import { ReadonlySignal, Signal } from '@preact/signals-core';
import type {
    CommandSchema,
    CommandRegistry,
    PromptEvent,
    CommandRunnerContextExport,
    CommandResult
} from '@/utils/command';
import type { MutableSignal } from '@/utils/mutable-signal';
import {createGameContext, IGameContext} from './game';

export type GameHostStatus = 'created' | 'running' | 'disposed';

export interface GameModule<TState extends Record<string, unknown>> {
    registry: CommandRegistry<IGameContext<TState>>;
    createInitialState: () => TState;
}

export class GameHost<TState extends Record<string, unknown>> {
    readonly context: IGameContext<TState>;
    readonly status: ReadonlySignal<GameHostStatus>;
    readonly activePromptSchema: ReadonlySignal<CommandSchema | null>;
    readonly activePromptPlayer: ReadonlySignal<string | null>;

    private _state: MutableSignal<TState>;
    private _commands: CommandRunnerContextExport<IGameContext<TState>>;
    private _status: Signal<GameHostStatus>;
    private _activePromptSchema: Signal<CommandSchema | null>;
    private _activePromptPlayer: Signal<string | null>;
    private _createInitialState: () => TState;
    private _eventListeners: Map<'setup' | 'dispose', Set<() => void>>;
    private _isDisposed = false;

    constructor(
        registry: CommandRegistry<IGameContext<TState>>,
        createInitialState: () => TState,
    ) {
        this._createInitialState = createInitialState;
        this._eventListeners = new Map();

        const initialState = createInitialState();
        this.context = createGameContext(registry, initialState);

        this._status = new Signal<GameHostStatus>('created');
        this.status = this._status;

        this._activePromptSchema = new Signal<CommandSchema | null>(null);
        this.activePromptSchema = this._activePromptSchema;

        this._activePromptPlayer = new Signal<string | null>(null);
        this.activePromptPlayer = this._activePromptPlayer;

        this._state = this.context._state;
        this._commands = this.context._commands;

        this._setupPromptTracking();
    }

    private _setupPromptTracking() {
        let currentPromptEvent: PromptEvent | null = null;

        this._commands.on('prompt', (e) => {
            currentPromptEvent = e as PromptEvent;
            this._activePromptSchema.value = currentPromptEvent.schema;
            this._activePromptPlayer.value = currentPromptEvent.currentPlayer;
        });

        this._commands.on('promptEnd', () => {
            currentPromptEvent = null;
            this._activePromptSchema.value = null;
            this._activePromptPlayer.value = null;
        });

        // Initial state
        this._activePromptSchema.value = null;
        this._activePromptPlayer.value = null;
    }

    onInput(input: string): string | null {
        if (this._isDisposed) {
            return 'GameHost is disposed';
        }
        return this._commands._tryCommit(input);
    }

    /**
     * 为下一个 produceAsync 注册中断 Promise（通常用于 UI 动画）。
     * @see MutableSignal.addInterruption
     */
    addInterruption(promise: Promise<void>): void {
        this._state.addInterruption(promise);
    }

    /**
     * 清除所有未完成的中断。
     * @see MutableSignal.clearInterruptions
     */
    clearInterruptions(): void {
        this._state.clearInterruptions();
    }

    setup(setupCommand: string): Promise<CommandResult<unknown>> {
        if (this._isDisposed) {
            throw new Error('GameHost is disposed');
        }

        this._commands._cancel();

        const initialState = this._createInitialState();
        this._state.value = initialState as any;

        const promise = this._commands.run(setupCommand);

        this._status.value = 'running';
        this._emitEvent('setup');
        
        return promise;
    }

    dispose(): void {
        if (this._isDisposed) {
            return;
        }

        this._isDisposed = true;
        this._commands._cancel();
        this._status.value = 'disposed';
        
        // Emit dispose event BEFORE clearing listeners
        this._emitEvent('dispose');
        this._eventListeners.clear();
    }

    on(event: 'setup' | 'dispose', listener: () => void): () => void {
        if (!this._eventListeners.has(event)) {
            this._eventListeners.set(event, new Set());
        }
        this._eventListeners.get(event)!.add(listener);

        return () => {
            this._eventListeners.get(event)?.delete(listener);
        };
    }

    private _emitEvent(event: 'setup' | 'dispose') {
        const listeners = this._eventListeners.get(event);
        if (listeners) {
            for (const listener of listeners) {
                listener();
            }
        }
    }
}

export function createGameHost<TState extends Record<string, unknown>>(
    module: GameModule<TState>,
): GameHost<TState> {
    return new GameHost(
        module.registry,
        module.createInitialState,
    );
}