package manifest

import (
	"fmt"
	"regexp"
)

var lowercaseSHA256Pattern = regexp.MustCompile(`^[0-9a-f]{64}$`)

// SemanticConfigFingerprint identifies the versioned, result-affecting
// configuration observed by one pipeline stage.
type SemanticConfigFingerprint struct {
	Version int    `json:"version"`
	Digest  string `json:"digest"`
}

// Validate checks the durable fingerprint contract.
func (f SemanticConfigFingerprint) Validate() error {
	if f.Version <= 0 {
		return fmt.Errorf("version must be positive")
	}
	if !lowercaseSHA256Pattern.MatchString(f.Digest) {
		return fmt.Errorf("digest must be a lowercase SHA-256 value")
	}
	return nil
}

// Equal reports whether two valid fingerprint records identify the same
// semantic configuration contract and payload.
func (f SemanticConfigFingerprint) Equal(other SemanticConfigFingerprint) bool {
	return f.Version == other.Version && f.Digest == other.Digest
}