class Template {
    constructor() {
        this.tpl = {};
    }

    async loadTemplate(name) {
        let self = this;
        if (!this.tpl[name]) {
            await fetch(templateDir + name + ".tpl").then((r) => r.text()).then(c => {
                self.tpl[name] = c;
            })
        }
    }

    async loadArray(names) {
        for (let name of names) {
            await this.loadTemplate(name);
        }
    }

    parseTemplate(name, data) {
        if (!this.tpl[name]) {
            return ""
        }
        let m, d = this.tpl[name];
        while ((m = templateEx.exec(d)) !== null) {
            if (m.index === templateEx.lastIndex) {
                templateEx.lastIndex++;
            }
            let key = m[0];
            let value = data[m[1]];
            if (value === undefined || value === null) {
                value = "";
            }
            d = d.replace(key, value)
        }
        return d;
    }

    parseFromAPI(url, name, cb) {
        fetch(url).then((r) => r.json()).then(d => {
            cb(this.parseTemplate(name, d))
        }).catch(console.error)
    }
}

const templateEx = /\$(.*?)\$/gm;
const templateDir = "out/tpl/"