sourceafBedSheet::FileHandler.fan

using web::WebReq
using afIoc::Inject

** A Request Handler that maps uris to files on the file system.
** 
** Example, to map all uris prefixed with '/pub/' to files under the '<app>/etc/web/' directory, 
** in your AppModule:
** 
** pre>
** @Contribute { serviceType=FileHandler# }
** static Void contributeFileHandler(MappedConfig conf) {
**   conf[`/pub/`] = `etc/web/`.toFile
** }
** <pre
** 
** Don't forget to `Route` '/pub/***' URIs to 'FileHandler':
**
** pre>
** @Contribute { serviceType=Routes# }
** static Void contributeRoutes(OrderedConfig conf) {
**   ...
**   conf.add(Route(`/pub/***`, FileHandler#service))
**   ...
** }
** <pre
** 
** Now all requests to '/pub/css/mystyle.css' will map to 'etc/web/css/mystyle.css'
** 
** @uses MappedConfig of 'Uri:File'
const mixin FileHandler {

    ** Returns a `File` on the file system, as mapped from the given uri.
    abstract File service(Uri remainingUri := ``)

}

internal const class FileHandlerImpl : FileHandler {
    
    @Inject
    private const HttpRequest req

    private const Uri:File dirMappings
    
    internal new make(Uri:File dirMappings, |This|? in := null) {
        in?.call(this)  // nullable for unit tests

        // verify file and uri mappings
        dirMappings.each |file, uri| {
            if (!file.exists)
                throw BedSheetErr(BsMsgs.fileHandlerFileNotExist(file))
            if (!file.isDir)
                throw BedSheetErr(BsMsgs.fileHandlerFileNotDir(file))
            if (!uri.isPathOnly)
                throw BedSheetErr(BsMsgs.fileHandlerUriNotPathOnly(uri))
            if (!uri.isPathAbs)
                throw BedSheetErr(BsMsgs.fileHandlerUriMustStartWithSlash(uri))
            if (!uri.isDir)
                throw BedSheetErr(BsMsgs.fileHandlerUriMustEndWithSlash(uri))
        }

        this.dirMappings = dirMappings.toImmutable
    }

    override File service(Uri remainingUri := ``) {
        
        // use pathStr to knockout any unwanted query str
        matchedUri := req.modRel.pathStr[0..<-remainingUri.pathStr.size].toUri

        // We pass 'false' to prevent Errs being thrown if the uri is a dir but doesn't end in '/'.
        // The 'false' appends a '/' automatically - it's nicer web behaviour
        // FUTURE: configure this behaviour once we've thought up a nice name for the config!
        return dirMappings[matchedUri].plus(remainingUri, false)
        
        // currently it's the FileResponseProcessor that throws a 404 if the file doesn't exist
    }
}