# =============================================================================
# Projet : AIR — Accounting Intermediate Representation
# Auteur : Simon-Pierre Boucher
# Contact : contact@spboucher.ai
# Fichier : model.py
# Description : ALSL v0.1 data model — policy sets, tax/classification policies, account roles.
# =============================================================================
"""ALSL (Accounting Language for Standards and Legislation) v0.1 model.

ALSL is AIR's TableGen: ALL fiscal and policy parameters (tax rates, rounding
modes, capitalization thresholds, chart-of-account mappings) live in versioned
policy sets — never in compiler code. v0.1 is a YAML subset; the full DSL
comes later.

Every tax policy must cite its source (a docs/research/ file or an official
URL) — uncited rates are rejected by the loader.
"""
from __future__ import annotations

from dataclasses import dataclass, field
from decimal import Decimal

from core.journal import Account, AccountType
from core.money import RoundingMode

ALSL_VERSION = "0.1"


@dataclass(frozen=True, slots=True)
class WhenClause:
    """Conditions under which a policy fires. All present fields must match."""

    jurisdiction: str | None = None            # exact match, e.g. "CA-QC"
    jurisdiction_in: tuple[str, ...] | None = None
    event_type: str | None = None              # e.g. "Purchase"
    min_amount: Decimal | None = None          # inclusive threshold on the subtotal
    currency: str | None = None                # currency the threshold is expressed in


@dataclass(frozen=True, slots=True)
class TaxComponent:
    """One tax to apply (e.g. GST at 0.05 on the subtotal)."""

    code: str                                  # "GST", "QST", "HST"
    rate: Decimal
    base: str = "subtotal"                     # v0.1: only "subtotal" (price before other taxes)
    payable_role: str = ""                     # account role credited on sales
    receivable_role: str = ""                  # account role debited on purchases (ITC/ITR)
    recoverable_on_purchase: bool = True


@dataclass(frozen=True, slots=True)
class TaxPolicy:
    name: str
    when: WhenClause
    components: tuple[TaxComponent, ...]
    source: str                                # citation — mandatory


@dataclass(frozen=True, slots=True)
class ClassificationPolicy:
    """e.g. capitalize purchases >= threshold as assets."""

    name: str
    when: WhenClause
    classify_as: str                           # "asset" | "expense"
    account_role: str                          # role receiving the debit (e.g. "equipment")
    source: str = ""


@dataclass(frozen=True, slots=True)
class RoundingPolicy:
    mode: RoundingMode = RoundingMode.HALF_UP
    source: str = ""


@dataclass(frozen=True, slots=True)
class PolicySet:
    """A versioned, self-contained rule set for one compilation."""

    alsl_version: str
    name: str                                  # e.g. "ca-qc"
    version: str                               # e.g. "2026.08"
    description: str = ""
    functional_currency: str = "CAD"
    rounding: RoundingPolicy = field(default=RoundingPolicy())
    accounts: dict[str, Account] = field(default_factory=dict)   # role -> Account
    tax_policies: tuple[TaxPolicy, ...] = ()
    classification_policies: tuple[ClassificationPolicy, ...] = ()

    def account(self, role: str) -> Account:
        try:
            return self.accounts[role]
        except KeyError:
            raise KeyError(
                f"policy set '{self.name}' defines no account for role '{role}'"
            ) from None


def parse_account_type(value: str) -> AccountType:
    return AccountType(value)