// Re-point every asset reference at the site's origin, and refuse to emit anything that
// would 404. A silently-missing image is precisely how the page goes back to lying about
// its own content — which is the failure this whole projection exists to end.
import { writeFile, mkdir, copyFile } from 'node:fs/promises'
import { existsSync } from 'node:fs'
import { basename, join } from 'node:path'
import { DIST, postcss, publicBase, publicDir } from './paths.mjs'

export async function projectAssets(html, css, id, { apply = true } = {}) {
  const base = `${publicBase(id)}/assets`
  const wanted = new Map()
  const unresolved = []

  const claim = (ref) => {
    const clean = ref.trim().replace(/^["']|["']$/g, '')
    if (/^(data:|https?:|#|mailto:)/i.test(clean)) return null      // external / inline: not ours
    if (!clean.startsWith('/')) { unresolved.push({ ref: clean, why: 'referencia relativa, sin base' }); return null }

    const onDisk = join(DIST, clean)
    if (!existsSync(onDisk)) { unresolved.push({ ref: clean, why: `no está en dist/` }); return null }

    const pub = `${base}/${basename(clean)}`
    wanted.set(clean, { onDisk, pub })
    return pub
  }

  html = html
    .replace(/(<img[^>]+src=")([^"]+)(")/g, (m, a, ref, z) => { const p = claim(ref); return p ? a + p + z : m })
    .replace(/(background-image:\s*url\()([^)]+)(\))/g, (m, a, ref, z) => { const p = claim(ref); return p ? a + p + z : m })

  const root = postcss.parse(css)
  root.walkDecls(d => {
    if (!d.value.includes('url(')) return
    d.value = d.value.replace(/url\(([^)]+)\)/g, (m, ref) => {
      const p = claim(ref)
      return p ? `url("${p}")` : m
    })
  })
  css = root.toString()

  if (unresolved.length) {
    const lines = unresolved.map(u => `  ${u.ref} — ${u.why}`).join('\n')
    throw new Error(`${unresolved.length} referencia(s) sin resolver; no se emite un deck con assets rotos:\n${lines}`)
  }

  if (apply) {
    const dest = join(publicDir(id), 'assets')
    await mkdir(dest, { recursive: true })
    for (const [, v] of wanted) await copyFile(v.onDisk, join(dest, basename(v.pub)))
  }

  return { html, css, copied: [...wanted.values()].map(v => v.pub) }
}