/**
 * Document Chunking Utilities
 *
 * Features:
 * - Configurable chunk size and overlap
 * - Sentence-aware splitting
 * - Paragraph-aware splitting
 * - Token-based chunking (approximate)
 * - Metadata tracking for reconstruction
 */
// Sentence boundary patterns
const SENTENCE_ENDINGS = /(?<=[.!?])\s+(?=[A-Z])/g;
const PARAGRAPH_BREAKS = /\n\n+/g;
/**
 * Split text into chunks with overlap
 */
export function chunkText(text, config = {}) {
    const finalConfig = {
        maxChunkSize: config.maxChunkSize ?? 512,
        overlap: config.overlap ?? 50,
        strategy: config.strategy ?? 'sentence',
        minChunkSize: config.minChunkSize ?? 100,
        includeMetadata: config.includeMetadata ?? true,
    };
    // Normalize whitespace
    const normalizedText = text.replace(/\s+/g, ' ').trim();
    let chunks;
    switch (finalConfig.strategy) {
        case 'character':
            chunks = chunkByCharacter(normalizedText, finalConfig);
            break;
        case 'sentence':
            chunks = chunkBySentence(normalizedText, finalConfig);
            break;
        case 'paragraph':
            chunks = chunkByParagraph(text, finalConfig); // Keep original for paragraphs
            break;
        case 'token':
            chunks = chunkByToken(normalizedText, finalConfig);
            break;
        default:
            chunks = chunkBySentence(normalizedText, finalConfig);
    }
    return {
        chunks,
        originalLength: text.length,
        totalChunks: chunks.length,
        config: finalConfig,
    };
}
/**
 * Simple character-based chunking with overlap
 */
function chunkByCharacter(text, config) {
    const chunks = [];
    const { maxChunkSize, overlap } = config;
    let pos = 0;
    let index = 0;
    while (pos < text.length) {
        const endPos = Math.min(pos + maxChunkSize, text.length);
        const chunkText = text.slice(pos, endPos);
        chunks.push({
            text: chunkText,
            index,
            startPos: pos,
            endPos,
            length: chunkText.length,
            tokenCount: Math.ceil(chunkText.length / 4),
        });
        // Move position with overlap
        pos = endPos - overlap;
        if (pos >= text.length - overlap) {
            break;
        }
        index++;
    }
    return chunks;
}
/**
 * Sentence-aware chunking - keeps sentences intact
 */
function chunkBySentence(text, config) {
    const { maxChunkSize, overlap, minChunkSize } = config;
    // Split into sentences
    const sentences = text.split(SENTENCE_ENDINGS).filter(s => s.trim().length > 0);
    const chunks = [];
    let currentChunk = '';
    let currentStart = 0;
    let index = 0;
    let textPos = 0;
    for (const sentence of sentences) {
        const trimmedSentence = sentence.trim();
        // If adding this sentence exceeds max size, save current chunk
        if (currentChunk.length + trimmedSentence.length > maxChunkSize && currentChunk.length >= minChunkSize) {
            chunks.push({
                text: currentChunk.trim(),
                index,
                startPos: currentStart,
                endPos: textPos,
                length: currentChunk.length,
                tokenCount: Math.ceil(currentChunk.length / 4),
            });
            // Start new chunk with overlap (last part of previous chunk)
            const overlapText = currentChunk.slice(-overlap);
            currentChunk = overlapText + ' ' + trimmedSentence;
            currentStart = textPos - overlap;
            index++;
        }
        else {
            currentChunk += (currentChunk.length > 0 ? ' ' : '') + trimmedSentence;
        }
        textPos += trimmedSentence.length + 1;
    }
    // Add final chunk
    if (currentChunk.trim().length > 0) {
        chunks.push({
            text: currentChunk.trim(),
            index,
            startPos: currentStart,
            endPos: text.length,
            length: currentChunk.length,
            tokenCount: Math.ceil(currentChunk.length / 4),
        });
    }
    return chunks;
}
/**
 * Paragraph-aware chunking
 */
function chunkByParagraph(text, config) {
    const { maxChunkSize, minChunkSize } = config;
    // Split by paragraph breaks
    const paragraphs = text.split(PARAGRAPH_BREAKS).filter(p => p.trim().length > 0);
    const chunks = [];
    let currentChunk = '';
    let currentStart = 0;
    let index = 0;
    let textPos = 0;
    for (const paragraph of paragraphs) {
        const trimmedPara = paragraph.trim();
        // If single paragraph exceeds max, fall back to sentence chunking
        if (trimmedPara.length > maxChunkSize) {
            if (currentChunk.length > 0) {
                chunks.push({
                    text: currentChunk.trim(),
                    index,
                    startPos: currentStart,
                    endPos: textPos,
                    length: currentChunk.length,
                    tokenCount: Math.ceil(currentChunk.length / 4),
                });
                index++;
            }
            // Chunk the large paragraph by sentence
            const subChunks = chunkBySentence(trimmedPara, config);
            for (const subChunk of subChunks) {
                chunks.push({
                    ...subChunk,
                    index,
                    startPos: textPos + subChunk.startPos,
                    endPos: textPos + subChunk.endPos,
                });
                index++;
            }
            currentChunk = '';
            currentStart = textPos + trimmedPara.length;
        }
        else if (currentChunk.length + trimmedPara.length > maxChunkSize && currentChunk.length >= minChunkSize) {
            chunks.push({
                text: currentChunk.trim(),
                index,
                startPos: currentStart,
                endPos: textPos,
                length: currentChunk.length,
                tokenCount: Math.ceil(currentChunk.length / 4),
            });
            currentChunk = trimmedPara;
            currentStart = textPos;
            index++;
        }
        else {
            currentChunk += (currentChunk.length > 0 ? '\n\n' : '') + trimmedPara;
        }
        textPos += trimmedPara.length + 2; // +2 for paragraph break
    }
    // Add final chunk
    if (currentChunk.trim().length > 0) {
        chunks.push({
            text: currentChunk.trim(),
            index,
            startPos: currentStart,
            endPos: text.length,
            length: currentChunk.length,
            tokenCount: Math.ceil(currentChunk.length / 4),
        });
    }
    return chunks;
}
/**
 * Token-based chunking (approximate - uses chars/4 as estimate)
 */
function chunkByToken(text, config) {
    // Convert token limits to character limits (rough estimate: 1 token ≈ 4 chars)
    const charConfig = {
        ...config,
        maxChunkSize: config.maxChunkSize * 4,
        overlap: config.overlap * 4,
        minChunkSize: config.minChunkSize * 4,
    };
    // Use sentence-aware chunking with converted limits
    return chunkBySentence(text, charConfig);
}
/**
 * Estimate token count for text
 */
export function estimateTokens(text) {
    // Simple estimation: ~4 characters per token on average
    return Math.ceil(text.length / 4);
}
/**
 * Reconstruct original text from chunks (approximate)
 */
export function reconstructFromChunks(chunks) {
    if (chunks.length === 0)
        return '';
    if (chunks.length === 1)
        return chunks[0].text;
    // Sort by index
    const sorted = [...chunks].sort((a, b) => a.index - b.index);
    // Simple concatenation (overlap removal is approximate)
    let result = sorted[0].text;
    for (let i = 1; i < sorted.length; i++) {
        const chunk = sorted[i];
        const prevChunk = sorted[i - 1];
        // Find overlap by looking for common suffix/prefix
        const overlapSize = Math.min(100, prevChunk.text.length, chunk.text.length);
        const prevSuffix = prevChunk.text.slice(-overlapSize);
        const currPrefix = chunk.text.slice(0, overlapSize);
        // Find longest common overlap
        let overlap = 0;
        for (let len = overlapSize; len > 0; len--) {
            if (currPrefix.startsWith(prevSuffix.slice(-len))) {
                overlap = len;
                break;
            }
        }
        result += ' ' + chunk.text.slice(overlap);
    }
    return result.replace(/\s+/g, ' ').trim();
}
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