update-book.yml

name: Update Progit Book

on:
  - workflow_dispatch

permissions:
  contents: write # need to be able to push

jobs:
  check-for-updates:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/github-script@v6
        with:
          script: |
            const getFileContents = async (path) => {
              const req = await fetch(`https://github.com/${context.repo.owner}/${context.repo.repo}/raw/${context.sha}/${path}`)
              if (req.status === 404) return undefined
              return req.text()
            }
          
            const getAllBooks = async () => {
              const book_rb = await getFileContents('script/book.rb')
              const begin = book_rb.indexOf('@@all_books = {')
              const end = book_rb.indexOf('}', begin + 1)
              if (begin < 0 || end < 0) throw new Error(`Could not find @@all_books in:\n${book_rb}`)
              return book_rb
                .substring(begin, end)
                .split('\n')
                .reduce((allBooks, line) => {
                  const match = line.match(/"([^"]+)" => "([^"]+)"/)
                  if (match) allBooks[match[1]] = match[2]
                  return allBooks
                }, {})
              return allBooks
            }
          
            // This is a very, very simplistic YAML parser, _just_ powerful enough to
            // parse the front matter written by us.
            //
            // Most importantly, support for continuation lines (lines ending in `|`) is
            // completely absent. Also, support for JSON-style definitions is missing.
            const parseFrontMatter = page => {
              if (!page.startsWith('---\n')) throw new Error(`Expected ---:\n${page.substring(0, 20)}...`)
              const end = page.indexOf('\n\n---', 4)
              if (end < 0) throw new Error(`Missing end of front matter:\n${page}`)
              const stack = [{}]
              const keys = []
              return page
                .substring(4, end)
                .split('\n')
                .reduce((frontMatter, line) => {
                  // parse these three line formats:
                  // - value
                  // key: value
                  // key:
                  const match = line.match(/^( *)(?:(?:(-)\s*|(\S+):)\s*("?(\S.*?)"?)?)$/)
                  if (!match) throw new Error(`Invalid YAML? '${line}'`)
                  const isArrayItem = match[2]
                  const key = match[3]
                  const hasValue = match[4]
                  const value = match[5]
          
                  const nestingLevel = match[1].length / 2 + (isArrayItem ? 1 : 0)
                  if (nestingLevel + 1 < stack.length) stack.splice(nestingLevel + 1, stack.length - nestingLevel - 1)
                  else if (nestingLevel >= stack.length) throw new Error(`Invalid nesting level:\n${line}`)
          
                  const o = stack[nestingLevel]
                  if (isArrayItem) {
                    if (Array.isArray(o)) o.push(value)
                    else if (typeof o !== 'object') throw new Error(`Could not turn parent into an array:\n${line}`)
                    else if (Object.keys(o).length > 0) throw new Error(`Trying to add an array item to an object:\n${line}\n${JSON.stringify(o, null, 2)}`)
                    else {
                      stack[nestingLevel - 1][keys[nestingLevel - 1]] = stack[nestingLevel] = [value]
                    }
                  }
                  else if (hasValue) o[key] = value
                  else {
                    o[key] = {}
                    stack.push(o[key])
                    keys[nestingLevel] = key
                  }
                  return frontMatter
                }, stack[0])
            }
          
            const getFrontMatterForLanguage = async (lang) => {
              const frontPage = await getFileContents(`book/${lang}/v2/index.html`)
              return parseFrontMatter(frontPage)
            }
  update-