import {
  LuaBuiltinFunction,
  type LuaEnv,
  LuaMultiRes,
  type LuaStackFrame,
  type LuaValue,
} from "../runtime.ts";
import { parseBlock } from "../parse.ts";
import { evalStatement } from "../eval.ts";

// Returns a function (callable chunk) or (nil, "error message") pair.
export function luaLoad(code: LuaValue, sf: LuaStackFrame): LuaValue {
  const s = typeof code === "string" ? code : String(code);

  try {
    const block = parseBlock(s, sf.astCtx || {});
    const globalEnvMaybe = sf.threadLocal.get("_GLOBAL");

    // Be vocal when no _GLOBAL is set
    if (!globalEnvMaybe) {
      console.warn("load() called without _GLOBAL in thread-local environment");
      return new LuaMultiRes([null, "Global environment not set"]);
    }

    const globalEnv: LuaEnv = globalEnvMaybe as LuaEnv;

    const runner = new LuaBuiltinFunction({
      callback: async (innerSf: LuaStackFrame) => {
        const res = await evalStatement(block, globalEnv, innerSf, true);
        if (res === undefined) {
          return null;
        } else {
          if (
            res &&
            typeof res === "object" &&
            (res as any).ctrl === "return"
          ) {
            return new LuaMultiRes((res as any).values);
          }
          if (res && typeof res === "object" && (res as any).ctrl === "break") {
            throw new Error("break outside loop");
          }
          if (res && typeof res === "object" && (res as any).ctrl === "goto") {
            throw new Error("unexpected goto signal");
          }
          return null;
        }
      },
      description: "Executes the Lua chunk compiled by `load`.",
      signatures: ["function(...)"],
      returns: [{ description: "Values returned by the compiled chunk." }],
    });

    return runner;
  } catch (e: any) {
    const msg = e && typeof e.message === "string" ? e.message : String(e);
    return new LuaMultiRes([null, msg]);
  }
}