/**
 * Convert repo developer-guide/*.md into man(7) page objects (same pipeline as handbook).
 */
import { readFile, readdir } from 'fs/promises'
import { join } from 'path'

import { handbookMdToDescription } from './ingest-handbook-for-man.mjs'

const SECTION = 7

function firstHeadingTitle(md) {
  const m = md.match(/^#\s+(.+)$/m)
  if (!m) return 'Bare OS developer guide'
  let t = m[1]
  t = t.replace(/\*\*([^*]+)\*\*/g, '$1')
  t = t.replace(/`([^`]+)`/g, '$1')
  return t.trim()
}

/**
 * @param {string} repoRoot
 * @returns {Promise<object[]>}
 */
export async function buildDeveloperGuideManPages(repoRoot) {
  const dir = join(repoRoot, 'developer-guide')
  let names
  try {
    names = (await readdir(dir)).filter((f) => f.endsWith('.md'))
  } catch {
    return []
  }

  names.sort((a, b) => {
    if (a === 'README.md') return -1
    if (b === 'README.md') return 1
    return a.localeCompare(b)
  })

  /** @type {{ file: string, name: string, title: string, aliases?: string[] }[]} */
  const meta = []
  for (const file of names) {
    if (file === 'README.md') {
      meta.push({
        file,
        name: 'bare-os-developer-guide',
        title: 'Bare OS developer guide — index and reading order',
        aliases: ['developer-guide', 'devguide']
      })
    } else {
      const base = file.replace(/\.md$/i, '')
      meta.push({
        file,
        name: 'devguide-' + base,
        title: '',
        aliases: []
      })
    }
  }

  const pages = []
  for (let j = 0; j < meta.length; j++) {
    const m = meta[j]
    const filePath = join(dir, m.file)
    const md = await readFile(filePath, 'utf8')
    const title = m.title || firstHeadingTitle(md)
    const description = handbookMdToDescription(md, 'developer-guide/' + m.file)
    const next = meta[j + 1]
    const prev = meta[j - 1]
    /** @type {{ name: string, section: number }[]} */
    const seeAlso = []
    if (next) seeAlso.push({ name: next.name, section: SECTION })
    if (prev) seeAlso.push({ name: prev.name, section: SECTION })
    seeAlso.push({ name: 'man', section: 1 })
    seeAlso.push({ name: 'bare-os-handbook', section: SECTION })

    const kw = new Set([
      'developer',
      'devguide',
      'develop',
      'script',
      'asyncfunction',
      'ctx',
      'bare-os',
      'guide'
    ])
    for (const t of m.name.split(/[^a-z0-9]+/i)) {
      if (t.length > 1) kw.add(t.toLowerCase())
    }
    for (const t of title.toLowerCase().split(/[^a-z0-9]+/)) {
      if (t.length > 2) kw.add(t)
    }

    const page = {
      name: m.name,
      section: SECTION,
      title,
      synopsis: [
        'man 7 ' + m.name,
        'Developer guide chapter (developer-guide/' + m.file + ')'
      ],
      description,
      descriptionMode: 'preserve',
      options: [],
      keywords: Array.from(kw),
      seeAlso,
      bareOsNotes:
        'Generated at build time from developer-guide/' +
        m.file +
        '. Mermaid diagrams omitted in terminal; see repo Markdown for figures.'
    }
    if (m.aliases && m.aliases.length) page.aliases = m.aliases
    pages.push(page)
  }

  return pages
}