"""Persistence operations for flow definitions, versions, runs, and tasks."""

from __future__ import annotations

from datetime import UTC, datetime
from uuid import UUID

from sqlalchemy.exc import IntegrityError
from sqlmodel import Session, func, select

from app.models import ApprovalTask, FlowDefinition, FlowRun, FlowVersion

from . import input_schema as form_schema
from .schemas import ApprovalCreate, FlowDefinitionCreate, FlowVersionCreate


class NotFoundError(Exception):
    pass


class ConflictError(Exception):
    pass


class InvalidError(Exception):
    pass


def create_definition(session: Session, data: FlowDefinitionCreate) -> FlowDefinition:
    if (
        data.continuation_flow_id is not None
        and session.get(FlowDefinition, data.continuation_flow_id) is None
    ):
        raise InvalidError("continuation_flow_id unknown")
    definition = FlowDefinition(
        name=data.name,
        description=data.description,
        continuation_flow_id=data.continuation_flow_id,
    )
    session.add(definition)
    try:
        session.commit()
    except IntegrityError as exc:
        session.rollback()
        raise ConflictError(f"flow {data.name!r} already exists") from exc
    session.refresh(definition)
    return definition


def get_definition(session: Session, flow_id: UUID) -> FlowDefinition:
    definition = session.get(FlowDefinition, flow_id)
    if definition is None:
        raise NotFoundError(f"flow {flow_id} not found")
    return definition


def list_definitions(session: Session) -> list[FlowDefinition]:
    return list(session.exec(select(FlowDefinition).order_by(FlowDefinition.name)).all())


def get_definition_by_source_path(session: Session, source_path: str) -> FlowDefinition | None:
    """Find the definition synced from a given backend/flows filename."""
    return session.exec(
        select(FlowDefinition).where(FlowDefinition.source_path == source_path)
    ).first()


def set_definition_name(session: Session, definition: FlowDefinition, name: str) -> FlowDefinition:
    """Rename a definition and record its source file. Name clashes 409."""
    definition.name = name
    session.add(definition)
    try:
        session.commit()
    except IntegrityError as exc:
        session.rollback()
        raise ConflictError(f"flow {name!r} already exists") from exc
    session.refresh(definition)
    return definition


def next_version_no(session: Session, flow_id: UUID) -> int:
    max_no = session.exec(
        select(func.max(FlowVersion.version_no)).where(FlowVersion.flow_id == flow_id)
    ).one()
    return (max_no or 0) + 1


def delete_definition_cascade(session: Session, definition: FlowDefinition) -> dict[str, int]:
    """Remove a definition and its whole subtree (tasks, runs, versions).

    Used when the canonical file disappears: the directory is the source of
    truth, so the derived registry follows. Commits once.
    """
    version_ids = list(
        session.exec(select(FlowVersion.id).where(FlowVersion.flow_id == definition.id)).all()
    )
    task_count = 0
    run_count = 0
    if version_ids:
        tasks = list(
            session.exec(select(ApprovalTask).where(ApprovalTask.version_id.in_(version_ids))).all()
        )
        runs = list(session.exec(select(FlowRun).where(FlowRun.version_id.in_(version_ids))).all())
        task_count, run_count = len(tasks), len(runs)
        for row in (*tasks, *runs):
            session.delete(row)
        for version in session.exec(
            select(FlowVersion).where(FlowVersion.flow_id == definition.id)
        ).all():
            session.delete(version)
    session.delete(definition)
    session.commit()
    return {
        "definitions": 1,
        "versions": len(version_ids),
        "runs": run_count,
        "tasks": task_count,
    }


def validate_flow_json(flow_json: dict) -> None:
    """Reject anything that is not a Langflow-export-shaped document."""
    if not isinstance(flow_json, dict):
        raise InvalidError("langflow_json must be an object")
    data = flow_json.get("data")
    if not isinstance(data, dict):
        raise InvalidError("langflow_json must contain a 'data' object")
    if not isinstance(data.get("nodes"), list) or not isinstance(data.get("edges"), list):
        raise InvalidError("langflow_json.data must contain 'nodes' and 'edges' lists")


def create_version(session: Session, flow_id: UUID, data: FlowVersionCreate) -> FlowVersion:
    get_definition(session, flow_id)
    validate_flow_json(data.langflow_json)
    version = FlowVersion(
        flow_id=flow_id,
        version_no=next_version_no(session, flow_id),
        langflow_json=data.langflow_json,
        author=data.author,
        # Single choke point: sync, import, and API creation all cache the
        # form schema here, so reads never re-parse.
        input_schema=form_schema.extract_form_schema(data.langflow_json),
    )
    session.add(version)
    session.commit()
    session.refresh(version)
    return version


def get_version(session: Session, version_id: UUID) -> FlowVersion:
    version = session.get(FlowVersion, version_id)
    if version is None:
        raise NotFoundError(f"flow version {version_id} not found")
    return version


def list_versions(session: Session, flow_id: UUID) -> list[FlowVersion]:
    get_definition(session, flow_id)
    return list(
        session.exec(
            select(FlowVersion)
            .where(FlowVersion.flow_id == flow_id)
            .order_by(FlowVersion.version_no)
        ).all()
    )


def get_version_by_no(session: Session, flow_id: UUID, version_no: int) -> FlowVersion:
    version = session.exec(
        select(FlowVersion).where(
            FlowVersion.flow_id == flow_id, FlowVersion.version_no == version_no
        )
    ).first()
    if version is None:
        raise NotFoundError(f"flow {flow_id} has no version {version_no}")
    return version


def get_latest_deployed_version(session: Session, flow_id: UUID) -> FlowVersion:
    version = session.exec(
        select(FlowVersion)
        .where(FlowVersion.flow_id == flow_id, FlowVersion.deployed_at.is_not(None))
        .order_by(FlowVersion.version_no.desc())
    ).first()
    if version is None:
        raise InvalidError(f"flow {flow_id} has no deployed version")
    return version


def mark_deployed(session: Session, version: FlowVersion, lfx_flow_id: str) -> FlowVersion:
    version.lfx_flow_id = lfx_flow_id
    version.deployed_at = datetime.now(UTC)
    session.add(version)
    session.commit()
    session.refresh(version)
    return version


def create_run(
    session: Session,
    version: FlowVersion,
    *,
    input: dict | None,
    tenant_id: str = "default",
    session_id: str | None = None,
) -> FlowRun:
    run = FlowRun(
        version_id=version.id,
        tenant_id=tenant_id,
        input=input,
        session_id=session_id or str(version.id),
    )
    session.add(run)
    session.commit()
    session.refresh(run)
    return run


def set_run_result(session: Session, run: FlowRun, status: str, output: dict | None) -> FlowRun:
    run.status = status
    run.output = output
    run.finished_at = datetime.now(UTC)
    session.add(run)
    session.commit()
    session.refresh(run)
    return run


def has_open_task(session: Session, run_id: UUID) -> bool:
    """True when a run has an open approval task (terminal-state mapping)."""
    return (
        session.exec(
            select(ApprovalTask).where(ApprovalTask.run_id == run_id, ApprovalTask.status == "open")
        ).first()
        is not None
    )


def get_run(session: Session, run_id: UUID) -> FlowRun:
    run = session.get(FlowRun, run_id)
    if run is None:
        raise NotFoundError(f"run {run_id} not found")
    return run


def list_runs(session: Session, flow_id: UUID, tenant_id: str | None = None) -> list[FlowRun]:
    get_definition(session, flow_id)
    query = (
        select(FlowRun)
        .join(FlowVersion, FlowVersion.id == FlowRun.version_id)
        .where(FlowVersion.flow_id == flow_id)
        .order_by(FlowRun.created_at.desc())
    )
    if tenant_id is not None:
        query = query.where(FlowRun.tenant_id == tenant_id)
    return list(session.exec(query).all())


def create_approval_task(session: Session, data: ApprovalCreate) -> ApprovalTask:
    run = session.get(FlowRun, data.run_id)
    if run is None:
        raise NotFoundError(f"run {data.run_id} not found")
    if (
        data.continuation_flow_id is not None
        and session.get(FlowDefinition, data.continuation_flow_id) is None
    ):
        raise InvalidError("continuation_flow_id unknown")
    existing = session.exec(
        select(ApprovalTask).where(
            ApprovalTask.run_id == data.run_id, ApprovalTask.status == "open"
        )
    ).first()
    if existing is not None:
        raise ConflictError(f"run {data.run_id} already has an open approval task")
    task = ApprovalTask(
        run_id=run.id,
        version_id=run.version_id,
        tenant_id=run.tenant_id,
        title=data.title,
        payload=data.payload,
        continuation_flow_id=data.continuation_flow_id,
    )
    session.add(task)
    run.status = "pending_approval"
    run.finished_at = datetime.now(UTC)
    session.add(run)
    session.commit()
    session.refresh(task)
    return task


def list_approval_tasks(session: Session, tenant_id: str | None = None) -> list[ApprovalTask]:
    query = select(ApprovalTask).order_by(ApprovalTask.created_at.desc())
    if tenant_id is not None:
        query = query.where(ApprovalTask.tenant_id == tenant_id)
    return list(session.exec(query).all())


def get_task(session: Session, task_id: UUID) -> ApprovalTask:
    task = session.get(ApprovalTask, task_id)
    if task is None:
        raise NotFoundError(f"approval task {task_id} not found")
    return task


def decide_task(
    session: Session,
    task: ApprovalTask,
    *,
    decision: str,
    approver: str = "",
    note: str = "",
) -> ApprovalTask:
    """Approve or reject an open task. Decided tasks are immutable (409)."""
    if task.status != "open":
        raise ConflictError(f"task {task.id} is already {task.status}")
    if decision not in ("approved", "rejected"):
        raise InvalidError(f"unknown decision {decision!r}")
    task.status = decision
    task.approver = approver
    task.decision_note = note
    task.decided_at = datetime.now(UTC)
    session.add(task)
    session.commit()
    session.refresh(task)
    return task