/**
 * App-attribution vocabulary for provider requests.
 *
 * Every product LLM adapter must identify the application on every provider
 * HTTP request (see the adapter contract on {@link ../index.ts LlmAdapter}):
 * a static, non-secret product identity, sent as the standard `User-Agent`.
 * Adapters obtain the headers from {@link attributionHeaders} instead of
 * hand-copying constants, so the identity cannot drift between
 * implementations. The policy and its rationale are pinned in
 * docs/rfc/implemented/architecture/2026-06-21-mandatory-app-attribution-headers.md.
 *
 * @module @deepseek-ai/dsh-llm/attribution
 */

import { createRequire } from 'node:module'

// The package's own manifest is the single source of the version so the
// User-Agent cannot drift from what is published (`./package.json` is an
// export of this package; the relative path resolves from both `src/` and
// the bundled `lib/`).
const { version } = createRequire(import.meta.url)('../package.json') as { version: string }

/**
 * Static public application identity sent to LLM providers.
 *
 * Every field is a public product fact, safe on every request: no secrets,
 * local paths, session ids, prompt text, or per-user identifiers belong here,
 * and nothing per-request may influence the values.
 */
export interface AppIdentity {
  /** `User-Agent` product token (lowercase, hyphenated). */
  product: string
  /** Product version; sourced from package metadata, never hand-copied. */
  version: string
  /** Public home URL of the app, used as the `User-Agent` comment. */
  url: string
}

/**
 * The harness's own identity: the default every adapter sends. Deployments
 * that need a white-label identity pass their own {@link AppIdentity} to
 * {@link attributionHeaders} — omission falls back to this default; nothing
 * can suppress attribution entirely.
 */
export const APP_IDENTITY: AppIdentity = {
  product: 'deepseek-harness',
  version,
  // FIXME: create the public deepseek-ai/deepseek-harness-sdk repository this
  // URL promises before the first release ships attribution pointing at it.
  url: 'https://github.com/deepseek-ai/deepseek-harness-sdk',
}

/**
 * The standard `User-Agent` value: `product/version (+url)`. The
 * parenthesized `+url` comment is the conventional self-identification form
 * (RFC 9110 §10.1.5 product + comment syntax).
 * @param identity - the identity to render; defaults to {@link APP_IDENTITY}.
 * @returns the ready-to-send header value.
 */
export function userAgent(identity: AppIdentity = APP_IDENTITY): string {
  return `${identity.product}/${identity.version} (+${identity.url})`
}

/**
 * Build the attribution headers an adapter must send on every provider
 * request. Header names are lowercase (HTTP field names are case-insensitive
 * on the wire).
 * @param identity - the identity to send; defaults to {@link APP_IDENTITY} — omission cannot suppress attribution.
 * @returns headers to merge into the provider request (currently just `user-agent`).
 */
export function attributionHeaders(
  identity: AppIdentity = APP_IDENTITY,
): Record<string, string> {
  return { 'user-agent': userAgent(identity) }
}
