/**
 * Run one configured command hook through the `ctx.bash` executor seam and parse
 * its outcome into a {@link HookOutput}. This is where the wire protocol's
 * EXECUTION half lives: feed the hook its JSON payload on stdin, hand it the
 * dialect's env vars, honor its timeout, capture stdout/stderr/exit, and decode.
 *
 * It runs hooks through `ctx.bash` (not a bespoke `spawn`) deliberately — the
 * bash seam already provides the scrubbed-but-overridable env, process-group
 * kills, and timeout the protocol needs, and `dsh-bash`'s `stdin`/`env` fields
 * are the trusted-plugin surface (added for exactly this) that a hook bridge —
 * an in-process plugin, not model output — is allowed to use.
 *
 * @module @deepseek-ai/dsh-hook-protocol/runner
 */

import type { BashExecutor } from '@deepseek-ai/dsh-bash'
import { parseHookOutput } from './codec.ts'
import type { CommandHook, HookOutput } from './types.ts'

/** Everything a single hook invocation needs beyond its command line. */
export interface RunHookOptions {
  /** The JSON payload object written to the hook's stdin (the bridge builds it). */
  payload: unknown
  /** Extra env vars for the hook process (`CLAUDE_PROJECT_DIR`, …); the bridge builds these. */
  env?: Record<string, string>
  /** Working directory for the hook (defaults to the executor's own default when omitted). */
  cwd?: string
  /** Abort signal — cancels the hook run when fired (the parent step aborts). */
  signal?: AbortSignal
  /** Default timeout (ms) when the hook config sets none. */
  defaultTimeoutMs: number
  /** Whether to append a trailing newline to the stdin payload (CC yes, Codex no). */
  trailingNewline: boolean
  /**
   * The event this hook is firing for (e.g. `'PreToolUse'`). When set, a
   * structured `hookSpecificOutput` block whose `hookEventName` names a DIFFERENT
   * event is treated as malformed and its event-scoped fields are discarded (see
   * {@link parseHookOutput}). Omit it to apply any block as-is.
   */
  expectedEventName?: string
}

/** The {@link HookOutput} plus the wall-clock duration of the run (for `hook/result`). */
export interface RunHookResult {
  output: HookOutput
  durationMs: number
}

/**
 * Run `hook` via `bash` with `options.payload` serialized to its stdin, then
 * decode the result. `now` is injected (a monotonic-ms source) so the duration
 * is testable without a real clock. The hook's configured `timeoutSec` (wire
 * unit: seconds) overrides `defaultTimeoutMs`. The command runs with the
 * dialect's `env` merged after the executor's credential scrub (the trusted-
 * plugin path). NEVER throws: an infrastructure failure (the executor rejecting)
 * is surfaced as a {@link HookOutput} with `exitCode: undefined`, so the caller's
 * merge logic treats it as a non-blocking error rather than crashing the turn.
 */
export async function runHook(
  bash: BashExecutor,
  hook: CommandHook,
  options: RunHookOptions,
  now: () => number,
): Promise<RunHookResult> {
  const started = now()
  const timeoutMs = hook.timeoutSec !== undefined ? hook.timeoutSec * 1000 : options.defaultTimeoutMs
  const stdin = JSON.stringify(options.payload) + (options.trailingNewline ? '\n' : '')

  const request = {
    command: hook.command,
    timeoutMs,
    stdin,
    ...options.cwd !== undefined ? { workdir: options.cwd } : {},
    ...options.env !== undefined ? { env: options.env } : {},
    ...options.signal ? { signal: options.signal } : {},
  }

  try {
    const result = await bash.run(bash.resolve(request))
    // BashRunResult.exitCode is `number | null` (null = died by signal); the
    // protocol's exit-code contract is numeric, so a signal death maps to
    // `undefined` (a non-blocking error — no clean exit code to act on).
    const exitCode = result.exitCode ?? undefined
    return {
      output: parseHookOutput(exitCode, result.stdout.text, result.stderr.text, options.expectedEventName),
      durationMs: now() - started,
    }
  } catch (error: unknown) {
    // The executor rejects only on infrastructure faults (unusable workdir,
    // missing shell). A hook that cannot run is a non-blocking error: no exit
    // code, the failure on stderr for the record. The turn proceeds.
    const message = error instanceof Error ? error.message : String(error)
    return {
      output: parseHookOutput(undefined, '', message),
      durationMs: now() - started,
    }
  }
}