"""add generic commodity-scoped meter cost periods

Revision ID: 20260822_19_meter_cost_periods
Revises: 20260822_18_contract_scopes
Create Date: 2026-08-22 00:00:00.000000

This additive migration creates a separate audit ledger for non-electricity
meter costs. It deliberately does not alter, migrate, or delete rows from the
existing electricity-only energy_cost_period table.
"""

from typing import Sequence, Union

import sqlalchemy as sa
from alembic import op


revision: str = "20260822_19_meter_cost_periods"
down_revision: Union[str, None] = "20260822_18_contract_scopes"
branch_labels: Union[str, Sequence[str], None] = None
depends_on: Union[str, Sequence[str], None] = None


class ExactDecimal(sa.TypeDecorator):
    """Use SQLite text storage while retaining Numeric semantics elsewhere."""

    impl = sa.Numeric
    cache_ok = True

    def __init__(self, precision: int, scale: int) -> None:
        self.precision = precision
        self.scale = scale
        super().__init__(precision=precision, scale=scale)

    def load_dialect_impl(self, dialect):
        if dialect.name == "sqlite":
            return dialect.type_descriptor(sa.String(self.precision + 2))
        return dialect.type_descriptor(sa.Numeric(self.precision, self.scale, asdecimal=True))


def upgrade() -> None:
    op.create_table(
        "meter_cost_period",
        sa.Column("id", sa.Integer(), autoincrement=True, nullable=False),
        sa.Column("commodity", sa.String(length=32), nullable=False),
        sa.Column("period_start", sa.DateTime(timezone=True), nullable=False),
        sa.Column("period_end", sa.DateTime(timezone=True), nullable=False),
        sa.Column("meter_id", sa.Integer(), nullable=True),
        sa.Column("source_binding_id", sa.Integer(), nullable=True),
        sa.Column("contract_version_id", sa.Integer(), nullable=True),
        # SQLite NUMERIC coercion binds Decimal values as binary floats.  Store
        # fixed-width decimal text there, while retaining Numeric semantics on
        # other supported dialects.
        sa.Column("quantity", ExactDecimal(15, 6), nullable=False),
        sa.Column("cost", ExactDecimal(15, 9), nullable=False),
        sa.Column("currency", sa.String(length=8), nullable=False),
        sa.Column("cost_breakdown", sa.JSON(), nullable=False),
        sa.Column("pricing_snapshot", sa.JSON(), nullable=False),
        sa.Column("quality", sa.String(length=32), nullable=False),
        sa.Column("degraded", sa.Boolean(), nullable=False, server_default=sa.false()),
        sa.Column("degraded_reason", sa.String(length=255), nullable=True),
        sa.Column("created_at", sa.DateTime(timezone=True), nullable=False),
        sa.Column("updated_at", sa.DateTime(timezone=True), nullable=False),
        sa.ForeignKeyConstraint(["meter_id"], ["meter.id"], ondelete="RESTRICT"),
        sa.ForeignKeyConstraint(
            ["source_binding_id"], ["meter_source_binding.id"], ondelete="RESTRICT"
        ),
        sa.ForeignKeyConstraint(
            ["contract_version_id"], ["energy_contract_version.id"], ondelete="RESTRICT"
        ),
        sa.CheckConstraint(
            "degraded OR (meter_id IS NOT NULL AND source_binding_id IS NOT NULL "
            "AND contract_version_id IS NOT NULL)",
            name="ck_meter_cost_period_normal_audit_links",
        ),
        sa.CheckConstraint("period_end > period_start", name="ck_meter_cost_period_positive_interval"),
        sa.CheckConstraint(
            "NOT degraded OR (degraded_reason IS NOT NULL AND length(trim(degraded_reason)) > 0)",
            name="ck_meter_cost_period_degraded_reason",
        ),
        sa.PrimaryKeyConstraint("id"),
        sa.UniqueConstraint("commodity", "period_start", name="uq_meter_cost_period_commodity_start"),
    )
    op.create_index(
        "ix_meter_cost_period_commodity_start", "meter_cost_period", ["commodity", "period_start"]
    )
    op.create_index(
        "ix_meter_cost_period_source_binding_id", "meter_cost_period", ["source_binding_id"]
    )


def downgrade() -> None:
    op.drop_index("ix_meter_cost_period_source_binding_id", table_name="meter_cost_period")
    op.drop_index("ix_meter_cost_period_commodity_start", table_name="meter_cost_period")
    op.drop_table("meter_cost_period")