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/**
* Minimal GitHub REST client: JSON requests with 429/403 rate-limit
* backoff-retry and rate-limit surfacing, plus the
* `application/vnd.github.diff` text endpoint.
*
* The token travels only in the Authorization header of outgoing requests;
* request bodies, error messages, and returned values never contain it.
* @module dsh-github/github
*/
import type { Config } from './config.ts'
/** GitHub rate-limit facts, surfaced to the model on every read result. */
export interface RateLimitInfo {
remaining: number | null
/** Epoch ms when the window resets; null when the response omitted it. */
resetAt: number | null
}
/** Domain failure of one GitHub API request, token-free by construction. */
export class GithubError extends Error {
readonly status: number
readonly rateLimit: RateLimitInfo
constructor(status: number, message: string, rateLimit: RateLimitInfo) {
super(message)
this.name = 'GithubError'
this.status = status
this.rateLimit = rateLimit
}
}
/** Successful JSON response with its rate-limit facts. */
export interface GithubJsonResponse<T> {
status: number
data: T
rateLimit: RateLimitInfo
}
export interface GithubRequestOptions {
/** JSON body for writes. */
body?: unknown
/** Override the Accept header (e.g. the diff media type). */
accept?: string
signal?: AbortSignal
}
interface ClientOptions {
apiBaseUrl: string
maxRetries: number
retryBaseMs: number
retryMaxWaitMs: number
/** Hard per-request deadline; aborts the fetch when exceeded. */
requestTimeoutMs: number
fetchImpl: typeof fetch
}
const JSON_ACCEPT = 'application/vnd.github+json'
const API_VERSION = '2022-11-28'
const USER_AGENT = 'dsh-github'
/** Methods safe to retry on network failures and 5xx responses (reads only; writes stay idempotent). */
const SAFE_RETRY_METHODS = new Set(['GET', 'HEAD'])
function rateLimitFromHeaders(headers: Headers): RateLimitInfo {
const remaining = headers.get('x-ratelimit-remaining')
const reset = headers.get('x-ratelimit-reset')
const remainingNum = remaining === null ? null : Number(remaining)
const resetNum = reset === null ? null : Number(reset)
return {
remaining: remainingNum !== null && Number.isFinite(remainingNum) ? remainingNum : null,
resetAt: resetNum !== null && Number.isFinite(resetNum) ? resetNum * 1000 : null,
}
}
/** Retry delay for a 429 response: Retry-After seconds or reset-epoch, else backoff. */
function retryDelayMs(headers: Headers, attempt: number, options: ClientOptions): number {
const retryAfter = headers.get('retry-after')
if (retryAfter !== null) {
const seconds = Number(retryAfter)
if (Number.isFinite(seconds) && seconds >= 0) return Math.min(seconds * 1000, options.retryMaxWaitMs)
}
const reset = headers.get('x-ratelimit-reset')
if (reset !== null) {
const until = Number(reset) * 1000 - Date.now()
if (Number.isFinite(until) && until > 0) return Math.min(until, options.retryMaxWaitMs)
}
return Math.min(options.retryBaseMs * 2 ** attempt, options.retryMaxWaitMs)
}
/** Wait while still honoring the caller's abort signal. */
function sleep(ms: number, signal?: AbortSignal): Promise<void> {
return new Promise((resolve, reject) => {
const aborter: AbortSignal | null = signal ?? null
if (aborter?.aborted === true) {
reject(aborter.reason instanceof Error ? aborter.reason : new Error('aborted'))
return
}
const timer = setTimeout(done, ms)
aborter?.addEventListener('abort', onAbort, { once: true })
function done(): void {
aborter?.removeEventListener('abort', onAbort)
resolve()
}
function onAbort(): void {
clearTimeout(timer)
reject(aborter?.reason instanceof Error ? aborter.reason : new Error('aborted'))
}
})
}
/**
* Shared authenticated transport over the GitHub API. It owns the
* Authorization header, the per-request timeout, and the 429/403 rate-limit
* retry loop; the REST and GraphQL clients both delegate here, so they share
* one token, one timeout, and one backoff policy. Errors never contain the
* token.
*/
export class GithubTransport {
constructor(
private readonly token: string,
private readonly options: ClientOptions,
) {}
/** Fetch with Authorization, timeout, and retry (429/403 rate limits always; reads also on network errors and 5xx). */
async request(method: string, path: string, options: GithubRequestOptions): Promise<Response> {
let attempt = 0
for (;;) {
const timeoutSignal = AbortSignal.timeout(this.options.requestTimeoutMs)
const signal = options.signal === undefined ? timeoutSignal : AbortSignal.any([options.signal, timeoutSignal])
let response: Response
try {
response = await this.options.fetchImpl(new URL(path, this.options.apiBaseUrl), {
method,
headers: {
Authorization: `Bearer ${this.token}`,
Accept: options.accept ?? JSON_ACCEPT,
'X-GitHub-Api-Version': API_VERSION,
'User-Agent': USER_AGENT,
...options.body !== undefined ? { 'Content-Type': 'application/json' } : {},
},
...options.body !== undefined ? { body: JSON.stringify(options.body) } : {},
signal,
})
} catch (error) {
if (options.signal?.aborted) throw options.signal.reason instanceof Error ? options.signal.reason : new Error('aborted')
// A deadline exceeded or a transport failure is retryable for safe
// (read) methods only; a caller abort above always fails fast.
if (SAFE_RETRY_METHODS.has(method) && attempt < this.options.maxRetries) {
await sleep(Math.min(this.options.retryBaseMs * 2 ** attempt, this.options.retryMaxWaitMs), options.signal)
attempt += 1
continue
}
throw error
}
// Retry primary (429) and secondary (403 + Retry-After) rate limits for
// every method, plus transient 5xx responses for safe read methods; a
// 403 without Retry-After is a permission denial and must fail fast.
const retryable =
response.status === 429
|| (response.status === 403 && response.headers.get('retry-after') !== null)
|| (SAFE_RETRY_METHODS.has(method) && (response.status === 502 || response.status === 503 || response.status === 504))
if (!retryable || attempt >= this.options.maxRetries) return response
await sleep(retryDelayMs(response.headers, attempt, this.options), options.signal)
attempt += 1
}
}
}
/**
* Authenticated GitHub REST client: JSON/text requests with the shared
* transport's 429/403 backoff-retry and rate-limit surfacing.
*/
export class GithubClient {
private readonly transport: GithubTransport
constructor(token: string, options: ClientOptions) {
this.transport = new GithubTransport(token, options)
}
/** One JSON request with retry; `GithubError` on any non-2xx status. */
async requestJson<T>(method: string, path: string, options: GithubRequestOptions = {}): Promise<GithubJsonResponse<T>> {
const response = await this.transport.request(method, path, { ...options, accept: options.accept ?? JSON_ACCEPT })
const rateLimit = rateLimitFromHeaders(response.headers)
if (!response.ok) {
let message = `GitHub API ${response.status} for ${method} ${path}`
try {
const parsed = await response.json() as { message?: unknown }
if (typeof parsed.message === 'string' && parsed.message.length > 0) message = parsed.message
} catch {
// Non-JSON error body: keep the status-based message.
}
throw new GithubError(response.status, message, rateLimit)
}
if (response.status === 204) return { status: response.status, data: undefined as T, rateLimit }
const data = await response.json() as T
return { status: response.status, data, rateLimit }
}
/** One text request (the diff media type) with retry. */
async requestText(method: string, path: string, options: GithubRequestOptions = {}): Promise<{ text: string; rateLimit: RateLimitInfo }> {
const response = await this.transport.request(method, path, { ...options, accept: 'application/vnd.github.diff' })
const rateLimit = rateLimitFromHeaders(response.headers)
if (!response.ok) {
let message = `GitHub API ${response.status} for ${method} ${path}`
try {
const parsed = await response.json() as { message?: unknown }
if (typeof parsed.message === 'string' && parsed.message.length > 0) message = parsed.message
} catch {
// Non-JSON error body: keep the status-based message.
}
throw new GithubError(response.status, message, rateLimit)
}
return { text: await response.text(), rateLimit }
}
}
/** Successful GraphQL response with its rate-limit facts. */
export interface GithubGraphqlResponse<T> {
data: T
rateLimit: RateLimitInfo
}
/**
* Authenticated GitHub GraphQL client over the shared transport. One POST to
* `/graphql` carries a document; `query` sends a single document and `batch`
* merges several aliased sub-queries into one request, sharing the transport's
* token, timeout, and 429 backoff with the REST client.
*/
export class GithubGraphqlClient {
private readonly transport: GithubTransport
constructor(token: string, options: ClientOptions) {
this.transport = new GithubTransport(token, options)
}
/**
* Run one GraphQL document. A non-2xx response or a GraphQL `errors` payload
* fails loud as a {@link GithubError}; the token never appears in messages.
* @param document - the GraphQL query/mutation document.
* @param variables - optional variables.
* @param signal - optional abort signal.
* @returns the `data` plus rate-limit facts.
*/
async query<T>(document: string, variables: Record<string, unknown> = {}, signal?: AbortSignal): Promise<GithubGraphqlResponse<T>> {
const response = await this.transport.request('POST', '/graphql', { body: { query: document, variables }, accept: JSON_ACCEPT, signal })
const rateLimit = rateLimitFromHeaders(response.headers)
if (!response.ok) {
let message = `GitHub API ${response.status} for POST /graphql`
try {
const parsed = await response.json() as { message?: unknown }
if (typeof parsed.message === 'string' && parsed.message.length > 0) message = parsed.message
} catch {
// Non-JSON error body: keep the status-based message.
}
throw new GithubError(response.status, message, rateLimit)
}
const payload = await response.json() as { data?: T; errors?: Array<{ message?: unknown }> }
const firstError = payload.errors?.find(error => typeof error.message === 'string' && error.message.length > 0)?.message
if (typeof firstError === 'string') {
throw new GithubError(200, `GraphQL error: ${firstError}`, rateLimit)
}
if (payload.data === undefined || payload.data === null) {
throw new GithubError(200, 'GraphQL query returned no data', rateLimit)
}
return { data: payload.data, rateLimit }
}
/**
* Batch several sub-queries into ONE GraphQL request using aliases. Each
* value is a single top-level field selection (e.g.
* `repository(owner:"o", name:"r") { id }`); the document sent is
* `query { <alias>: <field> … }` and the result maps each alias to its data.
* @param aliases - `alias → top-level field selection`.
* @param variables - optional shared variables.
* @param signal - optional abort signal.
* @returns `{ <alias>: data, … }` plus rate-limit facts.
*/
async batch<T>(aliases: Record<string, string>, variables: Record<string, unknown> = {}, signal?: AbortSignal): Promise<GithubGraphqlResponse<Record<string, T>>> {
const fields = Object.entries(aliases).map(([alias, field]) => `${alias}: ${field}`).join('\n')
return this.query<Record<string, T>>(`query { ${fields} }`, variables, signal)
}
}
/** Build a client from config; resolves the base URL once. */
export function clientOptionsFromConfig(config: Config, fetchImpl?: typeof fetch): ClientOptions {
return {
apiBaseUrl: config.apiBaseUrl.replace(/\/+$/, ''),
maxRetries: config.maxRetries,
retryBaseMs: config.retryBaseMs,
retryMaxWaitMs: config.retryMaxWaitMs,
requestTimeoutMs: config.requestTimeoutMs,
fetchImpl: fetchImpl ?? globalThis.fetch.bind(globalThis),
}
}
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