import fs from 'node:fs'
import path from 'node:path'
import { execFileSync } from 'node:child_process'

const root = process.cwd()
const files = [...new Set(execFileSync('git', ['ls-files', '--cached', '--others', '--exclude-standard', '-z'], { encoding: 'utf8' }).split('\0'))].filter(file => file.endsWith('.md'))
const stripCode = text => text.replace(/^```[^\n]*\n[\s\S]*?^```[^\n]*$/gm, '')
const slug = text => text.toLowerCase().replace(/`/g, '').replace(/[^\p{Letter}\p{Number}\p{Mark}_\- ]/gu, '').replace(/ /g, '-')
const anchors = file => {
  const source = stripCode(fs.readFileSync(file, 'utf8'))
  const used = new Map(), result = new Set()
  for (const [, heading] of source.matchAll(/^#{1,6}\s+(.+)$/gm)) {
    const name = slug(heading.trim()), count = used.get(name) ?? 0
    result.add(count ? `${name}-${count}` : name); used.set(name, count + 1)
  }
  for (const [, name] of source.matchAll(/\b(?:id|name)=["']([^"']+)["']/g)) result.add(name)
  return result
}
const problems = []; let internalLinks = 0
for (const file of files) for (const [, raw] of stripCode(fs.readFileSync(file, 'utf8')).matchAll(/!?\[[^\]\n]*\]\(([^)\n]+)\)/g)) {
  const href = raw.trim().replace(/^<|>$/g, '')
  if (/^(?:[a-z][a-z\d+.-]*:|\/\/)/i.test(href)) continue
  internalLinks++
  try {
    const [target, fragment] = href.split('#')
    const resolved = target ? path.resolve(path.dirname(file), decodeURIComponent(target)) : path.resolve(file)
    const relative = path.relative(root, resolved).replaceAll('\\', '/')
    let reason = relative.startsWith('_local/') || relative === '_local' ? 'local evidence is excluded from Git Clone' : !fs.existsSync(resolved) ? 'missing path' : null
    if (!reason && fragment && resolved.endsWith('.md') && !anchors(resolved).has(decodeURIComponent(fragment))) reason = 'missing heading'
    if (reason) problems.push({ file, href, reason })
  } catch (error) { problems.push({ file, href, reason: error.message }) }
}
console.log(JSON.stringify({ files: files.length, internalLinks, problems }, null, 2))
if (problems.length) process.exitCode = 1