/**
 * Rebuild the inlined running-status icon.
 *
 * Downloads the source animation (once), compresses it with ffmpeg to the
 * footprint the Chat running status paints, and regenerates
 * `src/client/icon-data.ts` as a base64 data URL — the browser half cannot
 * reference a package file, so the icon travels inside the client bundle.
 *
 * Requires ffmpeg on PATH. Usage: `pnpm icon:build`.
 */
import { execFileSync } from 'node:child_process'
import { existsSync, mkdirSync, readFileSync, writeFileSync } from 'node:fs'
import { dirname, join } from 'node:path'
import { fileURLToPath } from 'node:url'

/** Original animation, kept out of the bundle at 1.3 MiB. */
const SOURCE_URL =
  'https://i0.hdslb.com/bfs/new_dyn/a5a0a0adb386867b3f5db5713576f9f5107716290.gif'

/**
 * 64px covers the 32px painted icon at 2x; 128 colours hold the flat cartoon
 * fills; the source's 10fps is already the animation's own timing.
 */
const FILTER =
  'fps=10,scale=64:64:flags=lanczos,split[a][b];'
  + '[a]palettegen=max_colors=128:stats_mode=diff[p];'
  + '[b][p]paletteuse=dither=bayer:bayer_scale=3:diff_mode=rectangle'

const root = join(dirname(fileURLToPath(import.meta.url)), '..')
const assetsDir = join(root, 'assets')
const sourcePath = join(assetsDir, 'prts-neuron.source.gif')
const iconPath = join(assetsDir, 'prts-neuron.gif')
const modulePath = join(root, 'src', 'client', 'icon-data.ts')

mkdirSync(assetsDir, { recursive: true })
if (!existsSync(sourcePath)) {
  const response = await fetch(SOURCE_URL)
  if (!response.ok) throw new Error(`icon source download failed: ${response.status}`)
  writeFileSync(sourcePath, Buffer.from(await response.arrayBuffer()))
}
execFileSync('ffmpeg', ['-y', '-v', 'error', '-i', sourcePath, '-vf', FILTER, '-loop', '0', iconPath])

const base64 = readFileSync(iconPath).toString('base64')
const dataUrl = `data:image/gif;base64,${base64}`
const chunks = dataUrl.match(/.{1,100}/g) ?? []
const literal = chunks.map((chunk, index) => `${index === 0 ? "  '" : "  + '"}${chunk}'`).join('\n')
writeFileSync(modulePath, `/**
 * The running-status icon, inlined as a data URL.
 *
 * Generated by \`pnpm icon:build\` from \`assets/prts-neuron.gif\` — do not edit by
 * hand. The browser half can neither reach a package file nor rely on the
 * hotlink-protected source image, so the compressed animation ships inside the
 * client bundle: 64x64, 128 colours, 10fps, ~44 KiB of GIF, ~1.3% of the
 * original download.
 */
export const ICON_DATA_URL =
${literal}
`)
console.log(`icon: ${(dataUrl.length / 1024).toFixed(1)} KiB data URL -> ${modulePath}`)