# =============================================================================
# Projet : AIR — Accounting Intermediate Representation
# Auteur : Simon-Pierre Boucher
# Contact : contact@spboucher.ai
# Fichier : validation.py
# Description : Validation pass — structural checks + subtotal provenance definitions.
# =============================================================================
"""Validation pass: the front door of the compiler.

Checks structural well-formedness of the AIR document and defines each
event's subtotal in the provenance graph (the SSA origin every later
derivation points back to).
"""
from __future__ import annotations

from aic.diagnostics import Diagnostic, Severity
from aic.passes.base import Pass
from aic.unit import CompilationUnit
from core.events import EventType

TAXABLE_TYPES = (EventType.SALE, EventType.PURCHASE, EventType.REFUND)


class ValidationPass(Pass):
    name = "validation"

    def run(self, unit: CompilationUnit) -> list[Diagnostic]:
        diags: list[Diagnostic] = []
        seen: set[str] = set()

        for event in unit.document.events:
            loc = f"event {event.id}"

            if event.id in seen:
                diags.append(Diagnostic(
                    code="AIR-E200", severity=Severity.ERROR,
                    message=f"duplicate event id '{event.id}'",
                    location=loc,
                    suggestion="event ids must be unique within a document (use ULIDs)",
                    origin_pass=self.name,
                ))
                continue
            seen.add(event.id)

            # single transaction currency per event
            currencies = {i.unit_price.currency for i in event.items}
            if event.amount is not None:
                currencies.add(event.amount.currency)
            if len(currencies) > 1:
                diags.append(Diagnostic(
                    code="AIR-E201", severity=Severity.ERROR,
                    message=f"mixed currencies in one event: {sorted(currencies)}",
                    location=f"{loc}, field items[].unit_price",
                    suggestion="split into one event per currency",
                    origin_pass=self.name,
                ))
                continue

            subtotal = event.subtotal()
            if subtotal is None:
                diags.append(Diagnostic(
                    code="AIR-E202", severity=Severity.ERROR,
                    message="event has no amount: neither items nor a flat amount",
                    location=f"{loc}, fields items / amount",
                    suggestion="provide items[] with unit prices, or a flat amount",
                    origin_pass=self.name,
                ))
                continue
            if subtotal.is_negative():
                diags.append(Diagnostic(
                    code="AIR-E203", severity=Severity.ERROR,
                    message=f"negative subtotal {subtotal}",
                    location=f"{loc}, field items/amount",
                    suggestion="amounts are positive; direction comes from the event type "
                               "(use Refund instead of a negative Sale)",
                    origin_pass=self.name,
                ))
                continue

            if event.type in TAXABLE_TYPES and event.tax is None:
                diags.append(Diagnostic(
                    code="AIR-W200", severity=Severity.WARNING,
                    message=f"{event.type.value} event has no tax context; "
                            "it will compile untaxed",
                    location=f"{loc}, field tax",
                    suggestion="set tax.jurisdiction (e.g. 'CA-QC') or tax.exempt: true",
                    origin_pass=self.name,
                ))

            if event.type is EventType.REFUND and event.related_event is None:
                diags.append(Diagnostic(
                    code="AIR-W201", severity=Severity.WARNING,
                    message="Refund does not reference the Sale it reverses",
                    location=f"{loc}, field related_event",
                    suggestion="set related_event to the original Sale id for traceability",
                    origin_pass=self.name,
                ))

            state = unit.event_state(event.id)
            state.subtotal = subtotal
            node = unit.provenance.define(
                kind="event_subtotal",
                operation=f"subtotal:{event.type.value}",
                amount=subtotal,
                source_ref=event.id,
            )
            state.subtotal_node = node.id

        return diags