http: add basic metadata and provide it via serve

Co-authored-by: dougal <147946567+roucc@users.noreply.github.com>

backend/http/http.go

@@ -11,6 +11,7 @@ import (
 	"io"
 	"mime"
 	"net/http"
+	"net/textproto"
 	"net/url"
 	"path"
 	"strings"
@@ -37,6 +38,10 @@ func init() {
 		Description: "HTTP",
 		NewFs:       NewFs,
 		CommandHelp: commandHelp,
+		MetadataInfo: &fs.MetadataInfo{
+			System: systemMetadataInfo,
+			Help:   `HTTP metadata keys are case insensitive and are always returned in lower case.`,
+		},
 		Options: []fs.Option{{
 			Name:     "url",
 			Help:     "URL of HTTP host to connect to.\n\nE.g. \"https://example.com\", or \"https://user:pass@example.com\" to use a username and password.",
@@ -98,6 +103,40 @@ sizes of any files, and some files that don't exist may be in the listing.`,
 	fs.Register(fsi)
 }
 
+// system metadata keys which this backend owns
+var systemMetadataInfo = map[string]fs.MetadataHelp{
+	"cache-control": {
+		Help:    "Cache-Control header",
+		Type:    "string",
+		Example: "no-cache",
+	},
+	"content-disposition": {
+		Help:    "Content-Disposition header",
+		Type:    "string",
+		Example: "inline",
+	},
+	"content-disposition-filename": {
+		Help:    "Filename retrieved from Content-Disposition header",
+		Type:    "string",
+		Example: "file.txt",
+	},
+	"content-encoding": {
+		Help:    "Content-Encoding header",
+		Type:    "string",
+		Example: "gzip",
+	},
+	"content-language": {
+		Help:    "Content-Language header",
+		Type:    "string",
+		Example: "en-US",
+	},
+	"content-type": {
+		Help:    "Content-Type header",
+		Type:    "string",
+		Example: "text/plain",
+	},
+}
+
 // Options defines the configuration for this backend
 type Options struct {
 	Endpoint string          `config:"url"`
@@ -126,6 +165,13 @@ type Object struct {
 	size        int64
 	modTime     time.Time
 	contentType string
+
+	// Metadata as pointers to strings as they often won't be present
+	contentDisposition         *string // Content-Disposition: header
+	contentDispositionFilename *string // Filename retrieved from Content-Disposition: header
+	cacheControl               *string // Cache-Control: header
+	contentEncoding            *string // Content-Encoding: header
+	contentLanguage            *string // Content-Language: header
 }
 
 // statusError returns an error if the res contained an error
@@ -277,6 +323,7 @@ func NewFs(ctx context.Context, name, root string, m configmap.Mapper) (fs.Fs, e
 		ci:   ci,
 	}
 	f.features = (&fs.Features{
+		ReadMetadata:            true,
 		CanHaveEmptyDirectories: true,
 	}).Fill(ctx, f)
 
@@ -429,6 +476,29 @@ func parse(base *url.URL, in io.Reader) (names []string, err error) {
 	return names, nil
 }
 
+// parseFilename extracts the filename from a Content-Disposition header
+func parseFilename(contentDisposition string) (string, error) {
+	// Normalize the contentDisposition to canonical MIME format
+	mediaType, params, err := mime.ParseMediaType(contentDisposition)
+	if err != nil {
+		return "", fmt.Errorf("failed to parse contentDisposition: %v", err)
+	}
+
+	// Check if the contentDisposition is an attachment
+	if strings.ToLower(mediaType) != "attachment" {
+		return "", fmt.Errorf("not an attachment: %s", mediaType)
+	}
+
+	// Extract the filename from the parameters
+	filename, ok := params["filename"]
+	if !ok {
+		return "", fmt.Errorf("filename not found in contentDisposition")
+	}
+
+	// Decode filename if it contains special encoding
+	return textproto.TrimString(filename), nil
+}
+
 // Adds the configured headers to the request if any
 func addHeaders(req *http.Request, opt *Options) {
 	for i := 0; i < len(opt.Headers); i += 2 {
@@ -577,6 +647,9 @@ func (o *Object) String() string {
 
 // Remote the name of the remote HTTP file, relative to the fs root
 func (o *Object) Remote() string {
+	if o.contentDispositionFilename != nil {
+		return *o.contentDispositionFilename
+	}
 	return o.remote
 }
 
@@ -634,6 +707,29 @@ func (o *Object) decodeMetadata(ctx context.Context, res *http.Response) error {
 	o.modTime = t
 	o.contentType = res.Header.Get("Content-Type")
 	o.size = rest.ParseSizeFromHeaders(res.Header)
+	contentDisposition := res.Header.Get("Content-Disposition")
+	if contentDisposition != "" {
+		o.contentDisposition = &contentDisposition
+	}
+	if o.contentDisposition != nil {
+		var filename string
+		filename, err = parseFilename(*o.contentDisposition)
+		if err == nil && filename != "" {
+			o.contentDispositionFilename = &filename
+		}
+	}
+	cacheControl := res.Header.Get("Cache-Control")
+	if cacheControl != "" {
+		o.cacheControl = &cacheControl
+	}
+	contentEncoding := res.Header.Get("Content-Encoding")
+	if contentEncoding != "" {
+		o.contentEncoding = &contentEncoding
+	}
+	contentLanguage := res.Header.Get("Content-Language")
+	if contentLanguage != "" {
+		o.contentLanguage = &contentLanguage
+	}
 
 	// If NoSlash is set then check ContentType to see if it is a directory
 	if o.fs.opt.NoSlash {
@@ -772,6 +868,30 @@ func (f *Fs) Command(ctx context.Context, name string, arg []string, opt map[str
 	}
 }
 
+// Metadata returns metadata for an object
+//
+// It should return nil if there is no Metadata
+func (o *Object) Metadata(ctx context.Context) (metadata fs.Metadata, err error) {
+	metadata = make(fs.Metadata, 6)
+	if o.contentType != "" {
+		metadata["content-type"] = o.contentType
+	}
+
+	// Set system metadata
+	setMetadata := func(k string, v *string) {
+		if v == nil || *v == "" {
+			return
+		}
+		metadata[k] = *v
+	}
+	setMetadata("content-disposition", o.contentDisposition)
+	setMetadata("content-disposition-filename", o.contentDispositionFilename)
+	setMetadata("cache-control", o.cacheControl)
+	setMetadata("content-language", o.contentLanguage)
+	setMetadata("content-encoding", o.contentEncoding)
+	return metadata, nil
+}
+
 // Check the interfaces are satisfied
 var (
 	_ fs.Fs          = &Fs{}
@@ -779,4 +899,5 @@ var (
 	_ fs.Object      = &Object{}
 	_ fs.MimeTyper   = &Object{}
 	_ fs.Commander   = &Fs{}
+	_ fs.Metadataer  = &Object{}
 )