package asar

import (
	"crypto"
	"fmt"
)

const (
	ALGORITHM  = "SHA256"
	BLOCK_SIZE = 4 * 1024 * 1024
)

type FileIntegrity struct {
	Algorithm string   `json:"algorithm"`
	Hash      string   `json:"hash"`
	BlockSize int      `json:"blockSize"`
	Blocks    []string `json:"blocks"`
}

func getFileIntegrity(data []byte) *FileIntegrity {
	blockHashes := []string{}
	for i := 0; i < len(data); i += BLOCK_SIZE {
		end := i + BLOCK_SIZE
		if end > len(data) {
			end = len(data)
		}
		blockHashes = append(blockHashes, hashBlock(data[i:end]))
	}

	return &FileIntegrity{
		Algorithm: ALGORITHM,
		Hash:      hashBlock(data),
		BlockSize: BLOCK_SIZE,
		Blocks:    blockHashes,
	}
}

func hashBlock(block []byte) string {
	hash := crypto.SHA256.New()
	hash.Write(block)
	return fmt.Sprintf("%x", hash.Sum(nil))
}