// Generates the text emitters of engine/downlevel.zena (between the GENERATED markers) from the templates below,
// and engine/downlevel-text.wat, the text itself as a data segment at TEXT_BASE that scripts/build.sh merges
// into build/downlevel.wasm. `@` is the name entry passed to the emitter. (Zena strings would add a
// `wasm:js-string` import.)
import fs from "node:fs";
import { TEXT_BASE, TEXT_END, dataModule } from "./layout.mjs";

const TEMPLATES = {
  litVar: "var",
  litConst: "const",
  litModExp: "module.exports",
  litSemi: ";",
  litRb: "}",
  litDestr: "var {",
  litDestrEnd: "}=this;",
  // Like litDestrEnd, but closes over a dotted namespace chain's own outer segment (its IIFE's own bound
  // parameter, `o`) instead of `this` — for a merged *intermediate* segment's exports referenced bare
  // from a deeper, newly-opened segment's body (namespaceStart's ancestor destructure, engine/downlevel.zena).
  tDestrEndAs: "}=@;",
  tItem: "@,",
  tName: "@",
  tFn: ";(function(@)",
  // No longer includes its own leading `{`: namespaceStart emits that separately (`litLb`) so an
  // ancestor destructure (`destructureAs`, engine/downlevel.zena) can be inserted between the `{` that closes
  // the *previous* segment's signature and this one's own `var @;(function(@)`.
  litLb: "{",
  tDotFn: "var @;(function(@)",
  tCall: ").call(@||(@={}),@);",
  tCallX: ").call(@=this.@||(this.@={}),@);",
  tEiNum: ';var @;this.@=@;this[@]="@";',
  tEiEval: ';var @;this.@=@;typeof @=="string"||(this[@]="@");',
  tEiStr: ";var @;this.@=@;",
  tEnNum: ";this[this[@]]=@;",
  tEnEval: ';typeof this[@]=="string"||(this[this[@]]=@);',
  tThisIdx: "this[@]",
  litAuto0: "=0",
  tAutoI: "=@+1",
  tAutoN: "=this[@]+1",
  litAutoVoid: "=void 0",
  tAssign: "this.@=@;",
  tLive: 'Object.defineProperty(this,"@",{get(){return @},set(@$){@=@$},enumerable:true,configurable:true});',
  // Like tLive, but starts non-enumerable and only becomes enumerable the first time it's actually written
  // (its own setter flips it with a second, get/set-preserving defineProperty call) -- for an ambient namespace
  // member that might be written only from outside the namespace body, where downlevel mode can't know statically
  // whether a write is coming (engine/downlevel.zena's ambientVar). `tsc` only ever creates the member once
  // something actually assigns it; this matches that without needing to know in advance.
  tAmbientLive: 'Object.defineProperty(this,"@",{get(){return @},set(@$){@=@$;Object.defineProperty(this,"@",{enumerable:true})},enumerable:false,configurable:true});',
};

const WORDS = { Infinity: "wInfinity", NaN: "wNaN", eval: "wEval", arguments: "wArguments" };

// All templates live in one text, each ended by `~`, then the WORDS; an emitter is the offset of its template.
let text = "";
let fns = "";
for (const [name, t] of Object.entries(TEMPLATES)) {
  const usesName = t.includes("@");
  fns += `function ${name}(${usesName ? "o: i32" : ""}): void {\n  tpl(${text.length}, ${usesName ? "o" : "0"});\n}\n\n`;
  text += t + "~";
}
for (const [word, name] of Object.entries(WORDS)) {
  fns += `function ${name}(a: i32, b: i32): boolean {\n  return isWord(a, b, ${text.length}, ${word.length});\n}\n\n`;
  text += word;
}
let out = "// GENERATED by scripts/gen/downlevel-text.mjs from its template table. Do not edit by hand.\n";
out += `let TEXT: i32 = ${TEXT_BASE};\n\n`;
out += fns;

const file = new URL("../../engine/downlevel.zena", import.meta.url);
const src = fs.readFileSync(file, "utf8");
const begin = "// BEGIN GENERATED\n";
const end = "// END GENERATED\n";
const a = src.indexOf(begin);
const b = src.indexOf(end);
if (a < 0 || b < 0) throw new Error("downlevel.zena: GENERATED markers not found");
fs.writeFileSync(file, src.slice(0, a + begin.length) + out + src.slice(b));
const wat = new URL("../../engine/downlevel-text.wat", import.meta.url);
fs.writeFileSync(wat, dataModule("downlevel-text.mjs", TEXT_BASE, Buffer.from(text, "latin1"), TEXT_END));