"""
Dell asset lookup service.

Two modes (chosen automatically):

1. **No credentials** – Returns a partial pre-fill (brand=Dell, OS default, service_tag).
   Model and warranty must be filled in manually; a link to Dell's support page is provided.
   Dell's public website is protected by Akamai and cannot be scraped reliably.

2. **TechDirect API** – Full data including model, warranty dates, serial number.
   Register free at https://tdm.dell.com → API Services → Create an API key pair.
   Set DELL_CLIENT_ID and DELL_CLIENT_SECRET in your .env file.
"""
import logging
from datetime import datetime

import requests
from flask import current_app

log = logging.getLogger(__name__)

_TOKEN_URL = "https://apigtwb2c.us.dell.com/auth/oauth/v2/token"
_ASSET_URL = "https://apigtwb2c.us.dell.com/PROD/sbil/eapi/v5/asset-entitlements"
_SUPPORT_PAGE = "https://www.dell.com/support/home/en-us/product-support/servicetag/{tag}/overview"

_TYPE_MAP = [
    (["latitude", "inspiron", "xps", "vostro", "precision 5", "precision 7"], "Laptop"),
    (["optiplex", "precision tower", "precision 3", "precision 9",
      "optiplex micro", "optiplex small"], "Desktop"),
    (["poweredge", "server"], "Server"),
    (["wyse", "thin client"], "Other"),
    (["monitor", "display", "screen", "s24", "s27", "p24", "u27"], "Monitor"),
]


def _detect_type(description: str) -> str:
    desc = description.lower()
    for keywords, asset_type in _TYPE_MAP:
        if any(kw in desc for kw in keywords):
            return asset_type
    return "Laptop"  # sensible default for Dell business hardware


# ------------------------------------------------------------------
# Partial pre-fill (no credentials)
# ------------------------------------------------------------------

def _partial_prefill(tag: str) -> dict:
    """
    Return a minimal pre-fill dict using only what we know without querying Dell.
    Includes a link to Dell's support page so the user can look up the rest.
    """
    return {
        "service_tag": tag,
        "serial_number": "",
        "brand": "Dell",
        "model": "",
        "asset_type": "Laptop",
        "operating_system": "Windows 11 Pro",
        "warranty_expiry": "",
        "purchase_date": "",
        "source": "partial",
        "support_url": _SUPPORT_PAGE.format(tag=tag),
    }


# ------------------------------------------------------------------
# Official TechDirect API (requires credentials)
# ------------------------------------------------------------------

def _get_token(client_id: str, client_secret: str) -> str:
    resp = requests.post(
        _TOKEN_URL,
        data={
            "grant_type": "client_credentials",
            "client_id": client_id,
            "client_secret": client_secret,
        },
        timeout=10,
    )
    resp.raise_for_status()
    return resp.json()["access_token"]


def _lookup_api(tag: str, client_id: str, client_secret: str) -> dict:
    try:
        token = _get_token(client_id, client_secret)
    except Exception as exc:
        raise RuntimeError(f"Failed to obtain Dell API token: {exc}") from exc

    try:
        resp = requests.get(
            _ASSET_URL,
            params={"servicetags": tag},
            headers={"Authorization": f"Bearer {token}"},
            timeout=15,
        )
        resp.raise_for_status()
        data = resp.json()
    except Exception as exc:
        raise RuntimeError(f"Dell API request failed: {exc}") from exc

    if not data:
        raise RuntimeError(f"No data returned for service tag '{tag}'.")

    item = data[0] if isinstance(data, list) else data
    system_desc = item.get("productLineDescription") or item.get("systemDescription") or ""
    model = system_desc.strip()
    serial_number = (item.get("serviceTag") or tag).upper()

    warranty_expiry = None
    for ent in (item.get("entitlements") or []):
        end_str = ent.get("endDate") or ""
        if end_str:
            try:
                dt = datetime.fromisoformat(end_str[:10])
                if warranty_expiry is None or dt > warranty_expiry:
                    warranty_expiry = dt
            except ValueError:
                pass

    ship_date = item.get("shipDate") or ""
    purchase_date = None
    if ship_date:
        try:
            purchase_date = datetime.fromisoformat(ship_date[:10])
        except ValueError:
            pass

    return {
        "service_tag": tag,
        "serial_number": serial_number,
        "brand": "Dell",
        "model": model,
        "asset_type": _detect_type(f"{system_desc} {item.get('productFamily', '')}"),
        "operating_system": "Windows 11 Pro",
        "warranty_expiry": warranty_expiry.strftime("%Y-%m-%d") if warranty_expiry else "",
        "purchase_date": purchase_date.strftime("%Y-%m-%d") if purchase_date else "",
        "source": "techdirect_api",
        "support_url": _SUPPORT_PAGE.format(tag=tag),
    }


# ------------------------------------------------------------------
# Public entry point
# ------------------------------------------------------------------

def lookup_service_tag(service_tag: str) -> dict:
    """
    Look up a Dell service tag.

    Uses TechDirect API when DELL_CLIENT_ID + DELL_CLIENT_SECRET are configured;
    otherwise returns a partial pre-fill with a link to Dell's support page.
    """
    tag = service_tag.strip().upper()
    client_id = current_app.config.get("DELL_CLIENT_ID", "")
    client_secret = current_app.config.get("DELL_CLIENT_SECRET", "")

    if client_id and client_secret:
        log.debug("Dell lookup via TechDirect API for %s", tag)
        return _lookup_api(tag, client_id, client_secret)

    log.debug("Dell lookup returning partial pre-fill for %s (no API credentials)", tag)
    return _partial_prefill(tag)