import * as M from '../meta';
import { block, braces, Item, keyvalue, parens, seq } from "./block";
import { FieldType, SimpleType } from "../type";
import { renderType } from "./rendertype";

export function genConstructor(
    name: string,
    variant: string | undefined,
    arg: SimpleType,
    resultType: Item): Item
{
    const formals: Array<[string, FieldType]> = [];
    let simpleValue = false;

    function examine(t: FieldType, name: string): void {
        if (t.kind !== 'unit') {
            formals.push([name, t]);
        }
    }

    if (arg.kind === 'record') {
        arg.fields.forEach(examine);
    } else {
        examine(arg, 'value');
        simpleValue = variant === void 0;
    }

    const initializers: Item[] = (variant !== void 0)
        ? [keyvalue('_variant', JSON.stringify(variant))]
        : [];
    formals.forEach(([n, _t]) => initializers.push(seq(JSON.stringify(n), ': ', M.jsId(n))));

    const declArgs: Array<Item> = (formals.length > 1)
        ? [seq(braces(...formals.map(f => M.jsId(f[0]))), ': ',
               braces(...formals.map(f => seq(M.jsId(f[0]), ': ', renderType(f[1])))))]
        : formals.map(f => seq(M.jsId(f[0]), ': ', renderType(f[1])));

    return seq(`export function ${M.jsId(name)}`,
               parens(... declArgs),
               ': ', resultType, ' ', block(
                   seq(`return `,
                       ((arg.kind === 'unit' && initializers.length === 0)
                           ? 'null'
                           : (simpleValue
                               ? 'value'
                               : braces(... initializers))))));
}