package dbx

import (
	"errors"
	"fmt"
	"strings"

	"github.com/jackc/pgx/v5/pgconn"
)

// Sentinel errors.
var (
	ErrNoHealthyNode = errors.New("dbx: no healthy node available")
	ErrClusterClosed = errors.New("dbx: cluster is closed")
	ErrRetryExhausted = errors.New("dbx: retry attempts exhausted")
)

// IsRetryable reports whether the error is worth retrying.
// Connection errors, serialization failures, deadlocks, and too_many_connections are retryable.
func IsRetryable(err error) bool {
	if err == nil {
		return false
	}
	if IsConnectionError(err) {
		return true
	}
	code := PgErrorCode(err)
	switch code {
	case "40001", // serialization_failure
		"40P01", // deadlock_detected
		"53300": // too_many_connections
		return true
	}
	return false
}

// IsConnectionError reports whether the error indicates a connection problem (PG class 08).
func IsConnectionError(err error) bool {
	if err == nil {
		return false
	}
	code := PgErrorCode(err)
	if strings.HasPrefix(code, "08") {
		return true
	}
	// pgx wraps connection errors that may not have a PG code
	msg := err.Error()
	for _, s := range []string{
		"connection refused",
		"connection reset",
		"broken pipe",
		"EOF",
		"no connection",
		"conn closed",
		"timeout",
	} {
		if strings.Contains(msg, s) {
			return true
		}
	}
	return false
}

// IsConstraintViolation reports whether the error is a constraint violation (PG class 23).
func IsConstraintViolation(err error) bool {
	return strings.HasPrefix(PgErrorCode(err), "23")
}

// PgErrorCode extracts the PostgreSQL error code from err, or returns "" if not a PG error.
func PgErrorCode(err error) string {
	var pgErr *pgconn.PgError
	if errors.As(err, &pgErr) {
		return pgErr.Code
	}
	return ""
}

// retryError wraps the last error with ErrRetryExhausted context.
type retryError struct {
	attempts int
	last     error
}

func (e *retryError) Error() string {
	return fmt.Sprintf("%s: %d attempts, last error: %v", ErrRetryExhausted, e.attempts, e.last)
}

func (e *retryError) Unwrap() []error {
	return []error{ErrRetryExhausted, e.last}
}

func newRetryError(attempts int, last error) error {
	return &retryError{attempts: attempts, last: last}
}