/**
 * Post-restart orphan recovery for subagent sessions.
 *
 * After a SIGUSR1 gateway reload aborts in-flight subagent LLM calls,
 * this module scans for orphaned sessions (those with `abortedLastRun: true`
 * that are still tracked as active in the subagent registry) and sends a
 * synthetic resume message to restart their work.
 *
 * @see https://github.com/openclaw/openclaw/issues/47711
 */

import crypto from "node:crypto";
import { loadConfig } from "../config/config.js";
import {
  loadSessionStore,
  resolveAgentIdFromSessionKey,
  resolveStorePath,
  updateSessionStore,
  type SessionEntry,
} from "../config/sessions.js";
import { callGateway } from "../gateway/call.js";
import { readSessionMessages } from "../gateway/session-utils.fs.js";
import { createSubsystemLogger } from "../logging/subsystem.js";
import { replaceSubagentRunAfterSteer } from "./subagent-registry-runtime.js";
import type { SubagentRunRecord } from "./subagent-registry.types.js";

const log = createSubsystemLogger("subagent-orphan-recovery");

/** Delay before attempting recovery to let the gateway finish bootstrapping. */
const DEFAULT_RECOVERY_DELAY_MS = 5_000;

/**
 * Build the resume message for an orphaned subagent.
 */
function buildResumeMessage(task: string, lastHumanMessage?: string): string {
  const maxTaskLen = 2000;
  const truncatedTask = task.length > maxTaskLen ? `${task.slice(0, maxTaskLen)}...` : task;

  let message =
    `[System] Your previous turn was interrupted by a gateway reload. ` +
    `Your original task was:\n\n${truncatedTask}\n\n`;

  if (lastHumanMessage) {
    message += `The last message from the user before the interruption was:\n\n${lastHumanMessage}\n\n`;
  }

  message += `Please continue where you left off.`;
  return message;
}

function extractMessageText(msg: unknown): string | undefined {
  if (!msg || typeof msg !== "object") {
    return undefined;
  }
  const m = msg as Record<string, unknown>;
  if (typeof m.content === "string") {
    return m.content;
  }
  if (Array.isArray(m.content)) {
    const text = m.content
      .filter(
        (c: unknown) =>
          typeof c === "object" &&
          c !== null &&
          (c as Record<string, unknown>).type === "text" &&
          typeof (c as Record<string, unknown>).text === "string",
      )
      .map((c: unknown) => (c as Record<string, string>).text)
      .filter(Boolean)
      .join("\n");
    return text || undefined;
  }
  return undefined;
}

/**
 * Send a resume message to an orphaned subagent session via the gateway agent method.
 */
async function resumeOrphanedSession(params: {
  sessionKey: string;
  task: string;
  lastHumanMessage?: string;
  configChangeHint?: string;
  originalRunId: string;
  originalRun: SubagentRunRecord;
}): Promise<boolean> {
  let resumeMessage = buildResumeMessage(params.task, params.lastHumanMessage);
  if (params.configChangeHint) {
    resumeMessage += params.configChangeHint;
  }

  try {
    const result = await callGateway<{ runId: string }>({
      method: "agent",
      params: {
        message: resumeMessage,
        sessionKey: params.sessionKey,
        idempotencyKey: crypto.randomUUID(),
        deliver: false,
        lane: "subagent",
      },
      timeoutMs: 10_000,
    });
    const remapped = replaceSubagentRunAfterSteer({
      previousRunId: params.originalRunId,
      nextRunId: result.runId,
      fallback: params.originalRun,
    });
    if (!remapped) {
      log.warn(
        `resumed orphaned session ${params.sessionKey} but remap failed (old run already removed); treating resume as accepted to avoid duplicate restarts`,
      );
      return true;
    }
    log.info(`resumed orphaned session: ${params.sessionKey}`);
    return true;
  } catch (err) {
    log.warn(`failed to resume orphaned session ${params.sessionKey}: ${String(err)}`);
    return false;
  }
}

/**
 * Scan for and resume orphaned subagent sessions after a gateway restart.
 *
 * An orphaned session is one where:
 * 1. It has an active (not ended) entry in the subagent run registry
 * 2. Its session store entry has `abortedLastRun: true`
 *
 * For each orphaned session found, we:
 * 1. Clear the `abortedLastRun` flag
 * 2. Send a synthetic resume message to trigger a new LLM turn
 */
export async function recoverOrphanedSubagentSessions(params: {
  getActiveRuns: () => Map<string, SubagentRunRecord>;
  /** Persisted across retries so already-resumed sessions are not resumed again. */
  resumedSessionKeys?: Set<string>;
}): Promise<{ recovered: number; failed: number; skipped: number }> {
  const result = { recovered: 0, failed: 0, skipped: 0 };
  const resumedSessionKeys = params.resumedSessionKeys ?? new Set<string>();
  const configChangePattern = /openclaw\.json|openclaw gateway restart|config\.patch/i;

  try {
    const activeRuns = params.getActiveRuns();
    if (activeRuns.size === 0) {
      return result;
    }

    const cfg = loadConfig();
    const storeCache = new Map<string, Record<string, SessionEntry>>();

    for (const [runId, runRecord] of activeRuns.entries()) {
      // Only consider runs that haven't ended yet
      if (typeof runRecord.endedAt === "number" && runRecord.endedAt > 0) {
        continue;
      }

      const childSessionKey = runRecord.childSessionKey?.trim();
      if (!childSessionKey) {
        continue;
      }
      if (resumedSessionKeys.has(childSessionKey)) {
        result.skipped++;
        continue;
      }

      try {
        const agentId = resolveAgentIdFromSessionKey(childSessionKey);
        const storePath = resolveStorePath(cfg.session?.store, { agentId });

        let store = storeCache.get(storePath);
        if (!store) {
          store = loadSessionStore(storePath);
          storeCache.set(storePath, store);
        }

        const entry = store[childSessionKey];
        if (!entry) {
          result.skipped++;
          continue;
        }

        // Check if this session was aborted by the restart
        if (!entry.abortedLastRun) {
          result.skipped++;
          continue;
        }

        log.info(`found orphaned subagent session: ${childSessionKey} (run=${runId})`);

        const messages = readSessionMessages(entry.sessionId, storePath, entry.sessionFile);
        const lastHumanMessage = [...messages]
          .toReversed()
          .find((msg) => (msg as { role?: unknown } | null)?.role === "user");
        const configChangeDetected = messages.some((msg) => {
          if ((msg as { role?: unknown } | null)?.role !== "assistant") {
            return false;
          }
          const text = extractMessageText(msg);
          return typeof text === "string" && configChangePattern.test(text);
        });

        // Resume the session with the original task context.
        // We intentionally do NOT clear abortedLastRun before attempting
        // the resume — if callGateway fails (e.g. gateway still booting),
        // the flag stays true so the next restart can retry.
        const resumed = await resumeOrphanedSession({
          sessionKey: childSessionKey,
          task: runRecord.task,
          lastHumanMessage: extractMessageText(lastHumanMessage),
          configChangeHint: configChangeDetected
            ? "\n\n[config changes from your previous run were already applied — do not re-modify openclaw.json or restart the gateway]"
            : undefined,
          originalRunId: runId,
          originalRun: runRecord,
        });

        if (resumed) {
          resumedSessionKeys.add(childSessionKey);
          // Only clear the aborted flag after confirmed successful resume.
          try {
            await updateSessionStore(storePath, (currentStore) => {
              const current = currentStore[childSessionKey];
              if (current) {
                current.abortedLastRun = false;
                current.updatedAt = Date.now();
                currentStore[childSessionKey] = current;
              }
            });
          } catch (err) {
            log.warn(
              `resume succeeded but failed to update session store for ${childSessionKey}: ${String(err)}`,
            );
          }
          result.recovered++;
        } else {
          // Flag stays as abortedLastRun=true so next restart can retry
          log.warn(
            `resume failed for ${childSessionKey}; abortedLastRun flag preserved for retry on next restart`,
          );
          result.failed++;
        }
      } catch (err) {
        log.warn(`error processing orphaned session ${childSessionKey}: ${String(err)}`);
        result.failed++;
      }
    }
  } catch (err) {
    log.warn(`orphan recovery scan failed: ${String(err)}`);
    // Ensure retry logic fires for scan-level exceptions.
    if (result.failed === 0) {
      result.failed = 1;
    }
  }

  if (result.recovered > 0 || result.failed > 0) {
    log.info(
      `orphan recovery complete: recovered=${result.recovered} failed=${result.failed} skipped=${result.skipped}`,
    );
  }

  return result;
}

/** Maximum number of retry attempts for orphan recovery. */
const MAX_RECOVERY_RETRIES = 3;
/** Backoff multiplier between retries (exponential). */
const RETRY_BACKOFF_MULTIPLIER = 2;

/**
 * Schedule orphan recovery after a delay, with retry logic.
 * The delay gives the gateway time to fully bootstrap after restart.
 * If recovery fails (e.g. gateway not yet ready), retries with exponential backoff.
 */
export function scheduleOrphanRecovery(params: {
  getActiveRuns: () => Map<string, SubagentRunRecord>;
  delayMs?: number;
  maxRetries?: number;
}): void {
  const initialDelay = params.delayMs ?? DEFAULT_RECOVERY_DELAY_MS;
  const maxRetries = params.maxRetries ?? MAX_RECOVERY_RETRIES;

  const resumedSessionKeys = new Set<string>();

  const attemptRecovery = (attempt: number, delay: number) => {
    setTimeout(() => {
      void recoverOrphanedSubagentSessions({ ...params, resumedSessionKeys })
        .then((result) => {
          if (result.failed > 0 && attempt < maxRetries) {
            const nextDelay = delay * RETRY_BACKOFF_MULTIPLIER;
            log.info(
              `orphan recovery had ${result.failed} failure(s); retrying in ${nextDelay}ms (attempt ${attempt + 1}/${maxRetries})`,
            );
            attemptRecovery(attempt + 1, nextDelay);
          }
        })
        .catch((err) => {
          if (attempt < maxRetries) {
            const nextDelay = delay * RETRY_BACKOFF_MULTIPLIER;
            log.warn(
              `scheduled orphan recovery failed: ${String(err)}; retrying in ${nextDelay}ms (attempt ${attempt + 1}/${maxRetries})`,
            );
            attemptRecovery(attempt + 1, nextDelay);
          } else {
            log.warn(
              `scheduled orphan recovery failed after ${maxRetries} retries: ${String(err)}`,
            );
          }
        });
    }, delay).unref?.();
  };

  attemptRecovery(0, initialDelay);
}
