git-time-spent

#!/usr/bin/env ruby
#
# Lazy sources:
#
# - https://stackoverflow.com/a/6018744
# - https://stackoverflow.com/a/4179491

require 'time'

def ranges_overlap?(a, b)
  a.include?(b.begin) || b.include?(a.begin)
end

def merge_ranges(a, b)
  [a.begin, b.begin].min..[a.end, b.end].max
end

def merge_overlapping_ranges(overlapping_ranges)
  overlapping_ranges.sort_by(&:begin).inject([]) do |ranges, range|
    if !ranges.empty? && ranges_overlap?(ranges.last, range)
      ranges[0...-1] + [merge_ranges(ranges.last, range)]
    else
      ranges + [range]
    end
  end
end

# Find all timestamps in the git log
lines = `git log --format='format:%ai'`.split("\n")

# Pad them out to 30 minute ranges.
#
# This means that our calculations will assume you worked for 15 minutes before
# your first commit and 15 minutes after your last commit in a given session.
#
# A session is defined where the ranges overlap, so minimum of 30 minutes
# between a commit.
ranges_padded_to_30_mins = lines.map { |line| t = Time.parse(line); (t - 60 * 15)..(t + 60 * 15) }

# Merge into sessions and print out the duration of each session.
merge_overlapping_ranges(ranges_padded_to_30_mins).each_with_index do |range, i|
  puts "Session #{i + 1}: #{(Time.mktime(0) + (range.end - range.begin)).strftime("%H:%M:%S")}"
end