"""departments, per-department categories and budgets, approval workflows

Existing data is kept: everything created with version 1 is moved into a department called "IT".

Revision ID: 0002
Revises: 0001
"""
import sqlalchemy as sa
from alembic import op

revision = "0002"
down_revision = "0001"
branch_labels = None
depends_on = None


def _drop_unique_on(table: str, columns: list[str]) -> None:
    insp = sa.inspect(op.get_bind())
    for uc in insp.get_unique_constraints(table):
        if uc["column_names"] == columns:
            op.drop_constraint(uc["name"], table, type_="unique")


def upgrade() -> None:
    op.create_table(
        "departments",
        sa.Column("id", sa.Integer(), primary_key=True),
        sa.Column("name", sa.String(length=120), nullable=False, unique=True),
        sa.Column("active", sa.Boolean(), nullable=False, server_default=sa.true()),
        sa.Column("created_at", sa.DateTime(timezone=True), nullable=False, server_default=sa.func.now()),
    )
    op.create_table(
        "workflow_steps",
        sa.Column("id", sa.Integer(), primary_key=True),
        sa.Column("department_id", sa.Integer(), sa.ForeignKey("departments.id", ondelete="CASCADE"), nullable=False),
        sa.Column("position", sa.Integer(), nullable=False, server_default="0"),
        sa.Column("name", sa.String(length=120), nullable=False),
        sa.Column("approver_mode", sa.String(length=10), nullable=False, server_default="role"),
        sa.Column("approver_ids", sa.JSON(), nullable=True),
    )
    op.create_index("ix_workflow_steps_department_id", "workflow_steps", ["department_id"])

    op.add_column("users", sa.Column("department_id", sa.Integer(), nullable=True))
    op.add_column("categories", sa.Column("department_id", sa.Integer(), nullable=True))
    op.add_column("budget_years", sa.Column("department_id", sa.Integer(), nullable=True))
    op.add_column("budget_years", sa.Column("current_step", sa.Integer(), nullable=True))

    conn = op.get_bind()
    has_data = any(conn.execute(sa.text(f"SELECT 1 FROM {t} LIMIT 1")).first()
                   for t in ("users", "categories", "budget_years"))
    if has_data:
        conn.execute(sa.text("INSERT INTO departments (name, active, created_at) VALUES ('IT', true, now())"))
        dept_id = conn.execute(sa.text("SELECT id FROM departments WHERE name = 'IT'")).scalar_one()
        for table in ("users", "categories", "budget_years"):
            conn.execute(sa.text(f"UPDATE {table} SET department_id = :d"), {"d": dept_id})
        conn.execute(sa.text("UPDATE budget_years SET current_step = 0 WHERE status = 'in_review'"))

    op.alter_column("categories", "department_id", nullable=False)
    op.alter_column("budget_years", "department_id", nullable=False)
    op.create_foreign_key("fk_users_department", "users", "departments", ["department_id"], ["id"])
    op.create_foreign_key("fk_categories_department", "categories", "departments", ["department_id"], ["id"],
                          ondelete="CASCADE")
    op.create_foreign_key("fk_budget_years_department", "budget_years", "departments", ["department_id"], ["id"])
    op.create_index("ix_categories_department_id", "categories", ["department_id"])
    op.create_index("ix_budget_years_department_id", "budget_years", ["department_id"])

    _drop_unique_on("categories", ["name_en"])
    _drop_unique_on("budget_years", ["year"])
    op.create_unique_constraint("uq_categories_department_name", "categories", ["department_id", "name_en"])
    op.create_unique_constraint("uq_budget_years_department_year", "budget_years", ["department_id", "year"])


def downgrade() -> None:
    raise NotImplementedError("Restore a backup taken before the upgrade instead.")