#!/usr/bin/env ruby

fix = ARGV.shift if ARGV.first == "--fix"
files = Array(ARGV.shift || Dir.glob("./**/*.md"))

files.each do |file|
  content = File.read(file)

  # First, scan for all references ([#]: at beginning of line)
  # and look for duplicates
  refs = content.scan(/^\[\d+\]:/)
  dups = refs.combination(2).filter_map { |i, j| i if i == j }

  # If duplicate refs detected, this won't work, so bail out
  if dups.any?
    warn "Duplicate refs detected in #{file} (#{dups * ", "})"
    exit 1
  end

  idx = 0
  code_block = false
  cache = {}

  # Find all numbered links (in text + references) + code delimeters
  # (for fenced code blocks, "`" suffices because "```" is an odd number)
  updated = content.gsub(/\[\d+\]|`/) do |token|
    case token
    when "`"
      # We don't want to do substitution inside code blocks
      # (where `[#]` sometimes occurs) but we do want to toggle
      # whether or not we're in a code block
      code_block = !code_block
      token
    else
      # If we're in a code block, just return the token
      # Otherwise, check if the reference has already been assigned
      # - If so, return the cached value
      # - If not, bump the index, cache the value, and return it
      code_block ? token : cache[token] ||= "[#{idx += 1}]"
    end
  end

  if content != updated
    warn "Links in #{file} are not in order"

    if fix
      File.write(file, updated)
    else
      exit 1
    end
  end
end