/**
 * `string → ChatAttachment` — the producer for "Pasted text" chunks.
 *
 * When a long paste is converted into an attachment chip instead of
 * being dumped into the textarea (ChatGPT/Claude behaviour), the raw
 * text is minted into a `type:'text'` attachment. Its payload lives in
 * `text` (exact, newline-preserving); `url` is empty since there is no
 * blob backing it.
 *
 * Mirrors `fileToAttachment` so the picker, drag-drop, file-paste and
 * text-paste paths all funnel into the same `ChatAttachment` shape.
 */

import { createId } from '../core/ids';
import type { ChatAttachment } from '../types';

/** Default character threshold above which a paste becomes a chunk. */
export const DEFAULT_PASTE_TEXT_THRESHOLD = 2000;

/** Max length of the auto-derived title (first non-empty line). */
const TITLE_MAX = 32;

/**
 * Derive a short, human-readable title from the pasted text — the first
 * non-empty line, collapsed and ellipsised (e.g. "Valuing the Bali Vec…").
 * Falls back to a generic label for whitespace-only / empty input.
 */
export function deriveTextTitle(text: string): string {
  const firstLine = text
    .split(/\r?\n/)
    .map((l) => l.trim())
    .find((l) => l.length > 0);
  if (!firstLine) return 'Pasted text';
  // Strip leading markdown markers (heading `#`, blockquote `>`, list
  // bullets `-`/`*`/`+`) so a markdown paste reads as plain text on the
  // chip — the title is a label, not source. The payload is untouched.
  const stripped = firstLine
    .replace(/^#{1,6}\s+/, '')
    .replace(/^>\s+/, '')
    .replace(/^[-*+]\s+/, '')
    .trim();
  // Collapse internal runs of whitespace so a title never wraps oddly.
  const collapsed = (stripped || firstLine).replace(/\s+/g, ' ');
  return collapsed.length > TITLE_MAX
    ? `${collapsed.slice(0, TITLE_MAX).trimEnd()}…`
    : collapsed;
}

/**
 * Convert a pasted string into a `type:'text'` `ChatAttachment`.
 *
 * - `name`  — short title derived from the first line (shown on the chip).
 * - `text`  — the full, exact payload (sent to `onSubmit` alongside the
 *             message content).
 * - `url`   — empty: text chunks have no blob backing.
 * - `sizeBytes` — UTF-8 byte length, for an optional "N chars / KB" hint.
 */
export function textToAttachment(text: string): ChatAttachment {
  return {
    id: createId('att'),
    type: 'text',
    url: '',
    name: deriveTextTitle(text),
    mimeType: 'text/plain',
    sizeBytes: new Blob([text]).size,
    status: 'ready',
    text,
  };
}