package kb

import "unicode/utf8"

type ChunkerConfig struct{ Target, Min, Max, Overlap int }

func DefaultChunkerConfig() ChunkerConfig {
	return ChunkerConfig{Target: 1200, Min: 200, Max: 2000, Overlap: 150}
}
func ChunkDocument(doc Document, cfg ChunkerConfig) []Chunk {
	text := BuildChunkText(doc)
	if cfg.Target <= 0 {
		cfg = DefaultChunkerConfig()
	}
	rs := []rune(text)
	if len(rs) == 0 {
		return nil
	}
	var chunks []Chunk
	start := 0
	idx := 0
	for start < len(rs) {
		end := start + cfg.Target
		if end > len(rs) {
			end = len(rs)
		}
		if end-start > cfg.Max {
			end = start + cfg.Max
		}
		content := string(rs[start:end])
		if !utf8.ValidString(content) {
			content = string([]rune(content))
		}
		chunks = append(chunks, Chunk{ChunkIndex: idx, Language: doc.Language, RegionCode: doc.RegionCode, Title: doc.Title, Content: content, ContentHash: ContentHash(content), CharCount: len([]rune(content)), TokenEstimate: len([]rune(content)) / 4, Metadata: map[string]any{"external_id": doc.ExternalID, "source_uri": doc.SourceURI}})
		idx++
		if end == len(rs) {
			break
		}
		start = end - cfg.Overlap
		if start < 0 {
			start = 0
		}
	}
	return chunks
}