package httpx

import (
	"errors"
	"fmt"
	"net/http"
)

// Sentinel errors returned by httpx components.
var (
	ErrRetryExhausted = errors.New("httpx: all retry attempts exhausted")
	ErrCircuitOpen    = errors.New("httpx: circuit breaker is open")
	ErrNoHealthy      = errors.New("httpx: no healthy endpoints available")
)

// Error provides structured error information for failed HTTP operations.
type Error struct {
	// Op is the operation that failed (e.g. "Get", "Do").
	Op string
	// URL is the originally-requested URL.
	URL string
	// Endpoint is the resolved endpoint URL (after balancing).
	Endpoint string
	// StatusCode is the HTTP status code, if a response was received.
	StatusCode int
	// Retries is the number of retry attempts made.
	Retries int
	// Err is the underlying error.
	Err error
}

func (e *Error) Error() string {
	if e.Endpoint != "" && e.Endpoint != e.URL {
		return fmt.Sprintf("httpx: %s %s (endpoint %s): %v", e.Op, e.URL, e.Endpoint, e.Err)
	}
	return fmt.Sprintf("httpx: %s %s: %v", e.Op, e.URL, e.Err)
}

func (e *Error) Unwrap() error { return e.Err }

// ErrorMapper maps an HTTP response to an error. If the response is
// acceptable, the mapper should return nil. Used by Client to convert
// non-successful HTTP responses into Go errors.
type ErrorMapper func(resp *http.Response) error