const { getFuncProps } = require('../utils');
const moduleMap = require('./DepMap');

class Provider {
    constructor() {
        this._cache = {};
        this.init();
    }
    static getInstance() {
        if (!Provider.instance) {
            Provider.instance = new Provider();
        }
        return Provider.instance;
    }
    get cache() {
        return this._cache;
    }
    init() {
        this._cache = moduleMap;
    }
    regist(key, value) {
        this._cache[key] = value;
    }
    loadDep (depName) {
        const dep = moduleMap[depName];
        if (dep) {
            this._cache[depName] = require(dep);
        }
    }
    inject(fn, scope = {}) {
        const deps = getFuncProps(fn) || [];
        for(let i = 0, len = deps.length; i < len; i++) {
            const depName = deps[i];
            const dep = this.cache[depName];
            if(dep) {
                deps[i] = dep;
            } else {
                throw new Error('Cannot find dependence');
            }
        }
        return fn.apply(scope, deps);
    }
    getModule(depName) {
        if (!this.cache[depName]) {
            this.loadDep(depName);
        }
        return this.cache[depName] || {};
    }
}
const provider = Provider.getInstance();
global.Provider = provider;

module.exports = {
    inject: (...args) => provider.inject(...args),
    regist: (...args) => provider.regist(...args),
};