package bundle

import (
	"crypto/sha256"
	"encoding/hex"
	"fmt"
	"regexp"
	"strconv"
	"strings"
)

var digestPattern = regexp.MustCompile(`^sha256:[0-9a-f]{64}$`)

func validateDigest(value string) error {
	if !digestPattern.MatchString(value) {
		return fmt.Errorf("must be lowercase sha256:<64 hex>")
	}
	return nil
}

func FileDigest(data []byte) string {
	sum := sha256.Sum256(data)
	return "sha256:" + hex.EncodeToString(sum[:])
}

func BundleDigest(files []ManifestFile) string {
	canonical := CanonicalFilePayload(files)
	sum := sha256.Sum256([]byte(canonical))
	return "sha256:" + hex.EncodeToString(sum[:])
}

func CanonicalFilePayload(files []ManifestFile) string {
	var builder strings.Builder
	builder.WriteByte('[')
	for index, file := range files {
		if index > 0 {
			builder.WriteByte(',')
		}
		builder.WriteString(`{"path":`)
		builder.WriteString(strconv.Quote(file.Path))
		builder.WriteString(`,"sha256":`)
		builder.WriteString(strconv.Quote(file.SHA256))
		builder.WriteString(`,"size":`)
		builder.WriteString(strconv.FormatInt(file.Size, 10))
		builder.WriteByte('}')
	}
	builder.WriteByte(']')
	return builder.String()
}