"""
System routes for server monitoring and logs.
"""

import os
from pathlib import Path
from typing import Optional
from collections import deque

from fastapi import APIRouter, Depends, Query, HTTPException
from pydantic import BaseModel

from shared.auth.dependencies import get_current_user, CurrentUser


class LogEntry(BaseModel):
    """Single log entry."""
    line: str
    level: Optional[str] = None


class LogsResponse(BaseModel):
    """Response with log entries."""
    file: str
    lines: list[str]
    total_lines: int
    showing: int
    logs_path: Optional[str] = None
    file_exists: bool = True
    file_size_kb: Optional[float] = None


def create_system_router() -> APIRouter:
    """
    Create system router for logs and monitoring.
    """
    router = APIRouter()

    def get_logs_path() -> Path:
        """Get logs directory path based on environment."""
        # Windows production: C:\inetpub\wwwroot\roa2web\logs
        # Development: backend/logs or ./logs
        if os.name == 'nt':  # Windows
            prod_path = Path(r"C:\inetpub\wwwroot\roa2web\logs")
            if prod_path.exists():
                return prod_path

        # Development fallback
        dev_paths = [
            Path(__file__).parent.parent.parent / "backend" / "logs",
            Path(__file__).parent.parent.parent / "logs",
            Path("./logs"),
        ]
        for path in dev_paths:
            if path.exists():
                return path

        return Path("./logs")

    @router.get("/logs", response_model=LogsResponse)
    async def get_logs(
        file: str = Query(default="backend-stderr", description="Log file: backend-stderr or backend-stdout"),
        lines: int = Query(default=100, ge=10, le=1000, description="Number of lines to return"),
        filter: Optional[str] = Query(default=None, description="Filter text (case-insensitive)"),
        current_user: CurrentUser = Depends(get_current_user)
    ):
        """
        Get server log entries.

        Args:
            file: Log file name (backend-stderr or backend-stdout)
            lines: Number of lines to return (10-1000)
            filter: Optional filter text

        Returns:
            LogsResponse with log lines
        """
        # Validate file name to prevent path traversal
        allowed_files = ["backend-stderr", "backend-stdout"]
        if file not in allowed_files:
            raise HTTPException(status_code=400, detail=f"Invalid file. Allowed: {allowed_files}")

        logs_path = get_logs_path()
        log_file = logs_path / f"{file}.log"
        logs_path_str = str(logs_path.resolve())

        if not log_file.exists():
            return LogsResponse(
                file=file,
                lines=[f"Log file not found: {log_file}"],
                total_lines=0,
                showing=0,
                logs_path=logs_path_str,
                file_exists=False,
                file_size_kb=0
            )

        try:
            # Get file size
            file_size_kb = round(log_file.stat().st_size / 1024, 2)

            # Read file and get last N lines efficiently
            with open(log_file, 'r', encoding='utf-8', errors='replace') as f:
                # Use deque for efficient tail operation
                all_lines = deque(f, maxlen=lines * 2 if filter else lines)

            # Apply filter if provided
            if filter:
                filter_lower = filter.lower()
                filtered_lines = [line.rstrip() for line in all_lines if filter_lower in line.lower()]
                result_lines = list(filtered_lines)[-lines:]
            else:
                result_lines = [line.rstrip() for line in all_lines][-lines:]

            return LogsResponse(
                file=file,
                lines=result_lines,
                total_lines=len(result_lines),
                showing=len(result_lines),
                logs_path=logs_path_str,
                file_exists=True,
                file_size_kb=file_size_kb
            )

        except Exception as e:
            raise HTTPException(status_code=500, detail=f"Error reading logs: {str(e)}")

    @router.get("/logs/available")
    async def get_available_logs(
        current_user: CurrentUser = Depends(get_current_user)
    ):
        """
        Get list of available log files.
        """
        logs_path = get_logs_path()

        if not logs_path.exists():
            return {"logs_path": str(logs_path), "files": [], "exists": False}

        log_files = []
        for f in logs_path.glob("*.log"):
            stat = f.stat()
            log_files.append({
                "name": f.stem,
                "size_kb": round(stat.st_size / 1024, 1),
                "modified": stat.st_mtime
            })

        return {
            "logs_path": str(logs_path),
            "files": sorted(log_files, key=lambda x: x["name"]),
            "exists": True
        }

    return router