"""Memory updater for reading, writing, and updating memory data."""

import json
import os
import uuid
from datetime import datetime
from pathlib import Path
from typing import Any

from src.agents.memory.prompt import (
    MEMORY_UPDATE_PROMPT,
    format_conversation_for_update,
)
from src.config.memory_config import get_memory_config
from src.models import create_chat_model


def _get_memory_file_path() -> Path:
    """Get the path to the memory file."""
    config = get_memory_config()
    # Resolve relative to current working directory (backend/)
    return Path(os.getcwd()) / config.storage_path


def _create_empty_memory() -> dict[str, Any]:
    """Create an empty memory structure."""
    return {
        "version": "1.0",
        "lastUpdated": datetime.utcnow().isoformat() + "Z",
        "user": {
            "workContext": {"summary": "", "updatedAt": ""},
            "personalContext": {"summary": "", "updatedAt": ""},
            "topOfMind": {"summary": "", "updatedAt": ""},
        },
        "history": {
            "recentMonths": {"summary": "", "updatedAt": ""},
            "earlierContext": {"summary": "", "updatedAt": ""},
            "longTermBackground": {"summary": "", "updatedAt": ""},
        },
        "facts": [],
    }


# Global memory data cache
_memory_data: dict[str, Any] | None = None
# Track file modification time for cache invalidation
_memory_file_mtime: float | None = None


def get_memory_data() -> dict[str, Any]:
    """Get the current memory data (cached with file modification time check).

    The cache is automatically invalidated if the memory file has been modified
    since the last load, ensuring fresh data is always returned.

    Returns:
        The memory data dictionary.
    """
    global _memory_data, _memory_file_mtime

    file_path = _get_memory_file_path()

    # Get current file modification time
    try:
        current_mtime = file_path.stat().st_mtime if file_path.exists() else None
    except OSError:
        current_mtime = None

    # Invalidate cache if file has been modified or doesn't exist
    if _memory_data is None or _memory_file_mtime != current_mtime:
        _memory_data = _load_memory_from_file()
        _memory_file_mtime = current_mtime

    return _memory_data


def reload_memory_data() -> dict[str, Any]:
    """Reload memory data from file, forcing cache invalidation.

    Returns:
        The reloaded memory data dictionary.
    """
    global _memory_data, _memory_file_mtime

    file_path = _get_memory_file_path()
    _memory_data = _load_memory_from_file()

    # Update file modification time after reload
    try:
        _memory_file_mtime = file_path.stat().st_mtime if file_path.exists() else None
    except OSError:
        _memory_file_mtime = None

    return _memory_data


def _load_memory_from_file() -> dict[str, Any]:
    """Load memory data from file.

    Returns:
        The memory data dictionary.
    """
    file_path = _get_memory_file_path()

    if not file_path.exists():
        return _create_empty_memory()

    try:
        with open(file_path, encoding="utf-8") as f:
            data = json.load(f)
        return data
    except (json.JSONDecodeError, OSError) as e:
        print(f"Failed to load memory file: {e}")
        return _create_empty_memory()


def _save_memory_to_file(memory_data: dict[str, Any]) -> bool:
    """Save memory data to file and update cache.

    Args:
        memory_data: The memory data to save.

    Returns:
        True if successful, False otherwise.
    """
    global _memory_data, _memory_file_mtime
    file_path = _get_memory_file_path()

    try:
        # Ensure directory exists
        file_path.parent.mkdir(parents=True, exist_ok=True)

        # Update lastUpdated timestamp
        memory_data["lastUpdated"] = datetime.utcnow().isoformat() + "Z"

        # Write atomically using temp file
        temp_path = file_path.with_suffix(".tmp")
        with open(temp_path, "w", encoding="utf-8") as f:
            json.dump(memory_data, f, indent=2, ensure_ascii=False)

        # Rename temp file to actual file (atomic on most systems)
        temp_path.replace(file_path)

        # Update cache and file modification time
        _memory_data = memory_data
        try:
            _memory_file_mtime = file_path.stat().st_mtime
        except OSError:
            _memory_file_mtime = None

        print(f"Memory saved to {file_path}")
        return True
    except OSError as e:
        print(f"Failed to save memory file: {e}")
        return False


class MemoryUpdater:
    """Updates memory using LLM based on conversation context."""

    def __init__(self, model_name: str | None = None):
        """Initialize the memory updater.

        Args:
            model_name: Optional model name to use. If None, uses config or default.
        """
        self._model_name = model_name

    def _get_model(self):
        """Get the model for memory updates."""
        config = get_memory_config()
        model_name = self._model_name or config.model_name
        return create_chat_model(name=model_name, thinking_enabled=False)

    def update_memory(self, messages: list[Any], thread_id: str | None = None) -> bool:
        """Update memory based on conversation messages.

        Args:
            messages: List of conversation messages.
            thread_id: Optional thread ID for tracking source.

        Returns:
            True if update was successful, False otherwise.
        """
        config = get_memory_config()
        if not config.enabled:
            return False

        if not messages:
            return False

        try:
            # Get current memory
            current_memory = get_memory_data()

            # Format conversation for prompt
            conversation_text = format_conversation_for_update(messages)

            if not conversation_text.strip():
                return False

            # Build prompt
            prompt = MEMORY_UPDATE_PROMPT.format(
                current_memory=json.dumps(current_memory, indent=2),
                conversation=conversation_text,
            )

            # Call LLM
            model = self._get_model()
            response = model.invoke(prompt)
            response_text = str(response.content).strip()

            # Parse response
            # Remove markdown code blocks if present
            if response_text.startswith("```"):
                lines = response_text.split("\n")
                response_text = "\n".join(lines[1:-1] if lines[-1] == "```" else lines[1:])

            update_data = json.loads(response_text)

            # Apply updates
            updated_memory = self._apply_updates(current_memory, update_data, thread_id)

            # Save
            return _save_memory_to_file(updated_memory)

        except json.JSONDecodeError as e:
            print(f"Failed to parse LLM response for memory update: {e}")
            return False
        except Exception as e:
            print(f"Memory update failed: {e}")
            return False

    def _apply_updates(
        self,
        current_memory: dict[str, Any],
        update_data: dict[str, Any],
        thread_id: str | None = None,
    ) -> dict[str, Any]:
        """Apply LLM-generated updates to memory.

        Args:
            current_memory: Current memory data.
            update_data: Updates from LLM.
            thread_id: Optional thread ID for tracking.

        Returns:
            Updated memory data.
        """
        config = get_memory_config()
        now = datetime.utcnow().isoformat() + "Z"

        # Update user sections
        user_updates = update_data.get("user", {})
        for section in ["workContext", "personalContext", "topOfMind"]:
            section_data = user_updates.get(section, {})
            if section_data.get("shouldUpdate") and section_data.get("summary"):
                current_memory["user"][section] = {
                    "summary": section_data["summary"],
                    "updatedAt": now,
                }

        # Update history sections
        history_updates = update_data.get("history", {})
        for section in ["recentMonths", "earlierContext", "longTermBackground"]:
            section_data = history_updates.get(section, {})
            if section_data.get("shouldUpdate") and section_data.get("summary"):
                current_memory["history"][section] = {
                    "summary": section_data["summary"],
                    "updatedAt": now,
                }

        # Remove facts
        facts_to_remove = set(update_data.get("factsToRemove", []))
        if facts_to_remove:
            current_memory["facts"] = [f for f in current_memory.get("facts", []) if f.get("id") not in facts_to_remove]

        # Add new facts
        new_facts = update_data.get("newFacts", [])
        for fact in new_facts:
            confidence = fact.get("confidence", 0.5)
            if confidence >= config.fact_confidence_threshold:
                fact_entry = {
                    "id": f"fact_{uuid.uuid4().hex[:8]}",
                    "content": fact.get("content", ""),
                    "category": fact.get("category", "context"),
                    "confidence": confidence,
                    "createdAt": now,
                    "source": thread_id or "unknown",
                }
                current_memory["facts"].append(fact_entry)

        # Enforce max facts limit
        if len(current_memory["facts"]) > config.max_facts:
            # Sort by confidence and keep top ones
            current_memory["facts"] = sorted(
                current_memory["facts"],
                key=lambda f: f.get("confidence", 0),
                reverse=True,
            )[: config.max_facts]

        return current_memory


def update_memory_from_conversation(messages: list[Any], thread_id: str | None = None) -> bool:
    """Convenience function to update memory from a conversation.

    Args:
        messages: List of conversation messages.
        thread_id: Optional thread ID.

    Returns:
        True if successful, False otherwise.
    """
    updater = MemoryUpdater()
    return updater.update_memory(messages, thread_id)