/**
 * Overlay HTTP proxy variables onto the source `dsh` Node process only.
 * Bootstrap proxy names cannot come from `.env` files; this overlay is the
 * checkout-local way to give OpenRouter (and other HTTPS fetches) an HTTP
 * proxy without changing the calling shell.
 * @module
 */

import { existsSync, readFileSync } from 'node:fs'
import { fileURLToPath } from 'node:url'

/** Repo-root file the source launcher reads when present; gitignored. */
export const SOURCE_DSH_HTTP_PROXY_FILE = '.dsh-http-proxy.env'

/** Process variables Node, undici, and pi-ai consult for HTTP(S) proxies. */
export const SOURCE_DSH_PROXY_VAR_NAMES = [
  'HTTPS_PROXY',
  'HTTP_PROXY',
  'ALL_PROXY',
  'https_proxy',
  'http_proxy',
  'all_proxy',
] as const

const PROXY_VAR_NAME_SET = new Set<string>(SOURCE_DSH_PROXY_VAR_NAMES)

const LOCAL_NO_PROXY = 'localhost,127.0.0.1,::1'

/**
 * Write one HTTP(S) proxy URL onto every name Node and pi-ai read, including
 * leftover inherited SOCKS values the overlay file did not mention.
 */
function installHttpProxy(env: NodeJS.ProcessEnv, url: string): void {
  for (const name of SOURCE_DSH_PROXY_VAR_NAMES) {
    env[name] = url
  }
  env.NODE_USE_ENV_PROXY = '1'
  if (!env.NO_PROXY && !env.no_proxy) {
    env.NO_PROXY = LOCAL_NO_PROXY
    env.no_proxy = LOCAL_NO_PROXY
  }
}

/**
 * First non-SOCKS proxy URL among the names Node consults.
 * @param env - environment after overlay assignments.
 */
function firstHttpProxyUrl(env: NodeJS.ProcessEnv): string | undefined {
  for (const name of SOURCE_DSH_PROXY_VAR_NAMES) {
    const value = env[name]?.trim()
    if (value !== undefined && value !== '' && !isSocksProxyUrl(value)) return value
  }
  return undefined
}

/**
 * Set on the child after this wrapper respawns so `fetch` sees the HTTP overlay
 * at process start. Node `--env-file` does not replace an inherited SOCKS
 * `HTTPS_PROXY`, and `NODE_USE_ENV_PROXY` assigned after start is ignored.
 */
export const SOURCE_DSH_PROXY_REEXEC_MARKER = 'DSH_SOURCE_HTTP_PROXY_APPLIED'

/** @returns whether `value` is a SOCKS URL Node cannot use for fetch/pnpm. */
export function isSocksProxyUrl(value: string): boolean {
  return /^socks5h?:\/\//i.test(value.trim())
}

/**
 * Parse a dotenv-like overlay file into assignments.
 * @param text - file contents.
 * @returns name → value; empty lines and `#` comments are skipped.
 */
export function parseSourceDshHttpProxyFile(text: string): Record<string, string> {
  const out: Record<string, string> = {}
  for (const raw of text.split(/\r?\n/)) {
    const line = raw.trim()
    if (line === '' || line.startsWith('#')) continue
    const body = line.startsWith('export ') ? line.slice('export '.length).trim() : line
    const eq = body.indexOf('=')
    if (eq <= 0) continue
    const name = body.slice(0, eq).trim()
    let value = body.slice(eq + 1).trim()
    if (
      (value.startsWith('"') && value.endsWith('"'))
      || (value.startsWith("'") && value.endsWith("'"))
    ) {
      value = value.slice(1, -1)
    }
    if (name !== '') out[name] = value
  }
  return out
}

/**
 * Inputs for {@link applySourceDshHttpProxy}. Tests pass a fake env and file text.
 */
export interface ApplySourceDshHttpProxyInput {
  /** Mutable environment of this Node process (normally `process.env`). */
  env: NodeJS.ProcessEnv
  /** Contents of `.dsh-http-proxy.env`; `null` when the file is absent. */
  fileText: string | null
  /** Optional explicit HTTP overlay URL (`DSH_HTTP_PROXY`), which outranks the file. */
  overlayUrl?: string | undefined
}

/**
 * Apply an HTTP proxy overlay onto `env` for this process only.
 * @param input - env, optional file, optional `DSH_HTTP_PROXY`.
 * @throws when the winning overlay is a SOCKS URL.
 */
export function applySourceDshHttpProxy(input: ApplySourceDshHttpProxyInput): void {
  const overlayUrl = input.overlayUrl?.trim()
  if (overlayUrl) {
    if (isSocksProxyUrl(overlayUrl)) {
      throw new Error(
        `DSH_HTTP_PROXY=${overlayUrl}. Node cannot fetch through SOCKS. Use an HTTP proxy (for example http://127.0.0.1:3067).`,
      )
    }
    installHttpProxy(input.env, overlayUrl)
    return
  }
  if (input.fileText === null) return
  const assignments = parseSourceDshHttpProxyFile(input.fileText)
  for (const [name, value] of Object.entries(assignments)) {
    if (PROXY_VAR_NAME_SET.has(name) && isSocksProxyUrl(value)) {
      throw new Error(
        `${name}=${value}. Node cannot fetch through SOCKS. Use an HTTP proxy (for example http://127.0.0.1:3067).`,
      )
    }
    input.env[name] = value
  }
  const httpUrl = firstHttpProxyUrl(input.env)
  if (httpUrl !== undefined) installHttpProxy(input.env, httpUrl)
}

/**
 * HTTP overlay URL now on `env`, if any.
 * @param env - environment after {@link applySourceDshHttpProxy}.
 */
export function sourceDshAppliedHttpProxyUrl(env: NodeJS.ProcessEnv): string | undefined {
  return firstHttpProxyUrl(env)
}

/** Absolute path of the gitignored overlay file beside this repository root. */
export function sourceDshHttpProxyFilePath(): string {
  return fileURLToPath(new URL(`../${SOURCE_DSH_HTTP_PROXY_FILE}`, import.meta.url))
}

/**
 * Read the overlay file when it exists.
 * @param path - absolute path; defaults to the repo-root gitignored file.
 * @returns file text, or `null` when absent.
 */
export function readSourceDshHttpProxyFile(path = sourceDshHttpProxyFilePath()): string | null {
  if (!existsSync(path)) return null
  return readFileSync(path, 'utf8')
}

/**
 * Whether an overlay source is present (file or `DSH_HTTP_PROXY`).
 * @param overlayUrl - `DSH_HTTP_PROXY` value.
 * @param fileText - overlay file contents, or `null` when absent.
 */
export function sourceDshHttpProxyOverlayPresent(overlayUrl: string | undefined, fileText: string | null): boolean {
  return Boolean(overlayUrl?.trim()) || fileText !== null
}

/**
 * Whether this process must respawn so `fetch` binds the overlay at start.
 * @param env - the environment after {@link applySourceDshHttpProxy}.
 * @param overlayPresent - {@link sourceDshHttpProxyOverlayPresent}.
 */
export function shouldReexecSourceDshForFetchProxy(env: NodeJS.ProcessEnv, overlayPresent: boolean): boolean {
  return overlayPresent && env[SOURCE_DSH_PROXY_REEXEC_MARKER] !== '1'
}