"""Installer runner that executes milestones sequentially."""
from __future__ import annotations

from typing import Callable, Iterable

from .milestone import Milestone, ValidationResult
from .state import InstallerState

EventCallback = Callable[..., None]


class InstallerRunner:
    """Executes milestones sequentially and emits lifecycle events."""

    def __init__(self, milestones: Iterable[Milestone], state: InstallerState | None = None):
        self._milestones = {m.id: m for m in milestones}
        self._order = [m.id for m in milestones]
        self.state = state or InstallerState()
        self._listeners: dict[str, list[EventCallback]] = {
            'on_enter_milestone': [],
            'on_validation_error': [],
            'on_progress': [],
            'on_complete': [],
        }

    def on(self, event: str, callback: EventCallback) -> None:
        if event not in self._listeners:
            raise ValueError(f"Unknown event: {event}")
        self._listeners[event].append(callback)

    def emit(self, event: str, *args) -> None:
        for cb in self._listeners.get(event, []):
            cb(*args)

    def run(self, start_id: str | None = None) -> bool:
        if not self._order:
            self.emit('on_complete', None, self.state)
            return True

        current_id = start_id or self.state.current_id or self._order[0]

        while current_id:
            milestone = self._milestones.get(current_id)
            if milestone is None:
                self.state.errors.append(f"Unknown milestone id: {current_id}")
                self.emit('on_validation_error', None, self.state, [self.state.errors[-1]])
                return False

            self.state.current_id = current_id
            self.state.history.append(current_id)
            self.emit('on_enter_milestone', milestone, self.state)

            errors = milestone.validate(self.state)
            error_list = _normalize_validation(errors)
            if error_list:
                self.state.errors.extend(error_list)
                self.emit('on_validation_error', milestone, self.state, error_list)
                return False

            def _progress(message: str, percent: float | None = None) -> None:
                if percent is not None:
                    self.state.progress[current_id] = percent
                self.emit('on_progress', milestone, self.state, message, percent)

            milestone.execute(self.state, _progress)
            self.state.mark_completed(current_id)

            next_id = milestone.next(self.state)
            if not next_id:
                self.emit('on_complete', milestone, self.state)
                return True

            current_id = next_id

        self.emit('on_complete', None, self.state)
        return True


def _normalize_validation(result: ValidationResult) -> list[str]:
    if result is None:
        return []
    if isinstance(result, str):
        return [result]
    return [str(item) for item in result]