package ledger

import (
	"encoding/hex"
	"fmt"
	"strings"
	"time"
)

type TransactionState string

const (
	TransactionStateCreated            TransactionState = "CREATED"
	TransactionStatePendingTransaction TransactionState = "PENDING_TRANSACTION"
	TransactionStatePendingAdmin       TransactionState = "PENDING_ADMIN"
	TransactionStateSuccessful         TransactionState = "SUCCESSFUL"
	TransactionStateFailed             TransactionState = "FAILED"
	TransactionStateSuspended          TransactionState = "SUSPENDED"
)

func (s TransactionState) Valid() bool {
	switch s {
	case TransactionStateCreated,
		TransactionStatePendingTransaction,
		TransactionStatePendingAdmin,
		TransactionStateSuccessful,
		TransactionStateFailed,
		TransactionStateSuspended:
		return true
	default:
		return false
	}
}

type TransactionEvent struct {
	ID                  string
	SourceService       string
	IdempotencyKey      string
	SourceTransactionID string
	TrackingCode        string
	EventVersion        uint32
	State               TransactionState
	ErrorCode           string
	ErrorMessage        string
	OccurredAt          time.Time
	RecordedAt          time.Time
	CorrelationID       string
	ActorID             string
	Blockchain          BlockchainReference
	Metadata            map[string]string
	PayloadHash         string
}

func (e TransactionEvent) Validate() error {
	if e.ID == "" || e.SourceService == "" || e.IdempotencyKey == "" || e.SourceTransactionID == "" {
		return fmt.Errorf("transaction event identity fields are required")
	}
	if e.EventVersion == 0 {
		return fmt.Errorf("event version must be positive")
	}
	if !e.State.Valid() {
		return fmt.Errorf("invalid transaction state %q", e.State)
	}
	if e.OccurredAt.IsZero() {
		return fmt.Errorf("occurred time is required")
	}
	if len(e.PayloadHash) != 64 || e.PayloadHash != strings.ToLower(e.PayloadHash) {
		return fmt.Errorf("payload hash must be a lowercase SHA-256 hex string")
	}
	if _, err := hex.DecodeString(e.PayloadHash); err != nil {
		return fmt.Errorf("payload hash must be a lowercase SHA-256 hex string")
	}
	return nil
}