"""
Fusion Accounting - SEPA Direct Debit (pain.008)

Generates ISO 20022 ``pain.008.001.02`` XML documents for SEPA Direct
Debit collections.  Includes a mandate model
(``fusion.sdd.mandate``) to track debtor authorisations.

The XML structure follows the published
`ISO 20022 message definition
<https://www.iso20022.org/catalogue-messages/iso-20022-messages-archive>`_
and uses ``xml.etree.ElementTree`` for construction.

Namespace
---------
``urn:iso:std:iso:20022:tech:xsd:pain.008.001.02``
"""

import hashlib
import re
import uuid
import xml.etree.ElementTree as ET
from datetime import datetime

from odoo import api, fields, models, _
from odoo.exceptions import UserError, ValidationError

# ISO 20022 pain.008.001.02 namespace
PAIN_008_NS = 'urn:iso:std:iso:20022:tech:xsd:pain.008.001.02'

# Reuse validation helpers from SEPA Credit Transfer module
_IBAN_RE = re.compile(r'^[A-Z]{2}\d{2}[A-Z0-9]{4,30}$')
_BIC_RE = re.compile(r'^[A-Z0-9]{8}([A-Z0-9]{3})?$')


def _sanitise_text(value, max_len=140):
    """Remove characters not allowed in SEPA XML text fields."""
    if not value:
        return ''
    cleaned = re.sub(r"[^A-Za-z0-9 +\-/?.,:;'()\n]", '', value)
    return cleaned[:max_len].strip()


def _validate_iban(iban):
    """Validate and normalise an IBAN string."""
    if not iban:
        raise ValidationError(_("IBAN is required for SEPA Direct Debit."))
    normalised = iban.upper().replace(' ', '')
    if not _IBAN_RE.match(normalised):
        raise ValidationError(_(
            "'%(iban)s' does not look like a valid IBAN.",
            iban=iban,
        ))
    return normalised


def _validate_bic(bic):
    """Validate and normalise a BIC / SWIFT code."""
    if not bic:
        raise ValidationError(_(
            "BIC/SWIFT code is required for SEPA Direct Debit."
        ))
    normalised = bic.upper().replace(' ', '')
    if not _BIC_RE.match(normalised):
        raise ValidationError(_(
            "'%(bic)s' does not look like a valid BIC/SWIFT code.",
            bic=bic,
        ))
    return normalised


# ======================================================================
# Mandate Model
# ======================================================================


class FusionSDDMandate(models.Model):
    """Tracks a SEPA Direct Debit mandate authorisation.

    A mandate is the legal agreement through which a debtor (the
    customer) authorises the creditor (the company) to collect
    payments from their bank account.
    """

    _name = 'fusion.sdd.mandate'
    _description = 'SEPA Direct Debit Mandate'
    _order = 'create_date desc'
    _inherit = ['mail.thread', 'mail.activity.mixin']

    # ------------------------------------------------------------------
    # Fields
    # ------------------------------------------------------------------

    name = fields.Char(
        string='Mandate Reference',
        required=True,
        copy=False,
        readonly=True,
        default='/',
        tracking=True,
        help="Unique Mandate Reference (UMR) communicated to the "
             "debtor's bank.",
    )
    partner_id = fields.Many2one(
        comodel_name='res.partner',
        string='Debtor',
        required=True,
        tracking=True,
        help="The partner (customer) who signed this mandate.",
    )
    iban = fields.Char(
        string='Debtor IBAN',
        required=True,
        size=34,
        tracking=True,
        help="IBAN of the debtor's bank account.",
    )
    bic = fields.Char(
        string='Debtor BIC',
        size=11,
        tracking=True,
        help="BIC of the debtor's bank.",
    )
    mandate_ref = fields.Char(
        string='Unique Mandate Reference',
        required=True,
        copy=False,
        tracking=True,
        help="The unique reference identifying this mandate agreement.",
    )
    state = fields.Selection(
        selection=[
            ('draft', 'Draft'),
            ('active', 'Active'),
            ('revoked', 'Revoked'),
            ('closed', 'Closed'),
        ],
        string='Status',
        default='draft',
        required=True,
        tracking=True,
        help="Draft: mandate is being prepared.\n"
             "Active: mandate is signed and ready for collections.\n"
             "Revoked: debtor has withdrawn consent.\n"
             "Closed: mandate is no longer in use.",
    )
    scheme = fields.Selection(
        selection=[
            ('CORE', 'CORE'),
            ('B2B', 'B2B'),
        ],
        string='Scheme',
        default='CORE',
        required=True,
        tracking=True,
        help="CORE: consumer direct debit.\n"
             "B2B: business-to-business direct debit (no refund right).",
    )
    date_signed = fields.Date(
        string='Date Signed',
        default=fields.Date.context_today,
        help="Date when the mandate was signed by the debtor.",
    )
    company_id = fields.Many2one(
        comodel_name='res.company',
        string='Company',
        default=lambda self: self.env.company,
        required=True,
    )

    # ------------------------------------------------------------------
    # CRUD
    # ------------------------------------------------------------------

    @api.model_create_multi
    def create(self, vals_list):
        """Assign a sequence-based name if not provided."""
        for vals in vals_list:
            if vals.get('name', '/') == '/':
                vals['name'] = self.env['ir.sequence'].next_by_code(
                    'fusion.sdd.mandate'
                ) or _('New')
            if not vals.get('mandate_ref'):
                vals['mandate_ref'] = f'FUSIONMDT-{uuid.uuid4().hex[:8].upper()}'
        return super().create(vals_list)

    # ------------------------------------------------------------------
    # Actions
    # ------------------------------------------------------------------

    def action_activate(self):
        """Activate a draft mandate."""
        for mandate in self:
            if mandate.state != 'draft':
                raise UserError(_(
                    "Only draft mandates can be activated."
                ))
            mandate.state = 'active'

    def action_revoke(self):
        """Revoke an active mandate."""
        for mandate in self:
            if mandate.state != 'active':
                raise UserError(_(
                    "Only active mandates can be revoked."
                ))
            mandate.state = 'revoked'

    def action_close(self):
        """Close a mandate (no more collections)."""
        for mandate in self:
            if mandate.state not in ('active', 'revoked'):
                raise UserError(_(
                    "Only active or revoked mandates can be closed."
                ))
            mandate.state = 'closed'


# ======================================================================
# SEPA Direct Debit XML generation
# ======================================================================


class FusionSEPADirectDebit(models.Model):
    """Extends ``res.company`` with SEPA Direct Debit XML generation.

    The ``generate_pain_008`` method accepts a set of
    ``fusion.sdd.mandate`` records (each linked to an active mandate)
    and produces a compliant pain.008.001.02 XML file.
    """

    _inherit = 'res.company'

    fusion_sdd_creditor_identifier = fields.Char(
        string='SEPA Creditor Identifier',
        size=35,
        help="Your organisation's SEPA Creditor Identifier (CI), "
             "assigned by your national authority.",
    )

    # ------------------------------------------------------------------
    # Public API
    # ------------------------------------------------------------------

    def generate_pain_008(self, mandates, requested_date=None):
        """Build an ISO 20022 pain.008.001.02 XML for SEPA Direct Debits.

        :param mandates: ``fusion.sdd.mandate`` recordset.
        :param requested_date: Requested collection date (defaults to
            today).
        :return: UTF-8 encoded XML bytes.
        :rtype: bytes
        :raises UserError: when mandatory data is missing.
        """
        self.ensure_one()

        if not mandates:
            raise UserError(_(
                "No mandates provided for the SEPA Direct Debit file."
            ))

        inactive = mandates.filtered(lambda m: m.state != 'active')
        if inactive:
            raise UserError(_(
                "The following mandates are not active and cannot be "
                "included:\n%(mandates)s",
                mandates=', '.join(inactive.mapped('name')),
            ))

        company_iban = _validate_iban(self.fusion_company_iban)
        company_bic = _validate_bic(self.fusion_company_bic)

        if not self.fusion_sdd_creditor_identifier:
            raise UserError(_(
                "Please configure the SEPA Creditor Identifier on "
                "the company settings before generating a Direct "
                "Debit file."
            ))

        collection_date = requested_date or fields.Date.context_today(self)

        # Root element
        root = ET.Element('Document', xmlns=PAIN_008_NS)
        cstmr_dd = ET.SubElement(root, 'CstmrDrctDbtInitn')

        # -- Group Header --
        grp_hdr = ET.SubElement(cstmr_dd, 'GrpHdr')
        msg_id = self._pain008_message_id()
        ET.SubElement(grp_hdr, 'MsgId').text = msg_id
        ET.SubElement(grp_hdr, 'CreDtTm').text = datetime.utcnow().strftime(
            '%Y-%m-%dT%H:%M:%S'
        )
        ET.SubElement(grp_hdr, 'NbOfTxs').text = str(len(mandates))

        initg_pty = ET.SubElement(grp_hdr, 'InitgPty')
        ET.SubElement(initg_pty, 'Nm').text = _sanitise_text(
            self.name, max_len=70
        )

        # Group mandates by scheme (CORE / B2B)
        for scheme in ('CORE', 'B2B'):
            scheme_mandates = mandates.filtered(
                lambda m: m.scheme == scheme
            )
            if not scheme_mandates:
                continue
            self._add_pain008_payment_info(
                cstmr_dd, scheme_mandates, scheme,
                company_iban, company_bic,
                collection_date, msg_id,
            )

        tree = ET.ElementTree(root)
        ET.indent(tree, space='  ')
        xml_bytes = ET.tostring(
            root, encoding='UTF-8', xml_declaration=True
        )
        return xml_bytes

    # ------------------------------------------------------------------
    # Private helpers
    # ------------------------------------------------------------------

    def _pain008_message_id(self):
        """Generate a unique message identifier for the pain.008 file."""
        raw = f'{self.id}-SDD-{datetime.utcnow().isoformat()}'
        digest = hashlib.sha256(raw.encode()).hexdigest()[:16]
        return f'FUSION-SDD-{digest}'.upper()[:35]

    def _add_pain008_payment_info(
        self, parent, mandates, scheme,
        company_iban, company_bic,
        collection_date, msg_id,
    ):
        """Add a ``PmtInf`` block for a group of mandates sharing the
        same scheme.

        :param parent: ``CstmrDrctDbtInitn`` XML element.
        :param mandates: ``fusion.sdd.mandate`` recordset for this scheme.
        :param str scheme: ``'CORE'`` or ``'B2B'``.
        :param str company_iban: Validated company IBAN.
        :param str company_bic: Validated company BIC.
        :param collection_date: Requested collection date.
        :param str msg_id: Message identifier.
        """
        pmt_inf = ET.SubElement(parent, 'PmtInf')
        pmt_inf_id = f'{msg_id}-{scheme}'[:35]
        ET.SubElement(pmt_inf, 'PmtInfId').text = pmt_inf_id
        ET.SubElement(pmt_inf, 'PmtMtd').text = 'DD'  # Direct Debit
        ET.SubElement(pmt_inf, 'NbOfTxs').text = str(len(mandates))

        # Payment Type Information
        pmt_tp_inf = ET.SubElement(pmt_inf, 'PmtTpInf')
        svc_lvl = ET.SubElement(pmt_tp_inf, 'SvcLvl')
        ET.SubElement(svc_lvl, 'Cd').text = 'SEPA'
        lcl_instrm = ET.SubElement(pmt_tp_inf, 'LclInstrm')
        ET.SubElement(lcl_instrm, 'Cd').text = scheme
        ET.SubElement(pmt_tp_inf, 'SeqTp').text = 'RCUR'  # Recurring

        ET.SubElement(pmt_inf, 'ReqdColltnDt').text = (
            collection_date.isoformat()
            if isinstance(collection_date, date)
            else str(collection_date)
        )

        # Creditor (company)
        cdtr = ET.SubElement(pmt_inf, 'Cdtr')
        ET.SubElement(cdtr, 'Nm').text = _sanitise_text(self.name, 70)

        cdtr_acct = ET.SubElement(pmt_inf, 'CdtrAcct')
        cdtr_acct_id = ET.SubElement(cdtr_acct, 'Id')
        ET.SubElement(cdtr_acct_id, 'IBAN').text = company_iban

        cdtr_agt = ET.SubElement(pmt_inf, 'CdtrAgt')
        cdtr_agt_fin = ET.SubElement(cdtr_agt, 'FinInstnId')
        ET.SubElement(cdtr_agt_fin, 'BIC').text = company_bic

        ET.SubElement(pmt_inf, 'ChrgBr').text = 'SLEV'

        # Creditor Scheme Identification
        cdtr_schme_id = ET.SubElement(pmt_inf, 'CdtrSchmeId')
        cdtr_schme_id_el = ET.SubElement(cdtr_schme_id, 'Id')
        prvt_id = ET.SubElement(cdtr_schme_id_el, 'PrvtId')
        othr = ET.SubElement(prvt_id, 'Othr')
        ET.SubElement(othr, 'Id').text = _sanitise_text(
            self.fusion_sdd_creditor_identifier, 35
        )
        schme_nm = ET.SubElement(othr, 'SchmeNm')
        ET.SubElement(schme_nm, 'Prtry').text = 'SEPA'

        # Individual transactions
        for mandate in mandates:
            self._add_pain008_transaction(pmt_inf, mandate)

    def _add_pain008_transaction(self, pmt_inf, mandate):
        """Append a ``DrctDbtTxInf`` element for a single mandate.

        :param pmt_inf: The ``PmtInf`` XML element.
        :param mandate: A ``fusion.sdd.mandate`` record.
        """
        debtor_iban = _validate_iban(mandate.iban)

        dd_tx = ET.SubElement(pmt_inf, 'DrctDbtTxInf')

        # Payment Identification
        pmt_id = ET.SubElement(dd_tx, 'PmtId')
        ET.SubElement(pmt_id, 'EndToEndId').text = _sanitise_text(
            mandate.mandate_ref or mandate.name, 35
        )

        # Amount - use a default amount; callers should set this via
        # the payment amount linked to the mandate
        amt = ET.SubElement(dd_tx, 'InstdAmt')
        # Default to 0.00; the caller is expected to provide real
        # amounts via a companion payment record. This serves as the
        # structural placeholder per the schema.
        amt.text = '0.00'
        amt.set('Ccy', 'EUR')

        # Direct Debit Transaction Info (mandate details)
        dd_tx_inf = ET.SubElement(dd_tx, 'DrctDbtTx')
        mndt_rltd_inf = ET.SubElement(dd_tx_inf, 'MndtRltdInf')
        ET.SubElement(mndt_rltd_inf, 'MndtId').text = _sanitise_text(
            mandate.mandate_ref, 35
        )
        ET.SubElement(mndt_rltd_inf, 'DtOfSgntr').text = (
            mandate.date_signed.isoformat()
            if mandate.date_signed
            else fields.Date.context_today(self).isoformat()
        )

        # Debtor Agent (BIC)
        if mandate.bic:
            dbtr_agt = ET.SubElement(dd_tx, 'DbtrAgt')
            dbtr_agt_fin = ET.SubElement(dbtr_agt, 'FinInstnId')
            ET.SubElement(dbtr_agt_fin, 'BIC').text = (
                mandate.bic.upper().replace(' ', '')
            )

        # Debtor
        dbtr = ET.SubElement(dd_tx, 'Dbtr')
        ET.SubElement(dbtr, 'Nm').text = _sanitise_text(
            mandate.partner_id.name or '', 70
        )

        # Debtor Account
        dbtr_acct = ET.SubElement(dd_tx, 'DbtrAcct')
        dbtr_acct_id = ET.SubElement(dbtr_acct, 'Id')
        ET.SubElement(dbtr_acct_id, 'IBAN').text = debtor_iban