Support more flexible naming of host config file and resource (groups)

Author: sirthias

README.markdown

@@ -62,7 +62,27 @@ It provides all the details required for properly establishing an SSH connection
 If you don't provide an explicit `HostConfigProvider` the default one will be used. For every hostname you pass to the
 `SSH.apply` method this default `HostConfigProvider` expects a file `~/.scala-ssh/{hostname}`, which contains the
 properties of a `HostConfig` in a simple config file format (see below for details). The `HostResourceConfig` object
-gives you alternative `HostConfigProvider` implementations that read the host config from JAR resources.
+gives you alternative `HostConfigProvider` implementations that read the host config from classpath resources.
+
+If the file `~/.scala-ssh/{hostname}` (or the classpath resource `{hostname}`) doesn't exist _scala-ssh_ looks for more
+general files (or resources) in the following way:
+
+1. As long as the first segment of the host name (up to the first `.`) contains one or more digits replace the rightmost
+of these with `X` and look for a respectively named file or resource. Repeat until no digits left.
+2. Drop all characters up to (and including) the first `.` from the host name and look for a respectively named file or
+resource.
+3. Repeat from 1. as long as there are characters left.
+
+This means that for a host with name `node42.tier1.example.com` the following locations (either under `~/.scala-ssh/`
+or the classpath, depending on the `HostConfigProvider`) are tried:
+
+1. `node42.tier1.example.com`
+2. `node4X.tier1.example.com`
+3. `nodeXX.tier1.example.com`
+4. `tier1.example.com`
+5. `tierX.example.com`
+6. `example.com`
+7. `com`
 
 
 ## Host Config File Format

src/main/scala/com/decodified/scalassh/HostConfig.scala

@@ -23,6 +23,7 @@ import HostKeyVerifiers._
 import java.security.PublicKey
 import net.schmizz.sshj.common.SecurityUtils
 import net.schmizz.sshj.transport.verification.{OpenSSHKnownHosts, HostKeyVerifier}
+import annotation.tailrec
 
 trait HostConfigProvider extends (String => Validated[HostConfig])
 
@@ -156,34 +157,49 @@ object HostFileConfig {
   def apply(): HostConfigProvider = apply(DefaultHostFileDir)
   def apply(hostFilesDir: String): HostConfigProvider = new FromStringsHostConfigProvider {
     def rawLines(host: String) = {
-      val hostFile = new File(hostFilesDir + File.separator + host)
-      try {
-        Either.cond(
-          hostFile.exists,
-          hostFile.getAbsolutePath -> Source.fromFile(hostFile, "utf8").getLines(),
-          "Host file '%s' not found, either provide one or use a concrete HostConfig, PasswordLogin or PublicKeyLogin".format(hostFile)
-        )
-      } catch {
-        case e: IOException => Left("Could not read host file '%' due to %s".format(hostFile, e))
+      val locations = searchLocations(host).map(name => new File(hostFilesDir + File.separator + name))
+      locations.find(_.exists) match {
+        case Some(file) =>
+          try Right(file.getAbsolutePath -> Source.fromFile(file, "utf8").getLines())
+          catch { case e: IOException => Left("Could not read host file '%' due to %s".format(file, e)) }
+        case None =>
+          Left(("Host files '%s' not found, either provide one or use a concrete HostConfig, PasswordLogin or " +
+            "PublicKeyLogin").format(locations.mkString("', '")))
       }
     }
   }
+
+  def searchLocations(name: String): Stream[String] = {
+    if (name.isEmpty) Stream.empty
+    else name #:: {
+      val dotIx = name.indexOf('.')
+      @tailrec def findDigit(i: Int): Int = if (i < 0 || name.charAt(i).isDigit) i else findDigit(i - 1)
+      val digitIx = findDigit(if (dotIx > 0) dotIx - 1 else name.length - 1)
+      if (digitIx >= 0 && digitIx < dotIx)
+        searchLocations(name.updated(digitIx, 'X'))
+      else if (dotIx > 0)
+        searchLocations(name.substring(dotIx + 1))
+      else Stream.empty
+    }
+  }
 }
 
 object HostResourceConfig {
   def apply(): HostConfigProvider = apply("")
   def apply(resourceBase: String): HostConfigProvider = new FromStringsHostConfigProvider {
     def rawLines(host: String) = {
-      val hostResource = resourceBase + host
-      try {
-        val resourceStream = getClass.getClassLoader.getResourceAsStream(hostResource)
-        Either.cond(
-          resourceStream != null,
-          hostResource -> Source.fromInputStream(resourceStream, "utf8").getLines(),
-          "Host resource '%s' not found".format(hostResource)
-        )
-      } catch {
-        case e: IOException => Left("Could not read host resource '%' due to %s".format(hostResource, e))
+      val locations = HostFileConfig.searchLocations(host).map(resourceBase + _)
+      locations.map { r =>
+        r -> {
+          val inputStream = getClass.getClassLoader.getResourceAsStream(r)
+          try new StreamCopier().emptyToString(inputStream).split("\n").toList
+          catch { case _: Exception => null }
+        }
+      }.find(_._2 != null) match {
+        case Some(result) => Right(result)
+        case None =>
+          Left(("Host resources '%s' not found, either provide one or use a concrete HostConfig, PasswordLogin or " +
+            "PublicKeyLogin").format(locations.mkString("', '")))
       }
     }
   }

src/test/scala/com/decodified/scalassh/HostFileConfigSpec.scala

@@ -16,32 +16,46 @@
 
 package com.decodified.scalassh
 
-import org.specs2.Specification
+import org.specs2.mutable.Specification
 
-class HostFileConfigSpec extends Specification { def is =
+class HostFileConfigSpec extends Specification {
 
-  "Depending on the host file the HostFileConfig should produce a proper" ^
+  "Depending on the host file the HostFileConfig should produce a proper" >> {
     "PasswordLogin" ! {
-      config("password.com") mustEqual Right(HostConfig(PasswordLogin("bob", "123"), "password.com", enableCompression = true))
-    } ^
+      config("password.com") === Right(HostConfig(PasswordLogin("bob", "123"), "password.com", enableCompression = true))
+    }
     "unencrypted PublicKeyLogin" ! {
-      config("keyfile.com") mustEqual Right(HostConfig(PublicKeyLogin("alice", "/some/file"), "xyz.special.com", port = 30))
-    }^
+      config("keyfile.com") === Right(HostConfig(PublicKeyLogin("alice", "/some/file"), "xyz.special.com", port = 30))
+    }
     "encrypted PublicKeyLogin" ! {
-      config("enc-keyfile.com") mustEqual Right(HostConfig(PublicKeyLogin("alice", "superSecure", "/some/file" :: Nil), "enc-keyfile.com"))
-    } ^
+      config("enc-keyfile.com") === Right(HostConfig(PublicKeyLogin("alice", "superSecure", "/some/file" :: Nil), "enc-keyfile.com"))
+    }
     "error message if the file is missing" ! {
-      config("non-existing.com").left.get mustEqual "Host resource 'non-existing.com' not found"
-    } ^
+      config("non-existing.com").left.get === "Host resources 'non-existing.com', 'com' not found, either " +
+        "provide one or use a concrete HostConfig, PasswordLogin or PublicKeyLogin"
+    }
     "error message if the login-type is invalid" ! {
       config("invalid-login-type.com").left.get must startingWith("Illegal login-type setting 'fancy pants'")
-    } ^
+    }
     "error message if the username is missing" ! {
       config("missing-user.com").left.get must endWith("is missing required setting 'username'")
-    } ^
+    }
     "error message if the host file contains an illegal line" ! {
       config("illegal-line.com").left.get must endWith("contains illegal line:\nthis line triggers an error!")
     }
+  }
+
+  "The sequence of searched config locations for host `node42.tier1.example.com`" should
+    "be as described in the README" ! {
+      HostFileConfig.searchLocations("node42.tier1.example.com").toList ===
+        "node42.tier1.example.com" ::
+        "node4X.tier1.example.com" ::
+        "nodeXX.tier1.example.com" ::
+        "tier1.example.com" ::
+        "tierX.example.com" ::
+        "example.com" ::
+        "com" :: Nil
+    }
 
   val config = HostResourceConfig()
 }