import { StructOfArr } from "./types.ts";
import { zip } from "./utils.ts";

export class Rule<V extends string[]> {
    private separators: ({ kind: "word", word: string } | { kind: "end" })[];
    private vars: V;

    public constructor(separators: string[], vars: V) {
        this.separators = separators.map(word => ({ kind: "word", word }));
        this.vars = vars;
        this.separators.push({ kind: "end" });
    }

    public get(text: string): StructOfArr<V, string> | null {
        const first_sep = this.separators[0] ?? "";
        if (first_sep.kind === "end") {
            if (text.length > 0) return null;
            else return {} as StructOfArr<V, string>;
        }
        if (!text.includes(first_sep.word)) return null;
        let [val, rest] = text.split(first_sep.word, 2);
        const result = {} as Record<string, string>;
        for (const [key, sep] of zip(this.vars, this.separators.slice(1))) {
            if (sep.kind === "end") {
                result[key] = rest;
                break;
            }
            if (!rest.includes(sep.word)) return null;
            [val, rest] = rest.split(sep.word, 2);
            result[key] = val;
        }
        return result as StructOfArr<V, string>;
    }
}