import { Environment, Pattern, NamedPattern, lookup } from "./meta";
import * as M from './meta';
import { Value, Float, Bytes, is, isPointer, Record, Dictionary, Set } from "@preserves/core";
import { refPosition } from "./reader";

export function validator(env: Environment, p: Pattern): (v: Value<any>) => boolean {
    function walk(p: Pattern, v: Value<any>, recordOkAsTuple = false): boolean {
        switch (p.label) {
            case M.$atom:
                switch (p[0]) {
                    case M.$Boolean: return typeof v === 'boolean';
                    case M.$Float: return Float.isSingle(v);
                    case M.$Double: return Float.isDouble(v);
                    case M.$SignedInteger: return typeof v === 'number';
                    case M.$String: return typeof v === 'string';
                    case M.$ByteString: return Bytes.isBytes(v);
                    case M.$Symbol: return typeof v === 'symbol';
                }
            case M.$lit:
                return is(v, p[0]);
            case M.$ref:
                return lookup(refPosition(p), p, env,
                              (p) => walk(p, v),
                              (p) => walk(p, v),
                              (_mod, _modPath, p) => walk(p!, v));
            case M.$or:
                for (const pp of p[0]) {
                    if (walk(pp, v)) return true;
                }
                return false;
            case M.$and:
                for (const pp of p[0]) {
                    if (!walk(pp, v)) return false;
                }
                return true;
            case M.$pointer:
                return isPointer(v);
            case M.$rec:
                if (!Record.isRecord(v)) return false;
                if (!walk(p[0], v.label)) return false;
                return walk(p[1], v, true);
            case M.$tuple:
                if (!Array.isArray(v)) return false;
                if (!recordOkAsTuple && Record.isRecord(v)) return false;
                if (p[0].length !== v.length) return false;
                for (let i = 0; i < v.length; i++) {
                    if (!walknamed(p[0][i], v[i])) return false;
                }
                return true;
            case M.$tuple_STAR_:
                if (!Array.isArray(v)) return false;
                if (!recordOkAsTuple && Record.isRecord(v)) return false;
                if (p[0].length > v.length) return false;
                for (let i = 0; i < p[0].length; i++) {
                    if (!walknamed(p[0][i], v[i])) return false;
                }
                for (let i = p[0].length; i < v.length; i++) {
                    if (!walknamed(p[1], v[i])) return false;
                }
                return true;
            case M.$setof:
                if (!Set.isSet(v)) return false;
                for (const vv of v) {
                    if (!walk(p[0], vv)) return false;
                }
                return true;
            case M.$dictof:
                if (!Dictionary.isDictionary<Value<any>>(v)) return false;
                for (const e of v) {
                    if (!walk(p[0], e[0])) return false;
                    if (!walk(p[1], e[1])) return false;
                }
                return true;
            case M.$dict:
                if (!Dictionary.isDictionary<Value<any>>(v)) return false;
                for (const e of p[0]) {
                    const vv = v.get(e[0]);
                    if (vv === void 0) return false;
                    if (!walk(e[1], vv)) return false;
                }
                return true;
            default:
                ((_p: never) => {})(p);
                return false;
        }
    }

    function walknamed(p: NamedPattern, v: Value<any>): boolean {
        return (p.label === M.$named) ? walk(p[1], v) : walk(p, v);
    }

    return v => walk(p, v);
}