from __future__ import annotations

from collections.abc import Callable
from dataclasses import dataclass, field
from typing import TYPE_CHECKING, Any

from cloud.internal_api.models import AssignmentModel
from core.models import Task
from host_agent.execution import ExecutionFactories
from host_agent.planner_context import bind_planner_execution_context
from host_agent.progress import TaskProgressHolder, TaskProgressSnapshot
from runtime.task import is_cancellation_reason

if TYPE_CHECKING:
    from host_agent.mcp_lock import McpBusyTracker


@dataclass(frozen=True)
class AssignmentExecutionResult:
    status: str
    failure_reason: str | None = None
    metadata: dict[str, Any] = field(default_factory=dict)


class AssignmentExecutor:
    def __init__(
        self,
        factories: ExecutionFactories,
        *,
        mcp_busy_tracker: McpBusyTracker | None = None,
    ) -> None:
        self.factories = factories
        self._progress = TaskProgressHolder()
        self._mcp_busy_tracker = mcp_busy_tracker

    def latest_progress(self) -> TaskProgressSnapshot | None:
        """Latest step progress reported by the currently-running assignment."""
        return self._progress.snapshot()

    def execute(
        self,
        assignment: AssignmentModel,
        *,
        should_stop: Callable[[], bool] | None = None,
        stop_reason: Callable[[], str | None] | None = None,
    ) -> AssignmentExecutionResult:
        self._progress.clear()
        if self._mcp_busy_tracker is not None and (
            assignment.device_id in self._mcp_busy_tracker.busy_device_ids()
        ):
            return AssignmentExecutionResult(
                status="failed",
                failure_reason=(
                    f"device {assignment.device_id} is held by an active "
                    "MCP session"
                ),
            )
        with bind_planner_execution_context(assignment):
            if should_stop is not None and should_stop():
                reason = stop_reason() if stop_reason is not None else None
                return AssignmentExecutionResult(
                    status="cancelled" if is_cancellation_reason(reason) else "failed",
                    failure_reason=reason or "execution interrupted",
                )
            if assignment.workflow_definition_id is not None:
                return self._execute_workflow(
                    assignment, should_stop=should_stop, stop_reason=stop_reason
                )
            if assignment.goal is not None:
                return self._execute_goal(
                    assignment, should_stop=should_stop, stop_reason=stop_reason
                )
            return AssignmentExecutionResult(
                status="failed",
                failure_reason="assignment has neither goal nor workflow definition",
            )

    def _execute_goal(
        self,
        assignment: AssignmentModel,
        *,
        should_stop: Callable[[], bool] | None,
        stop_reason: Callable[[], str | None] | None,
    ) -> AssignmentExecutionResult:
        task = Task(goal=assignment.goal or "", device_id=assignment.device_id)
        if self.factories.metadata_store is not None:
            self.factories.metadata_store.create_task(
                task,
                source_task_id=assignment.task_id,
                source_attempt=assignment.attempt,
            )
        runner = self.factories.task_runner_factory()
        runner.on_step_progress = self._progress.update
        if should_stop is None:
            completed = runner.run(task)
        else:
            completed = runner.run(
                task, should_stop=should_stop, stop_reason=stop_reason
            )
        return AssignmentExecutionResult(
            status=_terminal_status(completed.status),
            failure_reason=completed.failure_reason,
            metadata={
                "runtime_task_id": completed.id,
                "runtime_status": completed.status,
            },
        )

    def _execute_workflow(
        self,
        assignment: AssignmentModel,
        *,
        should_stop: Callable[[], bool] | None,
        stop_reason: Callable[[], str | None] | None,
    ) -> AssignmentExecutionResult:
        definition_id = assignment.workflow_definition_id or ""
        definition = self.factories.workflow_store.get_definition(definition_id)
        if definition is None:
            return AssignmentExecutionResult(
                status="failed",
                failure_reason=f"unknown workflow definition {definition_id!r}",
            )
        runner = self.factories.workflow_runner_factory()
        if should_stop is None:
            run = runner.run(definition, device_id=assignment.device_id)
        else:
            run = runner.run(
                definition,
                device_id=assignment.device_id,
                should_stop=should_stop,
                stop_reason=stop_reason,
            )
        return AssignmentExecutionResult(
            status=_terminal_status(run.status),
            failure_reason=(
                None if run.status == "completed" else f"workflow ended as {run.status}"
            ),
            metadata={
                "workflow_run_id": run.id,
                "workflow_status": run.status,
            },
        )


def _terminal_status(runtime_status: str) -> str:
    if runtime_status == "completed":
        return "done"
    if runtime_status == "cancelled":
        return "cancelled"
    return "failed"