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109 lines
4.4 KiB
Go
109 lines
4.4 KiB
Go
// Package middleware provides some types and functions common among middleware.
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package middleware
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import (
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"net/http"
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"path"
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"time"
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)
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type (
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// Middleware is the middle layer which represents the traditional
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// idea of middleware: it chains one Handler to the next by being
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// passed the next Handler in the chain.
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Middleware func(Handler) Handler
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// Handler is like http.Handler except ServeHTTP returns a status code
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// and an error. The status code is for the client's benefit; the error
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// value is for the server's benefit. The status code will be sent to
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// the client while the error value will be logged privately. Sometimes,
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// an error status code (4xx or 5xx) may be returned with a nil error
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// when there is no reason to log the error on the server.
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//
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// If a HandlerFunc returns an error (status >= 400), it should NOT
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// write to the response. This philosophy makes middleware.Handler
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// different from http.Handler: error handling should happen at the
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// application layer or in dedicated error-handling middleware only
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// rather than with an "every middleware for itself" paradigm.
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//
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// The application or error-handling middleware should incorporate logic
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// to ensure that the client always gets a proper response according to
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// the status code. For security reasons, it should probably not reveal
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// the actual error message. (Instead it should be logged, for example.)
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//
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// Handlers which do write to the response should return a status value
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// < 400 as a signal that a response has been written. In other words,
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// only error-handling middleware or the application will write to the
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// response for a status code >= 400. When ANY handler writes to the
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// response, it should return a status code < 400 to signal others to
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// NOT write to the response again, which would be erroneous.
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Handler interface {
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ServeHTTP(http.ResponseWriter, *http.Request) (int, error)
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}
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// HandlerFunc is a convenience type like http.HandlerFunc, except
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// ServeHTTP returns a status code and an error. See Handler
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// documentation for more information.
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HandlerFunc func(http.ResponseWriter, *http.Request) (int, error)
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)
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// ServeHTTP implements the Handler interface.
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func (f HandlerFunc) ServeHTTP(w http.ResponseWriter, r *http.Request) (int, error) {
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return f(w, r)
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}
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// IndexFile looks for a file in /root/fpath/indexFile for each string
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// in indexFiles. If an index file is found, it returns the root-relative
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// path to the file and true. If no index file is found, empty string
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// and false is returned. fpath must end in a forward slash '/'
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// otherwise no index files will be tried (directory paths must end
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// in a forward slash according to HTTP).
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//
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// All paths passed into and returned from this function use '/' as the
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// path separator, just like URLs. IndexFle handles path manipulation
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// internally for systems that use different path separators.
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func IndexFile(root http.FileSystem, fpath string, indexFiles []string) (string, bool) {
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if fpath[len(fpath)-1] != '/' || root == nil {
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return "", false
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}
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for _, indexFile := range indexFiles {
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// func (http.FileSystem).Open wants all paths separated by "/",
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// regardless of operating system convention, so use
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// path.Join instead of filepath.Join
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fp := path.Join(fpath, indexFile)
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f, err := root.Open(fp)
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if err == nil {
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f.Close()
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return fp, true
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}
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}
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return "", false
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}
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// SetLastModifiedHeader checks if the provided modTime is valid and if it is sets it
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// as a Last-Modified header to the ResponseWriter. If the modTime is in the future
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// the current time is used instead.
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func SetLastModifiedHeader(w http.ResponseWriter, modTime time.Time) {
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if modTime.IsZero() || modTime.Equal(time.Unix(0, 0)) {
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// the time does not appear to be valid. Don't put it in the response
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return
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}
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// RFC 2616 - Section 14.29 - Last-Modified:
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// An origin server MUST NOT send a Last-Modified date which is later than the
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// server's time of message origination. In such cases, where the resource's last
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// modification would indicate some time in the future, the server MUST replace
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// that date with the message origination date.
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now := currentTime()
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if modTime.After(now) {
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modTime = now
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}
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w.Header().Set("Last-Modified", modTime.UTC().Format(http.TimeFormat))
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}
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// currentTime returns time.Now() everytime it's called. It's used for mocking in tests.
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var currentTime = func() time.Time {
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return time.Now()
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}
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