import { execFileSync } from 'node:child_process'
import { readdir, readFile, stat } from 'node:fs/promises'
import { join } from 'node:path'

export const stripSidenotes = (text) => {
  let result = ''
  for (let index = 0; index < text.length;) {
    if (text[index] === '^' && text[index + 1] === '[') {
      const end = text.indexOf(']', index + 2)
      if (end >= 0) {
        index = end + 1
        continue
      }
    }
    result += text[index++]
  }
  return result
}

export const dateFor = async (file) => {
  try {
    const gitDate = execFileSync(
      'git',
      ['log', '-1', '--date=format-local:%Y-%m-%dT%H:%M:%SZ', '--format=%ad', '--', file],
      { env: { ...process.env, TZ: 'UTC' }, stdio: ['ignore', 'pipe', 'ignore'] },
    ).toString().trim()
    if (gitDate) return gitDate
  } catch {}
  try {
    return (await stat(file)).mtime.toISOString()
  } catch {
    return ''
  }
}

export const readPages = async (dir, { includeDrafts = false } = {}) => {
  let entries
  try {
    entries = await readdir(dir, { withFileTypes: true })
  } catch (error) {
    if (error.code === 'ENOENT') return []
    throw error
  }
  const markdownEntries = entries
    .filter((entry) => entry.isFile() && entry.name.endsWith('.md') && entry.name !== '.md'
      && (includeDrafts || !entry.name.startsWith('.')))
    .sort((a, b) => a.name.localeCompare(b.name))
  const pages = await Promise.all(markdownEntries.map(async (entry) => {
    const file = join(dir, entry.name)
    const source = await readFile(file, 'utf8')
    const titleLine = source.split(/\r?\n/).find((line) => line.startsWith('# '))
    if (!titleLine) return undefined
    const draft = entry.name.startsWith('.')
    const name = (draft ? entry.name.slice(1) : entry.name).slice(0, -3)
    if (!name) return undefined
    return {
      name,
      title: stripSidenotes(titleLine.slice(2).trim()),
      file,
      source,
      date: await dateFor(file),
      draft,
    }
  }))
  const byName = new Map()
  for (const page of pages.filter(Boolean)) {
    const existing = byName.get(page.name)
    if (!existing || (existing.draft && !page.draft)) byName.set(page.name, page)
  }
  return [...byName.values()].sort((a, b) => a.name.localeCompare(b.name))
}