const DEFAULT_DIMENSIONS = 3;

function resolveDimensions(value) {
  const dimensions = Number(value ?? process.env.MEMORY_V2_LOCAL_EMBEDDING_DIMENSIONS ?? DEFAULT_DIMENSIONS);
  if (!Number.isInteger(dimensions) || dimensions < 1 || dimensions > 4096) {
    throw new Error(`Invalid MEMORY_V2_LOCAL_EMBEDDING_DIMENSIONS: ${value}`);
  }
  return dimensions;
}

function hashToken(token) {
  let hash = 2166136261;
  for (const char of String(token)) {
    hash ^= char.codePointAt(0);
    hash = Math.imul(hash, 16777619);
  }
  return hash >>> 0;
}

function tokenize(text) {
  return String(text ?? '')
    .toLowerCase()
    .replace(/[^a-z0-9\u4e00-\u9fa5]+/gu, ' ')
    .trim()
    .split(/\s+/)
    .filter(Boolean);
}

export function embedText(text, { dimensions = undefined } = {}) {
  const resolvedDimensions = resolveDimensions(dimensions);
  const vector = Array.from({ length: resolvedDimensions }, () => 0);
  const tokens = tokenize(text);
  for (const token of tokens.length ? tokens : ['empty']) {
    const hash = hashToken(token);
    const index = hash % resolvedDimensions;
    const sign = hash & 1 ? 1 : -1;
    vector[index] += sign * (1 + (token.length % 7));
  }
  const norm = Math.sqrt(vector.reduce((sum, value) => sum + value * value, 0)) || 1;
  return vector.map((value) => Number((value / norm).toFixed(8)));
}

export async function embedQuery(query, input = {}) {
  return embedText(query, {
    dimensions: input.dimensions ?? input.embeddingDimensions,
  });
}

export default embedQuery;