Data commit

Task/Simple-database/Ruby/simple-database.rb

@@ -0,0 +1,187 @@
+require 'date'
+require 'json'
+require 'securerandom'
+
+class SimpleDatabase
+  def initialize(dbname, *fields)
+    @dbname = dbname
+    @filename = @dbname + ".dat"
+    @fields = fields
+    @maxl = @fields.collect {|f| f.length}.max
+    @data = {
+      'fields' => fields,
+      'items' => {},
+      'history' => [],
+      'tags' => {},
+    }
+  end
+  attr_reader :dbname, :fields
+
+  def self.open(dbname)
+    db = new(dbname)
+    db.read
+    db
+  end
+
+  def read()
+    if not File.exists?(@filename)
+      raise ArgumentError, "Database #@dbname has not been created"
+    end
+    @data = JSON.parse(File.read(@filename))
+    @fields = @data['fields']
+    @maxl = @fields.collect {|f| f.length}.max
+  end
+
+  def write()
+    File.open(@filename, 'w') {|f| f.write(JSON.generate(@data))}
+  end
+
+  def add(*values)
+    id = SecureRandom.uuid
+    @data['items'][id] = Hash[ @fields.zip(values) ]
+    @data['history'] << [Time.now.to_f, id]
+    id
+  end
+
+  def tag(id, *tags)
+    tags.each do |tag|
+      if @data['tags'][tag].nil?
+        @data['tags'][tag] = [id]
+      else
+        @data['tags'][tag] << id
+      end
+    end
+    id
+  end
+
+  def latest
+    @data['history'].sort_by {|val| val[0]}.last.last
+  end
+
+  def get_item(id)
+    @data['items'][id]
+  end
+
+  def tags()
+    @data['tags'].keys.sort
+  end
+
+  def ids_for_tag(tag)
+    @data['tags'][tag]
+  end
+
+  def tags_for_id(id)
+    @data['tags'].keys.inject([]) do |tags, tag|
+      tags << tag if @data['tags'][tag].include?(id)
+      tags
+    end
+  end
+
+  def display(id)
+    item = get_item(id)
+    fmt = "%#{@maxl}s - %s\n"
+    puts fmt % ['id', id]
+    @fields.each {|f| print fmt % [f, item[f]]}
+    puts fmt % ['tags', tags_for_id(id).join(',')]
+    added = @data['history'].find {|x| x[1] == id}.first
+    puts fmt % ['date added', Time.at(added).ctime]
+    puts ""
+  end
+
+  def each()
+    @data['history'].each {|time, id| yield id}
+  end
+
+  def each_item_with_tag(tag)
+    @data['tags'][tag].each {|id| yield id}
+  end
+end
+def usage()
+  puts <<END
+usage: #{$0} command args ...
+
+commands:
+  help
+  create dbname field ...
+  fields dbname
+  add dbname value ...
+  tag dbname id tag ...
+  tags dbname
+  list dbname [tag ...]
+  latest dbname
+  latest_by_tag dbname
+END
+end
+
+def open_database(args)
+  dbname = args.shift
+  begin
+    SimpleDatabase.open(dbname)
+  rescue ArgumentError => e
+    STDERR.puts e.message
+    exit 1
+  end
+end
+
+def process_command_line(command, *args)
+  case command
+  when 'help'
+    usage
+
+  when 'create'
+    db = SimpleDatabase.new(*args)
+    db.write
+    puts "Database #{args[0]} created"
+
+  when 'fields'
+    db = open_database(args)
+    puts "Database #{db.dbname} fields:"
+    puts db.fields.join(',')
+
+  when 'add'
+    db = open_database(args)
+    id = db.add(*args)
+    db.write
+    puts "Database #{db.dbname} added id #{id}"
+
+  when 'tag'
+    db = open_database(args)
+    id = args.shift
+    db.tag(id, *args)
+    db.write
+    db.display(id)
+
+  when 'tags'
+    db = open_database(args)
+    puts "Database #{db.dbname} tags:"
+    puts db.tags.join(',')
+
+  when 'list'
+    db = open_database(args)
+    if args.empty?
+      db.each {|id| db.display(id)}
+    else
+      args.each do |tag|
+        puts "Items tagged #{tag}"
+        db.each_item_with_tag(tag) {|id| db.display(id)}
+      end
+    end
+
+  when 'latest'
+    db = open_database(args)
+    db.display(db.latest)
+
+  when 'latest_by_tag'
+    db = open_database(args)
+    db.tags.each do |tag|
+      puts tag
+      db.display(db.ids_for_tag(tag).last)
+    end
+
+  else
+    puts "Error: unknown command '#{command}'"
+    usage
+  end
+end
+
+process_command_line *ARGV