#!/usr/bin/env ruby

require "rdoc"

def store_for_class(name, stores:)
  stores.find do |store|
    store.find_class_named(name) || store.find_module_named(name)
  end
end

def format_comment(comment)
  out = RDoc::Markup::Document.new
  out << comment
  formatter = RDoc::Markup::ToMarkdown.new
  out.accept(formatter)
end

def comment_for_constant(name, stores:)
  *class_components, const_name = name.split(/::/)
  class_name = class_components.join("::")

  klass = store_for_class(class_name, stores: stores)&.yield_self {|store|
    store.find_class_named(class_name) || store.find_module_named(class_name)
  }

  constant = klass.constants.find do |const|
    const.name == const_name
  end

  if constant&.documented?
    format_comment(constant.comment)
  end
end

def comment_for_class(class_name, stores:)
  klass = store_for_class(class_name, stores: stores)&.yield_self {|store|
    store.find_class_named(class_name) || store.find_module_named(class_name)
  }

  if klass&.documented?
    format_comment(klass.comment)
  end
end

def comment_for_method(klass, method, stores:)
  method = store_for_class(klass, stores: stores)&.load_method(klass, method)

  if method&.documented?
    out = RDoc::Markup::Document.new

    out << method.comment

    if method.arglists
      out << RDoc::Markup::Heading.new(1, "arglists 💪👽🚨 << Delete this section")
      arglists = method.arglists.chomp.split("\n").map {|line| line + "\n" }
      out << RDoc::Markup::Verbatim.new(*arglists)
    end

    out.accept(RDoc::Markup::ToMarkdown.new)
  end
rescue RDoc::Store::MissingFileError
  nil
end

if ARGV.empty?
  puts 'query-rdoc [subject]'
  puts "  subject ::= ClassName         (class, module, or constant)"
  puts "            | ClassName.method  (singleton method)"
  puts "            | ClassName#method  (instance method)"
  exit
end

stores = []
RDoc::RI::Paths.each true, true, false, false do |path, type|
  STDERR.puts "Loading store from #{path}..."
  store = RDoc::RI::Store.new(path, type)
  store.load_all
  stores << store
end

subject = ARGV[0]

case
when match = subject.match(/(?<constant_name>[^#]+)#(?<method_name>.+)/)
  STDERR.puts "Finding instance method #{match[:constant_name]} # #{match[:method_name]} ..."
  comment = comment_for_method(match[:constant_name], "##{match[:method_name]}", stores: stores)
when match = subject.match(/(?<constant_name>[^.]+)\.(?<method_name>.+)/)
  STDERR.puts "Finding singleton method #{match[:constant_name]} . #{match[:method_name]} ..."
  comment = comment_for_method(match[:constant_name], "::#{match[:method_name]}", stores: stores)
else
  STDERR.puts "Finding class/module/constant #{subject} ..."
  comment = comment_for_class(subject, stores: stores) || comment_for_constant(subject, stores: stores)
end

if comment
  STDERR.puts "Printing document..."
  comment.each_line do |line|
    puts "# #{line}"
  end
else
  STDERR.puts "Nothing to print; failed to query the document..."
  exit 1
end