package wtxmgr

import "fmt"

// ErrorCode identifies a category of error.
type ErrorCode uint8

// These constants are used to identify a specific TxMgrError.
const (
	// ErrDatabase indicates an error with the underlying database. When this error code is set, the Err field of the
	// TxMgrError will be set to the underlying error returned from the database.
	ErrDatabase ErrorCode = iota
	// ErrData describes an error where data stored in the transaction database is incorrect. This may be due to missing
	// values, values of wrong txsizes, or data from different buckets that is inconsistent with itself. Recovering from
	// an ErrData requires rebuilding all transaction history or manual database surgery. If the failure was not due to
	// data corruption, this error category indicates a programming error in this package.
	ErrData
	// ErrInput describes an error where the variables passed into this function by the caller are obviously incorrect.
	// Examples include passing transactions which do not serialize, or attempting to insert a credit at an index for
	// which no transaction output exists.
	ErrInput
	// ErrAlreadyExists describes an error where creating the store cannot continue because a store already exists in
	// the namespace.
	ErrAlreadyExists
	// ErrNoExists describes an error where the store cannot be opened due to it not already existing in the namespace.
	// This error should be handled by creating a new store.
	ErrNoExists
	// ErrNeedsUpgrade describes an error during store opening where the database contains an older version of the
	// store.
	ErrNeedsUpgrade
	// ErrUnknownVersion describes an error where the store already exists but the database version is newer than latest
	// version known to this software. This likely indicates an outdated binary.
	ErrUnknownVersion
)

var errStrs = [...]string{
	ErrDatabase:       "ErrDatabase",
	ErrData:           "ErrData",
	ErrInput:          "ErrInput",
	ErrAlreadyExists:  "ErrAlreadyExists",
	ErrNoExists:       "ErrNoExists",
	ErrNeedsUpgrade:   "ErrNeedsUpgrade",
	ErrUnknownVersion: "ErrUnknownVersion",
}

// String returns the ErrorCode as a human-readable name.
func (e ErrorCode) String() string {
	if e < ErrorCode(len(errStrs)) {
		return errStrs[e]
	}
	return fmt.Sprintf("ErrorCode(%d)", e)
}

// TxMgrError provides a single type for errors that can happen during Store operation.
type TxMgrError struct {
	Code ErrorCode // Describes the kind of error
	Desc string    // Human readable description of the issue
	Err  error     // Underlying error, optional
}

// TxMgrError satisfies the error interface and prints human-readable errors.
func (e TxMgrError) Error() string {
	if e.Err != nil {
		return e.Desc + ": " + e.Err.Error()
	}
	return e.Desc
}
func storeError(c ErrorCode, desc string, e error) TxMgrError {
	return TxMgrError{Code: c, Desc: desc, Err: e}
}

// IsNoExists returns whether an error is a TxMgrError with the ErrNoExists error code.
func IsNoExists(e error) bool {
	serr, ok := e.(TxMgrError)
	return ok && serr.Code == ErrNoExists
}