"""Centralized logging setup for Hermes Agent.

Provides a single ``setup_logging()`` entry point that both the CLI and
gateway call early in their startup path.  All log files live under
``~/.hermes/logs/`` (profile-aware via ``get_hermes_home()``).

Log files produced:
    agent.log   — INFO+, all agent/tool/session activity (the main log)
    errors.log  — WARNING+, errors and warnings only (quick triage)
    gateway.log — INFO+, gateway-only events (created when mode="gateway")
    gui.log     — INFO+, dashboard/websocket/TUI-gateway events
                  (created when mode="gui")

All files use ``RotatingFileHandler`` with ``RedactingFormatter`` so
secrets are never written to disk.

Component separation:
    gateway.log only receives records from ``gateway.*`` loggers —
    platform adapters, session management, slash commands, delivery.
    gui.log receives dashboard-side records from ``hermes_cli.web_server``,
    ``hermes_cli.pty_bridge``, ``tui_gateway.*``, and ``uvicorn.*``.
    agent.log remains the catch-all (everything goes there).

Session context:
    Call ``set_session_context(session_id)`` at the start of a conversation
    and ``clear_session_context()`` when done.  All log lines emitted on
    that thread will include ``[session_id]`` for filtering/correlation.
"""

import io
import logging
import os
import sys
import threading
from logging.handlers import RotatingFileHandler
from pathlib import Path
from typing import Optional, Sequence

from hermes_constants import get_config_path, get_hermes_home

# Sentinel to track whether setup_logging() has already run.  The function
# is idempotent — calling it twice is safe but the second call is a no-op
# unless ``force=True``.
_logging_initialized = False

# Thread-local storage for per-conversation session context.
_session_context = threading.local()

# Default log format — includes timestamp, level, optional session tag,
# logger name, and message.  The ``%(session_tag)s`` field is guaranteed to
# exist on every LogRecord via _install_session_record_factory() below.
_LOG_FORMAT = "%(asctime)s %(levelname)s%(session_tag)s %(name)s: %(message)s"
_LOG_FORMAT_VERBOSE = "%(asctime)s - %(name)s - %(levelname)s%(session_tag)s - %(message)s"


def _safe_stderr():  # type: ignore[return]
    """Return a stderr stream that tolerates Unicode on all platforms.

    On Windows the console encoding is often a legacy MBCS codec
    (cp949, cp1252, …) that raises ``UnicodeEncodeError`` for characters
    like the em-dash (U+2014).  We wrap ``sys.stderr`` in a
    ``TextIOWrapper`` with ``errors='replace'`` so log lines are never
    lost — un-encodable characters are replaced with ``?`` instead of
    crashing the process.
    """
    stream = sys.stderr
    encoding = getattr(stream, "encoding", None) or "utf-8"
    # Already UTF-8 or surrogate-aware — no wrapping needed.
    if encoding.lower().replace("-", "") in ("utf8", "utf8surrogateescape"):
        return stream
    try:
        buf = getattr(stream, "buffer", None)
        if buf is not None:
            wrapped = io.TextIOWrapper(
                buf,
                encoding="utf-8",
                errors="replace",
                line_buffering=True,
            )
            # Prevent the wrapper from closing the underlying buffer
            # when it is garbage-collected.
            wrapped.close = lambda: None  # type: ignore[assignment]
            return wrapped
    except Exception:
        pass
    # Best-effort: if wrapping fails, return the original stream.
    return stream

# Third-party loggers that are noisy at DEBUG/INFO level.
_NOISY_LOGGERS = (
    "openai",
    "openai._base_client",
    "httpx",
    "httpcore",
    "asyncio",
    "hpack",
    "hpack.hpack",
    "grpc",
    "modal",
    "urllib3",
    "urllib3.connectionpool",
    "websockets",
    "charset_normalizer",
    "markdown_it",
)


# ---------------------------------------------------------------------------
# Public session context API
# ---------------------------------------------------------------------------

def set_session_context(session_id: str) -> None:
    """Set the session ID for the current thread.

    All subsequent log records on this thread will include ``[session_id]``
    in the formatted output.  Call at the start of ``run_conversation()``.
    """
    _session_context.session_id = session_id


def clear_session_context() -> None:
    """Clear the session ID for the current thread."""
    _session_context.session_id = None


# ---------------------------------------------------------------------------
# Record factory — injects session_tag into every LogRecord at creation
# ---------------------------------------------------------------------------

def _install_session_record_factory() -> None:
    """Replace the global LogRecord factory with one that adds ``session_tag``.

    Unlike a ``logging.Filter`` on a handler or logger, the record factory
    runs for EVERY record in the process — including records that propagate
    from child loggers and records handled by third-party handlers.  This
    guarantees ``%(session_tag)s`` is always available in format strings,
    eliminating the KeyError that would occur if a handler used our format
    without having a ``_SessionFilter`` attached.

    Idempotent — checks for a marker attribute to avoid double-wrapping if
    the module is reloaded.
    """
    current_factory = logging.getLogRecordFactory()
    if getattr(current_factory, "_hermes_session_injector", False):
        return  # already installed

    def _session_record_factory(*args, **kwargs):
        record = current_factory(*args, **kwargs)
        sid = getattr(_session_context, "session_id", None)
        record.session_tag = f" [{sid}]" if sid else ""  # type: ignore[attr-defined]
        return record

    _session_record_factory._hermes_session_injector = True  # type: ignore[attr-defined]
    logging.setLogRecordFactory(_session_record_factory)


# Install immediately on import — session_tag is available on all records
# from this point forward, even before setup_logging() is called.
_install_session_record_factory()


# ---------------------------------------------------------------------------
# Filters
# ---------------------------------------------------------------------------

class _ComponentFilter(logging.Filter):
    """Only pass records whose logger name starts with one of *prefixes*.

    Used to route gateway-specific records to ``gateway.log`` while
    keeping ``agent.log`` as the catch-all.
    """

    def __init__(self, prefixes: Sequence[str]) -> None:
        super().__init__()
        self._prefixes = tuple(prefixes)

    def filter(self, record: logging.LogRecord) -> bool:
        return record.name.startswith(self._prefixes)


# Logger name prefixes that belong to each component.
# Used by _ComponentFilter and exposed for ``hermes logs --component``.
COMPONENT_PREFIXES = {
    "gateway": ("gateway", "hermes_plugins"),
    "agent": ("agent", "run_agent", "model_tools", "batch_runner"),
    "tools": ("tools",),
    "cli": ("hermes_cli", "cli"),
    "cron": ("cron",),
    "gui": (
        "hermes_cli.web_server",
        "hermes_cli.pty_bridge",
        "tui_gateway",
        "uvicorn",
    ),
}


# ---------------------------------------------------------------------------
# Main setup
# ---------------------------------------------------------------------------

def setup_logging(
    *,
    hermes_home: Optional[Path] = None,
    log_level: Optional[str] = None,
    max_size_mb: Optional[int] = None,
    backup_count: Optional[int] = None,
    mode: Optional[str] = None,
    force: bool = False,
) -> Path:
    """Configure the Hermes logging subsystem.

    Safe to call multiple times — the second call is a no-op unless
    *force* is ``True``.

    Parameters
    ----------
    hermes_home
        Override for the Hermes home directory.  Falls back to
        ``get_hermes_home()`` (profile-aware).
    log_level
        Minimum level for the ``agent.log`` file handler.  Accepts any
        standard Python level name (``"DEBUG"``, ``"INFO"``, ``"WARNING"``).
        Defaults to ``"INFO"`` or the value from config.yaml ``logging.level``.
    max_size_mb
        Maximum size of each log file in megabytes before rotation.
        Defaults to 5 or the value from config.yaml ``logging.max_size_mb``.
    backup_count
        Number of rotated backup files to keep.
        Defaults to 3 or the value from config.yaml ``logging.backup_count``.
    mode
        Caller context: ``"cli"``, ``"gateway"``, ``"gui"``, ``"cron"``.
        When ``"gateway"``, an additional ``gateway.log`` file is created
        that receives only gateway-component records.
        When ``"gui"``, an additional ``gui.log`` file is created that
        receives dashboard and TUI-gateway component records.
    force
        Re-run setup even if it has already been called.

    Returns
    -------
    Path
        The ``logs/`` directory where files are written.
    """
    global _logging_initialized
    home = hermes_home or get_hermes_home()
    log_dir = home / "logs"
    log_dir.mkdir(parents=True, exist_ok=True)

    # Read config defaults (best-effort — config may not be loaded yet).
    cfg_level, cfg_max_size, cfg_backup = _read_logging_config()

    level_name = (log_level or cfg_level or "INFO").upper()
    level = getattr(logging, level_name, logging.INFO)
    max_bytes = (max_size_mb or cfg_max_size or 5) * 1024 * 1024
    backups = backup_count or cfg_backup or 3

    # Lazy import to avoid circular dependency at module load time.
    from agent.redact import RedactingFormatter

    root = logging.getLogger()

    # --- agent.log (INFO+) — the main activity log -------------------------
    _add_rotating_handler(
        root,
        log_dir / "agent.log",
        level=level,
        max_bytes=max_bytes,
        backup_count=backups,
        formatter=RedactingFormatter(_LOG_FORMAT),
    )

    # --- errors.log (WARNING+) — quick triage log --------------------------
    _add_rotating_handler(
        root,
        log_dir / "errors.log",
        level=logging.WARNING,
        max_bytes=2 * 1024 * 1024,
        backup_count=2,
        formatter=RedactingFormatter(_LOG_FORMAT),
    )

    # --- gateway.log (INFO+, gateway component only) ------------------------
    if mode == "gateway":
        _add_rotating_handler(
            root,
            log_dir / "gateway.log",
            level=logging.INFO,
            max_bytes=5 * 1024 * 1024,
            backup_count=3,
            formatter=RedactingFormatter(_LOG_FORMAT),
            log_filter=_ComponentFilter(COMPONENT_PREFIXES["gateway"]),
        )

    # --- gui.log (INFO+, dashboard/tui-gateway components) -----------------
    if mode == "gui":
        _add_rotating_handler(
            root,
            log_dir / "gui.log",
            level=logging.INFO,
            max_bytes=10 * 1024 * 1024,
            backup_count=5,
            formatter=RedactingFormatter(_LOG_FORMAT),
            log_filter=_ComponentFilter(COMPONENT_PREFIXES["gui"]),
        )

    if _logging_initialized and not force:
        return log_dir

    # Ensure root logger level is low enough for the handlers to fire.
    if root.level == logging.NOTSET or root.level > level:
        root.setLevel(level)

    # Suppress noisy third-party loggers.
    for name in _NOISY_LOGGERS:
        logging.getLogger(name).setLevel(logging.WARNING)

    _logging_initialized = True
    return log_dir


def setup_verbose_logging() -> None:
    """Enable DEBUG-level console logging for ``--verbose`` / ``-v`` mode.

    Called by ``AIAgent.__init__()`` when ``verbose_logging=True``.
    """
    from agent.redact import RedactingFormatter

    root = logging.getLogger()

    # Avoid adding duplicate stream handlers.
    for h in root.handlers:
        if isinstance(h, logging.StreamHandler) and not isinstance(h, RotatingFileHandler):
            if getattr(h, "_hermes_verbose", False):
                return

    handler = logging.StreamHandler(_safe_stderr())
    handler.setLevel(logging.DEBUG)
    handler.setFormatter(RedactingFormatter(_LOG_FORMAT_VERBOSE, datefmt="%H:%M:%S"))
    handler._hermes_verbose = True  # type: ignore[attr-defined]
    root.addHandler(handler)

    # Lower root logger level so DEBUG records reach all handlers.
    if root.level > logging.DEBUG:
        root.setLevel(logging.DEBUG)

    # Keep third-party libraries at WARNING to reduce noise.
    for name in _NOISY_LOGGERS:
        logging.getLogger(name).setLevel(logging.WARNING)
    # rex-deploy at INFO for sandbox status.
    logging.getLogger("rex-deploy").setLevel(logging.INFO)


# ---------------------------------------------------------------------------
# Internal helpers
# ---------------------------------------------------------------------------

class _ManagedRotatingFileHandler(RotatingFileHandler):
    """RotatingFileHandler that ensures group-writable perms in managed mode
    AND survives external rotation.

    Two responsibilities:

    1.  In managed mode (NixOS), the stateDir uses setgid (2770) so new files
        inherit the hermes group. However, both ``_open()`` (initial creation)
        and ``doRollover()`` create files via ``open()``, which uses the
        process umask — typically 0022, producing 0644. This subclass applies
        ``chmod 0660`` after both operations so the gateway and interactive
        users can share log files.

    2.  ``RotatingFileHandler`` keeps an open file descriptor.  If anything
        rotates the file *externally* (``logrotate``, manual ``mv``,
        another process rotating under us, a transient unlink), our fd
        keeps pointing at the renamed/unlinked inode and every subsequent
        write goes to ``gateway.log.1`` instead of ``gateway.log`` — silent
        log loss for the file every operator expects to read.  Before each
        emit we ``stat`` ``baseFilename`` and compare it against the open
        stream's inode; on mismatch we reopen.  This is the same pattern
        as stdlib ``WatchedFileHandler.reopenIfNeeded()``, adapted for
        rotating handlers.
    """

    def __init__(self, *args, **kwargs):
        from hermes_cli.config import is_managed
        self._managed = is_managed()
        super().__init__(*args, **kwargs)
        # Snapshot the inode of the currently open stream so emit() can
        # detect external rotation without an extra fstat per write.
        self._stat_dev: Optional[int] = None
        self._stat_ino: Optional[int] = None
        self._record_stream_stat()

    def _chmod_if_managed(self):
        if self._managed:
            try:
                os.chmod(self.baseFilename, 0o660)
            except OSError:
                pass

    def _record_stream_stat(self) -> None:
        """Snapshot dev/ino of ``baseFilename`` so we can detect external rotation."""
        try:
            st = os.stat(self.baseFilename)
            self._stat_dev, self._stat_ino = st.st_dev, st.st_ino
        except OSError:
            self._stat_dev, self._stat_ino = None, None

    def _reopen_if_externally_rotated(self) -> None:
        """Reopen the stream when ``baseFilename`` no longer matches our fd.

        Triggered when ``baseFilename`` was renamed (logrotate), unlinked,
        or replaced by a different inode.  Silent + best-effort: any error
        falls back to the existing (possibly stale) stream so logging keeps
        working instead of dying on a stat failure.
        """
        try:
            st = os.stat(self.baseFilename)
        except FileNotFoundError:
            # File was rotated/unlinked underneath us.  Close + reopen so a
            # fresh inode is created at the expected path.
            try:
                if self.stream is not None:
                    self.stream.close()
            except Exception:
                pass
            self.stream = None  # type: ignore[assignment]
            try:
                self.stream = self._open()
                self._record_stream_stat()
            except Exception:
                # Couldn't reopen — leave stream=None; next emit will
                # bail rather than write to a stale inode.
                pass
            return
        except OSError:
            return  # transient — try again on the next emit

        if self._stat_dev is None or self._stat_ino is None:
            self._stat_dev, self._stat_ino = st.st_dev, st.st_ino
            return

        if (st.st_dev, st.st_ino) != (self._stat_dev, self._stat_ino):
            # baseFilename now points at a DIFFERENT inode than the one we
            # hold open.  Close the old stream and open the new file.
            try:
                if self.stream is not None:
                    self.stream.close()
            except Exception:
                pass
            self.stream = None  # type: ignore[assignment]
            try:
                self.stream = self._open()
                self._stat_dev, self._stat_ino = st.st_dev, st.st_ino
            except Exception:
                pass

    def emit(self, record: logging.LogRecord) -> None:
        # Cheap-ish stat-per-record check; the kernel caches inode metadata
        # so the syscall is sub-microsecond on a hot file.
        if self.stream is not None or os.path.exists(self.baseFilename):
            self._reopen_if_externally_rotated()
        super().emit(record)

    def _open(self):
        stream = super()._open()
        self._chmod_if_managed()
        return stream

    def doRollover(self):
        super().doRollover()
        self._chmod_if_managed()
        # Our own rollover writes a new baseFilename; refresh the snapshot
        # so the next emit doesn't mistake it for external rotation.
        self._record_stream_stat()


def _add_rotating_handler(
    logger: logging.Logger,
    path: Path,
    *,
    level: int,
    max_bytes: int,
    backup_count: int,
    formatter: logging.Formatter,
    log_filter: Optional[logging.Filter] = None,
) -> None:
    """Add a ``RotatingFileHandler`` to *logger*, skipping if one already
    exists for the same resolved file path (idempotent).

    Parameters
    ----------
    log_filter
        Optional filter to attach to the handler (e.g. ``_ComponentFilter``
        for gateway.log).
    """
    resolved = path.resolve()
    for existing in logger.handlers:
        if (
            isinstance(existing, RotatingFileHandler)
            and Path(getattr(existing, "baseFilename", "")).resolve() == resolved
        ):
            return  # already attached

    path.parent.mkdir(parents=True, exist_ok=True)
    handler = _ManagedRotatingFileHandler(
        str(path), maxBytes=max_bytes, backupCount=backup_count,
        encoding="utf-8",
    )
    handler.setLevel(level)
    handler.setFormatter(formatter)
    if log_filter is not None:
        handler.addFilter(log_filter)
    logger.addHandler(handler)


def _read_logging_config():
    """Best-effort read of ``logging.*`` from config.yaml.

    Returns ``(level, max_size_mb, backup_count)`` — any may be ``None``.
    """
    try:
        import yaml
        config_path = get_config_path()
        if config_path.exists():
            with open(config_path, "r", encoding="utf-8") as f:
                cfg = yaml.safe_load(f) or {}
            log_cfg = cfg.get("logging", {})
            if isinstance(log_cfg, dict):
                return (
                    log_cfg.get("level"),
                    log_cfg.get("max_size_mb"),
                    log_cfg.get("backup_count"),
                )
    except Exception:
        pass
    return (None, None, None)
