package shared

import (
	"bytes"
	"fmt"

	"gitea.maximumdirect.net/eric/notarius/internal/framework/contracts"
)

// ChunkPromptMaterial prepares the chunk-scoped source material used by D&D
// extractors when constructing their prompt inputs.
func ChunkPromptMaterial(req contracts.TypedExtractionRequest) (contracts.LLMInputMaterial, error) {
	material := req.SourceInput.Clone()
	if len(material.Content) == 0 {
		material = contracts.NewLLMInputMaterial("source", req.Chunk.MediaType, req.Chunk.Content, "", "")
	}
	if !bytes.Equal(material.Content, req.Chunk.Content) {
		return contracts.LLMInputMaterial{}, fmt.Errorf("source input must match chunk %q content", req.Chunk.ID)
	}
	if material.Name == "" {
		material.Name = "source"
	}
	if material.MediaType == "" {
		material.MediaType = req.Chunk.MediaType
	}
	if material.SizeBytes == 0 {
		material.SizeBytes = int64(len(material.Content))
	}
	return material, nil
}