You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: analyze_url_flag.go
    path of file: ./repos/cockroach/pkg/security/clientsecopts
    
    the code of the file until where you have to start completion: // Copyright 2022 The Cockroach Authors.
//
// Use of this software is governed by the Business Source License
// included in the file licenses/BSL.txt.
//
// As of the Change Date specified in that file, in accordance with
// the Business Source License, use of this software will be governed
// by the Apache License, Version 2.0, included in the file
// licenses/APL.txt.

package clientsecopts

import (
	"fmt"
	"path/filepath"

	"github.com/cockroachdb/cockroach/pkg/security/certnames"
	"github.com/cockroachdb/cockroach/pkg/security/username"
	"github.com/cockroachdb/cockroach/pkg/server/pgurl"
)

// CLIFlagInterfaceForClientURL is an interface to the state of the
// variables attached to discrete flags (e.g. --host, --insecure)
// that can be passed before or after --url.
//
// It is used by AnalyzeClientURL below to peek into the state
// of flags set before --url and prepare state for subsequent
// flags passed after --url.
//
// NB: We use an interface here instead of directly depending on
// packages pflag and cliflags, so as to simplify the build
// dependencies and increase readability.
type CLIFlagInterfaceForClientURL interface {
	// StrictTLS returns true when the URL should enforce that TLS
	// client certs and CA cert should be placed into a single common
	// directory, and the server identity be fully verified.
	//
	// This 
    
func AnalyzeClientURL(newURL string, flags CLIFlagInterfaceForClientURL) (*pgurl.URL, error) {
	parsedURL, err := pgurl.Parse(newURL)
	if err != nil {
		return nil, err
	}

	if user := parsedURL.GetUsername(); user != "" {
		flags.SetUser(user)
	}

	// If some host/port information is available, forward it to
	// --host / --port.
	net, host, port := parsedURL.GetNetworking()
	if host != "" {
		flags.SetHost(host)
	}
	if port != "" {
		flags.SetPort(port)
	}

	// If a database is specified, and the command supports databases,
	// forward it to --database.
	if db := parsedURL.GetDatabase(); db != "" {
		flags.SetDatabase(db)
	}

	tlsUsed, tlsMode, caCertPath := parsedURL.GetTLSOptions()

	if tlsUsed && tlsMode == pgurl.TLSUnspecified && net == pgurl.ProtoTCP {
		// The sslmode argument was not specified and we are using TCP.
		// We may want to inject a default value in that case.
		// (We don't inject a transport if using unix sockets.)
		//
		// Is there a value to go by from a previous --insecure flag? If
		// so, use that.
		if insecureSpecified, insecureValue := flags.InsecureFlag(); insecureSpecified {
			var tp pgurl.TransportOption
			if insecureValue {
				tp = pgurl.TransportNone()
				tlsUsed = false
			} else {
				tlsMode = pgurl.TLSVerifyFull
				tp = pgurl.TransportTLS(tlsMode, caCertPath)
			}
			parsedURL.WithTransport(tp)
		} else {
			// No --insecure specified. We default to maximum security.
			tlsMode = pgurl.TLSVerifyFull
			parsedURL.WithTransport(pgurl.TransportTLS(tlsMode, caCertPath))
		}
	}

	if !tlsUsed {
		if flags.StrictTLS() {
			// For "strict" mode (RPC client commands) we don't support non-TLS
			// yet. See https://github.com/cockroachdb/cockroach/issues/54007
			// Instead, we see a request for no TLS to imply insecure mode.
			flags.SetInsecure(true)
		}
	} else {
		if flags.StrictTLS() {
			switch tlsMode {
			case pgurl.TLSVerifyFull:
				// This is valid.
			default:
				return nil, flags.NewStrictTLSConfigurationError()
			}
		}
		flags.SetInsecure(false)

		if flags.StrictTLS() {
			// The "flags.StrictTLS()" flag means the client command is using our
			// certificate manager instead of the certificate handler in
			// lib/pq.
			//
			// Our certificate manager is peculiar in that it requires
			// every file in the same directory (the "certs dir") and also
			// the files to be named after a fixed naming convention.
			//
			// Meanwhile, the URL format for security flags consists
			// of 3 options (sslrootcert, sslcert, sslkey) that *may*
			// refer to arbitrary files in arbitrary directories.
			// Regular SQL drivers are fine with that (including lib/pq)
			// but our cert manager definitely not (or, at least, not yet).
			//
			// So here we have to reverse-engineer the parameters needed
			// for the certificate manager from the URL and verify that
			// they conform to the restrictions of our cert manager. There
			// are three things that need to happen:
			//
			// - if the flag --certs-dir is not specified in the command
			//   line, we need to derive a path for the certificate
			//   directory from the URL options; our cert manager needs
			//   this as input.
			//
			// - we must verify that all 3 url options that determine
			//   files refer to the same directory; our cert manager does
			//   not know how to work otherwise.
			//
			// - we must also verify that the 3 options specify a file
			//   name that is compatible with our cert manager (namely,
			//   "ca.crt", "client.USERNAME.crt" and
			//   "client.USERNAME.key").
			//
			// For more information, see
			// https://github.com/cockroachdb/cockroach/issues/82075

			candidateCertsDir := ""
			hasCertsDir := false
			if certsDirSpecified, certsDir := flags.CertsDirFlag(); certsDirSpecified {
				// If a --certs-dir flag was preceding --url, we want to
				// check that the paths inside the URL match the value of
				// that explicit --certs-dir.
				//
				// If --certs-dir was not specified, we'll pick up
				// the first directory encountered below.
				candidateCertsDir = certsDir
				candidateCertsDir, err = filepath.Abs(candidateCertsDir)
				if err != nil {
					return nil, err
				}
			}

			// tryCertsDir digs into the SSL URL options to extract a valid
			// certificate directory. It also checks that the file names are those
			// expected by the certificate manager.
			tryCertsDir := func(optName, opt, expectedFilename string) error {
				if opt == "" {
					// Option not set: nothing to do.
					return nil
				}

				// Check the expected base file name.
				base := filepath.Base(opt)
				if base != expectedFilename {
					return fmt.Errorf("invalid file name for %q: expected %q, got %q", optName, expectedFilename, base)
				}

				// Extract the directory part.
				dir := filepath.Dir(opt)
				dir, err = filepath.Abs(dir)
				if err != nil {
					return err
				}
				if candidateCertsDir != "" {
					// A certificate directory has already been found in a previous option;
					// check that the new option uses the same.
					if candidateCertsDir != dir {
						return fmt.Errorf("non-homogeneous certificate directory: %s=%q, expected %q", optName, opt, candidateCertsDir)
					}
				} else {
					// First time seeing a directory, remember it.
					candidateCertsDir = dir
					hasCertsDir = true
				}

				return nil
			}

			userName := username.RootUserName()
			if hasConnUser, connUser := flags.UserFlag(); hasConnUser {
				userName, _ = username.MakeSQLUsernameFromUserInput(connUser, username.PurposeValidation)
			}
			if err := tryCertsDir("sslrootcert", caCertPath, certnames.CACertFilename()); err != nil {
				return nil, err
			}
			if clientCertEnabled, clientCertPath, clientKeyPath := parsedURL.GetAuthnCert(); clientCertEnabled {
				if err := tryCertsDir("sslcert", clientCertPath, certnames.ClientCertFilename(userName)); err != nil {
					return nil, err
				}
				if err := tryCertsDir("sslkey", clientKeyPath, certnames.ClientKeyFilename(userName)); err != nil {
					return nil, err
				}
			}

			if hasCertsDir {
				flags.SetCertsDir(candidateCertsDir)
			}
		}
	}

	// Check that the URL so far is valid.
	err = parsedURL.Validate()
	return parsedURL, err
}