#!/usr/bin/env ruby

require 'json'
require 'tempfile'

MARKER_BEGIN = '<!-- Mermaid generator - Section start -->'
MARKER_END = '<!-- Mermaid generator - Section end -->'

# Generate Mermaid diagrams from a Markdown file.
# Modify the Markdown file if the Mermaid diagram is to be referenced for the first time.
#
# Parameters::
# * *file* (String): Markdown file to be parsed
def gen_mermaid(file)
  markdown = []
  mermaid_content = nil
  in_markers = false
  idx_mermaid = 0
  File.read(file).split("\n").each do |line|
    # Logic is simple: Mermaid code blocks should be encapsulated between comment markers that will also include the generated diagram and the details setion.
    # We always regenerate the content between existing comment markers.
    # If those comment markers are missing, we will find Mermaid code blocks to add them.
    # We always re-generate all diagrams.
    if line == MARKER_BEGIN
      in_markers = true
    elsif line == MARKER_END
      in_markers = false
    elsif line == '```mermaid'
      mermaid_content = []
    elsif line == '```'
      # End any block, including Mermaid block
      if mermaid_content.nil?
        markdown << line
      else
        # We have a diagram to generate
        gen_file = "docs/gen/mermaid/#{file}-#{idx_mermaid}.png"
        puts "Generate #{file} / Diagram ##{idx_mermaid} => #{gen_file}..."
        FileUtils.mkdir_p File.dirname(gen_file)
        Tempfile.create('mermaid') do |mermaid_file|
          mermaid_file.write(mermaid_content.join("\n"))
          mermaid_file.flush
          mmdc_cmd = "./node_modules/.bin/mmdc -p #{@puppeteer_conf} -i #{mermaid_file.path} -o #{gen_file} -w 2048"
          raise "Error while running mmdc: #{mmdc_cmd}" unless system mmdc_cmd
        end
        markdown.concat [
          MARKER_BEGIN,
          "![Mermaid diagram](/#{gen_file})",
          '<details>',
          '<summary><sub><sup>Diagram code</sup></sub></summary>',
          '',
          '```mermaid'
        ] + mermaid_content + [
          '```',
          '</details>',
          MARKER_END
        ]
        idx_mermaid += 1
        mermaid_content = nil
      end
    elsif !mermaid_content.nil?
      # We are in a Mermaid content
      mermaid_content << line
    elsif !in_markers
      markdown << line
    end
  end
  File.write(file, markdown.map { |line| "#{line}\n" }.join) if idx_mermaid.positive?
end

Tempfile.create('puppeteer') do |puppeteer_file|
  puppeteer_file.write({ args: ['--no-sandbox'] }.to_json)
  puppeteer_file.flush
  @puppeteer_conf = puppeteer_file.path
  ARGV.each { |file| gen_mermaid(file) }
end