/* eslint-disable no-irregular-whitespace */
import { types, flow } from 'mobx-state-tree';

// Utility to pause execution inside a flow
const sleep = (ms: number) => new Promise<void>(res => setTimeout(res, ms));

// Simple function to generate a unique ID
export const generateId = () => {
  return Date.now().toString(36) + Math.random().toString(36).substring(2);
};

// Utility for efficient batched content updates
let batchedContent = '';
let batchUpdateTimeout: NodeJS.Timeout | null = null;
const BATCH_UPDATE_DELAY = 50; // ms

export const batchContentUpdate = (message: any, content: string) => {
  if (!content) return;

  // Add the content to the batch
  batchedContent += content;

  // If we already have a timeout scheduled, do nothing
  if (batchUpdateTimeout) return;

  // Schedule a timeout to apply the batched content
  batchUpdateTimeout = setTimeout(() => {
    if (message && batchedContent) {
      message.append(batchedContent);
      batchedContent = '';
    }
    batchUpdateTimeout = null;
  }, BATCH_UPDATE_DELAY);
};

const Message = types
  .model('Message', {
    id: types.optional(types.identifier, generateId),
    content: types.string,
    role: types.enumeration(['user', 'assistant']),
  })
  // Runtime-only flags that never persist or get serialized
  .volatile(() => ({
    /** Indicates that characters are still being streamed in */
    isStreaming: false,
  }))
  .actions(self => {
    // Basic mutators ---------------------------------------------------------
    const setContent = (newContent: string) => {
      self.content = newContent;
    };

    const append = (newContent: string) => {
      self.content += newContent;
    };

    /**
     * Stream content into the message for a smooth “typing” effect.
     * @param newContent The full text to stream in.
     * @param chunkSize  How many characters to reveal per tick (default 3).
     * @param delay      Delay (ms) between ticks (default 20 ms).
     */
    const streamContent = flow(function* (newContent: string, chunkSize = 3, delay = 20) {
      self.isStreaming = true;
      let pointer = 0;

      // Reveal the content chunk‑by‑chunk
      while (pointer < newContent.length) {
        append(newContent.slice(pointer, pointer + chunkSize));
        pointer += chunkSize;
        yield sleep(delay);
      }

      self.isStreaming = false; // finished
    });

    return { setContent, append, streamContent };
  });

export default Message;