#
#  Copyright 2026 The InfiniFlow Authors. All Rights Reserved.
#
#  Licensed under the Apache License, Version 2.0 (the "License");
#  you may not use this file except in compliance with the License.
#  You may obtain a copy of the License at
#
#      http://www.apache.org/licenses/LICENSE-2.0
#
#  Unless required by applicable law or agreed to in writing, software
#  distributed under the License is distributed on an "AS IS" BASIS,
#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
#  See the License for the specific language governing permissions and
#  limitations under the License.
#

"""Surface selected internal INFO logs to the client as ``<think>`` content.

During an agentic ``rag_agent`` turn we attach a context-scoped logging sink so
the pipeline's bracket-tagged progress logs — ``[agentic-rag]``,
``[formalize_question]``, ``[pre_search]``, ``[Planner]``, ``[orchestrator]``,
``[agentic]``, ``[Hybrid search]``, ``[BM25 search]``, ``[Web search]``,
``[ToolLoop]``, ``[FunctionTool]`` … — can be streamed to the front end as
reasoning without instrumenting every call site.

The sink is stored in a :class:`contextvars.ContextVar`, so only the async task
tree of the current request (which inherits the context) forwards its logs —
concurrent requests stay isolated. Logs emitted from ``thread_pool_exec``
workers that did not inherit the context are simply skipped.
"""

from __future__ import annotations

import contextvars
import logging
from typing import Callable

# Per-request sink: a callable(str) that forwards one log line, or None when no
# agentic turn is streaming in the current context.
_think_log_sink: contextvars.ContextVar[Callable[[str], None] | None] = contextvars.ContextVar(
    "think_log_sink", default=None
)

# Only bracket-tagged INFO lines from these logger namespaces are surfaced.
_SCOPED_PREFIXES = ("rag.advanced_rag", "rag.llm.chat_model", "rag.llm.tool_decorator")

_installed = False


class ThinkLogHandler(logging.Handler):
    """Forward in-scope, bracket-tagged records to the active per-request sink."""

    def emit(self, record: logging.LogRecord) -> None:
        sink = _think_log_sink.get()
        if sink is None:
            return
        name = record.name or ""
        if not name.startswith(_SCOPED_PREFIXES):
            return
        try:
            msg = record.getMessage()
        except Exception:
            return
        # Only the bracket-tagged progress lines ("[Hybrid search] ...").
        if not msg or not msg.lstrip().startswith("["):
            return
        try:
            sink("<br>"+msg.strip())
        except Exception:
            # Never let think-log forwarding break the request or the logging
            # subsystem itself.
            pass


def install_think_log_handler() -> None:
    """Install the forwarding handler on the root logger exactly once."""
    global _installed
    if _installed:
        return
    handler = ThinkLogHandler(level=logging.INFO)
    logging.getLogger().addHandler(handler)
    _installed = True


def set_think_log_sink(sink: Callable[[str], None] | None):
    """Activate ``sink`` for the current context; returns the reset token."""
    return _think_log_sink.set(sink)


def reset_think_log_sink(token) -> None:
    try:
        _think_log_sink.reset(token)
    except Exception:
        pass