From b3296bd1e54baa82a8b622aed46c95d43b794a50 Mon Sep 17 00:00:00 2001
From: Luka Vandervelden <lukc@upyum.com>
Date: Tue, 20 Nov 2018 07:35:49 +0900
Subject: [PATCH] WIP partitioning.

---
 orm.cr | 126 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 124 insertions(+), 2 deletions(-)

diff --git a/orm.cr b/orm.cr
index cb1bade..778bbc2 100644
--- a/orm.cr
+++ b/orm.cr
@@ -2,8 +2,39 @@
 require "json"
 
 class FS::Hash(K, V)
+	class PartitionData(V)
+		property name : String
+		property key_proc : Proc(V, String)
+
+		def initialize(@name, @key_proc)
+		end
+	end
+
+	@partitions = [] of PartitionData(V)
+ 
 	def initialize(@directory_name : String)
-		initialize
+		Dir.mkdir_p @directory_name
+	end
+
+	##
+	# name is the name that will be used on the file system.
+	def new_partition(name : String, &block : Proc(V, String))
+		@partitions.push PartitionData(V).new name, block
+
+		Dir.mkdir_p "#{@directory_name}/.by_#{name}"
+	end
+
+	def get_partition(name : String, key : K)
+		r_value = Array(V).new
+
+		partition_directory = "#{@directory_name}/.by_#{name}/#{key}"
+		Dir.each_child partition_directory do |child|
+			pp child
+
+			r_value << V.from_json File.read "#{partition_directory}/#{child}"
+		end
+
+		r_value
 	end
 
 	def []?(key)
@@ -20,7 +51,21 @@ class FS::Hash(K, V)
 	end
 
 	def []=(key, value)
+		# FIXME: Update partitions pointing to previous value (in any) 
+
 		File.write file_path(key), value.to_json
+
+		@partitions.each do |index|
+			index_key = index.key_proc.call value
+
+			symlink = file_path(key, index.name, index_key)
+
+			Dir.mkdir_p File.dirname symlink
+
+			File.delete symlink if File.exists? symlink
+
+			File.symlink symlink_path(key), symlink
+		end
 	end
 
 	def delete(key)
@@ -32,11 +77,29 @@ class FS::Hash(K, V)
 			# FIXME: Only intercept “no such file" errors
 		end
 
+		unless value.nil?
+			@partitions.each do |index|
+				index_key = index.key_proc.call value
+
+				symlink = file_path(key, index.name, index_key)
+
+				puts "old index #{key.to_s} => #{index_key}"
+				puts "symlink is #{symlink}"
+
+				File.delete symlink
+			end
+		end
+
 		value
 	end
 
+	##
+	# CAUTION: Very slow. Try not to use.
+	# Can be useful for making dumps or to restore a database, however.
 	def each
 		Dir.each_child @directory_name do |child|
+			next if child.match /^\./
+
 			full_path = "#{@directory_name}/#{child}"
 
 			begin
@@ -57,18 +120,30 @@ class FS::Hash(K, V)
 		"#{@directory_name}/#{key.to_s}.json"
 	end
 
+	private def file_path(key : String, index_name : String, index_key : String)
+		"#{@directory_name}/.by_#{index_name}/#{index_key}/#{key}.json"
+	end
+
+	private def symlink_path(key : K)
+		"../../#{key.to_s}.json"
+	end
+
 	private def read(file_path : String)
 		V.from_json File.read file_path
 	end
 end
 
+# Basic mapping testing.
+
 a = FS::Hash(String, JSON::Any).new "test-storage"
 
+a["a"] = JSON::Any.new "now exists"
+
 pp! a["a"]
 pp! a["no file found"]?
 pp! a["invalid json"]?
 
-pp! a["new entry"] = "blip blop"
+pp! a["new entry"] = JSON::Any.new "blip blop"
 pp! a.delete "new entry"
 pp! a.delete "non-existant entry"
 
@@ -76,3 +151,50 @@ a.each do |k, v|
 	pp! k, v
 end
 
+# Indexation testing.
+
+require "uuid"
+
+class Article
+	JSON.mapping({
+		id: String,
+		title: String,
+		author: String
+	})
+
+	def initialize(@id, @title, @author)
+	end
+
+	getter author
+	getter id
+end
+
+articles = FS::Hash(String, Article).new "articles"
+by_author = articles.new_partition "author", &.author
+
+article = Article.new UUID.random.to_s, "Bleh foo bar", "Satsuki"
+articles[article.id] = article
+
+article = Article.new UUID.random.to_s, "Bleh foo bar", "Natsuki"
+articles[article.id] = article
+
+article = Article.new UUID.random.to_s, "Bleh foo bar", "Mutsuki"
+articles[article.id] = article
+
+articles.delete articles.get_partition("author", "Natsuki")[0].id
+
+article = Article.new UUID.random.to_s, "Bleh foo bar", "Satsuki"
+articles[article.id] = article
+
+articles.delete articles.get_partition("author", "Satsuki")[1].id
+
+article = Article.new UUID.random.to_s, "Bleh foo bar", "Satsuki"
+articles[article.id] = article
+
+article = Article.new UUID.random.to_s, "Bleh foo bar", "Nagatsuki"
+articles[article.id] = article
+
+articles.each do |a, b|
+	p a, b
+end
+