History

"""Command history manager for input persistence."""

from future import annotations

import json from pathlib import Path # noqa: TC003 - used at runtime in type hints

class HistoryManager: """Manages command history with file persistence.

Uses append-only writes for concurrent safety. Multiple agents can
safely write to the same history file without corruption.
"""

def __init__(self, history_file: Path, max_entries: int = 100) -> None:
    """Initialize the history manager.

    Args:
        history_file: Path to the JSON-lines history file
        max_entries: Maximum number of entries to keep
    """
    self.history_file = history_file
    self.max_entries = max_entries
    self._entries: list[str] = []
    self._current_index: int = -1
    self._temp_input: str = ""
    self._load_history()

def _load_history(self) -> None:
    """Load history from file."""
    if not self.history_file.exists():
        return

    try:
        with self.history_file.open("r", encoding="utf-8") as f:
            entries = []
            for raw_line in f:
                line = raw_line.rstrip("\n\r")
                if not line:
                    continue
                try:
                    entry = json.loads(line)
                except json.JSONDecodeError:
                    entry = line
                entries.append(entry if isinstance(entry, str) else str(entry))
            self._entries = entries[-self.max_entries :]
    except (OSError, UnicodeDecodeError):
        self._entries = []

def _append_to_file(self, text: str) -> None:
    """Append a single entry to history file (concurrent-safe)."""
    try:
        self.history_file.parent.mkdir(parents=True, exist_ok=True)
        with self.history_file.open("a", encoding="utf-8") as f:
            f.write(json.dumps(text) + "\n")
    except OSError:
        pass

def _compact_history(self) -> None:
    """Rewrite history file to remove old entries.

    Only called when entries exceed 2x max_entries to minimize rewrites.
    """
    try:
        self.history_file.parent.mkdir(parents=True, exist_ok=True)
        with self.history_file.open("w", encoding="utf-8") as f:
            for entry in self._entries:
                f.write(json.dumps(entry) + "\n")
    except OSError:
        pass

def add(self, text: str) -> None:
    """Add a command to history.

    Args:
        text: The command text to add
    """
    text = text.strip()
    # Skip empty or slash commands
    if not text or text.startswith("/"):
        return

    # Skip duplicates of the last entry
    if self._entries and self._entries[-1] == text:
        return

    self._entries.append(text)

    # Append to file (fast, concurrent-safe)
    self._append_to_file(text)

    # Compact only when we have 2x max entries (rare operation)
    if len(self._entries) > self.max_entries * 2:
        self._entries = self._entries[-self.max_entries :]
        self._compact_history()

    self.reset_navigation()

def get_previous(self, current_input: str, prefix: str = "") -> str | None:
    """Get the previous history entry.

    Args:
        current_input: Current input text (saved on first navigation)
        prefix: Optional prefix to filter entries

    Returns:
        Previous matching entry or None
    """
    if not self._entries:
        return None

    # Save current input on first navigation
    if self._current_index == -1:
        self._temp_input = current_input
        self._current_index = len(self._entries)

    # Search backwards for matching entry
    for i in range(self._current_index - 1, -1, -1):
        if self._entries[i].startswith(prefix):
            self._current_index = i
            return self._entries[i]

    return None

def get_next(self, prefix: str = "") -> str | None:
    """Get the next history entry.

    Args:
        prefix: Optional prefix to filter entries

    Returns:
        Next matching entry, original input at end, or None
    """
    if self._current_index == -1:
        return None

    # Search forwards for matching entry
    for i in range(self._current_index + 1, len(self._entries)):
        if self._entries[i].startswith(prefix):
            self._current_index = i
            return self._entries[i]

    # Return to original input at the end
    result = self._temp_input
    self.reset_navigation()
    return result

def reset_navigation(self) -> None:
    """Reset navigation state."""
    self._current_index = -1
    self._temp_input = ""