"""Version Accounting Mirrors per Client + Financial Year.

Revision ID: 20260918_accounting_mirror_ver
Revises: 20260918_accounting_mirror_reg
"""
from alembic import op
import sqlalchemy as sa

revision = "20260918_accounting_mirror_ver"
down_revision = "20260918_accounting_mirror_reg"
branch_labels = None
depends_on = None


def upgrade() -> None:
    bind = op.get_bind()
    inspector = sa.inspect(bind)
    columns = {c["name"] for c in inspector.get_columns("accounting_mirror_registry")}

    if "version_no" not in columns:
        op.add_column("accounting_mirror_registry", sa.Column("version_no", sa.Integer(), nullable=False, server_default="1"))
    if "is_current" not in columns:
        op.add_column("accounting_mirror_registry", sa.Column("is_current", sa.Boolean(), nullable=False, server_default=sa.true()))
    if "supersedes_mirror_id" not in columns:
        op.add_column("accounting_mirror_registry", sa.Column("supersedes_mirror_id", sa.Integer(), nullable=True))
        op.create_foreign_key(
            "fk_accounting_mirror_registry_supersedes",
            "accounting_mirror_registry",
            "accounting_mirror_registry",
            ["supersedes_mirror_id"],
            ["id"],
            ondelete="SET NULL",
        )

    uniques = {u.get("name") for u in inspector.get_unique_constraints("accounting_mirror_registry")}
    if "uq_accounting_mirror_registry_client_fy" in uniques:
        op.drop_constraint("uq_accounting_mirror_registry_client_fy", "accounting_mirror_registry", type_="unique")
    if "uq_accounting_mirror_registry_client_fy_version" not in uniques:
        op.create_unique_constraint(
            "uq_accounting_mirror_registry_client_fy_version",
            "accounting_mirror_registry",
            ["tenant_id", "client_id", "financial_year", "version_no"],
        )

    indexes = {i.get("name") for i in inspector.get_indexes("accounting_mirror_registry")}
    if "ix_accounting_mirror_registry_version_no" not in indexes:
        op.create_index("ix_accounting_mirror_registry_version_no", "accounting_mirror_registry", ["version_no"], unique=False)
    if "ix_accounting_mirror_registry_is_current" not in indexes:
        op.create_index("ix_accounting_mirror_registry_is_current", "accounting_mirror_registry", ["is_current"], unique=False)
    if "ix_accounting_mirror_registry_supersedes_mirror_id" not in indexes:
        op.create_index("ix_accounting_mirror_registry_supersedes_mirror_id", "accounting_mirror_registry", ["supersedes_mirror_id"], unique=False)

    # Existing registry rows become version 1/current without touching their
    # file path, company metadata, dates or status.
    op.execute(sa.text("UPDATE accounting_mirror_registry SET version_no = 1 WHERE version_no IS NULL"))
    op.execute(sa.text("UPDATE accounting_mirror_registry SET is_current = TRUE WHERE is_current IS NULL"))


def downgrade() -> None:
    op.drop_index("ix_accounting_mirror_registry_supersedes_mirror_id", table_name="accounting_mirror_registry")
    op.drop_index("ix_accounting_mirror_registry_is_current", table_name="accounting_mirror_registry")
    op.drop_index("ix_accounting_mirror_registry_version_no", table_name="accounting_mirror_registry")
    op.drop_constraint("uq_accounting_mirror_registry_client_fy_version", "accounting_mirror_registry", type_="unique")
    op.create_unique_constraint(
        "uq_accounting_mirror_registry_client_fy",
        "accounting_mirror_registry",
        ["tenant_id", "client_id", "financial_year"],
    )
    op.drop_constraint("fk_accounting_mirror_registry_supersedes", "accounting_mirror_registry", type_="foreignkey")
    op.drop_column("accounting_mirror_registry", "supersedes_mirror_id")
    op.drop_column("accounting_mirror_registry", "is_current")
    op.drop_column("accounting_mirror_registry", "version_no")