dodb.cr/orm.cr

136 lines
2.6 KiB
Crystal

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)
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 : K) : V?
begin
read file_path key
rescue
# FIXME: Only rescue JSON and “no such file” errors.
return nil
end
end
def [](key : K) : V
read file_path key
end
def []=(key : K, value : V)
# 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 : K)
value = self[key]?
begin
File.delete file_path key
rescue
# 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
# FIXME: Only intercept JSON parsing errors.
field = read full_path
rescue
next
end
# FIXME: Will only work for String. :(
key = child.gsub /\.json$/, ""
yield key, field
end
end
private def file_path(key : K)
"#{@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