/** Small pure helpers shared across the extension. Kept dependency-free so they are trivial to test. */

/**
 * Collapses whitespace and clips to `max` characters, adding an ellipsis when clipped.
 * Used for list rows and session titles, where a stray newline would break the layout.
 */
export function truncate(text: string, max: number): string {
  const collapsed = text.replace(/\s+/g, " ").trim();
  if (collapsed.length <= max) return collapsed;
  return `${collapsed.slice(0, Math.max(0, max - 1)).trimEnd()}…`;
}

/** "just now", "12m ago", "3h ago", then an absolute date once it is older than a day. */
export function formatRelativeTime(timestamp: number, now: number = Date.now()): string {
  const deltaSeconds = Math.round((now - timestamp) / 1000);

  if (!Number.isFinite(deltaSeconds) || deltaSeconds < 0) return "just now";
  if (deltaSeconds < 45) return "just now";

  const minutes = Math.round(deltaSeconds / 60);
  if (minutes < 60) return `${minutes}m ago`;

  const hours = Math.round(minutes / 60);
  if (hours < 24) return `${hours}h ago`;

  const days = Math.round(hours / 24);
  if (days < 7) return `${days}d ago`;

  return new Date(timestamp).toLocaleDateString(undefined, { month: "short", day: "numeric" });
}

export type RecencyGroup = "Today" | "Yesterday" | "This week" | "Older";

/**
 * Buckets a timestamp for the conversation sidebar.
 *
 * Raycast groups its sidebar this way, and it buys the grouping that per-row
 * timestamps were trying to convey, without putting a timestamp on every row.
 */
export function recencyGroup(timestamp: number, now: number = Date.now()): RecencyGroup {
  const startOfToday = new Date(now);
  startOfToday.setHours(0, 0, 0, 0);
  const start = startOfToday.getTime();

  const DAY = 86_400_000;

  if (timestamp >= start) return "Today";
  if (timestamp >= start - DAY) return "Yesterday";
  if (timestamp >= start - 7 * DAY) return "This week";
  return "Older";
}

/**
 * A byte count for a person to read: "6.6 GB", "326 B".
 *
 * Decimal units, not the 1024-based ones a memory figure would use, because
 * that is what every other tool in this ecosystem prints: `ollama list` shows
 * 6550813657 bytes as 6.6 GB, and a number that disagreed with the terminal the
 * user just looked at would read as a bug in this extension.
 *
 * `undefined` for a size that is absent or nonsense, so a caller can leave the
 * field out rather than print "NaN B".
 */
export function formatBytes(bytes: number | undefined): string | undefined {
  if (bytes === undefined || !Number.isFinite(bytes) || bytes < 0) return undefined;
  if (bytes < 1000) return `${Math.round(bytes)} B`;

  const units = ["kB", "MB", "GB", "TB"];
  let value = bytes / 1000;
  let unit = 0;

  while (value >= 1000 && unit < units.length - 1) {
    value /= 1000;
    unit += 1;
  }

  return `${value.toFixed(1)} ${units[unit]}`;
}

/** Pulls a human-readable message out of anything that can be thrown. */
export function errorMessage(error: unknown): string {
  if (error instanceof Error) return error.message;
  if (typeof error === "string") return error;
  try {
    return JSON.stringify(error);
  } catch {
    return String(error);
  }
}

/** True when a rejected promise came from an AbortController rather than a real failure. */
export function isAbortError(error: unknown): boolean {
  return error instanceof Error && (error.name === "AbortError" || error.message.includes("aborted"));
}

/**
 * Builds the first line of a prompt into a session title.
 * Prompt text often starts with markdown decoration, which reads badly in a list row.
 */
export function titleFromPrompt(prompt: string, max: number): string {
  const firstLine = prompt.split("\n").find((line) => line.trim().length > 0) ?? prompt;
  const cleaned = firstLine.replace(/^[#>*\-\s]+/, "").trim();
  return truncate(cleaned || "New chat", max);
}