@qiwi/cyclone/target/esnext/machine.js

"State machine" for basic purposes

import { INVALID_UNLOCK_KEY, LOCK_VIOLATION, MachineError, TRANSITION_VIOLATION, UNREACHABLE_STATE } from './error.js';
import { generateDate, generateId } from './generator.js';
import { log } from './log.js';
export const DELIMITER = '>';
export const DEFAULT_HANDLER = (...last) => last.pop();
export const DEFAULT_HISTORY_SIZE = 10;
export const DEFAULT_OPTS = {
    transitions: {},
    historySize: DEFAULT_HISTORY_SIZE,
    immutable: false
};
export class Machine {
    /**
     * Machine options.
     * @property
     */
    opts;
    /**
     * State history.
     * @property
     */
    history;
    /**
     * Lock key.
     * @property
     */
    key;
    /**
     * Unique machine id
     * @property
     */
    id;
    /**
     * Transition handler map
     * @property
     */
    transitions;
    constructor(opts) {
        this.opts = { ...DEFAULT_OPTS, ...opts };
        this.history = [];
        this.key = null;
        this.id = generateId();
        this.transitions = opts.transitions;
        if (typeof opts.initialState === 'string') {
            this.history.push({
                state: opts.initialState,
                data: opts.initialData,
                id: generateId(),
                date: generateDate()
            });
        }
        return this;
    }
    /**
     * Provides next state transition.
     * @param state Next state name.
     * @param payload Any data for handler.
     */
    next(state, ...payload) {
        if (this.key) {
            throw new MachineError(LOCK_VIOLATION);
        }
        const handler = Machine.getHandler(state, this.history, this.transitions);
        const current = this.current();
        const data = handler(current.data, ...payload);
        const id = generateId();
        const date = generateDate();
        this.history.push({
            state,
            data,
            id,
            date
        });
        if (this.history.length > Machine.getHistoryLimit(this.opts.historySize)) {
            log.debug('history limit reached');
            this.history.shift();
        }
        return this;
    }
    /**
     * Returns the machine's digest: state name and stored data.
     */
    current() {
        return { ...this.history[this.history.length - 1] };
    }
    /**
     * Returns the last state, that satisfies the condition
     */
    last(condition) {
        if (condition === undefined) {
            return this.current();
        }
        const filter = typeof condition === 'string'
            ? ({ state }) => state === condition
            : condition;
        return [...this.history].reverse().find(filter);
    }
    /**
     * Reverts current state to the previous.
     * @param state
     */
    prev(state) {
        if (this.key) {
            throw new MachineError(LOCK_VIOLATION);
        }
        if (this.history.length < 2) {
            throw new MachineError(UNREACHABLE_STATE);
        }
        if (state === undefined) {
            this.history.pop();
            return this;
        }
        const last = this.last(state);
        if (!last) {
            throw new MachineError(UNREACHABLE_STATE);
        }
        this.history.length = this.history.indexOf(last) + 1;
        return this;
    }
    /**
     * Locks the machine. Any transitions are prohibited before unlocking.
     * @param key
     */
    lock(key) {
        this.key = key || `lock${generateId()}`;
        return this;
    }
    /**
     * Unlocks the machine.
     * @param key
     */
    unlock(key) {
        if (this.key !== key) {
            throw new MachineError(INVALID_UNLOCK_KEY);
        }
        this.key = null;
        return this;
    }
    static getHistoryLimit(historySize) {
        if (historySize === undefined) {
            return DEFAULT_HISTORY_SIZE;
        }
        if (historySize === -1) {
            return Number.POSITIVE_INFINITY;
        }
        return historySize;
    }
    static getHandler(next, history, transitions) {
        const targetTransition = this.getTargetTransition(next, history);
        const nextTransition = this.getTransition(targetTransition, transitions);
        if (!nextTransition) {
            throw new MachineError(TRANSITION_VIOLATION);
        }
        const handler = transitions[nextTransition];
        return typeof handler === 'function'
            ? handler
            : DEFAULT_HANDLER;
    }
    static getTransition(targetTransition, transitions) {
        // TODO Support wildcards
        // TODO Support OR operator
        // TODO Generate patterns in constructor
        return Object.keys(transitions)
            .filter(transition => targetTransition.length > transition.length
            ? new RegExp(`.*${transition}$`).test(targetTransition)
            : targetTransition === transition)
            .sort((a, b) => b.length - a.length)[0];
    }
    static getTargetTransition(next, history) {
        return [...history.map(({ state }) => state), next]
            .join(DELIMITER);
    }
    /**
     * Returns the last passes argument as a result
     * @param {any} state
     * @param {any} [payload]
     * @return {any}
     */
    DEFAULT_HANDLER = DEFAULT_HANDLER;
}