# =============================================================================
# Projet : AIR — Accounting Intermediate Representation
# Auteur : Simon-Pierre Boucher
# Contact : contact@spboucher.ai
# Fichier : backend.py
# Description : Native backend — posts into AIR's own ledger (standalone mode, no ERP needed).
# =============================================================================
"""Native backend: AIR as a self-sufficient accounting system.

When no third-party system (QuickBooks, Xero, ...) is used, compiled journals
post into AIR's own append-only, hash-chained ledger, from which all
statements (general ledger, trial balance, income statement, balance sheet)
are generated in multiple formats.
"""
from __future__ import annotations

from pathlib import Path

from backends.base import (
    Backend,
    BackendCapabilities,
    PostingReceipt,
    ReversalReceipt,
    TargetPayload,
)
from core.journal import CompiledJournal
from kernel.ledger import Ledger


class NativeLedgerBackend(Backend):
    def __init__(self, ledger_path: str | Path | None = None):
        self.ledger = Ledger(path=Path(ledger_path) if ledger_path else None)

    def capabilities(self) -> BackendCapabilities:
        return BackendCapabilities(
            name="native",
            posts_remotely=False,
            native_reversal=True,
            multi_currency=True,
            idempotency="native",
            notes="AIR's own append-only hash-chained ledger; full reporting built in",
        )

    def compile(self, journal: CompiledJournal) -> TargetPayload:
        # The native target consumes the journal as-is: no lowering needed.
        return TargetPayload(backend="native", format="journal", body=journal)

    def post(self, payload: TargetPayload, idempotency_key: str) -> PostingReceipt:
        journal = payload.body
        assert isinstance(journal, CompiledJournal)
        appended = self.ledger.post_journal(journal, idempotency_key)
        return PostingReceipt(
            backend="native",
            reference=str(self.ledger.path or "<memory>"),
            idempotency_key=idempotency_key,
            details={"entries_appended": str(appended)},
        )

    def reverse(self, receipt: PostingReceipt) -> ReversalReceipt:
        # Reverse every entry posted under the receipt's idempotency key.
        reversed_ids = []
        for entry in list(self.ledger.entries):
            if entry.id.startswith("rev_"):
                continue
            contra = self.ledger.reverse_entry(
                entry.id, f"rev:{receipt.idempotency_key}:{entry.id}"
            )
            reversed_ids.append(contra.id)
        return ReversalReceipt(
            backend="native",
            reference=",".join(reversed_ids),
            reversed_reference=receipt.idempotency_key,
        )