package starnet

import (
	"context"
	"crypto/tls"
	"crypto/x509"
	"errors"
	"fmt"
	"net"
	"net/url"
	"strings"
)

var (
	// ErrInvalidMethod 无效的 HTTP 方法
	ErrInvalidMethod = errors.New("starnet: invalid HTTP method")

	// ErrInvalidURL 无效的 URL
	ErrInvalidURL = errors.New("starnet: invalid URL")

	// ErrInvalidIP 无效的 IP 地址
	ErrInvalidIP = errors.New("starnet: invalid IP address")

	// ErrInvalidDNS 无效的 DNS 服务器
	ErrInvalidDNS = errors.New("starnet: invalid DNS server")

	// ErrNilClient HTTP Client 为 nil
	ErrNilClient = errors.New("starnet: http client is nil")

	// ErrNilReader Reader 为 nil
	ErrNilReader = errors.New("starnet: reader is nil")

	// ErrFileNotFound 文件不存在
	ErrFileNotFound = errors.New("starnet: file not found")

	// ErrRequestNotPrepared 请求未准备好
	ErrRequestNotPrepared = errors.New("starnet: request not prepared")

	// ErrBodyAlreadyConsumed Body 已被消费
	ErrBodyAlreadyConsumed = errors.New("starnet: response body already consumed")

	// ErrRespBodyTooLarge 响应体超过允许上限
	ErrRespBodyTooLarge = errors.New("starnet: response body too large")

	// ErrPingInvalidTimeout ping 超时参数无效
	ErrPingInvalidTimeout = errors.New("starnet: invalid ping timeout")

	// ErrPingPermissionDenied ping 需要更高权限（raw socket）
	ErrPingPermissionDenied = errors.New("starnet: ping permission denied")

	// ErrPingProtocolUnsupported ping 协议/地址族不受当前平台支持
	ErrPingProtocolUnsupported = errors.New("starnet: ping protocol unsupported")

	// ErrPingNoResolvedTarget ping 目标无法解析为可用地址
	ErrPingNoResolvedTarget = errors.New("starnet: ping target not resolved")
)

// wrapError 包装错误，添加上下文信息
func wrapError(err error, format string, args ...interface{}) error {
	if err == nil {
		return nil
	}
	msg := fmt.Sprintf(format, args...)
	return fmt.Errorf("%s: %w", msg, err)
}

var (
	// ErrNilConn indicates a nil net.Conn argument.
	ErrNilConn = errors.New("starnet: nil connection")

	// ErrNonTLSNotAllowed indicates plain TCP was detected while non-TLS is forbidden.
	ErrNonTLSNotAllowed = errors.New("starnet: non-TLS connection not allowed")

	// ErrNotTLS indicates caller asked for TLS-only object but conn is plain TCP.
	ErrNotTLS = errors.New("starnet: connection is not TLS")

	// ErrNoTLSConfig indicates TLS was detected but no usable TLS config is available.
	ErrNoTLSConfig = errors.New("starnet: no TLS config available")
)

// ErrorKind is a normalized high-level category for request errors.
type ErrorKind string

const (
	ErrorKindNone     ErrorKind = "none"
	ErrorKindCanceled ErrorKind = "canceled"
	ErrorKindTimeout  ErrorKind = "timeout"
	ErrorKindDNS      ErrorKind = "dns"
	ErrorKindTLS      ErrorKind = "tls"
	ErrorKindProxy    ErrorKind = "proxy"
	ErrorKindOther    ErrorKind = "other"
)

// IsCanceled reports whether err is a cancellation-related error.
func IsCanceled(err error) bool {
	if err == nil {
		return false
	}
	if errors.Is(err, context.Canceled) {
		return true
	}

	msg := strings.ToLower(err.Error())
	return strings.Contains(msg, "context canceled") ||
		strings.Contains(msg, "operation was canceled") ||
		strings.Contains(msg, "request canceled")
}

// ClassifyError maps low-level errors to a stable category for business handling.
func ClassifyError(err error) ErrorKind {
	if err == nil {
		return ErrorKindNone
	}
	if IsCanceled(err) {
		return ErrorKindCanceled
	}
	if IsProxy(err) {
		return ErrorKindProxy
	}
	if IsDNS(err) {
		return ErrorKindDNS
	}
	if IsTLS(err) {
		return ErrorKindTLS
	}
	if IsTimeout(err) {
		return ErrorKindTimeout
	}
	return ErrorKindOther
}

// IsTimeout reports whether err is a timeout-related error.
func IsTimeout(err error) bool {
	if err == nil {
		return false
	}
	if errors.Is(err, context.DeadlineExceeded) {
		return true
	}

	var uerr *url.Error
	if errors.As(err, &uerr) && uerr.Timeout() {
		return true
	}

	var nerr net.Error
	if errors.As(err, &nerr) && nerr.Timeout() {
		return true
	}

	msg := strings.ToLower(err.Error())
	return strings.Contains(msg, "timeout") || strings.Contains(msg, "deadline exceeded")
}

// IsDNS reports whether err is a DNS resolution related error.
func IsDNS(err error) bool {
	if err == nil {
		return false
	}

	var derr *net.DNSError
	if errors.As(err, &derr) {
		return true
	}

	msg := strings.ToLower(err.Error())
	if strings.Contains(msg, "no such host") ||
		strings.Contains(msg, "server misbehaving") ||
		strings.Contains(msg, "temporary failure in name resolution") {
		return true
	}

	return strings.Contains(msg, "lookup ") &&
		(strings.Contains(msg, "dns") || strings.Contains(msg, "i/o timeout"))
}

// IsTLS reports whether err is TLS/Certificate related.
func IsTLS(err error) bool {
	if err == nil {
		return false
	}
	if errors.Is(err, ErrNotTLS) || errors.Is(err, ErrNoTLSConfig) || errors.Is(err, ErrNonTLSNotAllowed) {
		return true
	}

	var recErr tls.RecordHeaderError
	if errors.As(err, &recErr) {
		return true
	}

	var uaErr x509.UnknownAuthorityError
	if errors.As(err, &uaErr) {
		return true
	}

	var hnErr x509.HostnameError
	if errors.As(err, &hnErr) {
		return true
	}

	var certErr x509.CertificateInvalidError
	if errors.As(err, &certErr) {
		return true
	}

	var rootsErr x509.SystemRootsError
	if errors.As(err, &rootsErr) {
		return true
	}

	msg := strings.ToLower(err.Error())
	return strings.Contains(msg, "tls:") || strings.Contains(msg, "x509:")
}

// IsProxy reports whether err is proxy related.
func IsProxy(err error) bool {
	if err == nil {
		return false
	}

	if isProxyMessage(strings.ToLower(err.Error())) {
		return true
	}

	var uerr *url.Error
	if errors.As(err, &uerr) {
		if strings.Contains(strings.ToLower(uerr.Op), "proxy") {
			return true
		}
		if uerr.Err != nil && isProxyMessage(strings.ToLower(uerr.Err.Error())) {
			return true
		}
	}

	var opErr *net.OpError
	if errors.As(err, &opErr) && strings.Contains(strings.ToLower(opErr.Op), "proxy") {
		return true
	}

	return false
}

func isProxyMessage(msg string) bool {
	return strings.Contains(msg, "proxyconnect") ||
		strings.Contains(msg, "proxy error") ||
		strings.Contains(msg, "proxy authentication required") ||
		strings.Contains(msg, "proxy: unknown scheme") ||
		strings.Contains(msg, "socks connect") ||
		strings.Contains(msg, "socks5")
}