#!/usr/bin/env python3
# Copyright (C) 2026 Bryan Joshua Pedini - gpl-3-or-later

import subprocess
import json
import sys

def get_tailscale_prefs():
    """
    Executes 'tailscale debug prefs' and returns the parsed JSON output.
    """
    try:
        # Run the command and capture stdout
        result = subprocess.run(
            ["tailscale", "debug", "prefs"],
            capture_output=True,
            text=True,
            check=True
        )
        return json.loads(result.stdout)
    except FileNotFoundError:
        print("Error: 'tailscale' command not found. Please ensure Tailscale is installed.", file=sys.stderr)
        sys.exit(1)
    except subprocess.CalledProcessError as e:
        print(f"Error running 'tailscale debug prefs': {e.stderr}", file=sys.stderr)
        sys.exit(1)
    except json.JSONDecodeError as e:
        print(f"Error parsing JSON output: {e}", file=sys.stderr)
        sys.exit(1)

def process_advertise_routes(routes_array, append_func):
    """
    Processes the AdvertiseRoutes array according to the specific logic:
    - Separates exit node routes (0.0.0.0/0, ::/0) from standard routes.
    - Appends '--advertise-exit-node' if exit node routes are found.
    - Appends '--advertise-routes=' with a comma-separated list of standard routes.
    """
    exit_node_routes = {"0.0.0.0/0", "::/0"}
    has_exit_node = False
    standard_routes = []

    if routes_array:
        for route in routes_array:
            if route in exit_node_routes:
                has_exit_node = True
            else:
                standard_routes.append(route)

    # If exit node routes are present, append the specific flag
    if has_exit_node:
        append_func("--advertise-exit-node")

    # If standard routes are present, append them as a comma-separated list
    if standard_routes:
        routes_str = ",".join(standard_routes)
        append_func(f"--advertise-routes={routes_str}")

def main():
    # 1. Get the JSON data from the command
    prefs = get_tailscale_prefs()

    # Initialize the main string list
    cmd_parts = ["tailscale up"]

    # Helper function to append to the main string list
    def append_to_cmd(string_part):
        cmd_parts.append(string_part)

    # 2. Process RouteAll
    # Default is false, so we only append if it is true
    if prefs.get("RouteAll", False):
        append_to_cmd("--accept-routes")

    # 3. Process CorpDNS
    # Default is true, so we only append if it is false (to set --accept-dns=false)
    if not prefs.get("CorpDNS", True):
        append_to_cmd("--accept-dns=false")

    # 4. Process AdvertiseRoutes
    # We use the dedicated function for the array logic
    routes = prefs.get("AdvertiseRoutes")
    if routes:
        process_advertise_routes(routes, append_to_cmd)

    # Output the resulting string
    print(" ".join(cmd_parts))

if __name__ == "__main__":
    main()