commit-velocity

#!/usr/bin/env ruby
# frozen_string_literal: true

# Commit Velocity Visualizer
# Shows commit count by month with trend analysis, anomaly detection,
# and contributor breakdown.
#
# Credit: https://piechowski.io/post/git-commands-before-reading-code/
#
# Usage:
#   commit-velocity              # full history
#   commit-velocity --last 24    # last 24 months
#   commit-velocity --by-author  # include top contributor breakdown
#   commit-velocity --quarterly  # show quarterly rollups too
#   commit-velocity --author "Jane Doe"  # single author month-by-month
#   commit-velocity --weekly             # weekly instead of monthly buckets

require "date"
require "optparse"

options = { last: nil, by_author: false, quarterly: false, author: nil, weekly: false }
OptionParser.new do |opts|
  opts.banner = "Usage: commit-velocity [options]"
  opts.on("--last N", Integer, "Show only the last N periods") { |n| options[:last] = n }
  opts.on("--by-author", "Show top contributors per period") { options[:by_author] = true }
  opts.on("--quarterly", "Show quarterly rollup summary") { options[:quarterly] = true }
  opts.on("--author NAME", "Show period-by-period for a single author") { |n| options[:author] = n }
  opts.on("--weekly", "Use weekly buckets instead of monthly") { options[:weekly] = true }
end.parse!

# --- Gather data ---

date_fmt = options[:weekly] ? "%G-W%V" : "%Y-%m"
period_label = options[:weekly] ? "Week" : "Month"

if options[:author]
  # Find matching author name (case-insensitive substring match)
  all_authors = `git log --format='%aN'`.lines.map(&:strip).reject(&:empty?).uniq
  matched = all_authors.select { |a| a.downcase.include?(options[:author].downcase) }.uniq
  if matched.empty?
    puts "No author matching '#{options[:author]}' found."
    exit 1
  elsif matched.size > 1
    puts "Multiple authors match '#{options[:author]}':"
    matched.each { |a| puts "  - #{a}" }
    puts "Be more specific."
    exit 1
  end
  author_name = matched.first
  raw = `git log --author='#{author_name}' --format='%ad' --date=format:'#{date_fmt}'`.lines.map(&:strip).reject(&:empty?)

  # Also get total repo counts for comparison
  raw_total = `git log --format='%ad' --date=format:'#{date_fmt}'`.lines.map(&:strip).reject(&:empty?)
  total_counts = raw_total.tally
else
  raw = `git log --format='%ad' --date=format:'#{date_fmt}'`.lines.map(&:strip).reject(&:empty?)
  total_counts = nil
  author_name = nil
end
counts = raw.tally.sort_by { |period, _| period }

if options[:last]
  counts = counts.last(options[:last])
end

if counts.empty?
  puts "No commit data found."
  exit
end

months = counts.map(&:first)
values = counts.map(&:last)
max_val = values.max
min_val = values.min
avg_val = values.sum.to_f / values.size

# --- Colors ---

def color(code, text)
  "\e[#{code}m#{text}\e[0m"
end

def bar_color(val, avg, prev)
  if prev && val < prev * 0.6
    "31" # red — sharp drop
  elsif val > avg * 1.3
    "32" # green — well above average
  elsif val < avg * 0.7
    "33" # yellow — below average
  else
    "36" # cyan — normal
  end
end

def trend_arrow(val, prev)
  return " " if prev.nil?
  delta = ((val - prev).to_f / prev * 100).round(0)
  if delta > 20
    "\e[32m▲+#{delta}%\e[0m"
  elsif delta < -20
    "\e[31m▼#{delta}%\e[0m"
  elsif delta > 0
    "\e[32m↑+#{delta}%\e[0m"
  elsif delta < 0
    "\e[33m↓#{delta}%\e[0m"
  else
    "  →0%"
  end
end

# --- 3-month moving average ---

def moving_avg(values, window = 3)
  values.each_with_index.map do |_, i|
    start = [0, i - window + 1].max
    slice = values[start..i]
    slice.sum.to_f / slice.size
  end
end

ma = moving_avg(values)

# --- Render chart ---

bar_width = 50
puts
if author_name
  puts color("1", "  COMMIT VELOCITY — #{author_name}")
  puts color("90", "  #{months.first} → #{months.last}  •  #{values.sum} commits by this author")
else
  puts color("1", "  COMMIT VELOCITY")
  puts color("90", "  #{months.first} → #{months.last}  •  #{values.sum} total commits")
end
puts

# Header
if author_name
  puts color("90", "  #{period_label.ljust(10)} Count  Share   #{' ' * (bar_width - 4)}  Trend       3mo avg")
else
  puts color("90", "  #{period_label.ljust(10)} Count  #{' ' * (bar_width - 4)}  Trend       3mo avg")
end
puts color("90", "  #{'─' * (10 + 6 + bar_width + 30)}")

values.each_with_index do |val, i|
  month = months[i]
  prev = i > 0 ? values[i - 1] : nil
  bc = bar_color(val, avg_val, prev)

  filled = (val.to_f / max_val * bar_width).round
  bar = color(bc, "█" * filled) + color("90", "░" * (bar_width - filled))

  trend = trend_arrow(val, prev)
  ma_str = ma[i].round(0).to_s.rjust(5)

  count_str = val.to_s.rjust(5)
  month_str = month.ljust(10)

  if author_name
    total_for_month = total_counts[month] || 1
    share = (val.to_f / total_for_month * 100).round(1)
    share_str = "#{share.to_s.rjust(5)}%"
    puts "  #{month_str} #{count_str}  #{share_str}  #{bar}  #{trend.ljust(20)} #{color('90', ma_str)}"
  else
    puts "  #{month_str} #{count_str}  #{bar}  #{trend.ljust(20)} #{color('90', ma_str)}"
  end
end

puts color("90", "  #{'─' * (10 + 6 + bar_width + 30)}")
summary = "  #{color('90', 'avg')}: #{avg_val.round(0)}   " \
          "#{color('32', 'max')}: #{max_val} (#{months[values.index(max_val)]})   " \
          "#{color('31', 'min')}: #{min_val} (#{months[values.index(min_val)]})"
if author_name
  overall_share = (values.sum.to_f / months.sum { |m| total_counts[m] || 0 } * 100).round(1)
  summary += "   #{color('90', 'overall share')}: #{overall_share}%"
end
puts summary
puts

# Also flag if current (partial) period is on pace to drop
current_period = Date.today.strftime(date_fmt)
if months.last == current_period
  if options[:weekly]
    day_of_week = Date.today.cwday # 1=Mon, 7=Sun
    days_elapsed = day_of_week
    days_in_period = 7
  else
    days_elapsed = Date.today.day
    days_in_period = Date.civil(Date.today.year, Date.today.month, -1).day
  end
  projected = (values.last.to_f / days_elapsed * days_in_period).round(0)
  if values.size > 1
    prev_full = values[-2]
    proj_delta = ((projected - prev_full).to_f / prev_full * 100).round(0)
    puts color("90", "  ℹ #{months.last} is partial (#{days_elapsed}/#{days_in_period} days). " \
               "Projected: ~#{projected} commits (#{proj_delta > 0 ? '+' : ''}#{proj_delta}% vs #{months[-2]})")
    puts
  end
end

# --- Quarterly rollup ---

if options[:quarterly]
  puts color("1", "  QUARTERLY ROLLUP")
  puts

  quarters = counts.group_by { |month, _|
    y, m = month.split("-").map(&:to_i)
    q = ((m - 1) / 3) + 1
    "#{y}-Q#{q}"
  }

  q_data = quarters.map { |q, entries|
    total = entries.sum { |_, c| c }
    [q, total, entries.size]
  }

  q_max = q_data.map { |_, t, _| t }.max

  q_data.each_with_index do |(q, total, month_count), i|
    filled = (total.to_f / q_max * 40).round
    bar = color("36", "█" * filled) + color("90", "░" * (40 - filled))
    avg = (total.to_f / month_count).round(0)
    partial = month_count < 3 ? color("90", " (partial)") : ""
    puts "  #{q.ljust(8)} #{total.to_s.rjust(5)}  #{bar}  avg #{avg}/mo#{partial}"
  end
  puts
end

# --- Top contributors ---

if options[:by_author]
  puts color("1", "  TOP CONTRIBUTORS (last 6 months)")
  puts

  since = (Date.today << 6).strftime("%Y-%m-%d")
  author_raw = `git log --since='#{since}' --format='%aN'`.lines.map(&:strip).reject(&:empty?)
  author_counts = author_raw.tally.sort_by { |_, c| -c }.first(10)
  total_recent = author_raw.size
  a_max = author_counts.first&.last || 1

  author_colors = %w[36 32 35 33 34 31 96 92 95 93]
  author_counts.each_with_index do |(name, count), i|
    pct = (count.to_f / total_recent * 100).round(1)
    filled = (count.to_f / a_max * 30).round
    c = author_colors[i % author_colors.size]
    bar = color(c, "█" * filled) + color("90", "░" * (30 - filled))
    puts "  #{color(c, name.ljust(25))} #{count.to_s.rjust(5)} (#{pct.to_s.rjust(5)}%)  #{bar}"
  end
  puts
end