"""finance_budgets — the finance domain's annual spend budget (USD).

Revision ID: 304
Revises: 303
Create Date: 2026-06-18

PR2 of the finance closed-loop theme: a budget the materialised actuals
(``finance_spend_facts``) are measured against, scoped by an optional
``(fiscal_year, cost_type, department, cost_center)`` tuple (any dimension
NULL = "all"). Distinct from ``procurement_budgets`` (forward PO-commitment
locking). Standalone table, no FK — same rebuildable-projection rationale
as the sibling finance tables, and dodges TiDB CHAR/VARCHAR FK strictness.
Idempotent / re-runnable (guards on table presence).
"""
from __future__ import annotations

import sqlalchemy as sa

from alembic import op

revision = "304"
down_revision = "303"
branch_labels = None
depends_on = None

TABLE = "finance_budgets"


def _table_exists(bind, name: str) -> bool:
    return bind.execute(
        sa.text(
            "SELECT 1 FROM information_schema.TABLES "
            "WHERE TABLE_SCHEMA = DATABASE() AND TABLE_NAME = :n"
        ),
        {"n": name},
    ).scalar() is not None


def upgrade() -> None:
    bind = op.get_bind()
    if _table_exists(bind, TABLE):
        return
    op.create_table(
        TABLE,
        sa.Column("id", sa.BigInteger(), autoincrement=True, nullable=False),
        sa.Column("fiscal_year", sa.Integer(), nullable=False),
        sa.Column("cost_type", sa.String(length=32), nullable=True),
        sa.Column("department", sa.String(length=128), nullable=True),
        sa.Column("cost_center", sa.String(length=64), nullable=True),
        sa.Column("amount_usd", sa.Numeric(precision=16, scale=2), nullable=False),
        sa.Column("owner_person_id", sa.String(length=36), nullable=True),
        sa.Column("note", sa.Text(), nullable=True),
        sa.Column(
            "last_alerted_threshold", sa.Integer(),
            server_default="0", nullable=False,
        ),
        sa.Column(
            "created_at", sa.DateTime(timezone=True),
            server_default=sa.text("CURRENT_TIMESTAMP"), nullable=False,
        ),
        sa.Column(
            "updated_at", sa.DateTime(timezone=True),
            server_default=sa.text("CURRENT_TIMESTAMP"), nullable=False,
        ),
        sa.PrimaryKeyConstraint("id"),
        sa.UniqueConstraint(
            "fiscal_year", "cost_type", "department", "cost_center",
            name="uq_finance_budget_scope",
        ),
        mysql_engine="InnoDB",
        mysql_charset="utf8mb4",
        mysql_collate="utf8mb4_unicode_ci",
    )
    op.create_index("ix_finance_budgets_year", TABLE, ["fiscal_year"])


def downgrade() -> None:
    bind = op.get_bind()
    if _table_exists(bind, TABLE):
        op.drop_table(TABLE)