import { v4 as uuidv4 } from 'uuid';
import { AudioSegment } from '../types';

// Progressive chunking constants
const CHUNK_SIZE_START = 150;   // Very small for first few segments (fast gen)
const CHUNK_SIZE_RAMP = 400;    // Medium size
const CHUNK_SIZE_FULL = 1000;   // Full size for efficiency
const RAMP_UP_COUNT = 2;        // How many small segments before ramping up

/**
 * Splits text into segments that start small and get larger.
 * This allows playback to begin almost immediately (streaming feel)
 * while maintaining efficiency for the rest of the article.
 */
export const segmentText = (fullText: string): AudioSegment[] => {
  if (!fullText) return [];

  const segments: AudioSegment[] = [];
  
  // 1. Split by rough sentence structure first to avoid breaking mid-sentence
  // We match delimiters but keep them attached to the previous sentence
  const rawSentences = fullText.match(/[^.!?]+[.!?]+["']?|.+/g) || [fullText];
  
  let currentBuffer = "";
  let segmentCount = 0;

  for (const sentence of rawSentences) {
    const cleanSentence = sentence.trim();
    if (!cleanSentence) continue;

    // Determine target size based on how far into the article we are
    let targetSize = CHUNK_SIZE_FULL;
    if (segmentCount === 0) targetSize = CHUNK_SIZE_START; // First segment: Super fast
    else if (segmentCount <= RAMP_UP_COUNT) targetSize = CHUNK_SIZE_RAMP; // Next few: Medium

    // Predicted size if we add this sentence
    const predictedSize = currentBuffer.length + cleanSentence.length;

    // If buffer is empty, just add it
    if (currentBuffer.length === 0) {
      currentBuffer = cleanSentence;
    } 
    // If adding makes it too big, flush current buffer
    else if (predictedSize > targetSize) {
      segments.push(createSegment(currentBuffer));
      segmentCount++;
      currentBuffer = cleanSentence;
    } 
    // Otherwise, append
    else {
      currentBuffer += " " + cleanSentence;
    }
  }

  // Flush remaining
  if (currentBuffer) {
    segments.push(createSegment(currentBuffer));
  }

  return segments;
};

const createSegment = (text: string): AudioSegment => ({
  id: uuidv4(),
  text: text.trim(),
  isLoading: false,
  hasError: false
});