import { useState, useCallback } from "kaioken";
import { TensorContainerObject, data, layers, linspace, train, sequential } from "@tensorflow/tfjs";
import { read, utils } from "xlsx";

import type { Tensor, Rank } from "@tensorflow/tfjs";
import type { WorkSheet } from "xlsx";

interface Data extends TensorContainerObject {
  xs: Tensor;
  ys: Tensor;
}
type DSet = data.Dataset<Data>;

export default function SheetJSToTFJSCSV() {
  const [output, setOutput] = useState("");
  const [results, setResults] = useState<[number, number][]>([]);
  const [disabled, setDisabled] = useState(false);

  function worksheet_to_csv_url(worksheet: WorkSheet) {
    /* generate CSV */
    const csv = utils.sheet_to_csv(worksheet);

    /* CSV -> Uint8Array -> Blob */
    const u8 = new TextEncoder().encode(csv);
    const blob = new Blob([u8], { type: "text/csv" });

    /* generate a blob URL */
    return URL.createObjectURL(blob);
  }

  const doit = useCallback(async () => {
    setResults([]); setOutput(""); setDisabled(true);
    try {
      /* fetch file */
      const f = await fetch("https://docs.sheetjs.com/cd.xls");
      const ab = await f.arrayBuffer();
      /* parse file and get first worksheet */
      const wb = read(ab);
      const ws = wb.Sheets[wb.SheetNames[0]];

      /* generate blob URL */
      const url = worksheet_to_csv_url(ws);

      /* feed to tf.js */
      const dataset = data.csv(url, {
        hasHeader: true,
        configuredColumnsOnly: true,
        columnConfigs:{
          "Horsepower": {required: false, default: 0},
          "Miles_per_Gallon":{required: false, default: 0, isLabel:true}
        }
      });

      /* pre-process data */
      let flat = (dataset as unknown as DSet)
        .map(({xs,ys}) =>({xs: Object.values(xs), ys: Object.values(ys)}))
        .filter(({xs,ys}) => [...xs,...ys].every(v => v>0));

      /* normalize manually :( */
      let minX = Infinity, maxX = -Infinity, minY = Infinity, maxY = -Infinity;
      await flat.forEachAsync(({xs, ys}) => {
        minX = Math.min(minX, xs[0]); maxX = Math.max(maxX, xs[0]);
        minY = Math.min(minY, ys[0]); maxY = Math.max(maxY, ys[0]);
      });
      flat = flat.map(({xs, ys}) => ({xs:xs.map(v => (v-minX)/(maxX - minX)),ys:ys.map(v => (v-minY)/(maxY-minY))}));
      let batch = flat.batch(32);

      /* build and train model */
      const model = sequential();
      model.add(layers.dense({inputShape: [1], units: 1}));
      model.compile({ optimizer: train.sgd(0.000001), loss: 'meanSquaredError' });
      await model.fitDataset(batch, { epochs: 100, callbacks: { onEpochEnd: async (epoch, logs) => {
        setOutput(`${epoch}:${logs?.loss}`);
      }}});

      /* predict values */
      const inp = linspace(0, 1, 9);
      const pred = model.predict(inp) as Tensor<Rank>;
      const xs = await inp.dataSync(), ys = await pred.dataSync();
      setResults(Array.from(xs).map((x, i) => [ x * (maxX - minX) + minX, ys[i] * (maxY - minY) + minY ]));
      setOutput("");
    } catch(e) { setOutput(`ERROR: ${String(e)}`); } finally { setDisabled(false);}
  }, []);

  return ( <>
    <button onclick={doit} disabled={disabled}>Click to run</button><br/>
    {output && <pre>{output}</pre> || <></>}
    {results.length && <table><thead><tr><th>Horsepower</th><th>MPG</th></tr></thead><tbody>
    {results.map((r,i) => <tr key={i}><td>{r[0]}</td><td>{r[1].toFixed(2)}</td></tr>)}
    </tbody></table> || <></>}
  </> );
}
