136 lines
2.6 KiB
Crystal
136 lines
2.6 KiB
Crystal
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require "json"
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class FS::Hash(K, V)
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class PartitionData(V)
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property name : String
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property key_proc : Proc(V, String)
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def initialize(@name, @key_proc)
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end
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end
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@partitions = [] of PartitionData(V)
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def initialize(@directory_name : String)
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Dir.mkdir_p @directory_name
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end
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##
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# name is the name that will be used on the file system.
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def new_partition(name : String, &block : Proc(V, String))
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@partitions.push PartitionData(V).new name, block
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Dir.mkdir_p "#{@directory_name}/.by_#{name}"
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end
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def get_partition(name : String, key : K)
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r_value = Array(V).new
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partition_directory = "#{@directory_name}/.by_#{name}/#{key}"
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Dir.each_child partition_directory do |child|
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pp child
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r_value << V.from_json File.read "#{partition_directory}/#{child}"
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end
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r_value
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end
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def []?(key : K) : V?
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begin
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read file_path key
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rescue
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# FIXME: Only rescue JSON and “no such file” errors.
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return nil
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end
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end
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def [](key : K) : V
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read file_path key
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end
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def []=(key : K, value : V)
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# FIXME: Update partitions pointing to previous value (in any)
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File.write file_path(key), value.to_json
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@partitions.each do |index|
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index_key = index.key_proc.call value
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symlink = file_path(key, index.name, index_key)
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Dir.mkdir_p File.dirname symlink
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File.delete symlink if File.exists? symlink
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File.symlink symlink_path(key), symlink
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end
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end
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def delete(key : K)
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value = self[key]?
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begin
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File.delete file_path key
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rescue
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# FIXME: Only intercept “no such file" errors
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end
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unless value.nil?
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@partitions.each do |index|
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index_key = index.key_proc.call value
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symlink = file_path(key, index.name, index_key)
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puts "old index #{key.to_s} => #{index_key}"
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puts "symlink is #{symlink}"
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File.delete symlink
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end
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end
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value
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end
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##
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# CAUTION: Very slow. Try not to use.
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# Can be useful for making dumps or to restore a database, however.
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def each
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Dir.each_child @directory_name do |child|
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next if child.match /^\./
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full_path = "#{@directory_name}/#{child}"
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begin
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# FIXME: Only intercept JSON parsing errors.
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field = read full_path
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rescue
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next
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end
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# FIXME: Will only work for String. :(
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key = child.gsub /\.json$/, ""
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yield key, field
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end
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end
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private def file_path(key : K)
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"#{@directory_name}/#{key.to_s}.json"
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end
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private def file_path(key : String, index_name : String, index_key : String)
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"#{@directory_name}/.by_#{index_name}/#{index_key}/#{key}.json"
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end
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private def symlink_path(key : K)
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"../../#{key.to_s}.json"
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end
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private def read(file_path : String)
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V.from_json File.read file_path
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end
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end
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