// Copyright 2015 Matthew Holt and The Caddy Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package httpcaddyfile

import (
	"encoding/base64"
	"encoding/pem"
	"fmt"
	"html"
	"net/http"
	"os"
	"reflect"
	"strconv"
	"strings"
	"time"

	"github.com/caddyserver/certmagic"
	"github.com/mholt/acmez/acme"
	"go.uber.org/zap/zapcore"

	"github.com/caddyserver/caddy/v2"
	"github.com/caddyserver/caddy/v2/caddyconfig"
	"github.com/caddyserver/caddy/v2/caddyconfig/caddyfile"
	"github.com/caddyserver/caddy/v2/modules/caddyhttp"
	"github.com/caddyserver/caddy/v2/modules/caddytls"
)

func init() {
	RegisterDirective("bind", parseBind)
	RegisterDirective("tls", parseTLS)
	RegisterHandlerDirective("fs", parseFilesystem)
	RegisterHandlerDirective("root", parseRoot)
	RegisterHandlerDirective("vars", parseVars)
	RegisterHandlerDirective("redir", parseRedir)
	RegisterHandlerDirective("respond", parseRespond)
	RegisterHandlerDirective("abort", parseAbort)
	RegisterHandlerDirective("error", parseError)
	RegisterHandlerDirective("route", parseRoute)
	RegisterHandlerDirective("handle", parseHandle)
	RegisterDirective("handle_errors", parseHandleErrors)
	RegisterHandlerDirective("invoke", parseInvoke)
	RegisterDirective("log", parseLog)
	RegisterHandlerDirective("skip_log", parseSkipLog)
}

// parseBind parses the bind directive. Syntax:
//
//	bind <addresses...>
func parseBind(h Helper) ([]ConfigValue, error) {
	var lnHosts []string
	for h.Next() {
		lnHosts = append(lnHosts, h.RemainingArgs()...)
	}
	return h.NewBindAddresses(lnHosts), nil
}

// parseTLS parses the tls directive. Syntax:
//
//	tls [<email>|internal]|[<cert_file> <key_file>] {
//	    protocols <min> [<max>]
//	    ciphers   <cipher_suites...>
//	    curves    <curves...>
//	    client_auth {
//	        mode                   [request|require|verify_if_given|require_and_verify]
//	        trusted_ca_cert        <base64_der>
//	        trusted_ca_cert_file   <filename>
//	        trusted_leaf_cert      <base64_der>
//	        trusted_leaf_cert_file <filename>
//	    }
//	    alpn                          <values...>
//	    load                          <paths...>
//	    ca                            <acme_ca_endpoint>
//	    ca_root                       <pem_file>
//	    key_type                      [ed25519|p256|p384|rsa2048|rsa4096]
//	    dns                           <provider_name> [...]
//	    propagation_delay             <duration>
//	    propagation_timeout           <duration>
//	    resolvers                     <dns_servers...>
//	    dns_ttl                       <duration>
//	    dns_challenge_override_domain <domain>
//	    on_demand
//	    reuse_private_keys
//	    eab                           <key_id> <mac_key>
//	    issuer                        <module_name> [...]
//	    get_certificate               <module_name> [...]
//	    insecure_secrets_log          <log_file>
//	}
func parseTLS(h Helper) ([]ConfigValue, error) {
	cp := new(caddytls.ConnectionPolicy)
	var fileLoader caddytls.FileLoader
	var folderLoader caddytls.FolderLoader
	var certSelector caddytls.CustomCertSelectionPolicy
	var acmeIssuer *caddytls.ACMEIssuer
	var keyType string
	var internalIssuer *caddytls.InternalIssuer
	var issuers []certmagic.Issuer
	var certManagers []certmagic.Manager
	var onDemand bool
	var reusePrivateKeys bool

	for h.Next() {
		// file certificate loader
		firstLine := h.RemainingArgs()
		switch len(firstLine) {
		case 0:
		case 1:
			if firstLine[0] == "internal" {
				internalIssuer = new(caddytls.InternalIssuer)
			} else if !strings.Contains(firstLine[0], "@") {
				return nil, h.Err("single argument must either be 'internal' or an email address")
			} else {
				if acmeIssuer == nil {
					acmeIssuer = new(caddytls.ACMEIssuer)
				}
				acmeIssuer.Email = firstLine[0]
			}

		case 2:
			certFilename := firstLine[0]
			keyFilename := firstLine[1]

			// tag this certificate so if multiple certs match, specifically
			// this one that the user has provided will be used, see #2588:
			// https://github.com/caddyserver/caddy/issues/2588 ... but we
			// must be careful about how we do this; being careless will
			// lead to failed handshakes
			//
			// we need to remember which cert files we've seen, since we
			// must load each cert only once; otherwise, they each get a
			// different tag... since a cert loaded twice has the same
			// bytes, it will overwrite the first one in the cache, and
			// only the last cert (and its tag) will survive, so any conn
			// policy that is looking for any tag other than the last one
			// to be loaded won't find it, and TLS handshakes will fail
			// (see end of issue #3004)
			//
			// tlsCertTags maps certificate filenames to their tag.
			// This is used to remember which tag is used for each
			// certificate files, since we need to avoid loading
			// the same certificate files more than once, overwriting
			// previous tags
			tlsCertTags, ok := h.State["tlsCertTags"].(map[string]string)
			if !ok {
				tlsCertTags = make(map[string]string)
				h.State["tlsCertTags"] = tlsCertTags
			}

			tag, ok := tlsCertTags[certFilename]
			if !ok {
				// haven't seen this cert file yet, let's give it a tag
				// and add a loader for it
				tag = fmt.Sprintf("cert%d", len(tlsCertTags))
				fileLoader = append(fileLoader, caddytls.CertKeyFilePair{
					Certificate: certFilename,
					Key:         keyFilename,
					Tags:        []string{tag},
				})
				// remember this for next time we see this cert file
				tlsCertTags[certFilename] = tag
			}
			certSelector.AnyTag = append(certSelector.AnyTag, tag)

		default:
			return nil, h.ArgErr()
		}

		var hasBlock bool
		for nesting := h.Nesting(); h.NextBlock(nesting); {
			hasBlock = true

			switch h.Val() {
			case "protocols":
				args := h.RemainingArgs()
				if len(args) == 0 {
					return nil, h.Errf("protocols requires one or two arguments")
				}
				if len(args) > 0 {
					if _, ok := caddytls.SupportedProtocols[args[0]]; !ok {
						return nil, h.Errf("wrong protocol name or protocol not supported: '%s'", args[0])
					}
					cp.ProtocolMin = args[0]
				}
				if len(args) > 1 {
					if _, ok := caddytls.SupportedProtocols[args[1]]; !ok {
						return nil, h.Errf("wrong protocol name or protocol not supported: '%s'", args[1])
					}
					cp.ProtocolMax = args[1]
				}

			case "ciphers":
				for h.NextArg() {
					if !caddytls.CipherSuiteNameSupported(h.Val()) {
						return nil, h.Errf("wrong cipher suite name or cipher suite not supported: '%s'", h.Val())
					}
					cp.CipherSuites = append(cp.CipherSuites, h.Val())
				}

			case "curves":
				for h.NextArg() {
					if _, ok := caddytls.SupportedCurves[h.Val()]; !ok {
						return nil, h.Errf("Wrong curve name or curve not supported: '%s'", h.Val())
					}
					cp.Curves = append(cp.Curves, h.Val())
				}

			case "client_auth":
				cp.ClientAuthentication = &caddytls.ClientAuthentication{}
				for nesting := h.Nesting(); h.NextBlock(nesting); {
					subdir := h.Val()
					switch subdir {
					case "verifier":
						if !h.NextArg() {
							return nil, h.ArgErr()
						}

						vType := h.Val()
						modID := "tls.client_auth." + vType
						unm, err := caddyfile.UnmarshalModule(h.Dispenser, modID)
						if err != nil {
							return nil, err
						}

						_, ok := unm.(caddytls.ClientCertificateVerifier)
						if !ok {
							return nil, h.Dispenser.Errf("module %s is not a caddytls.ClientCertificatVerifier", modID)
						}

						cp.ClientAuthentication.VerifiersRaw = append(cp.ClientAuthentication.VerifiersRaw, caddyconfig.JSONModuleObject(unm, "verifier", vType, h.warnings))
					case "mode":
						if !h.Args(&cp.ClientAuthentication.Mode) {
							return nil, h.ArgErr()
						}
						if h.NextArg() {
							return nil, h.ArgErr()
						}

					case "trusted_ca_cert",
						"trusted_leaf_cert":
						if !h.NextArg() {
							return nil, h.ArgErr()
						}
						if subdir == "trusted_ca_cert" {
							cp.ClientAuthentication.TrustedCACerts = append(cp.ClientAuthentication.TrustedCACerts, h.Val())
						} else {
							cp.ClientAuthentication.TrustedLeafCerts = append(cp.ClientAuthentication.TrustedLeafCerts, h.Val())
						}

					case "trusted_ca_cert_file",
						"trusted_leaf_cert_file":
						if !h.NextArg() {
							return nil, h.ArgErr()
						}
						filename := h.Val()
						certDataPEM, err := os.ReadFile(filename)
						if err != nil {
							return nil, err
						}
						// while block is not nil, we have more certificates in the file
						for block, rest := pem.Decode(certDataPEM); block != nil; block, rest = pem.Decode(rest) {
							if block.Type != "CERTIFICATE" {
								return nil, h.Errf("no CERTIFICATE pem block found in %s", filename)
							}
							if subdir == "trusted_ca_cert_file" {
								cp.ClientAuthentication.TrustedCACerts = append(
									cp.ClientAuthentication.TrustedCACerts,
									base64.StdEncoding.EncodeToString(block.Bytes),
								)
							} else {
								cp.ClientAuthentication.TrustedLeafCerts = append(
									cp.ClientAuthentication.TrustedLeafCerts,
									base64.StdEncoding.EncodeToString(block.Bytes),
								)
							}
						}
						// if we decoded nothing, return an error
						if len(cp.ClientAuthentication.TrustedCACerts) == 0 && len(cp.ClientAuthentication.TrustedLeafCerts) == 0 {
							return nil, h.Errf("no CERTIFICATE pem block found in %s", filename)
						}

					default:
						return nil, h.Errf("unknown subdirective for client_auth: %s", subdir)
					}
				}

			case "alpn":
				args := h.RemainingArgs()
				if len(args) == 0 {
					return nil, h.ArgErr()
				}
				cp.ALPN = args

			case "load":
				folderLoader = append(folderLoader, h.RemainingArgs()...)

			case "ca":
				arg := h.RemainingArgs()
				if len(arg) != 1 {
					return nil, h.ArgErr()
				}
				if acmeIssuer == nil {
					acmeIssuer = new(caddytls.ACMEIssuer)
				}
				acmeIssuer.CA = arg[0]

			case "key_type":
				arg := h.RemainingArgs()
				if len(arg) != 1 {
					return nil, h.ArgErr()
				}
				keyType = arg[0]

			case "eab":
				arg := h.RemainingArgs()
				if len(arg) != 2 {
					return nil, h.ArgErr()
				}
				if acmeIssuer == nil {
					acmeIssuer = new(caddytls.ACMEIssuer)
				}
				acmeIssuer.ExternalAccount = &acme.EAB{
					KeyID:  arg[0],
					MACKey: arg[1],
				}

			case "issuer":
				if !h.NextArg() {
					return nil, h.ArgErr()
				}
				modName := h.Val()
				modID := "tls.issuance." + modName
				unm, err := caddyfile.UnmarshalModule(h.Dispenser, modID)
				if err != nil {
					return nil, err
				}
				issuer, ok := unm.(certmagic.Issuer)
				if !ok {
					return nil, h.Errf("module %s (%T) is not a certmagic.Issuer", modID, unm)
				}
				issuers = append(issuers, issuer)

			case "get_certificate":
				if !h.NextArg() {
					return nil, h.ArgErr()
				}
				modName := h.Val()
				modID := "tls.get_certificate." + modName
				unm, err := caddyfile.UnmarshalModule(h.Dispenser, modID)
				if err != nil {
					return nil, err
				}
				certManager, ok := unm.(certmagic.Manager)
				if !ok {
					return nil, h.Errf("module %s (%T) is not a certmagic.CertificateManager", modID, unm)
				}
				certManagers = append(certManagers, certManager)

			case "dns":
				if !h.NextArg() {
					return nil, h.ArgErr()
				}
				provName := h.Val()
				if acmeIssuer == nil {
					acmeIssuer = new(caddytls.ACMEIssuer)
				}
				if acmeIssuer.Challenges == nil {
					acmeIssuer.Challenges = new(caddytls.ChallengesConfig)
				}
				if acmeIssuer.Challenges.DNS == nil {
					acmeIssuer.Challenges.DNS = new(caddytls.DNSChallengeConfig)
				}
				modID := "dns.providers." + provName
				unm, err := caddyfile.UnmarshalModule(h.Dispenser, modID)
				if err != nil {
					return nil, err
				}
				acmeIssuer.Challenges.DNS.ProviderRaw = caddyconfig.JSONModuleObject(unm, "name", provName, h.warnings)

			case "resolvers":
				args := h.RemainingArgs()
				if len(args) == 0 {
					return nil, h.ArgErr()
				}
				if acmeIssuer == nil {
					acmeIssuer = new(caddytls.ACMEIssuer)
				}
				if acmeIssuer.Challenges == nil {
					acmeIssuer.Challenges = new(caddytls.ChallengesConfig)
				}
				if acmeIssuer.Challenges.DNS == nil {
					acmeIssuer.Challenges.DNS = new(caddytls.DNSChallengeConfig)
				}
				acmeIssuer.Challenges.DNS.Resolvers = args

			case "propagation_delay":
				arg := h.RemainingArgs()
				if len(arg) != 1 {
					return nil, h.ArgErr()
				}
				delayStr := arg[0]
				delay, err := caddy.ParseDuration(delayStr)
				if err != nil {
					return nil, h.Errf("invalid propagation_delay duration %s: %v", delayStr, err)
				}
				if acmeIssuer == nil {
					acmeIssuer = new(caddytls.ACMEIssuer)
				}
				if acmeIssuer.Challenges == nil {
					acmeIssuer.Challenges = new(caddytls.ChallengesConfig)
				}
				if acmeIssuer.Challenges.DNS == nil {
					acmeIssuer.Challenges.DNS = new(caddytls.DNSChallengeConfig)
				}
				acmeIssuer.Challenges.DNS.PropagationDelay = caddy.Duration(delay)

			case "propagation_timeout":
				arg := h.RemainingArgs()
				if len(arg) != 1 {
					return nil, h.ArgErr()
				}
				timeoutStr := arg[0]
				var timeout time.Duration
				if timeoutStr == "-1" {
					timeout = time.Duration(-1)
				} else {
					var err error
					timeout, err = caddy.ParseDuration(timeoutStr)
					if err != nil {
						return nil, h.Errf("invalid propagation_timeout duration %s: %v", timeoutStr, err)
					}
				}
				if acmeIssuer == nil {
					acmeIssuer = new(caddytls.ACMEIssuer)
				}
				if acmeIssuer.Challenges == nil {
					acmeIssuer.Challenges = new(caddytls.ChallengesConfig)
				}
				if acmeIssuer.Challenges.DNS == nil {
					acmeIssuer.Challenges.DNS = new(caddytls.DNSChallengeConfig)
				}
				acmeIssuer.Challenges.DNS.PropagationTimeout = caddy.Duration(timeout)

			case "dns_ttl":
				arg := h.RemainingArgs()
				if len(arg) != 1 {
					return nil, h.ArgErr()
				}
				ttlStr := arg[0]
				ttl, err := caddy.ParseDuration(ttlStr)
				if err != nil {
					return nil, h.Errf("invalid dns_ttl duration %s: %v", ttlStr, err)
				}
				if acmeIssuer == nil {
					acmeIssuer = new(caddytls.ACMEIssuer)
				}
				if acmeIssuer.Challenges == nil {
					acmeIssuer.Challenges = new(caddytls.ChallengesConfig)
				}
				if acmeIssuer.Challenges.DNS == nil {
					acmeIssuer.Challenges.DNS = new(caddytls.DNSChallengeConfig)
				}
				acmeIssuer.Challenges.DNS.TTL = caddy.Duration(ttl)

			case "dns_challenge_override_domain":
				arg := h.RemainingArgs()
				if len(arg) != 1 {
					return nil, h.ArgErr()
				}
				if acmeIssuer == nil {
					acmeIssuer = new(caddytls.ACMEIssuer)
				}
				if acmeIssuer.Challenges == nil {
					acmeIssuer.Challenges = new(caddytls.ChallengesConfig)
				}
				if acmeIssuer.Challenges.DNS == nil {
					acmeIssuer.Challenges.DNS = new(caddytls.DNSChallengeConfig)
				}
				acmeIssuer.Challenges.DNS.OverrideDomain = arg[0]

			case "ca_root":
				arg := h.RemainingArgs()
				if len(arg) != 1 {
					return nil, h.ArgErr()
				}
				if acmeIssuer == nil {
					acmeIssuer = new(caddytls.ACMEIssuer)
				}
				acmeIssuer.TrustedRootsPEMFiles = append(acmeIssuer.TrustedRootsPEMFiles, arg[0])

			case "on_demand":
				if h.NextArg() {
					return nil, h.ArgErr()
				}
				onDemand = true

			case "reuse_private_keys":
				if h.NextArg() {
					return nil, h.ArgErr()
				}
				reusePrivateKeys = true

			case "insecure_secrets_log":
				if !h.NextArg() {
					return nil, h.ArgErr()
				}
				cp.InsecureSecretsLog = h.Val()

			default:
				return nil, h.Errf("unknown subdirective: %s", h.Val())
			}
		}

		// a naked tls directive is not allowed
		if len(firstLine) == 0 && !hasBlock {
			return nil, h.ArgErr()
		}
	}

	// begin building the final config values
	configVals := []ConfigValue{}

	// certificate loaders
	if len(fileLoader) > 0 {
		configVals = append(configVals, ConfigValue{
			Class: "tls.cert_loader",
			Value: fileLoader,
		})
	}
	if len(folderLoader) > 0 {
		configVals = append(configVals, ConfigValue{
			Class: "tls.cert_loader",
			Value: folderLoader,
		})
	}

	// some tls subdirectives are shortcuts that implicitly configure issuers, and the
	// user can also configure issuers explicitly using the issuer subdirective; the
	// logic to support both would likely be complex, or at least unintuitive
	if len(issuers) > 0 && (acmeIssuer != nil || internalIssuer != nil) {
		return nil, h.Err("cannot mix issuer subdirective (explicit issuers) with other issuer-specific subdirectives (implicit issuers)")
	}
	if acmeIssuer != nil && internalIssuer != nil {
		return nil, h.Err("cannot create both ACME and internal certificate issuers")
	}

	// now we should either have: explicitly-created issuers, or an implicitly-created
	// ACME or internal issuer, or no issuers at all
	switch {
	case len(issuers) > 0:
		for _, issuer := range issuers {
			configVals = append(configVals, ConfigValue{
				Class: "tls.cert_issuer",
				Value: issuer,
			})
		}

	case acmeIssuer != nil:
		// implicit ACME issuers (from various subdirectives) - use defaults; there might be more than one
		defaultIssuers := caddytls.DefaultIssuers()

		// if a CA endpoint was set, override multiple implicit issuers since it's a specific one
		if acmeIssuer.CA != "" {
			defaultIssuers = []certmagic.Issuer{acmeIssuer}
		}

		for _, issuer := range defaultIssuers {
			switch iss := issuer.(type) {
			case *caddytls.ACMEIssuer:
				issuer = acmeIssuer
			case *caddytls.ZeroSSLIssuer:
				iss.ACMEIssuer = acmeIssuer
			}
			configVals = append(configVals, ConfigValue{
				Class: "tls.cert_issuer",
				Value: issuer,
			})
		}

	case internalIssuer != nil:
		configVals = append(configVals, ConfigValue{
			Class: "tls.cert_issuer",
			Value: internalIssuer,
		})
	}

	// certificate key type
	if keyType != "" {
		configVals = append(configVals, ConfigValue{
			Class: "tls.key_type",
			Value: keyType,
		})
	}

	// on-demand TLS
	if onDemand {
		configVals = append(configVals, ConfigValue{
			Class: "tls.on_demand",
			Value: true,
		})
	}
	for _, certManager := range certManagers {
		configVals = append(configVals, ConfigValue{
			Class: "tls.cert_manager",
			Value: certManager,
		})
	}

	// reuse private keys TLS
	if reusePrivateKeys {
		configVals = append(configVals, ConfigValue{
			Class: "tls.reuse_private_keys",
			Value: true,
		})
	}

	// custom certificate selection
	if len(certSelector.AnyTag) > 0 {
		cp.CertSelection = &certSelector
	}

	// connection policy -- always add one, to ensure that TLS
	// is enabled, because this directive was used (this is
	// needed, for instance, when a site block has a key of
	// just ":5000" - i.e. no hostname, and only on-demand TLS
	// is enabled)
	configVals = append(configVals, ConfigValue{
		Class: "tls.connection_policy",
		Value: cp,
	})

	return configVals, nil
}

// parseRoot parses the root directive. Syntax:
//
//	root [<matcher>] <path>
func parseRoot(h Helper) (caddyhttp.MiddlewareHandler, error) {
	var root string
	for h.Next() {
		if !h.NextArg() {
			return nil, h.ArgErr()
		}
		root = h.Val()
		if h.NextArg() {
			return nil, h.ArgErr()
		}
	}
	return caddyhttp.VarsMiddleware{"root": root}, nil
}

// parseFilesystem parses the fs directive. Syntax:
//
//	fs <filesystem>
func parseFilesystem(h Helper) (caddyhttp.MiddlewareHandler, error) {
	var name string
	for h.Next() {
		if !h.NextArg() {
			return nil, h.ArgErr()
		}
		name = h.Val()
		if h.NextArg() {
			return nil, h.ArgErr()
		}
	}
	return caddyhttp.VarsMiddleware{"fs": name}, nil
}

// parseVars parses the vars directive. See its UnmarshalCaddyfile method for syntax.
func parseVars(h Helper) (caddyhttp.MiddlewareHandler, error) {
	v := new(caddyhttp.VarsMiddleware)
	err := v.UnmarshalCaddyfile(h.Dispenser)
	return v, err
}

// parseRedir parses the redir directive. Syntax:
//
//	redir [<matcher>] <to> [<code>]
//
// <code> can be "permanent" for 301, "temporary" for 302 (default),
// a placeholder, or any number in the 3xx range or 401. The special
// code "html" can be used to redirect only browser clients (will
// respond with HTTP 200 and no Location header; redirect is performed
// with JS and a meta tag).
func parseRedir(h Helper) (caddyhttp.MiddlewareHandler, error) {
	if !h.Next() {
		return nil, h.ArgErr()
	}

	if !h.NextArg() {
		return nil, h.ArgErr()
	}
	to := h.Val()

	var code string
	if h.NextArg() {
		code = h.Val()
	}

	var body string
	var hdr http.Header
	switch code {
	case "permanent":
		code = "301"
	case "temporary", "":
		code = "302"
	case "html":
		// Script tag comes first since that will better imitate a redirect in the browser's
		// history, but the meta tag is a fallback for most non-JS clients.
		const metaRedir = `<!DOCTYPE html>
<html>
	<head>
		<title>Redirecting...</title>
		<script>window.location.replace("%s");</script>
		<meta http-equiv="refresh" content="0; URL='%s'">
	</head>
	<body>Redirecting to <a href="%s">%s</a>...</body>
</html>
`
		safeTo := html.EscapeString(to)
		body = fmt.Sprintf(metaRedir, safeTo, safeTo, safeTo, safeTo)
		hdr = http.Header{"Content-Type": []string{"text/html; charset=utf-8"}}
		code = "200" // don't redirect non-browser clients
	default:
		// Allow placeholders for the code
		if strings.HasPrefix(code, "{") {
			break
		}
		// Try to validate as an integer otherwise
		codeInt, err := strconv.Atoi(code)
		if err != nil {
			return nil, h.Errf("Not a supported redir code type or not valid integer: '%s'", code)
		}
		// Sometimes, a 401 with Location header is desirable because
		// requests made with XHR will "eat" the 3xx redirect; so if
		// the intent was to redirect to an auth page, a 3xx won't
		// work. Responding with 401 allows JS code to read the
		// Location header and do a window.location redirect manually.
		// see https://stackoverflow.com/a/2573589/846934
		// see https://github.com/oauth2-proxy/oauth2-proxy/issues/1522
		if codeInt < 300 || (codeInt > 399 && codeInt != 401) {
			return nil, h.Errf("Redir code not in the 3xx range or 401: '%v'", codeInt)
		}
	}

	// don't redirect non-browser clients
	if code != "200" {
		hdr = http.Header{"Location": []string{to}}
	}

	return caddyhttp.StaticResponse{
		StatusCode: caddyhttp.WeakString(code),
		Headers:    hdr,
		Body:       body,
	}, nil
}

// parseRespond parses the respond directive.
func parseRespond(h Helper) (caddyhttp.MiddlewareHandler, error) {
	sr := new(caddyhttp.StaticResponse)
	err := sr.UnmarshalCaddyfile(h.Dispenser)
	if err != nil {
		return nil, err
	}
	return sr, nil
}

// parseAbort parses the abort directive.
func parseAbort(h Helper) (caddyhttp.MiddlewareHandler, error) {
	h.Next() // consume directive
	for h.Next() || h.NextBlock(0) {
		return nil, h.ArgErr()
	}
	return &caddyhttp.StaticResponse{Abort: true}, nil
}

// parseError parses the error directive.
func parseError(h Helper) (caddyhttp.MiddlewareHandler, error) {
	se := new(caddyhttp.StaticError)
	err := se.UnmarshalCaddyfile(h.Dispenser)
	if err != nil {
		return nil, err
	}
	return se, nil
}

// parseRoute parses the route directive.
func parseRoute(h Helper) (caddyhttp.MiddlewareHandler, error) {
	allResults, err := parseSegmentAsConfig(h)
	if err != nil {
		return nil, err
	}

	for _, result := range allResults {
		switch result.Value.(type) {
		case caddyhttp.Route, caddyhttp.Subroute:
		default:
			return nil, h.Errf("%s directive returned something other than an HTTP route or subroute: %#v (only handler directives can be used in routes)", result.directive, result.Value)
		}
	}

	return buildSubroute(allResults, h.groupCounter, false)
}

func parseHandle(h Helper) (caddyhttp.MiddlewareHandler, error) {
	return ParseSegmentAsSubroute(h)
}

func parseHandleErrors(h Helper) ([]ConfigValue, error) {
	subroute, err := ParseSegmentAsSubroute(h)
	if err != nil {
		return nil, err
	}
	return []ConfigValue{
		{
			Class: "error_route",
			Value: subroute,
		},
	}, nil
}

// parseInvoke parses the invoke directive.
func parseInvoke(h Helper) (caddyhttp.MiddlewareHandler, error) {
	h.Next() // consume directive
	if !h.NextArg() {
		return nil, h.ArgErr()
	}
	for h.Next() || h.NextBlock(0) {
		return nil, h.ArgErr()
	}

	// remember that we're invoking this name
	// to populate the server with these named routes
	if h.State[namedRouteKey] == nil {
		h.State[namedRouteKey] = map[string]struct{}{}
	}
	h.State[namedRouteKey].(map[string]struct{})[h.Val()] = struct{}{}

	// return the handler
	return &caddyhttp.Invoke{Name: h.Val()}, nil
}

// parseLog parses the log directive. Syntax:
//
//	log <logger_name> {
//	    hostnames <hostnames...>
//	    output <writer_module> ...
//	    format <encoder_module> ...
//	    level  <level>
//	}
func parseLog(h Helper) ([]ConfigValue, error) {
	return parseLogHelper(h, nil)
}

// parseLogHelper is used both for the parseLog directive within Server Blocks,
// as well as the global "log" option for configuring loggers at the global
// level. The parseAsGlobalOption parameter is used to distinguish any differing logic
// between the two.
func parseLogHelper(h Helper, globalLogNames map[string]struct{}) ([]ConfigValue, error) {
	// When the globalLogNames parameter is passed in, we make
	// modifications to the parsing behavior.
	parseAsGlobalOption := globalLogNames != nil

	var configValues []ConfigValue
	for h.Next() {
		// Logic below expects that a name is always present when a
		// global option is being parsed; or an optional override
		// is supported for access logs.
		var logName string

		if parseAsGlobalOption {
			if h.NextArg() {
				logName = h.Val()

				// Only a single argument is supported.
				if h.NextArg() {
					return nil, h.ArgErr()
				}
			} else {
				// If there is no log name specified, we
				// reference the default logger. See the
				// setupNewDefault function in the logging
				// package for where this is configured.
				logName = caddy.DefaultLoggerName
			}

			// Verify this name is unused.
			_, used := globalLogNames[logName]
			if used {
				return nil, h.Err("duplicate global log option for: " + logName)
			}
			globalLogNames[logName] = struct{}{}
		} else {
			// An optional override of the logger name can be provided;
			// otherwise a default will be used, like "log0", "log1", etc.
			if h.NextArg() {
				logName = h.Val()

				// Only a single argument is supported.
				if h.NextArg() {
					return nil, h.ArgErr()
				}
			}
		}

		cl := new(caddy.CustomLog)

		// allow overriding the current site block's hostnames for this logger;
		// this is useful for setting up loggers per subdomain in a site block
		// with a wildcard domain
		customHostnames := []string{}

		for h.NextBlock(0) {
			switch h.Val() {
			case "hostnames":
				if parseAsGlobalOption {
					return nil, h.Err("hostnames is not allowed in the log global options")
				}
				args := h.RemainingArgs()
				if len(args) == 0 {
					return nil, h.ArgErr()
				}
				customHostnames = append(customHostnames, args...)

			case "output":
				if !h.NextArg() {
					return nil, h.ArgErr()
				}
				moduleName := h.Val()

				// can't use the usual caddyfile.Unmarshaler flow with the
				// standard writers because they are in the caddy package
				// (because they are the default) and implementing that
				// interface there would unfortunately create circular import
				var wo caddy.WriterOpener
				switch moduleName {
				case "stdout":
					wo = caddy.StdoutWriter{}
				case "stderr":
					wo = caddy.StderrWriter{}
				case "discard":
					wo = caddy.DiscardWriter{}
				default:
					modID := "caddy.logging.writers." + moduleName
					unm, err := caddyfile.UnmarshalModule(h.Dispenser, modID)
					if err != nil {
						return nil, err
					}
					var ok bool
					wo, ok = unm.(caddy.WriterOpener)
					if !ok {
						return nil, h.Errf("module %s (%T) is not a WriterOpener", modID, unm)
					}
				}
				cl.WriterRaw = caddyconfig.JSONModuleObject(wo, "output", moduleName, h.warnings)

			case "format":
				if !h.NextArg() {
					return nil, h.ArgErr()
				}
				moduleName := h.Val()
				moduleID := "caddy.logging.encoders." + moduleName
				unm, err := caddyfile.UnmarshalModule(h.Dispenser, moduleID)
				if err != nil {
					return nil, err
				}
				enc, ok := unm.(zapcore.Encoder)
				if !ok {
					return nil, h.Errf("module %s (%T) is not a zapcore.Encoder", moduleID, unm)
				}
				cl.EncoderRaw = caddyconfig.JSONModuleObject(enc, "format", moduleName, h.warnings)

			case "level":
				if !h.NextArg() {
					return nil, h.ArgErr()
				}
				cl.Level = h.Val()
				if h.NextArg() {
					return nil, h.ArgErr()
				}

			case "include":
				if !parseAsGlobalOption {
					return nil, h.Err("include is not allowed in the log directive")
				}
				for h.NextArg() {
					cl.Include = append(cl.Include, h.Val())
				}

			case "exclude":
				if !parseAsGlobalOption {
					return nil, h.Err("exclude is not allowed in the log directive")
				}
				for h.NextArg() {
					cl.Exclude = append(cl.Exclude, h.Val())
				}

			default:
				return nil, h.Errf("unrecognized subdirective: %s", h.Val())
			}
		}

		var val namedCustomLog
		val.hostnames = customHostnames

		isEmptyConfig := reflect.DeepEqual(cl, new(caddy.CustomLog))

		// Skip handling of empty logging configs

		if parseAsGlobalOption {
			// Use indicated name for global log options
			val.name = logName
		} else {
			if logName != "" {
				val.name = logName
			} else if !isEmptyConfig {
				// Construct a log name for server log streams
				logCounter, ok := h.State["logCounter"].(int)
				if !ok {
					logCounter = 0
				}
				val.name = fmt.Sprintf("log%d", logCounter)
				logCounter++
				h.State["logCounter"] = logCounter
			}
			if val.name != "" {
				cl.Include = []string{"http.log.access." + val.name}
			}
		}
		if !isEmptyConfig {
			val.log = cl
		}
		configValues = append(configValues, ConfigValue{
			Class: "custom_log",
			Value: val,
		})
	}
	return configValues, nil
}

// parseSkipLog parses the skip_log directive. Syntax:
//
//	skip_log [<matcher>]
func parseSkipLog(h Helper) (caddyhttp.MiddlewareHandler, error) {
	for h.Next() {
		if h.NextArg() {
			return nil, h.ArgErr()
		}
	}
	return caddyhttp.VarsMiddleware{"skip_log": true}, nil
}