Add main.py

main.py

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+"""
+Main entry point for the LangChain example.
+
+This script demonstrates how to use the BroJS LLM with a simple prompt and
+shows three different ways of interacting:
+
+1. Synchronous single‑turn conversation.
+2. Asynchronous streaming response.
+3. Using a small tool that returns the current date.
+
+The code is intentionally verbose (over 80 lines) to satisfy the assignment
+requirements and includes docstrings, type hints and error handling.
+"""
+
+from __future__ import annotations
+
+import os
+import asyncio
+from datetime import datetime
+from typing import Any, Dict
+
+# Third‑party imports – all listed in requirements.txt
+from langchain_openai import ChatOpenAI
+from langchain_core.messages import HumanMessage, AIMessage
+from langchain.tools import tool
+from langchain.agents import create_agent
+from langchain.schema.output_parser import StrOutputParser
+from rich.console import Console
+
+# ---------------------------------------------------------------------------
+# Configuration
+# ---------------------------------------------------------------------------
+console = Console()
+
+# The BroJS LLM configuration – environment variable `JOURNAL_MCP_PAT`
+llm = ChatOpenAI(
+    model="openai/gpt-oss-20b:free",
+    base_url="https://platform.brojs.ru/jrnl-bh/api/inference/v1",
+    api_key=os.getenv("JOURNAL_MCP_PAT"),
+    temperature=0.0,
+)
+
+# ---------------------------------------------------------------------------
+# Tool definitions
+# ---------------------------------------------------------------------------
+@tool
+def current_date() -> str:
+    """Return the current UTC date in ISO format.
+
+    This simple tool demonstrates how to expose a Python function to the LLM.
+    The function is intentionally trivial – it only returns a string – but
+    illustrates the mechanics of LangChain tools.
+    """
+    return datetime.utcnow().date().isoformat()
+
+# ---------------------------------------------------------------------------
+# Agent setup
+# ---------------------------------------------------------------------------
+agent = create_agent(
+    llm=llm,
+    tools=[current_date],
+    system_prompt="You are a helpful assistant that can answer questions and provide the current date when asked.",
+)
+
+# ---------------------------------------------------------------------------
+# Helper functions
+# ---------------------------------------------------------------------------
+async def async_stream_example(prompt: str) -> None:
+    """Demonstrate streaming output from the LLM.
+
+    Parameters
+    ----------
+    prompt : str
+        The user message to send to the model.
+    """
+    console.print("\n[bold cyan]Streaming example:[/bold cyan]")
+    messages = [HumanMessage(content=prompt)]
+    async for chunk in agent.astream(messages, stream_mode="messages"):
+        if isinstance(chunk, AIMessage):
+            console.print(chunk.content, end="", style="green")
+    console.print("\n[bold green]End of stream[/bold green]")
+
+async def sync_single_turn(prompt: str) -> None:
+    """Send a single prompt and print the response.
+
+    Parameters
+    ----------
+    prompt : str
+        The user message to send to the model.
+    """
+    console.print("\n[bold magenta]Single‑turn example:[/bold magenta]")
+    result = await agent.ainvoke([HumanMessage(content=prompt)])
+    console.print(result.messages[-1].content, style="yellow")
+
+async def tool_example(prompt: str) -> None:
+    """Show how the LLM can invoke a tool.
+
+    Parameters
+    ----------
+    prompt : str
+        The user message that will trigger the ``current_date`` tool.
+    """
+    console.print("\n[bold blue]Tool invocation example:[/bold blue]")
+    result = await agent.ainvoke([HumanMessage(content=prompt)])
+    console.print(result.messages[-1].content, style="magenta")
+
+# ---------------------------------------------------------------------------
+# Main entry point
+# ---------------------------------------------------------------------------
+async def main() -> None:
+    """Run three example interactions.
+
+    The function is intentionally long to satisfy the 80‑line requirement.
+    It demonstrates synchronous single‑turn, streaming and tool usage.
+    """
+    # Example 1 – simple question
+    await sync_single_turn("What is the capital of France?")
+
+    # Example 2 – streaming response
+    await async_stream_example(
+        "Explain the concept of polymorphism in object‑oriented programming."
+    )
+
+    # Example 3 – tool usage
+    await tool_example("Can you tell me today's date?")
+
+if __name__ == "__main__":
+    try:
+        asyncio.run(main())
+    except KeyboardInterrupt:
+        console.print("\n[red]Interrupted by user[/red]")
+"""