Add a readonly backend

readonly/config.go

@@ -0,0 +1,54 @@
+package readonly
+
+import (
+	"errors"
+	"net/url"
+
+	"github.com/graymeta/stow"
+)
+
+const (
+	// ConfigWrappedKind is a key whose value is the type of backend being wrapped.
+	ConfigWrappedKind = "wrapped_kind"
+	// ConfigWrapped is the key whose value is the config for the backend being wrapped.
+	ConfigWrapped = "wrapped"
+)
+
+// Kind is the kid of Location this package provides
+const Kind = "readonly"
+
+func init() {
+	validatefn := func(config stow.Config) error {
+		wrappedKind, ok := config.Config(ConfigWrappedKind)
+		if !ok || wrappedKind == "" {
+			return errors.New("missing wrapped kind")
+		}
+		wrappedConfig, ok := config.NestedConfig(ConfigWrapped)
+		if !ok {
+			return errors.New("missing config for wrapped")
+		}
+		return stow.Validate(wrappedKind, wrappedConfig)
+	}
+	makefn := func(config stow.Config) (stow.Location, error) {
+		wrappedKind, ok := config.Config(ConfigWrappedKind)
+		if !ok || wrappedKind == "" {
+			return nil, errors.New("missing wrapped kind")
+		}
+		wrappedConfig, ok := config.NestedConfig(ConfigWrapped)
+		if !ok {
+			return nil, errors.New("missing config for wrapped")
+		}
+
+		w, err := stow.Dial(wrappedKind, wrappedConfig)
+		if err != nil {
+			return nil, err
+		}
+
+		return &location{wrapped: w}, nil
+	}
+	kindfn := func(u *url.URL) bool {
+		return u.Scheme == Kind
+	}
+
+	stow.Register(Kind, makefn, kindfn, validatefn)
+}

readonly/container.go

@@ -0,0 +1,66 @@
+package readonly
+
+import (
+	"errors"
+	"io"
+
+	"github.com/graymeta/stow"
+)
+
+type container struct {
+	wrapped stow.Container
+}
+
+// ID gets a unique string describing this Container.
+func (c *container) ID() string {
+	return c.wrapped.ID()
+}
+
+// Name gets a human-readable name describing this Container.
+func (c *container) Name() string {
+	return c.wrapped.Name()
+}
+
+// Item gets an item by its ID.
+func (c *container) Item(id string) (stow.Item, error) {
+	it, err := c.wrapped.Item(id)
+	if err != nil {
+		return nil, err
+	}
+
+	return &item{wrapped: it}, nil
+}
+
+// Items gets a page of items with the specified
+// prefix for this Container.
+// The specified cursor is a pointer to the start of
+// the items to get. It it obtained from a previous
+// call to this method, or should be CursorStart for the
+// first page.
+// count is the number of items to return per page.
+// The returned cursor can be checked with IsCursorEnd to
+// decide if there are any more items or not.
+func (c *container) Items(prefix, cursor string, count int) ([]stow.Item, string, error) {
+	its, startAfter, err := c.wrapped.Items(prefix, cursor, count)
+	if err != nil {
+		return nil, "", err
+	}
+
+	wrapped := make([]stow.Item, len(its))
+	for i, val := range its {
+		wrapped[i] = &item{wrapped: val}
+	}
+
+	return wrapped, startAfter, nil
+}
+
+// RemoveItem removes the Item with the specified ID.
+func (c *container) RemoveItem(id string) error {
+	return errors.New("readonly")
+}
+
+// Put creates a new Item with the specified name, and contents
+// read from the reader.
+func (c *container) Put(name string, r io.Reader, size int64, metadata map[string]interface{}) (stow.Item, error) {
+	return nil, errors.New("readonly")
+}

readonly/item.go

@@ -0,0 +1,61 @@
+package readonly
+
+import (
+	"io"
+	"net/url"
+	"time"
+
+	"github.com/graymeta/stow"
+)
+
+type item struct {
+	wrapped stow.Item
+}
+
+// ID gets a unique string describing this Item.
+func (i *item) ID() string {
+	return i.wrapped.ID()
+}
+
+// Name gets a human-readable name describing this Item.
+func (i *item) Name() string {
+	return i.wrapped.Name()
+}
+
+// URL gets a URL for this item.
+// For example:
+// local: file:///path/to/something
+// azure: azure://host:port/api/something
+//    s3: s3://host:post/etc
+func (i *item) URL() *url.URL {
+	return i.wrapped.URL()
+}
+
+// Size gets the size of the Item's contents in bytes.
+func (i *item) Size() (int64, error) {
+	return i.wrapped.Size()
+}
+
+// Open opens the Item for reading.
+// Calling code must close the io.ReadCloser.
+func (i *item) Open() (io.ReadCloser, error) {
+	return i.wrapped.Open()
+}
+
+// ETag is a string that is different when the Item is
+// different, and the same when the item is the same.
+// Usually this is the last modified datetime.
+func (i *item) ETag() (string, error) {
+	return i.wrapped.ETag()
+}
+
+// LastMod returns the last modified date of the file.
+func (i *item) LastMod() (time.Time, error) {
+	return i.wrapped.LastMod()
+}
+
+// Metadata gets a map of key/values that belong
+// to this Item.
+func (i *item) Metadata() (map[string]interface{}, error) {
+	return i.wrapped.Metadata()
+}

readonly/location.go

@@ -0,0 +1,73 @@
+package readonly
+
+import (
+	"errors"
+	"net/url"
+
+	"github.com/graymeta/stow"
+)
+
+type location struct {
+	wrapped stow.Location
+}
+
+// Closes the underlying location.
+func (l *location) Close() error {
+	return l.wrapped.Close()
+}
+
+// CreateContainer creates a new Container with the
+// specified name.
+func (l *location) CreateContainer(name string) (stow.Container, error) {
+	return nil, errors.New("readonly")
+}
+
+// Containers gets a page of containers
+// with the specified prefix from this Location.
+// The specified cursor is a pointer to the start of
+// the containers to get. It it obtained from a previous
+// call to this method, or should be CursorStart for the
+// first page.
+// count is the number of items to return per page.
+// The returned cursor can be checked with IsCursorEnd to
+// decide if there are any more items or not.
+func (l *location) Containers(prefix string, cursor string, count int) ([]stow.Container, string, error) {
+	cs, startAfter, err := l.wrapped.Containers(prefix, cursor, count)
+	if err != nil {
+		return nil, "", err
+	}
+
+	wrapped := make([]stow.Container, len(cs))
+	for i, val := range cs {
+		wrapped[i] = &container{wrapped: val}
+	}
+
+	return wrapped, startAfter, nil
+}
+
+// Container gets the Container with the specified
+// identifier.
+func (l *location) Container(id string) (stow.Container, error) {
+	c, err := l.wrapped.Container(id)
+	if err != nil {
+		return nil, err
+	}
+
+	return &container{wrapped: c}, nil
+}
+
+// RemoveContainer removes the container with the specified ID.
+func (l *location) RemoveContainer(id string) error {
+	return errors.New("readonly")
+}
+
+// ItemByURL gets an Item at this location with the
+// specified URL.
+func (l *location) ItemByURL(url *url.URL) (stow.Item, error) {
+	i, err := l.wrapped.ItemByURL(url)
+	if err != nil {
+		return nil, err
+	}
+
+	return &item{wrapped: i}, nil
+}

stow.go

@@ -149,8 +149,14 @@ type Config interface {
 	// Config gets a string configuration value and a
 	// bool indicating whether the value was present or not.
 	Config(name string) (string, bool)
+	// NestedConfig gets a key/value configuration and a
+	// bool indicating whehter the value was present or not.
+	NestedConfig(name string) (Config, bool)
 	// Set sets the configuration name to specified value
 	Set(name, value string)
+	// SetNestedConfig sets the configuration name to the
+	// specified key/value configuration.
+	SetNestedConfig(name string, value Config)
 }
 
 // Register adds a Location implementation, with two helper functions.
@@ -221,12 +227,19 @@ func KindByURL(u *url.URL) (string, error) {
 
 // ConfigMap is a map[string]string that implements
 // the Config method.
-type ConfigMap map[string]string
+type ConfigMap map[string]interface{}
 
 // Config gets a string configuration value and a
 // bool indicating whether the value was present or not.
 func (c ConfigMap) Config(name string) (string, bool) {
-	val, ok := c[name]
+	val, ok := c[name].(string)
+	return val, ok
+}
+
+// NestedConfig gets a key/value configuration and a
+// bool indicating whehter the value was present or not.
+func (c ConfigMap) NestedConfig(name string) (Config, bool) {
+	val, ok := c[name].(Config)
 	return val, ok
 }
 
@@ -235,6 +248,12 @@ func (c ConfigMap) Set(name, value string) {
 	c[name] = value
 }
 
+// SetNestedConfig sets the configuration name to the
+// specified key/value configuration.
+func (c ConfigMap) SetNestedConfig(name string, value Config) {
+	c[name] = value
+}
+
 // errUnknownKind indicates that a kind is unknown.
 type errUnknownKind string