"""Xero integration layer for the ordering portal.

This is a **clean, stubbed interface**. No Xero credentials are hard-coded — all
configuration comes from environment variables (``XERO_*``). When credentials
are absent (the default in dev/alpha), the service runs in "stub" mode: it
records what *would* be sent and returns a deterministic fake invoice id so the
rest of the order lifecycle can be exercised end-to-end.

To go live, implement the real HTTP calls inside :func:`_submit_to_xero_api`
(see the TODOs) — no caller needs to change.

Service responsibilities (per spec):
* Map a customer (ClientAccount) to a Xero contact.
* Map catalogue products to Xero item codes.
* Create a draft invoice equivalent for a confirmed order.
* Record Xero response ids/status (via XeroSyncLog, written by the caller).
* Handle failures gracefully (never raise into the request path).
"""
from __future__ import annotations

import os
from dataclasses import dataclass, field
from datetime import datetime

from app.models.client_access import ClientAccount
from app.models.ordering import Order


@dataclass
class XeroConfig:
    client_id: str | None = None
    client_secret: str | None = None
    tenant_id: str | None = None
    base_url: str = "https://api.xero.com/api.xro/2.0"

    @property
    def configured(self) -> bool:
        return bool(self.client_id and self.client_secret and self.tenant_id)

    @classmethod
    def from_env(cls) -> "XeroConfig":
        return cls(
            client_id=os.getenv("XERO_CLIENT_ID") or None,
            client_secret=os.getenv("XERO_CLIENT_SECRET") or None,
            tenant_id=os.getenv("XERO_TENANT_ID") or None,
            base_url=os.getenv("XERO_API_BASE_URL", "https://api.xero.com/api.xro/2.0"),
        )


@dataclass
class XeroSubmissionResult:
    status: str  # "success" | "failed"
    xero_invoice_id: str | None
    message: str
    request_summary: str
    stubbed: bool = False
    line_items: list[dict] = field(default_factory=list)


def map_customer_to_contact(customer: ClientAccount) -> dict:
    """Map a customer account onto a Xero contact payload."""
    return {
        # TODO: persist and reuse a real Xero ContactID once the contact has
        # been created/matched in Xero. For now we key on the client code.
        "ContactNumber": customer.client_code,
        "Name": customer.name,
    }


def map_product_to_item_code(product_sku: str) -> str:
    """Map a catalogue SKU onto a Xero item code.

    TODO: support an explicit SKU→Xero item-code mapping table if the codes
    diverge. Today the SKU is used directly.
    """
    return product_sku


def build_invoice_payload(order: Order, customer: ClientAccount) -> dict:
    """Build the Xero draft-invoice payload for a confirmed order."""
    line_items = []
    for line in order.lines:
        if line.requires_quote or line.unit_price is None:
            # Quote-only lines can't carry a price; skip until quoted.
            continue
        unit_price = line.admin_override_price if line.admin_override_price is not None else line.unit_price
        line_items.append(
            {
                "ItemCode": map_product_to_item_code(line.product_sku),
                "Description": line.product_name,
                "Quantity": line.quantity,
                "UnitAmount": unit_price,
                "AccountCode": os.getenv("XERO_SALES_ACCOUNT_CODE", "200"),
                # Prices are GST-exclusive throughout the platform.
                "TaxType": os.getenv("XERO_TAX_TYPE", "OUTPUT"),
            }
        )
    return {
        "Type": "ACCREC",
        "Status": "DRAFT",
        "Contact": map_customer_to_contact(customer),
        "Reference": order.purchase_order_number or order.order_number or f"Order {order.id}",
        "LineAmountTypes": "Exclusive",
        "LineItems": line_items,
    }


def _submit_to_xero_api(config: XeroConfig, payload: dict) -> XeroSubmissionResult:
    """Real Xero submission. Stubbed until credentials/endpoints are wired.

    TODO (go-live):
      1. Obtain an OAuth2 token (client-credentials or stored refresh token).
      2. POST ``payload`` to ``{config.base_url}/Invoices`` with the
         ``Xero-tenant-id`` header set to ``config.tenant_id``.
      3. Parse ``Invoices[0].InvoiceID`` from the response.
      4. Map non-2xx responses onto ``status="failed"`` with the error body.
    """
    summary = f"{len(payload.get('LineItems', []))} line(s) for {payload['Contact']['Name']}"
    # Real call would go here. Intentionally not implemented yet.
    return XeroSubmissionResult(
        status="failed",
        xero_invoice_id=None,
        message="Xero live submission is not implemented yet (stub interface).",
        request_summary=summary,
        stubbed=False,
        line_items=payload.get("LineItems", []),
    )


def submit_order_to_xero(order: Order, customer: ClientAccount) -> XeroSubmissionResult:
    """Submit a confirmed order to Xero, or stub it when unconfigured.

    Never raises — failures are returned as ``status="failed"`` results so the
    order lifecycle can record the attempt and continue.
    """
    config = XeroConfig.from_env()
    payload = build_invoice_payload(order, customer)
    summary = f"{len(payload['LineItems'])} line(s) for {payload['Contact']['Name']}"

    if not config.configured:
        # Stub mode: deterministic fake invoice id so downstream flows work.
        fake_id = f"STUB-INV-{order.id:06d}"
        return XeroSubmissionResult(
            status="success",
            xero_invoice_id=fake_id,
            message="Xero not configured — order recorded in stub mode.",
            request_summary=summary,
            stubbed=True,
            line_items=payload["LineItems"],
        )

    try:
        return _submit_to_xero_api(config, payload)
    except Exception as exc:  # pragma: no cover - defensive: never break the request path
        return XeroSubmissionResult(
            status="failed",
            xero_invoice_id=None,
            message=f"Xero submission error: {exc}",
            request_summary=summary,
            stubbed=False,
            line_items=payload["LineItems"],
        )


def xero_status_snapshot() -> dict:
    config = XeroConfig.from_env()
    return {
        "configured": config.configured,
        "mode": "live" if config.configured else "stub",
        "base_url": config.base_url,
        "checked_at": datetime.utcnow().isoformat(),
        "missing_env": [
            name
            for name, value in (
                ("XERO_CLIENT_ID", config.client_id),
                ("XERO_CLIENT_SECRET", config.client_secret),
                ("XERO_TENANT_ID", config.tenant_id),
            )
            if not value
        ],
    }