"""Pure-Python helpers for backfilling fusion.reconcile.precedent
from existing account.partial.reconcile rows during migration.

Strategy:
- Each account.partial.reconcile that involves at least one
  account.bank.statement.line's reconcile-account line is a candidate.
- One precedent per qualifying partial. The (statement_line.id, account_id,
  amount) triple is encoded into matched_account_ids so a second run can
  detect and skip already-backfilled rows (idempotency).
"""

import logging

from .memo_tokenizer import tokenize_memo

_logger = logging.getLogger(__name__)


def _identify_bank_side(partial):
    """Return (bank_move_line, counterpart_move_line, statement_line_id)
    or (None, None, None) if neither side is a bank statement line."""
    debit_line = partial.debit_move_id
    credit_line = partial.credit_move_id

    if debit_line.move_id.statement_line_id:
        return debit_line, credit_line, debit_line.move_id.statement_line_id.id
    if credit_line.move_id.statement_line_id:
        return credit_line, debit_line, credit_line.move_id.statement_line_id.id
    return None, None, None


def backfill_precedents(env, *, company_id=None, batch_size=500, limit=10000):
    """Walk account.partial.reconcile and create fusion.reconcile.precedent
    rows for any reconcile that involves a bank statement line.

    Idempotent: skips partials whose (statement_line, account, amount)
    signature is already present in fusion.reconcile.precedent (encoded
    via matched_account_ids).

    Returns dict with `created` and `skipped` counts.
    """
    Precedent = env['fusion.reconcile.precedent'].sudo()
    Partial = env['account.partial.reconcile'].sudo()
    Line = env['account.bank.statement.line'].sudo()

    in_test_mode = env.cr.__class__.__name__ == 'TestCursor'

    # Pre-filter to partials that touch a bank statement line on either side.
    # In a real DB we typically have 10x more invoice<->payment partials than
    # bank-rec partials; filtering here keeps the loop bounded and makes the
    # default limit reflect "real" candidates rather than every partial ever.
    domain = [
        '|',
        ('debit_move_id.move_id.statement_line_id', '!=', False),
        ('credit_move_id.move_id.statement_line_id', '!=', False),
    ]
    if company_id:
        domain.append(('company_id', '=', company_id))
    partials = Partial.search(domain, limit=limit, order='id asc')

    created = 0
    skipped = 0
    for partial in partials:
        bank_line, counterpart, bsl_id = _identify_bank_side(partial)
        if not bsl_id:
            skipped += 1
            continue

        signature_account = str(counterpart.account_id.id)

        existing = Precedent.search([
            ('partner_id', '=',
             counterpart.partner_id.id if counterpart.partner_id else False),
            ('amount', '=', abs(partial.amount)),
            ('matched_account_ids', '=ilike', f'%{signature_account}%'),
            ('source', '=', 'backfill'),
        ], limit=1)
        if existing:
            skipped += 1
            continue

        statement_line = Line.browse(bsl_id)
        try:
            currency = (partial.debit_currency_id
                        or partial.company_id.currency_id)
            Precedent.create({
                'company_id': partial.company_id.id,
                'partner_id': (counterpart.partner_id.id
                               if counterpart.partner_id else False),
                'amount': abs(partial.amount),
                'currency_id': currency.id,
                'date': statement_line.date or partial.create_date.date(),
                'memo_tokens': ','.join(
                    tokenize_memo(statement_line.payment_ref or '')),
                'journal_id': statement_line.journal_id.id,
                'matched_move_line_count': 1,
                'matched_account_ids': signature_account,
                'reconciler_user_id': partial.create_uid.id,
                'reconciled_at': partial.create_date,
                'source': 'backfill',
            })
            created += 1
            if created % batch_size == 0:
                if not in_test_mode:
                    env.cr.commit()
                _logger.info(
                    "Backfill progress: %d created, %d skipped",
                    created, skipped)
        except Exception as e:  # noqa: BLE001
            _logger.warning("Backfill skip partial %s: %s", partial.id, e)
            skipped += 1

    _logger.info(
        "precedent_backfill complete: %d created, %d skipped",
        created, skipped)
    return {'created': created, 'skipped': skipped}