/**
 * @description
 * This is a modified version of parse-dictd to be used with Deno, using only
 * std dependencies.
 *
 * @reference https://github.com/nvdnkpr/parse-dictd
 */
import { TextLineStream } from "jsr:@std/streams/text-line-stream";
import { toTransformStream } from "jsr:@std/streams/to-transform-stream";

const az = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
const codes = {};
for (let i = 0; i < 64; i++) codes[az.charAt(i)] = i;

const dzUtf8Stream = (await Deno.open("spa-eng/spa-eng.dict.dz")).readable
  .pipeThrough(new DecompressionStream("gzip"))
  .pipeThrough(new TextDecoderStream());

const indexUtf8Stream = (await Deno.open("spa-eng/spa-eng.index")).readable
  .pipeThrough(new TextDecoderStream());

const r = await parse(dzUtf8Stream, indexUtf8Stream);
await Deno.writeTextFile("dict.json", JSON.stringify(r, null, "\t"));

async function parse(
  dstream: ReadableStream<string>,
  istream: ReadableStream<string>,
) {
  const offsets: Record<number, { word: string }> = {};
  let pos = 0;

  // Transform the index stream into objects by processing each line
  const indexStream = istream
    .pipeThrough(new TextLineStream()) // Split the index stream by lines
    .pipeThrough(toTransformStream(async function* (src) {
      for await (const chunk of src) {
        const fields = chunk.trim().split("\t");
        if (fields.length !== 3) continue;
        offsets[decode(fields[1])] = { word: fields[0] };
        yield;
      }
    }));

  await Array.fromAsync(indexStream);

  const outputStream = dstream
    .pipeThrough(new TextLineStream())
    .pipeThrough(toTransformStream(async function* (src) {
      for await (const line of src) {
        const to = line.trim()
          .replace(/[^\x20-\x7E]/g, "")
          .replace(/^\w+:/, "")
          .trim().split(",");

        if (offsets[pos]) {
          yield { from: offsets[pos].word, to };
        }

        pos += new TextEncoder().encode(line).length;
      }
    }));

  const results = {};

  for await (const output of outputStream) {
    if (output) results[output.from] = output.to;
  }

  return results;
}

function decode(s) {
  let index = 0;
  const len = s.length;
  for (let i = 0; i < len; i++) {
    index += codes[s.charAt(i)] * Math.pow(64, len - i - 1);
  }
  return index;
}