"""
Service de récupération de l'historique shell depuis les hôtes distants via SSH.

Ce service permet de récupérer le fichier ~/.bash_history des hôtes
pour afficher les commandes exécutées dans le terminal.
"""
from __future__ import annotations

import asyncio
import hashlib
import logging
import os
import shutil
import subprocess
import sys
from datetime import datetime, timezone
from typing import Dict, List, Optional, Any

try:
    import asyncssh
    _asyncssh_import_error: Optional[BaseException] = None
except ModuleNotFoundError as e:
    asyncssh = None
    _asyncssh_import_error = e

from app.core.config import settings

logger = logging.getLogger("homelab.shell_history")

# Log prefix for standardized output
LOG_PREFIX = "[SHELL_HISTORY]"


class ShellHistoryError(Exception):
    """Error fetching shell history."""
    pass


class ShellHistoryService:
    """Service for fetching shell command history from remote hosts via SSH."""

    def __init__(self):
        self.ssh_key_path = settings.ssh_key_path
        self.ssh_user = settings.ssh_user
        self.ssh_remote_user = settings.ssh_remote_user
        self.connect_timeout = 5
        self.exec_timeout = 10

    async def _run_ssh_subprocess(self, host_ip: str, username: str, remote_cmd: str) -> str:
        """Run a remote command via system ssh as a fallback when asyncssh isn't installed."""
        ssh_bin = shutil.which("ssh")
        if not ssh_bin:
            raise ShellHistoryError("Missing dependency: ssh binary not found in PATH")

        key_path = self.ssh_key_path
        if not key_path or not os.path.exists(key_path):
            raise ShellHistoryError(
                f"SSH key not found at '{key_path}'. Configure SSH_KEY_PATH / settings.ssh_key_path."
            )

        args = [
            ssh_bin,
            "-i",
            key_path,
            "-o",
            "BatchMode=yes",
            "-o",
            f"ConnectTimeout={self.connect_timeout}",
            "-o",
            "StrictHostKeyChecking=accept-new",
            "-o",
            "UserKnownHostsFile=/dev/null",
            f"{username}@{host_ip}",
            remote_cmd,
        ]

        try:
            proc = await asyncio.create_subprocess_exec(
                *args,
                stdout=asyncio.subprocess.PIPE,
                stderr=asyncio.subprocess.PIPE,
            )
            stdout, stderr = await asyncio.wait_for(
                proc.communicate(),
                timeout=self.connect_timeout + self.exec_timeout,
            )
        except asyncio.TimeoutError as e:
            raise ShellHistoryError(f"Timeout reading history from {host_ip}") from e
        except FileNotFoundError as e:
            raise ShellHistoryError("ssh binary not available") from e

        if proc.returncode not in (0, None):
            err = (stderr or b"").decode(errors="ignore").strip()
            if not err:
                err = (stdout or b"").decode(errors="ignore").strip()
            raise ShellHistoryError(f"SSH error connecting to {host_ip}: {err or proc.returncode}")

        return (stdout or b"").decode(errors="ignore")

    async def _ssh_connect(self, host_ip: str) -> "asyncssh.SSHClientConnection":
        """Establish SSH connection to a host."""
        if asyncssh is None:
            err = None
            try:
                err = str(_asyncssh_import_error) if _asyncssh_import_error else None
            except Exception:
                err = None
            raise ShellHistoryError(
                "Missing dependency: asyncssh. Install it to enable shell history retrieval. "
                f"(python={sys.executable}, import_error={err})"
            )

        tried_users: List[str] = []
        last_err: Optional[BaseException] = None

        for username in [self.ssh_remote_user, self.ssh_user]:
            if not username or username in tried_users:
                continue
            tried_users.append(username)
            try:
                conn = await asyncio.wait_for(
                    asyncssh.connect(
                        host_ip,
                        username=username,
                        client_keys=[self.ssh_key_path],
                        known_hosts=None,
                    ),
                    timeout=self.connect_timeout
                )
                return conn
            except asyncio.TimeoutError as e:
                last_err = e
                continue
            except Exception as e:
                last_err = e
                continue

        if isinstance(last_err, asyncio.TimeoutError):
            raise ShellHistoryError(f"SSH connection timeout to {host_ip}")
        raise ShellHistoryError(f"SSH error connecting to {host_ip}: {last_err}")

    async def fetch_bash_history(
        self,
        host_ip: str,
        limit: int = 100,
        user: str = "automation"
    ) -> List[Dict[str, Any]]:
        """
        Fetch bash history from a remote host.

        Args:
            host_ip: IP address of the host
            limit: Maximum number of commands to return
            user: User whose history to fetch (default: automation)

        Returns:
            List of command dicts with 'command', 'command_hash', 'line_number'
        """
        conn = None
        try:
            # Read .bash_history file (last N lines, reversed for recent first)
            # Force bash to write history by sourcing .bashrc or use history -a
            # The simplest approach: just read the file
            cmd = f"tail -n {limit * 2} ~{user}/.bash_history 2>/dev/null || tail -n {limit * 2} ~/.bash_history 2>/dev/null || echo ''"

            if asyncssh is None:
                output = ""
                tried_users: List[str] = []
                last_err: Optional[BaseException] = None
                for login_user in [self.ssh_remote_user, self.ssh_user]:
                    if not login_user or login_user in tried_users:
                        continue
                    tried_users.append(login_user)
                    try:
                        output = await self._run_ssh_subprocess(host_ip, login_user, cmd)
                        last_err = None
                        break
                    except ShellHistoryError as e:
                        last_err = e
                        continue
                if last_err is not None and not output:
                    raise last_err
            else:
                conn = await self._ssh_connect(host_ip)
                result = await asyncio.wait_for(
                    conn.run(cmd, check=False),
                    timeout=self.exec_timeout
                )
                output = result.stdout or ""

            lines = output.strip().split('\n')
            
            # Filter and deduplicate
            seen_hashes = set()
            commands = []
            
            # Process in reverse order (most recent first)
            for i, line in enumerate(reversed(lines)):
                line = line.strip()
                if not line:
                    continue
                # Skip history metadata lines (timestamps starting with #)
                if line.startswith('#') and line[1:].isdigit():
                    continue
                
                cmd_hash = hashlib.sha256(line.encode()).hexdigest()[:16]
                
                # Deduplicate
                if cmd_hash in seen_hashes:
                    continue
                seen_hashes.add(cmd_hash)
                
                commands.append({
                    "command": line,
                    "command_hash": cmd_hash,
                    "line_number": len(lines) - i,
                    "last_used": datetime.now(timezone.utc).isoformat(),
                    "execution_count": 1,  # We don't have real count from bash_history
                })
                
                if len(commands) >= limit:
                    break

            logger.info(f"{LOG_PREFIX} Fetched {len(commands)} commands from {host_ip}")
            return commands

        except asyncio.TimeoutError:
            raise ShellHistoryError(f"Timeout reading history from {host_ip}")
        except Exception as e:
            raise ShellHistoryError(f"Error reading history from {host_ip}: {e}")
        finally:
            if conn:
                conn.close()

    async def fetch_zsh_history(
        self,
        host_ip: str,
        limit: int = 100,
        user: str = "automation"
    ) -> List[Dict[str, Any]]:
        """
        Fetch zsh history from a remote host.
        Similar to bash but reads .zsh_history.
        """
        conn = None
        try:
            cmd = f"tail -n {limit * 2} ~{user}/.zsh_history 2>/dev/null || tail -n {limit * 2} ~/.zsh_history 2>/dev/null || echo ''"

            if asyncssh is None:
                output = ""
                tried_users: List[str] = []
                last_err: Optional[BaseException] = None
                for login_user in [self.ssh_remote_user, self.ssh_user]:
                    if not login_user or login_user in tried_users:
                        continue
                    tried_users.append(login_user)
                    try:
                        output = await self._run_ssh_subprocess(host_ip, login_user, cmd)
                        last_err = None
                        break
                    except ShellHistoryError as e:
                        last_err = e
                        continue
                if last_err is not None and not output:
                    raise last_err
            else:
                conn = await self._ssh_connect(host_ip)
                result = await asyncio.wait_for(
                    conn.run(cmd, check=False),
                    timeout=self.exec_timeout
                )
                output = result.stdout or ""

            lines = output.strip().split('\n')
            
            seen_hashes = set()
            commands = []
            
            for i, line in enumerate(reversed(lines)):
                line = line.strip()
                if not line:
                    continue
                # Zsh extended history format: : timestamp:0;command
                if line.startswith(': ') and ';' in line:
                    line = line.split(';', 1)[1]
                
                cmd_hash = hashlib.sha256(line.encode()).hexdigest()[:16]
                
                if cmd_hash in seen_hashes:
                    continue
                seen_hashes.add(cmd_hash)
                
                commands.append({
                    "command": line,
                    "command_hash": cmd_hash,
                    "line_number": len(lines) - i,
                    "last_used": datetime.now(timezone.utc).isoformat(),
                    "execution_count": 1,
                })
                
                if len(commands) >= limit:
                    break

            return commands

        except Exception as e:
            raise ShellHistoryError(f"Error reading zsh history from {host_ip}: {e}")
        finally:
            if conn:
                conn.close()

    async def fetch_combined_history(
        self,
        host_ip: str,
        limit: int = 100,
        user: str = "automation"
    ) -> List[Dict[str, Any]]:
        """
        Fetch history from both bash and zsh, combined and deduplicated.
        """
        bash_commands = []
        zsh_commands = []

        try:
            bash_commands = await self.fetch_bash_history(host_ip, limit, user)
        except ShellHistoryError:
            pass  # Bash history not available

        try:
            zsh_commands = await self.fetch_zsh_history(host_ip, limit, user)
        except ShellHistoryError:
            pass  # Zsh history not available

        # Combine and deduplicate
        seen_hashes = set()
        combined = []
        
        for cmd in bash_commands + zsh_commands:
            if cmd["command_hash"] not in seen_hashes:
                seen_hashes.add(cmd["command_hash"])
                combined.append(cmd)
                if len(combined) >= limit:
                    break

        return combined


# Singleton instance
shell_history_service = ShellHistoryService()