import os
import socket
import threading
import gradio as gr

# Force CPU by default (safe for Spaces and small hosts)
os.environ.setdefault("CUDA_VISIBLE_DEVICES", "-1")

from metrics import get_hf_bleurt, get_hf_rouge
from ui.manual_tab import build_manual_tab
from ui.csv_tab import build_csv_tab


def _parse_auth_from_env():
    """
    Read APP_USERS env var if present.
    Format: APP_USERS="alice:StrongPass,bob:AnotherPass"
    Returns list[tuple[str, str]] or None.
    """
    users_env = os.getenv("APP_USERS", "").strip()
    if not users_env:
        return None
    pairs = []
    for part in users_env.split(","):
        if ":" in part:
            u, p = part.split(":", 1)
            u, p = u.strip(), p.strip()
            if u and p:
                pairs.append((u, p))
    return pairs or None


def _is_port_free(port: int) -> bool:
    with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
        s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
        try:
            s.bind(("0.0.0.0", port))
        except OSError:
            return False
        return True


def _find_free_port(preferred: int = 7860, scan_to: int = 7960) -> int:
    if _is_port_free(preferred):
        return preferred
    for p in range(preferred + 1, scan_to + 1):
        if _is_port_free(p):
            return p
    with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
        s.bind(("0.0.0.0", 0))
        return s.getsockname()[1]


def _running_in_spaces() -> bool:
    # Common envs on HF Spaces
    return bool(os.getenv("SPACE_ID") or os.getenv("SPACE_REPO_URL") or os.getenv("HF_SPACE"))


if __name__ == "__main__":
    # Preload heavy metrics in background so UI stays responsive
    try:
        threading.Thread(target=get_hf_bleurt, daemon=True).start()
        threading.Thread(target=get_hf_rouge, daemon=True).start()
    except Exception:
        pass

    # Build UI
    iface = gr.TabbedInterface(
        interface_list=[build_manual_tab(), build_csv_tab()],
        tab_names=["Manual Input", "CSV Upload"],
    )

    # Optional basic auth via env (works both locally and on Spaces)
    auth_creds = _parse_auth_from_env()

    # Decide runtime mode
    in_spaces = _running_in_spaces()

    # Respect platform-provided port if any, else pick a free one
    env_port = os.getenv("PORT") or os.getenv("GRADIO_SERVER_PORT")
    port = int(env_port) if env_port else _find_free_port(7860, 7960)

    # Queue (handle different Gradio versions)
    try:
        iface.queue(concurrency_count=1, max_size=20)
    except TypeError:
        iface.queue()

    if in_spaces:
        # On Spaces: bind publicly & enable share (Spaces sandbox blocks localhost)
        iface.launch(
            server_name="0.0.0.0",
            server_port=port,
            show_error=True,
            auth=auth_creds,
            auth_message="Restricted • Enter company credentials",
            ssr_mode=False,   # avoids svelte-i18n SSR issues on Spaces
            share=True,       # Spaces needs a public URL
        )
    else:
        # Local DEV: true private local URL (no gradio.live)
        iface.launch(
            server_name="127.0.0.1",  # <-- use this URL in your browser
            server_port=port,
            show_error=True,
            auth=auth_creds,
            share=False,              # <-- prevents expiring public link
        )