import { readFileSync, writeFileSync, mkdirSync, rmSync, existsSync } from 'fs'
import { resolve, join } from 'path'
import { createRequire } from 'module'

/**
 * Generate static SVG assets + an SCSS partial that re-applies HOT v17 classic
 * theme icons via real URLs (not data: URIs).
 *
 * Why: deployed app runs under CSP `img-src 'self'`. HOT v17's classic theme
 * embeds icons as `data:image/svg+xml,...` in `-webkit-mask-image` rules, which
 * the CSP blocks. We switch to `ht-theme-classic-no-icons.min.css` and re-add
 * the icon rules pointing at same-origin SVG files emitted from this script.
 *
 * Inputs (HOT's own modules, so semantic names + selector list track upstream):
 *   handsontable/themes/theme/classic                          → { classicTheme: { icons } }
 *   handsontable/themes/static/variables/helpers/iconsMap      → iconsMap(icons, themePrefix)
 *
 * Outputs:
 *   client/src/assets/hot-icons/<kebab-name>.svg
 *   client/src/_hot-icons.scss
 *
 * Idempotent: clears the output dir and rewrites both outputs each run.
 * Skips silently if handsontable isn't installed yet (pre-install runs).
 */
const require = createRequire(import.meta.url)

const ASSETS_DIR = resolve('src/assets/hot-icons')
const SCSS_OUT = resolve('src/_hot-icons.scss')
const ASSET_URL_PREFIX = './assets/hot-icons/'

const themePath = resolve('node_modules/handsontable/themes/theme/classic.js')
const mapPath = resolve('node_modules/handsontable/themes/static/variables/helpers/iconsMap.js')

if (!existsSync(themePath) || !existsSync(mapPath)) {
  console.log('skip: handsontable theme modules not found (likely pre-install run)')
  process.exit(0)
}

const { classicTheme } = require(themePath)
const { iconsMap } = require(mapPath)

const icons = classicTheme.icons
const cssTemplate = iconsMap(icons, 'ht-theme-classic')

const kebab = (s) => s.replace(/([a-z0-9])([A-Z])/g, '$1-$2').toLowerCase()

rmSync(ASSETS_DIR, { recursive: true, force: true })
mkdirSync(ASSETS_DIR, { recursive: true })

const writeMap = {}
for (const [name, dataUri] of Object.entries(icons)) {
  if (typeof dataUri !== 'string' || !dataUri.startsWith('data:image/svg+xml')) continue
  const decoded = decodeURIComponent(dataUri.replace(/^data:image\/svg\+xml(;charset=utf-8)?,/, ''))
  const fname = kebab(name) + '.svg'
  writeFileSync(join(ASSETS_DIR, fname), decoded)
  writeMap[dataUri] = ASSET_URL_PREFIX + fname
}

let scss = cssTemplate
for (const [uri, url] of Object.entries(writeMap)) {
  scss = scss.split(`url("${uri}")`).join(`url("${url}")`)
}

const header = '/* Auto-generated by scripts/gen-hot-icons.mjs — do not edit by hand.\n' +
               '   Regenerated on postinstall; rerun manually via `node scripts/gen-hot-icons.mjs`. */\n\n'

writeFileSync(SCSS_OUT, header + scss + '\n')

console.log(`hot-icons: wrote ${Object.keys(writeMap).length} SVGs + ${SCSS_OUT}`)