From 675cb1cdd8e9b6db4d313ef456784e8672e555ad Mon Sep 17 00:00:00 2001
From: Luka Vandervelden <lukc@upyum.com>
Date: Wed, 11 Dec 2019 22:08:26 +0100
Subject: [PATCH] Custom exceptions for common errors.

---
 src/fsdb.cr            | 12 ++++++------
 src/fsdb/exceptions.cr | 17 +++++++++++++++++
 src/fsdb/index.cr      | 18 +++++++++++++-----
 3 files changed, 36 insertions(+), 11 deletions(-)
 create mode 100644 src/fsdb/exceptions.cr

diff --git a/src/fsdb.cr b/src/fsdb.cr
index 098881d..b1256ee 100644
--- a/src/fsdb.cr
+++ b/src/fsdb.cr
@@ -52,15 +52,15 @@ class FSDB::DataBase(K, V)
 	end
 
 	def []?(key : K) : V?
-		begin
-			read file_path key
-		rescue
-			# FIXME: Only rescue JSON and “no such file” errors.
-			return nil
-		end
+		self[key]
+	rescue MissingEntry
+		# FIXME: Only rescue JSON and “no such file” errors.
+		return nil
 	end
 
 	def [](key : K) : V
+		raise MissingEntry.new(key) unless ::File.exists? file_path key
+
 		read file_path key
 	end
 
diff --git a/src/fsdb/exceptions.cr b/src/fsdb/exceptions.cr
new file mode 100644
index 0000000..ea89972
--- /dev/null
+++ b/src/fsdb/exceptions.cr
@@ -0,0 +1,17 @@
+
+class FSDB::MissingEntry < Exception
+	getter index : String?
+	getter key   : String
+
+	def initialize(@index, @key)
+		super "no entry in index '#{@index}' for key '#{@key}''"
+	end
+
+	def initialize(@key)
+		super "no entry for key '#{@key}' in database"
+	end
+end
+
+class FSDB::IndexOverload < Exception
+end
+
diff --git a/src/fsdb/index.cr b/src/fsdb/index.cr
index e02ffcb..a67d6b3 100644
--- a/src/fsdb/index.cr
+++ b/src/fsdb/index.cr
@@ -1,6 +1,7 @@
 require "file_utils"
 require "json"
 
+require "./exceptions.cr"
 require "./indexer.cr"
 
 class FSDB::Index(V) < FSDB::Indexer(V)
@@ -51,8 +52,18 @@ class FSDB::Index(V) < FSDB::Indexer(V)
 		::File.delete symlink
 	end
 
-	def get(index : String) : V?
-		V.from_json ::File.read "#{file_path_index index}"
+	def get(index : String) : V
+		file_path = file_path_index index
+
+		raise MissingEntry.new(@name, index) unless ::File.exists? file_path
+
+		V.from_json ::File.read file_path
+	end
+
+	def get?(index : String) : V?
+		get index
+	rescue MissingEntry
+		nil
 	end
 
 	private def dir_path_indices
@@ -68,6 +79,3 @@ class FSDB::Index(V) < FSDB::Indexer(V)
 	end
 end
 
-class FSDB::IndexOverload < Exception
-end
-