/**
 * The training payload handed to an algorithm, kept free of any numbl
 * import so the main thread can assemble it without pulling the whole
 * interpreter into its bundle; the worker turns it into runtime values.
 */
import type { SnippetLibrary } from './types.ts';

export interface TrainingArrays {
  names: string[];
  pre: number;
  /** Per type: column-major [snipLen x count] snippet matrix. */
  snips: { data: Float64Array; snipLen: number; count: number }[];
}

/** Assemble per-type training matrices from a library and a train split. */
export function buildTraining(lib: SnippetLibrary, trainIndices: number[][]): TrainingArrays {
  const snipLen = lib.pre + lib.post;
  const snips = trainIndices.map((idx) => {
    const data = new Float64Array(snipLen * idx.length);
    idx.forEach((si, j) => {
      const s = lib.snippets[si].samples;
      for (let i = 0; i < snipLen; i++) data[j * snipLen + i] = s[i] ?? 0;
    });
    return { data, snipLen, count: idx.length };
  });
  return { names: lib.names, pre: lib.pre, snips };
}