const MAX_REQUEST_LABEL_CHARACTERS = 48;
const MIN_RUN_ID_PREFIX_CHARACTERS = 8;

export interface LabelledRun {
  runId: string;
  featureName?: string;
  request?: string;
}

function requestRunLabel(request: string) {
  const normalized = request.trim().replace(/\s+/g, " ");
  const characters = [...normalized];
  if (characters.length <= MAX_REQUEST_LABEL_CHARACTERS) return normalized;
  const keptCharacters = characters.slice(0, MAX_REQUEST_LABEL_CHARACTERS - 1);
  const candidate = keptCharacters.join("");
  const nextCharacter = characters[MAX_REQUEST_LABEL_CHARACTERS - 1];
  const lastWhitespace = candidate.search(/\s+\S*$/);
  const bounded =
    nextCharacter !== undefined && /\s/.test(nextCharacter)
      ? candidate.trimEnd()
      : lastWhitespace > 0
        ? candidate.slice(0, lastWhitespace).trimEnd()
        : candidate;
  return `${bounded}…`;
}

export function deriveRunLabel(run: LabelledRun) {
  const featureName = run.featureName?.trim();
  if (featureName) return featureName;
  const request = run.request?.trim();
  return request ? requestRunLabel(request) : run.runId;
}

function uniqueRunIdPrefix(runId: string, peers: string[]) {
  const characters = [...runId];
  for (
    let length = Math.min(MIN_RUN_ID_PREFIX_CHARACTERS, characters.length);
    length < characters.length;
    length++
  ) {
    const prefix = characters.slice(0, length).join("");
    if (peers.every((peer) => !peer.startsWith(prefix))) return prefix;
  }
  return runId;
}

/** Derives presentation labels and disambiguates only collisions in this list. */
export function deriveRunLabels<T extends LabelledRun>(runs: readonly T[]) {
  const baseLabels = runs.map(deriveRunLabel);
  const collisions = new Map<string, number[]>();
  for (const [index, label] of baseLabels.entries()) {
    const indexes = collisions.get(label) ?? [];
    indexes.push(index);
    collisions.set(label, indexes);
  }
  return baseLabels.map((label, index) => {
    const indexes = collisions.get(label)!;
    if (indexes.length === 1) return label;
    const run = runs[index]!;
    const peers = indexes
      .filter((peerIndex) => peerIndex !== index)
      .map((peerIndex) => runs[peerIndex]!.runId);
    return `${label} · ${uniqueRunIdPrefix(run.runId, peers)}`;
  });
}