[WIP] (#102) Content Proxy: add initial cache settings

Emulsion.ContentProxy/FileCache.fs

@@ -7,13 +7,19 @@ open System.Text
 
 open Serilog
 
+// TODO: Total cache limit
 type FileCache(logger: ILogger,
                settings: FileCacheSettings,
                sha256: SHA256) =
 
     let getFromCache uri (cacheKey: string) = async {
-        let hash = sha256.ComputeHash(Encoding.UTF8.GetBytes(cacheKey)) |> Convert.ToBase64String
+        let hash =
+            cacheKey
+            |> Encoding.UTF8.GetBytes
+            |> sha256.ComputeHash
+            |> Convert.ToBase64String
         let path = Path.Combine(settings.CacheDirectory, hash)
+        do! Async.SwitchToThreadPool()
         return
             if File.Exists path then
                 Some(new FileStream(path, FileMode.Open, FileAccess.Read, FileShare.Delete))
@@ -23,26 +29,26 @@ type FileCache(logger: ILogger,
 
     let ensureFreeCache size = async {
         if size > settings.FileSizeLimit then
-            return None
+            return false
         else
-            failwith "TODO"
+            failwith "TODO: Sanity check that cache only has files"
     }
 
     member _.DownloadLink(uri: Uri, cacheKey: string, size: int64): Async<Stream option> = async {
         logger.Information("Cache lookup for content {Uri} (cache key {CacheKey})", uri, cacheKey)
         match! getFromCache uri cacheKey with
         | Some content ->
-            logger.Information("Cache hit for content {Uri} (cache key {CacheKey})", uri, cacheKey,)
+            logger.Information("Cache hit for content {Uri} (cache key {CacheKey})", uri, cacheKey)
             return Some content
         | None ->
-            logger.Information("No cache hit for content {Uri} (cache key {CacheKey}), will download", uri, cacheKey,)
-            let! cache = ensureFreeCache size
+            logger.Information("No cache hit for content {Uri} (cache key {CacheKey}), will download", uri, cacheKey)
+            let! shouldCache = ensureFreeCache size
             if shouldCache then
                 logger.Information("Resource {Uri} (cache key {CacheKey}, {Size} bytes) will fit into cache, caching", uri, cacheKey, size)
                 let! result = downloadIntoCacheAndGet uri
-                logger.Information("Resource {Uri} (cache key {CacheKey}, {Size} bytes) downloaded", uri, cacheKey,, size)
+                logger.Information("Resource {Uri} (cache key {CacheKey}, {Size} bytes) downloaded", uri, cacheKey, size)
                 return result
             else
-                logger.Information("Resource {Uri} (cache key {CacheKey}) won't fit into cache, directly downloading", uri, cacheKey,)
+                logger.Information("Resource {Uri} (cache key {CacheKey}) won't fit into cache, directly downloading", uri, cacheKey)
                 return! download uri
     }

Emulsion.Settings/Settings.fs

@@ -34,12 +34,17 @@ type HostingSettings = {
     HashIdSalt: string
 }
 
+type FileCacheSettings = {
+    FileSizeLimitBytes: uint64
+}
+
 type EmulsionSettings = {
     Xmpp: XmppSettings
     Telegram: TelegramSettings
     Log: LogSettings
     Database: DatabaseSettings option
     Hosting: HostingSettings option
+    FileCache: FileCacheSettings option
 }
 
 let defaultConnectionTimeout = TimeSpan.FromMinutes 5.0
@@ -56,6 +61,12 @@ let private readTimeSpan defaultVal key section =
     |> Option.defaultValue defaultVal
 
 let read (config : IConfiguration) : EmulsionSettings =
+    let uint64OrDefault value ``default`` =
+        value
+        |> Option.ofObj
+        |> Option.map uint64
+        |> Option.defaultValue ``default``
+
     let readXmpp (section : IConfigurationSection) = {
         Login = section["login"]
         Password = section["password"]
@@ -91,9 +102,14 @@ let read (config : IConfiguration) : EmulsionSettings =
             }
         | None, None, None -> None
         | other -> failwith $"Parameter pack {other} represents invalid hosting settings."
+    let readFileCache(section: IConfigurationSection) = Some {
+        // TODO: should be None if the directory is not defined
+        FileSizeLimitBytes = uint64OrDefault section["fileSizeLimitBytes"] 1048576UL
+    }
 
     { Xmpp = readXmpp <| config.GetSection("xmpp")
       Telegram = readTelegram <| config.GetSection("telegram")
       Log = readLog <| config.GetSection "log"
       Database = readDatabase <| config.GetSection "database"
-      Hosting = readHosting <| config.GetSection "hosting" }
+      Hosting = readHosting <| config.GetSection "hosting"
+      FileCache = readFileCache <| config.GetSection "fileCache" }

README.md

@@ -26,6 +26,9 @@ settings, there're defaults:
         "messageTimeout": "00:05:00",
         "pingInterval": null,
         "pingTimeout": "00:00:30"
+    },
+    "fileCache": {
+        "fileSizeLimitBytes": 1048576
     }
 }
 ```
@@ -36,7 +39,7 @@ Note that `pingInterval` of `null` disables XMPP ping support.
 
 ### Telegram Content Proxy
 
-There's **unfinished** Telegram content proxy support, for XMPP users to access Telegram content without directly opening links on t.me. Right now, it will only generate a redirect to the corresponding t.me URI, so it doesn't help a lot. But in the future, proper content proxy will be supported.
+There's Telegram content proxy support, for XMPP users to access Telegram content without directly opening links on t.me.
 
 To enable it, configure the `database` and `hosting` configuration file sections:
 
@@ -49,7 +52,8 @@ To enable it, configure the `database` and `hosting` configuration file sections
         "externalUriBase": "https://example.com/api/",
         "bindUri": "http://*:5000/",
         "hashIdSalt": "test"
-    }
+    },
+    "fileCache": {}
 }
 ```
 
@@ -61,6 +65,8 @@ If all the parameters are set, then Emulsion will save the incoming messages int
 
 The content identifiers in question are generated from the database ones using the [hashids.net][hashids.net] library, `hashIdSalt` is used in generation. This should complicate guessing of content ids for any external party not reading the chat directly.
 
+If the `fileCache` section is not set, then the content proxy will only generate redirects to corresponding t.me URIs.
+
 ### Recommended Network Configuration
 
 Current configuration system allows the following:

emulsion.example.json

@@ -24,5 +24,6 @@
         "externalUriBase": "https://example.com/api/",
         "bindUri": "http://*:5000",
         "hashIdSalt": "test"
-    }
+    },
+    "fileCache": {}
 }