"""Flow engine domain models (SQLModel tables)."""

from datetime import UTC, datetime
from uuid import UUID, uuid4

from sqlalchemy import JSON, Column, DateTime, UniqueConstraint
from sqlmodel import Field, SQLModel


def utcnow() -> datetime:
    return datetime.now(UTC)


def _ts_column() -> Column:
    return Column(DateTime(timezone=True))


def _json_column() -> Column:
    # Generic JSON: JSONB on Postgres, JSON/TEXT elsewhere.
    return Column(JSON)


class FlowDefinition(SQLModel, table=True):
    """A named decision flow (e.g. 'Bauvorhaben pruefen'). Versions live separately."""

    __tablename__ = "flow_definitions"

    id: UUID = Field(default_factory=uuid4, primary_key=True)
    name: str = Field(index=True, unique=True, max_length=200)
    description: str = Field(default="", max_length=2000)
    status: str = Field(default="active", max_length=20)  # active | archived
    # Filename under backend/flows/ this definition is synced from
    # (e.g. "simple_rule.json"). None for definitions created via the API.
    source_path: str | None = Field(default=None, max_length=255)
    # Flow to run after a human approval on this flow's runs (nullable).
    continuation_flow_id: UUID | None = Field(default=None, foreign_key="flow_definitions.id")
    created_at: datetime = Field(default_factory=utcnow, sa_column=_ts_column())


class FlowVersion(SQLModel, table=True):
    """An immutable version of a flow: the exact Langflow JSON that runs."""

    __tablename__ = "flow_versions"
    __table_args__ = (UniqueConstraint("flow_id", "version_no"),)

    id: UUID = Field(default_factory=uuid4, primary_key=True)
    flow_id: UUID = Field(foreign_key="flow_definitions.id", index=True)
    version_no: int = Field(index=True)
    langflow_json: dict = Field(default_factory=dict, sa_column=_json_column())
    # Flow id under which LFX serves this version (set on deploy).
    lfx_flow_id: str | None = Field(default=None, max_length=200)
    deployed_at: datetime | None = Field(default=None, sa_column=_ts_column())
    author: str = Field(default="", max_length=200)
    created_at: datetime = Field(default_factory=utcnow, sa_column=_ts_column())
    # Cached form schema for this exact JSON (see app/flows/input_schema.py).
    # Computed at version creation; nullable for pre-Phase-3 rows.
    input_schema: dict | None = Field(default=None, sa_column=_json_column())


class FlowRun(SQLModel, table=True):
    """One execution of a flow version."""

    __tablename__ = "flow_runs"

    id: UUID = Field(default_factory=uuid4, primary_key=True)
    version_id: UUID = Field(foreign_key="flow_versions.id", index=True)
    tenant_id: str = Field(default="default", index=True, max_length=200)
    # running | completed | pending_approval | failed
    status: str = Field(default="running", index=True, max_length=30)
    input: dict | None = Field(default=None, sa_column=_json_column())
    output: dict | None = Field(default=None, sa_column=_json_column())
    session_id: str | None = Field(default=None, max_length=200)
    created_at: datetime = Field(default_factory=utcnow, sa_column=_ts_column())
    finished_at: datetime | None = Field(default=None, sa_column=_ts_column())


class ApprovalTask(SQLModel, table=True):
    """Human task created by a flow that reached a terminal approval state."""

    __tablename__ = "approval_tasks"

    id: UUID = Field(default_factory=uuid4, primary_key=True)
    run_id: UUID = Field(foreign_key="flow_runs.id", index=True)
    version_id: UUID = Field(foreign_key="flow_versions.id", index=True)
    tenant_id: str = Field(default="default", index=True, max_length=200)
    title: str = Field(default="", max_length=500)
    payload: dict = Field(default_factory=dict, sa_column=_json_column())
    continuation_flow_id: UUID | None = Field(default=None)
    approver: str | None = Field(default=None, max_length=200)
    # open | approved | rejected
    status: str = Field(default="open", index=True, max_length=20)
    decision_note: str = Field(default="", max_length=2000)
    created_at: datetime = Field(default_factory=utcnow, sa_column=_ts_column())
    decided_at: datetime | None = Field(default=None, sa_column=_ts_column())