Migrate Ghost json export to Markdown files for static generation

ghost_migrate.rb

require 'json'
require 'open-uri'

class GhostMigrate

  attr_accessor :archive, :posts, :tags, :posts_tags, :template, :base_url

  def run(filename, url)
    @archive = JSON.parse(File.read(filename))
    @posts = archive["db"][0]["data"]["posts"]
    @tags = archive["db"][0]["data"]["tags"]
    @posts_tags = archive["db"][0]["data"]["posts_tags"]
    @template = DATA.read
    @base_url = url
    posts.each_with_index do |p,i|
      File.open("ghost-#{i}.md", "w") do |f|
        f.write post(p)
      end
    end
  end

  def post(post_data)
    title = post_data["title"]
    uuid = post_data["uuid"]
    id = post_data["id"]
    permalink = post_data["slug"]
    date = post_data["published_at"]#[0...10]
    image = (download_image post_data["feature_image"], id) || "none"
    markdown = JSON.parse(post_data["mobiledoc"])["cards"][0][1]["markdown"]
    template % [id, title, permalink, date, formatted_tags(id), image, markdown]
  end

  def formatted_tags(post_id)
    tag_ids = posts_tags.find_all { |pt| pt["post_id"] == post_id }.map { |pt| pt["tag_id"] }
    selected_tags = tag_ids.inject([]) do |r,ti|
      r << "  - \"#{(tags.find { |t| t["id"] == ti })["name"]}\""
    end
    selected_tags.join("\n")
  end

  def download_image(url, id)
    return unless url
    image_url = base_url + url
    image_name = File.basename url
    image_output = "img/#{id}-#{image_name}"
    unless File.exist?(image_output)
      image_data = open(image_url, &:read)
      File.open(image_output, "w") do |f|
        f.write(image_data)
      end
    end
    image_output
  end

end

if __FILE__ == $0
  puts "MIGRATE!"
  GhostMigrate.new.run ARGV[0], ARGV[1]
end

__END__
---
id: %s
title: "%s"
permalink: %s/index.html
date: %s
tags:
%s
layout: layouts/post.njk
feature_image: %s
---
%s