from __future__ import annotations

from dataclasses import dataclass
from typing import Any

from api.task_status import ACTIVE_TASK_STATUSES, normalize_task_status, status_value
from api.workplan_status import normalize_workstream_status


TASK_STARTED_STATUS = "progress"
TASK_NOT_STARTED_STATUS = "todo"
TASK_ACTIVE_STATUSES = ACTIVE_TASK_STATUSES
PARENT_ACTIVATION_STATUSES = {"proposed", "ready", "backlog"}


@dataclass(frozen=True)
class LifecycleTransitionResult:
    entity_type: str
    previous_status: str
    target_status: str
    changed: bool
    parent_activated: bool = False


def should_activate_parent_for_task_start(
    *,
    previous_task_status: Any,
    new_task_status: Any,
    parent_workstream_status: Any,
) -> bool:
    """Return whether a task start should move its parent to active."""
    return (
        status_value(previous_task_status) == TASK_NOT_STARTED_STATUS
        and status_value(new_task_status) == TASK_STARTED_STATUS
        and normalize_workstream_status(parent_workstream_status)
        in PARENT_ACTIVATION_STATUSES
    )


def has_active_task_status(task_statuses: list[Any] | tuple[Any, ...]) -> bool:
    """Return whether any task status represents currently active work."""
    return any(status_value(status) in TASK_ACTIVE_STATUSES for status in task_statuses)


def should_activate_parent_for_active_tasks(
    *,
    parent_workstream_status: Any,
    task_statuses: list[Any] | tuple[Any, ...],
) -> bool:
    """Return whether existing task state implies an active parent workstream."""
    return (
        normalize_workstream_status(parent_workstream_status)
        in PARENT_ACTIVATION_STATUSES
        and has_active_task_status(task_statuses)
    )


def activate_parent_for_task_start(
    *,
    previous_task_status: Any,
    new_task_status: Any,
    parent_workstream: Any,
) -> bool:
    """Activate a planning-state parent workstream when real task work starts."""
    if parent_workstream is None:
        return False
    if not should_activate_parent_for_task_start(
        previous_task_status=previous_task_status,
        new_task_status=new_task_status,
        parent_workstream_status=getattr(parent_workstream, "status", None),
    ):
        return False
    parent_workstream.status = "active"
    return True


def transition_workstream_status(
    workstream: Any,
    target_status: Any,
) -> LifecycleTransitionResult:
    """Apply a canonical workstream status transition."""
    previous_status = normalize_workstream_status(getattr(workstream, "status", None))
    normalised_target = normalize_workstream_status(target_status)
    workstream.status = normalised_target
    return LifecycleTransitionResult(
        entity_type="workstream",
        previous_status=previous_status,
        target_status=normalised_target,
        changed=previous_status != normalised_target,
    )


def transition_task_status(
    task: Any,
    target_status: Any,
    *,
    parent_workstream: Any = None,
    previous_task_status: Any = None,
    status_coercer: Any = None,
) -> LifecycleTransitionResult:
    """Apply a task status transition and activate the parent when work starts."""
    previous_status = status_value(
        getattr(task, "status", None)
        if previous_task_status is None
        else previous_task_status
    )
    normalised_target = normalize_task_status(target_status)
    task.status = status_coercer(normalised_target) if status_coercer else normalised_target
    parent_activated = activate_parent_for_task_start(
        previous_task_status=previous_status,
        new_task_status=normalised_target,
        parent_workstream=parent_workstream,
    )
    return LifecycleTransitionResult(
        entity_type="task",
        previous_status=previous_status,
        target_status=normalised_target,
        changed=previous_status != normalised_target,
        parent_activated=parent_activated,
    )