"""tk_task state machine — pure logic (架构文档 §6.2 task 域, FR-TASK-01).

统一任务中心 is the only long-running-task view in the system; every long task
(report / tryon / hairstyle / matting / render) moves through these states.
"""

from __future__ import annotations

from enum import StrEnum

from packages.domain.errors import InvalidTaskTransitionError


class TaskStatus(StrEnum):
    PENDING = "pending"  # created, quota reserved, not yet queued
    QUEUED = "queued"  # handed to Celery
    RUNNING = "running"
    SUCCEEDED = "succeeded"
    FAILED = "failed"
    CANCELED = "canceled"


class TaskType(StrEnum):
    REPORT = "report"
    TRYON = "tryon"
    HAIRSTYLE = "hairstyle"
    MATTING = "matting"
    RENDER = "render"
    PING = "ping"  # scaffold-only: proves the async path end to end


TERMINAL_STATUSES: frozenset[TaskStatus] = frozenset(
    {TaskStatus.SUCCEEDED, TaskStatus.FAILED, TaskStatus.CANCELED}
)

#: Refunds are owed for every terminal state other than success (FR-TRY-05).
REFUNDABLE_STATUSES: frozenset[TaskStatus] = frozenset({TaskStatus.FAILED, TaskStatus.CANCELED})

ALLOWED_TRANSITIONS: dict[TaskStatus, frozenset[TaskStatus]] = {
    TaskStatus.PENDING: frozenset({TaskStatus.QUEUED, TaskStatus.FAILED, TaskStatus.CANCELED}),
    TaskStatus.QUEUED: frozenset({TaskStatus.RUNNING, TaskStatus.FAILED, TaskStatus.CANCELED}),
    TaskStatus.RUNNING: frozenset(
        {TaskStatus.SUCCEEDED, TaskStatus.FAILED, TaskStatus.CANCELED, TaskStatus.QUEUED}
    ),
    TaskStatus.SUCCEEDED: frozenset(),
    TaskStatus.FAILED: frozenset({TaskStatus.QUEUED}),  # retry re-queues
    TaskStatus.CANCELED: frozenset(),
}


def can_transition(current: TaskStatus, target: TaskStatus) -> bool:
    return target in ALLOWED_TRANSITIONS[current]


def assert_transition(current: TaskStatus, target: TaskStatus) -> None:
    if not can_transition(current, target):
        raise InvalidTaskTransitionError(current=current.value, target=target.value)


def is_terminal(status: TaskStatus) -> bool:
    return status in TERMINAL_STATUSES


def needs_refund(status: TaskStatus) -> bool:
    return status in REFUNDABLE_STATUSES


def progress_for(status: TaskStatus) -> int:
    return {
        TaskStatus.PENDING: 0,
        TaskStatus.QUEUED: 5,
        TaskStatus.RUNNING: 50,
        TaskStatus.SUCCEEDED: 100,
        TaskStatus.FAILED: 100,
        TaskStatus.CANCELED: 100,
    }[status]