ChatCompletionResponseStreamChoice(
            index=0,
            delta=DeltaMessage(content=new_text),
            finish_reason=None
        )
        chunk = ChatCompletionResponse(model=model_id, choices=[choice_data], object="chat.completion.chunk")
        yield "data: {}\n\n".format(chunk.json(exclude_unset=True, ensure_ascii=False))

    choice_data = ChatCompletionResponseStreamChoice(
        index=0,
        delta=DeltaMessage(),
        finish_reason="stop"
    )
    chunk = ChatCompletionResponse(model=model_id, choices=[choice_data], object="chat.completion.chunk")
    yield "data: {}\n\n".format(chunk.json(exclude_unset=True, ensure_ascii=False))


if __name__ == "__main__":
    tokenizer = AutoTokenizer.from_pretrained("chatglm2-6b", trust_remote_code=True)
    model = AutoModel.from_pretrained("chatglm2-6b", trust_remote_code=True).cuda()
    # 多显卡支持，使用下面两行代替上面一行，将num_gpus改为你实际的显卡数量
    # from utils import load_model_on_gpus
    # model = load_model_on_gpus("THUDM/chatglm2-6b", num_gpus=2)
    model.eval()

    uvicorn.run(app, host='0.0.0.0', port=8000, workers=1)