import uuid
from datetime import date

from sqlalchemy import (
    BigInteger,
    Boolean,
    CheckConstraint,
    Date,
    ForeignKey,
    ForeignKeyConstraint,
    Integer,
    String,
    UniqueConstraint,
    Uuid,
)
from sqlalchemy.orm import Mapped, mapped_column

from app.db.base import Base, PkMixin, TimestampMixin

ACCOUNT_KINDS = ("cash", "debit", "credit")
ACCOUNT_STATUSES = ("active", "archived")
OPERATION_TYPES = ("expense", "income", "transfer", "refund")
OPERATION_STATUSES = ("confirmed", "voided")


class Account(Base, PkMixin, TimestampMixin):
    """Financial account. Balance is always derived: opening + confirmed postings."""

    __tablename__ = "accounts"
    __table_args__ = (
        CheckConstraint("kind IN ('cash', 'debit', 'credit')", name="kind_valid"),
        CheckConstraint("status IN ('active', 'archived')", name="status_valid"),
        CheckConstraint("currency = 'RUB'", name="currency_rub_only"),
        UniqueConstraint("space_id", "id", name="uq_accounts_space_id"),
    )

    space_id: Mapped[uuid.UUID] = mapped_column(
        Uuid, ForeignKey("financial_spaces.id", ondelete="CASCADE"), nullable=False, index=True
    )
    name: Mapped[str] = mapped_column(String(200), nullable=False)
    kind: Mapped[str] = mapped_column(String(16), nullable=False)
    currency: Mapped[str] = mapped_column(String(3), nullable=False, default="RUB")
    opening_amount_kopecks: Mapped[int] = mapped_column(BigInteger, nullable=False, default=0)
    opened_on: Mapped[date] = mapped_column(Date, nullable=False)
    bank_code: Mapped[str | None] = mapped_column(String(32), nullable=True)
    masked_identifier: Mapped[str | None] = mapped_column(String(32), nullable=True)
    fingerprint: Mapped[str | None] = mapped_column(String(128), nullable=True)
    status: Mapped[str] = mapped_column(String(16), nullable=False, default="active")
    version: Mapped[int] = mapped_column(Integer, nullable=False, default=1)

    __mapper_args__ = {"version_id_col": version}


class Operation(Base, PkMixin, TimestampMixin):
    """User financial fact. amount_kopecks is always positive; direction lives in postings."""

    __tablename__ = "operations"
    __table_args__ = (
        CheckConstraint("type IN ('expense', 'income', 'transfer', 'refund')", name="type_valid"),
        CheckConstraint("status IN ('confirmed', 'voided')", name="status_valid"),
        CheckConstraint("amount_kopecks > 0", name="amount_positive"),
        CheckConstraint(
            "NOT (type = 'transfer' AND counter_account_id IS NULL)",
            name="transfer_requires_counter",
        ),
        ForeignKeyConstraint(
            ["space_id", "account_id"],
            ["accounts.space_id", "accounts.id"],
            name="fk_operations_account_tenant",
        ),
        ForeignKeyConstraint(
            ["space_id", "counter_account_id"],
            ["accounts.space_id", "accounts.id"],
            name="fk_operations_counter_account_tenant",
        ),
        ForeignKeyConstraint(
            ["space_id", "category_id"],
            ["categories.space_id", "categories.id"],
            name="fk_operations_category_tenant",
        ),
        ForeignKeyConstraint(
            ["space_id", "income_source_id"],
            ["income_sources.space_id", "income_sources.id"],
            name="fk_operations_income_source_tenant",
        ),
        ForeignKeyConstraint(
            ["space_id", "payee_id"],
            ["payees.space_id", "payees.id"],
            name="fk_operations_payee_tenant",
        ),
        ForeignKeyConstraint(
            ["space_id", "parent_operation_id"],
            ["operations.space_id", "operations.id"],
            name="fk_operations_parent_tenant",
        ),
        UniqueConstraint("space_id", "request_key", name="uq_operations_space_request_key"),
        UniqueConstraint("space_id", "id", name="uq_operations_space_id"),
    )

    space_id: Mapped[uuid.UUID] = mapped_column(
        Uuid, ForeignKey("financial_spaces.id", ondelete="CASCADE"), nullable=False, index=True
    )
    type: Mapped[str] = mapped_column(String(16), nullable=False)
    status: Mapped[str] = mapped_column(String(16), nullable=False, default="confirmed")
    amount_kopecks: Mapped[int] = mapped_column(BigInteger, nullable=False)
    account_id: Mapped[uuid.UUID] = mapped_column(Uuid, nullable=False, index=True)
    counter_account_id: Mapped[uuid.UUID | None] = mapped_column(Uuid, nullable=True)
    category_id: Mapped[uuid.UUID | None] = mapped_column(Uuid, nullable=True, index=True)
    income_source_id: Mapped[uuid.UUID | None] = mapped_column(Uuid, nullable=True)
    payee_id: Mapped[uuid.UUID | None] = mapped_column(Uuid, nullable=True)
    parent_operation_id: Mapped[uuid.UUID | None] = mapped_column(Uuid, nullable=True)
    occurred_on: Mapped[date] = mapped_column(Date, nullable=False, index=True)
    posted_on: Mapped[date | None] = mapped_column(Date, nullable=True)
    description: Mapped[str | None] = mapped_column(String(500), nullable=True)
    void_reason: Mapped[str | None] = mapped_column(String(500), nullable=True)
    request_key: Mapped[str | None] = mapped_column(String(120), nullable=True)
    created_by_user_id: Mapped[uuid.UUID | None] = mapped_column(
        Uuid, ForeignKey("users.id", ondelete="SET NULL"), nullable=True
    )
    version: Mapped[int] = mapped_column(Integer, nullable=False, default=1)

    __mapper_args__ = {"version_id_col": version}


class Posting(Base, PkMixin, TimestampMixin):
    """Signed balance change of one account within one operation.

    Sign convention (uniform for asset and credit accounts, from the account's
    perspective): income and refunds post positive; expenses post negative;
    transfers post negative on the source and positive on the destination.
    Credit accounts normally carry a non-positive balance; debt = -balance.
    """

    __tablename__ = "postings"
    __table_args__ = (
        CheckConstraint("amount_kopecks <> 0", name="amount_nonzero"),
        ForeignKeyConstraint(
            ["space_id", "operation_id"],
            ["operations.space_id", "operations.id"],
            ondelete="CASCADE",
            name="fk_postings_operation_tenant",
        ),
        ForeignKeyConstraint(
            ["space_id", "account_id"],
            ["accounts.space_id", "accounts.id"],
            name="fk_postings_account_tenant",
        ),
        UniqueConstraint("space_id", "id", name="uq_postings_space_id"),
    )

    space_id: Mapped[uuid.UUID] = mapped_column(
        Uuid, ForeignKey("financial_spaces.id", ondelete="CASCADE"), nullable=False, index=True
    )
    operation_id: Mapped[uuid.UUID] = mapped_column(Uuid, nullable=False, index=True)
    account_id: Mapped[uuid.UUID] = mapped_column(Uuid, nullable=False, index=True)
    amount_kopecks: Mapped[int] = mapped_column(BigInteger, nullable=False)


class Category(Base, PkMixin, TimestampMixin):
    """Budget category. Kept in ledger module to avoid circular imports."""

    __tablename__ = "categories"
    __table_args__ = (
        CheckConstraint("kind IN ('monthly', 'savings_envelope')", name="kind_valid"),
        ForeignKeyConstraint(
            ["space_id", "linked_account_id"],
            ["accounts.space_id", "accounts.id"],
            name="fk_categories_linked_account_tenant",
        ),
        UniqueConstraint("space_id", "id", name="uq_categories_space_id"),
    )

    space_id: Mapped[uuid.UUID] = mapped_column(
        Uuid, ForeignKey("financial_spaces.id", ondelete="CASCADE"), nullable=False, index=True
    )
    kind: Mapped[str] = mapped_column(String(16), nullable=False)
    system_key: Mapped[str | None] = mapped_column(String(64), nullable=True)
    name_override: Mapped[str | None] = mapped_column(String(200), nullable=True)
    custom_name: Mapped[str | None] = mapped_column(String(200), nullable=True)
    linked_account_id: Mapped[uuid.UUID | None] = mapped_column(Uuid, nullable=True)
    archived: Mapped[bool] = mapped_column(Boolean, nullable=False, default=False)