import { tokenize, parse, runtime } from "@thi.ng/sexpr";

[...tokenize(`(* (+ 3 5) 10)`)];
// [ '(', '*', '(', '+', '3', '5', ')', '10', ')']

parse(tokenize(`(* (+ 3 5) 10)`));

import { Fn2 } from "@thi.ng/api";
import { defmulti, DEFAULT } from "@thi.ng/defmulti";
import { ASTNode, Implementations, Sym } from "@thi.ng/sexpr";

// multi-dispatch fn for DSL builtins
// we will call this function for each S-expression
// and will delegate to the actual implementation based on
// the expression's first item (a symbol name)
const builtins = defmulti<Sym, ASTNode[], any>((x) => x.value);

// build runtime w/ impls for all AST node types
// the generics are the types of: the custom environment (if used)
// and the result type(s)
const rt = runtime<Implementations<any,any>, any, any>({
    // delegate to builtins
    expr: (x, env) => builtins(<Sym>x.children[0], x.children, env),
    // lookup symbol in environment
    sym: (x, env) => env[x.value],
    // strings and numbers evaluate verbatim
    str: (x) => x.value,
    num: (x) => x.value
});

// helper HOF for math ops
const op = (fn: Fn2<number, number, number>) =>
    (_: ASTNode, vals: ASTNode[], env: any) =>
        vals.slice(2).reduce(
            (acc, x) => fn(acc, rt(x, env)),
            rt(vals[1], env)
        );

// add builtins
builtins.addAll({
    "+": op((acc, x) => acc + x),
    "*": op((acc, x) => acc * x),
    "-": op((acc, x) => acc - x),
    "/": op((acc, x) => acc / x),
    count: (_, [__, x]) => rt(x).length
});

// add default/fallback implementation
// to allow calling functions stored in environment
builtins.add(DEFAULT, (x, [_, ...args], env) => {
    const f = env[(<Sym>x).value];
    assert(!!f, "missing impl");
    return f.apply(null, args.map((a) => rt(a, env)));
});

// evaluator
const $eval = (src: string, env: any = {}) =>
    rt(parse(tokenize(src)).children[0], env);

// evaluate expression w/ given env bindings
$eval(`(* foo (+ 1 2 3 (count "abcd")))`, { foo: 10 });
// 100
// i.e. 100 = 10 * (1 + 2 + 3 + 4)

// call env function
$eval(
    `(join (+ 1 2) (* 3 4))`,
    { join: (...xs: any[]) => xs.join(",") }
);
// "3,12"

// define syntax overrides (keep default whitespace rules)
const syntax = { scopes: [["<", ">"], ["{", "}"]], string: "'" };

parse(tokenize(`<nest { a '2' b 3 }>`, syntax), syntax);