/**
 * Package-asset format shared by the client build preset, the Host asset
 * route, and repository gates: the supported media types, the export that
 * publishes built assets, the content revision, and the document-relative
 * browser reference. Changing any value here changes a published URL or
 * package-manifest requirement, so the preset, the route, and the gates read
 * it from this one module.
 * @module @deepseek-ai/dsh-client-modules/src/assets
 */

import { createHash } from 'node:crypto'

/** Route segment between a package name and its asset path. */
export const PACKAGE_ASSET_SEGMENT = 'assets'

/** Media type served for each supported asset extension, keyed by the lowercase extension with its dot. */
export const PACKAGE_ASSET_MEDIA_TYPES: ReadonlyMap<string, string> = new Map([
  ['.svg', 'image/svg+xml'],
  ['.png', 'image/png'],
  ['.webp', 'image/webp'],
  ['.jpg', 'image/jpeg'],
  ['.jpeg', 'image/jpeg'],
])

/** Package export key that publishes built assets. */
export const PACKAGE_ASSET_EXPORT = './assets/*'

/** The only accepted target of {@link PACKAGE_ASSET_EXPORT}. */
export const PACKAGE_ASSET_EXPORT_TARGET = './lib/assets/*'

/** The `files` entry that publishes {@link PACKAGE_ASSET_EXPORT_TARGET}. */
export const PACKAGE_ASSET_FILES_ENTRY = 'lib/assets'

/** Hex digits kept from the content digest; the same length as client artifact revisions. */
const PACKAGE_ASSET_REVISION_LENGTH = 12

/**
 * Look up the media type of an asset path.
 * @param assetPath - file path or URL path; only its final extension is read, case-insensitively.
 * @returns the served media type, or undefined when the extension is unsupported.
 */
export function packageAssetMediaType(assetPath: string): string | undefined {
  const name = assetPath.slice(Math.max(assetPath.lastIndexOf('/'), assetPath.lastIndexOf('\\')) + 1)
  const dot = name.lastIndexOf('.')
  return dot <= 0 ? undefined : PACKAGE_ASSET_MEDIA_TYPES.get(name.slice(dot).toLowerCase())
}

/**
 * Compute the content revision of one built asset. The build writes it into
 * the emitted file name, so a URL names exactly one content and a rebuilt
 * asset gets a new URL.
 * @param bytes - exact bytes written under `lib/assets/`.
 * @returns the first 12 hexadecimal digits of the SHA-1 digest.
 */
export function packageAssetRevision(bytes: Uint8Array): string {
  return createHash('sha1').update(bytes).digest('hex').slice(0, PACKAGE_ASSET_REVISION_LENGTH)
}

/**
 * Name the emitted file of one asset by inserting its revision before the extension.
 * @param assetPath - `/`-separated path below `src/client/assets/`, such as `icons/whale@2x.png`.
 * @param rev - {@link packageAssetRevision} of the asset bytes.
 * @returns the path below `lib/assets/`, such as `icons/whale@2x-<rev>.png`.
 */
export function packageAssetRevisionedPath(assetPath: string, rev: string): string {
  const dot = assetPath.lastIndexOf('.')
  return dot > assetPath.lastIndexOf('/') + 1
    ? `${assetPath.slice(0, dot)}-${rev}${assetPath.slice(dot)}`
    : `${assetPath}-${rev}`
}

/**
 * Build the browser reference to one built asset. The reference is relative
 * to the shell document, like every other app-owned route, so it resolves
 * under any document mount and from injected `<style>` text.
 * @param packageName - owning package name, emitted verbatim; a scoped name keeps its `/`.
 * @param emittedPath - {@link packageAssetRevisionedPath} result below `lib/assets/`; each segment is
 *   percent-encoded, including `!`, `'`, `(`, `)`, and `*`, so the reference is also a valid unquoted CSS `url()`.
 * @returns `plugins/<packageName>/assets/<path>`.
 */
export function packageAssetReference(packageName: string, emittedPath: string): string {
  const path = emittedPath.split('/')
    .map(segment => encodeURIComponent(segment).replace(/[!'()*]/gu, char => `%${char.charCodeAt(0).toString(16).toUpperCase()}`))
    .join('/')
  return `plugins/${packageName}/${PACKAGE_ASSET_SEGMENT}/${path}`
}