# -*- coding: utf-8 -*-
# Copyright 2026 Nexa Systems Inc.
# License OPL-1
from odoo import fields, models


class FusionBillingAccountLink(models.Model):
    """Identity resolution: maps an app's external account id to one res.partner.

    Folds the NexaCloud user / NexaDesk tenant / NexaMaps client for the same
    real-world client onto a single partner (the unified customer). See spec §5.1.
    """

    _name = "fusion.billing.account.link"
    _description = "Fusion Billing — External Account → Partner Link"
    _order = "service_id, external_id"

    service_id = fields.Many2one(
        "fusion.billing.service", required=True, ondelete="cascade", index=True,
    )
    external_id = fields.Char(
        required=True, index=True,
        help="The app's own account id (NexaCloud user, NexaDesk tenant, Maps client).",
    )
    external_email = fields.Char()
    partner_id = fields.Many2one(
        "res.partner", required=True, ondelete="restrict", index=True,
    )

    _service_external_uniq = models.Constraint(
        "unique(service_id, external_id)",
        "An external account can only link to one partner per service.",
    )