add InfluxDB.convert_timestamp utility

Author: dmke

lib/influxdb.rb

@@ -4,6 +4,7 @@
 require "influxdb/max_queue"
 require "influxdb/point_value"
 require "influxdb/config"
+require "influxdb/timestamp_conversion"
 
 require "influxdb/writer/async"
 require "influxdb/writer/udp"

lib/influxdb/timestamp_conversion.rb

@@ -0,0 +1,23 @@
+module InfluxDB #:nodoc:
+  TIMESTAMP_CONVERSIONS = {
+    "ns" => 1e9.to_r,
+    nil  => 1e9.to_r,
+    "u"  => 1e6.to_r,
+    "ms" => 1e3.to_r,
+    "s"  => 1.to_r,
+    "m"  => 1.to_r / 60,
+    "h"  => 1.to_r / 60 / 60,
+  }.freeze
+  private_constant :TIMESTAMP_CONVERSIONS
+
+  # Converts a Time to a timestamp with the given precision.
+  #
+  # `convert_timestamp(Time.now, "ms")` might return `1543533308243`.
+  def self.convert_timestamp(time, time_precision)
+    factor = TIMESTAMP_CONVERSIONS.fetch(time_precision.to_s) do
+      raise "Invalid time precision: #{time_precision}"
+    end
+
+    (time.to_r * factor).to_i
+  end
+end

spec/influxdb/time_conversion_spec.rb

@@ -0,0 +1,26 @@
+require "spec_helper"
+
+RSpec.describe InfluxDB do
+  describe ".convert_timestamp" do
+    let(:sometime) { Time.parse("2017-12-11 16:20:29.111222333 UTC") }
+
+    {
+      "ns" => 1_513_009_229_111_222_333,
+      nil  => 1_513_009_229_111_222_333,
+      "u"  => 1_513_009_229_111_222,
+      "ms" => 1_513_009_229_111,
+      "s"  => 1_513_009_229,
+      "m"  => 25_216_820,
+      "h"  => 420_280,
+    }.each do |precision, converted_value|
+      it "should return the timestamp in #{precision.inspect}" do
+        expect(described_class.convert_timestamp(sometime, precision)).to eq(converted_value)
+      end
+    end
+
+    it "should raise an excpetion when precision is unrecognized" do
+      expect { described_class.convert_timestamp(sometime, "whatever") }
+        .to raise_exception(/invalid time precision.*whatever/i)
+    end
+  end
+end