require 'digest'
require 'json'
require 'rack'
require 'storage'

class DataStorageServer
  MAX_BYTES=4096

  def initialize(storage: Storage.new)
    @storage = storage
  end

  def get(path)
    oid = id_from(path)
    return not_found unless @storage.key?(oid)

    ok(body: @storage[oid])
  end

  def put(io)
    data = io.read(MAX_BYTES)
    return bad_request unless data
    return bad_request unless io.eof?

    oid = Digest::SHA256.hexdigest(data)
    @storage[oid] = data
    render(status: '201', body: JSON.generate({ size: data.size, oid: oid }))
  end

  def destroy(path)
    oid = id_from(path)
    return not_found unless @storage.key?(oid)

    @storage.delete(oid)
    ok
  end

  def call(env)
    case env['REQUEST_METHOD']
    when 'GET'
      get(env['PATH_INFO'])
    when 'PUT'
      put(env['rack.input'])
    when 'DELETE'
      destroy(env['PATH_INFO'])
    else
      not_found
    end
  end

  private

  def id_from(path)
    path.split('/')[-1]
  end

  def not_found
    render(status: '404')
  end

  def bad_request
    render(status: '400')
  end

  def ok(status: '200', headers: {}, body: nil)
    render(status: status, headers: headers, body: body)
  end

  def render(status:, headers: {}, body: nil)
    [status, headers, [body].compact]
  end
end