import { TranscriptSequence } from "../../lib/transcript-sequence";
import { useTranscriptLiveStream } from "../../context/LiveUpdatesProvider";
import { usePageVisibility } from "../../lib/page-visibility";
import { liveRunEvent, mergeRunEvents } from "../../lib/live-run-event";
import { useCallback, useContext, useEffect, useMemo, useRef, useState } from "react";
import { QueryClientContext } from "@tanstack/react-query";
import type { HeartbeatRunEvent } from "@paperclipai/shared";
import type { TranscriptEntry } from "@/adapters";
import { heartbeatsApi } from "@/api/heartbeats";
import { nativeRunEventsToTranscript } from "./native-run-events";
import { readTranscriptRequest } from "./read-transcript-request";

const EVENT_PAGE_SIZE = 1_000;
const EVENT_POLL_INTERVAL_MS = 2_000;

interface SavedNativeHistory {
  events: HeartbeatRunEvent[];
  cursor: number;
}

const historyKey = (companyId: string, run: NativeRunTranscriptSource) =>
  ["native-run-transcript", companyId, run.id, Boolean(run.conversationOnly), run.status] as const;

export interface NativeRunTranscriptSource {
  id: string;
  status: string;
  conversationOnly?: boolean;
  runtimeMode?: "legacy" | "native";
}

export interface NativeRunTranscriptError {
  message: string;
  failedAt: string;
}

function isLive(status: string): boolean {
  return status === "queued" || status === "running";
}

export function useNativeRunTranscripts(runs: readonly NativeRunTranscriptSource[], options: { companyId?: string | null; enabled?: boolean } = {}) {
  const queryClient = useContext(QueryClientContext);
  const { visible } = usePageVisibility();
  const nativeRunsKey = runs
    .filter((run) => run.runtimeMode === "native")
    .map((run) => `${run.id}:${run.status}:${Boolean(run.conversationOnly)}`)
    .sort()
    .join(",");
  const nativeRuns = useMemo(
    () => runs.filter((run) => run.runtimeMode === "native").map((run) => ({ ...run })),
    // The key carries every field this hook consumes.
    // eslint-disable-next-line react-hooks/exhaustive-deps
    [nativeRunsKey],
  );
  const savedHistory = useMemo(() => {
    const saved = new Map<string, SavedNativeHistory>();
    if (queryClient && options.companyId && options.enabled !== false) {
      for (const run of nativeRuns) {
        if (isLive(run.status)) continue;
        const history = queryClient.getQueryData<SavedNativeHistory>(historyKey(options.companyId, run));
        if (history) saved.set(run.id, history);
      }
    }
    return saved;
  }, [queryClient, options.companyId, options.enabled, nativeRuns]);
  const [eventsByRun, setEventsByRun] = useState<Map<string, HeartbeatRunEvent[]>>(new Map());
  const persistedEventsByRunRef = useRef(new Map<string, HeartbeatRunEvent[]>());
  const [errorsByRun, setErrorsByRun] = useState<Map<string, NativeRunTranscriptError>>(new Map());
  const [hydratedRunIds, setHydratedRunIds] = useState<ReadonlySet<string>>(new Set());
  const [hydratedStatusByRun, setHydratedStatusByRun] = useState(new Map<string, string>());
  const [retryGeneration, setRetryGeneration] = useState(0);
  const retry = useCallback(() => setRetryGeneration((value) => value + 1), []);
  const projectionCacheRef = useRef(new Map<string, { events: HeartbeatRunEvent[]; transcript: TranscriptEntry[] }>());
  const cursorByRunRef = useRef(new Map<string, number>());
  const conversationOnlyByRunRef = useRef(new Map<string, boolean>());

  const sequencesRef = useRef(new Map<string, TranscriptSequence>());
  const sequence = (id: string) => {
    let value = sequencesRef.current.get(id);
    if (!value) { value = new TranscriptSequence(); sequencesRef.current.set(id, value); }
    return value;
  };
  const gapPendingRef = useRef(new Set<string>());
  const historyReadsRef = useRef(new Map<string, AbortSignal>());
  const interruptedReadsRef = useRef(new Set<string>());
  const refreshByRunRef = useRef(new Map<string, (force?: boolean) => void>());
  const previousCompanyRef = useRef(options.companyId);
  const refreshContextRef = useRef<readonly unknown[]>([]);
  useEffect(() => {
    if (previousCompanyRef.current === options.companyId) return;
    previousCompanyRef.current = options.companyId;
    setEventsByRun(new Map()); setErrorsByRun(new Map()); setHydratedRunIds(new Set()); setHydratedStatusByRun(new Map());
    projectionCacheRef.current.clear(); cursorByRunRef.current.clear(); conversationOnlyByRunRef.current.clear();
    persistedEventsByRunRef.current.clear();
    sequencesRef.current.clear(); gapPendingRef.current.clear(); interruptedReadsRef.current.clear();
  }, [options.companyId]);
  const stream = useTranscriptLiveStream(nativeRuns.filter(run => isLive(run.status)).map(run => run.id), options, event => {
    const runId = typeof event.payload.runId === "string" ? event.payload.runId : null;
    if (!runId || !nativeRuns.some(run => run.id === runId)) return;
    if (event.type === "heartbeat.run.status" && typeof event.payload.status === "string" && !isLive(event.payload.status)) {
      refreshByRunRef.current.get(runId)?.(true); return;
    }
    const row = liveRunEvent(event);
    if (!row) return;
    const cursor = sequence(runId);
    const envelope = row.payload?.prpEvent;
    const hasTranscriptBody = envelope !== null && typeof envelope === "object" && !Array.isArray(envelope);
    if (!hasTranscriptBody) cursor.requireHistory(row.seq);
    if (cursor.observe(row.seq) && !gapPendingRef.current.has(runId)) {
      gapPendingRef.current.add(runId);
      refreshByRunRef.current.get(runId)?.();
    }
    if (hasTranscriptBody) setEventsByRun(previous => new Map(previous).set(runId, mergeRunEvents(previous.get(runId) ?? [], [row])));
  });


  useEffect(() => {
    const context = [retryGeneration, visible, options.enabled, options.companyId, stream.healthy, stream.epoch];
    const refreshExisting = context.some((value, index) => value !== refreshContextRef.current[index]);
    refreshContextRef.current = context;
    if (!visible || options.enabled === false) return;
    const changedModes = new Set<string>();
    for (const run of nativeRuns) {
      const mode = Boolean(run.conversationOnly);
      if (conversationOnlyByRunRef.current.get(run.id) !== mode) {
        changedModes.add(run.id); cursorByRunRef.current.delete(run.id); sequencesRef.current.delete(run.id);
      }
      if (changedModes.has(run.id) || !persistedEventsByRunRef.current.has(run.id)) {
        persistedEventsByRunRef.current.set(run.id, savedHistory.get(run.id)?.events ?? []);
      }
      conversationOnlyByRunRef.current.set(run.id, mode);
    }
    let cancelled = false;
    const controller = new AbortController();
    const timers = new Map<string, number>();
    const pendingRefresh = new Set<string>();
    const retainedIds = new Set(nativeRuns.map((run) => run.id));
    for (const id of interruptedReadsRef.current) if (!retainedIds.has(id)) interruptedReadsRef.current.delete(id);
    const retainMap = <T,>(previous: Map<string, T>) => {
      const next = new Map([...previous].filter(([id]) => retainedIds.has(id)));
      return next.size === previous.size ? previous : next;
    };
    setEventsByRun(previous => {
      let next = retainMap(previous);
      for (const [id, saved] of savedHistory) {
        if (!next.has(id) || changedModes.has(id)) {
          if (next === previous) next = new Map(next);
          next.set(id, mergeRunEvents(saved.events, next.get(id) ?? []));
        }
      }
      return next;
    });
    setErrorsByRun(retainMap);
    setHydratedStatusByRun(retainMap);
    setHydratedRunIds((previous) => {
      const next = new Set([...previous].filter((id) => retainedIds.has(id)));
      return next.size === previous.size ? previous : next;
    });
    for (const id of cursorByRunRef.current.keys()) {
      if (!retainedIds.has(id)) {
        cursorByRunRef.current.delete(id); sequencesRef.current.delete(id); gapPendingRef.current.delete(id);
      }
    }
    for (const id of persistedEventsByRunRef.current.keys()) {
      if (!retainedIds.has(id)) persistedEventsByRunRef.current.delete(id);
    }

    const refreshRun = async (run: NativeRunTranscriptSource) => {
      if (cancelled || historyReadsRef.current.has(run.id)) return;
      pendingRefresh.delete(run.id);
      window.clearTimeout(timers.get(run.id));
      timers.delete(run.id);
      historyReadsRef.current.set(run.id, controller.signal);
      let failed = false;
      try {
        const saved = savedHistory.get(run.id);
        let cursor = cursorByRunRef.current.get(run.id) ?? saved?.cursor ?? 0;
        const observedBeforeRead = sequence(run.id).observed;
        const incoming: HeartbeatRunEvent[] = [];
        for (;;) {
          const page = await readTranscriptRequest(
            (signal) => (run.conversationOnly ? heartbeatsApi.conversationEvents : heartbeatsApi.events)(run.id, cursor, EVENT_PAGE_SIZE, { signal }),
            controller.signal,
          );
          if (cancelled) return;
          const last = page.at(-1);
          const nextCursor = last ? Math.max(cursor, last.seq) : cursor;
          incoming.push(...page.filter((event) => event.seq > cursor));
          if (page.length < EVENT_PAGE_SIZE || nextCursor === cursor) {
            cursor = nextCursor;
            break;
          }
          cursor = nextCursor;
        }
        // Commit this run's cursor with its rows. A slow sibling must neither
        // hold its readiness hostage nor stall live polling for this run.
        const coveredCursor = run.conversationOnly ? Math.max(cursor, observedBeforeRead) : cursor;
        cursorByRunRef.current.set(run.id, coveredCursor);
        sequence(run.id).confirm(coveredCursor);
        failed = sequence(run.id).needsCatchup;
        if (!failed) gapPendingRef.current.delete(run.id);
        if (incoming.length > 0) setEventsByRun((previous) => {
          const next = new Map(previous);
          next.set(run.id, mergeRunEvents(previous.get(run.id) ?? saved?.events ?? [], incoming));
          return next;
        });
        const previousEvents = persistedEventsByRunRef.current.get(run.id) ?? [];
        const persistedEvents = incoming.length ? mergeRunEvents(previousEvents, incoming) : previousEvents;
        persistedEventsByRunRef.current.set(run.id, persistedEvents);
        if (!failed && !isLive(run.status) && queryClient && options.companyId) {
          const key = historyKey(options.companyId, run);
          queryClient.setQueryData<SavedNativeHistory>(key, {
            events: persistedEvents,
            cursor: coveredCursor,
          });
        }
        setErrorsByRun((previous) => {
          if (!previous.has(run.id)) return previous;
          const next = new Map(previous);
          next.delete(run.id);
          return next;
        });
        interruptedReadsRef.current.delete(run.id);
        setHydratedStatusByRun((previous) => {
          if (previous.get(run.id) === run.status) return previous;
          return new Map(previous).set(run.id, run.status);
        });
      } catch (error) {
        if (cancelled) return;
        failed = true;
        setErrorsByRun((previous) => {
          if (previous.has(run.id)) return previous;
          const next = new Map(previous);
          next.set(run.id, {
            message: error instanceof Error ? error.message : "Native run activity could not be loaded",
            failedAt: new Date().toISOString(),
          });
          return next;
        });
      }
      if (historyReadsRef.current.get(run.id) === controller.signal) historyReadsRef.current.delete(run.id);
      if (cancelled) return;
      setHydratedRunIds((previous) => previous.has(run.id) ? previous : new Set([...previous, run.id]));
      if (pendingRefresh.has(run.id)) {
        void refreshRun(run);
      } else if ((isLive(run.status) && !stream.healthy) || failed) {
        const timer = window.setTimeout(() => {
          timers.delete(run.id);
          void refreshRun(run);
        }, EVENT_POLL_INTERVAL_MS);
        timers.set(run.id, timer);
      }
    };
    for (const run of nativeRuns) {
      refreshByRunRef.current.set(run.id, (force = false) => {
        if (force) pendingRefresh.add(run.id);
        void refreshRun(run);
      });
      if (refreshExisting || changedModes.has(run.id) || interruptedReadsRef.current.has(run.id) || isLive(run.status)
        || hydratedStatusByRun.get(run.id) !== run.status || errorsByRun.has(run.id) || sequence(run.id).needsCatchup) void refreshRun(run);
    }
    return () => {
      cancelled = true;
      refreshByRunRef.current.clear();
      controller.abort();
      for (const [id, signal] of historyReadsRef.current) if (signal === controller.signal) {
        interruptedReadsRef.current.add(id);
        historyReadsRef.current.delete(id);
      }
      for (const timer of timers.values()) window.clearTimeout(timer);
    };
  }, [nativeRuns, retryGeneration, visible, options.enabled, options.companyId, stream.healthy, stream.epoch, queryClient, savedHistory]);

  const transcriptByRun = useMemo(() => {
    const transcripts = new Map<string, TranscriptEntry[]>();
    for (const run of nativeRuns) {
      const events = eventsByRun.get(run.id) ?? savedHistory.get(run.id)?.events;
      if (!events) continue;
      let cached = projectionCacheRef.current.get(run.id);
      if (!cached || cached.events !== events) {
        cached = { events, transcript: nativeRunEventsToTranscript(events) };
        projectionCacheRef.current.set(run.id, cached);
      }
      transcripts.set(run.id, cached.transcript);
    }
    for (const id of projectionCacheRef.current.keys()) {
      if (!transcripts.has(id)) projectionCacheRef.current.delete(id);
    }
    return transcripts;
  }, [eventsByRun, nativeRuns, savedHistory]);

  const terminalHydratedRunIds = useMemo(() => new Set(nativeRuns
    .filter((run) => !isLive(run.status) && hydratedStatusByRun.get(run.id) === run.status)
    .map((run) => run.id)), [nativeRuns, hydratedStatusByRun]);

  const availableRunIds = useMemo(() => new Set([...savedHistory.keys(), ...hydratedRunIds]), [savedHistory, hydratedRunIds]);
  const availableTerminalRunIds = useMemo(() => new Set([...savedHistory.keys(), ...terminalHydratedRunIds]), [savedHistory, terminalHydratedRunIds]);
  return {
    transcriptByRun, errorsByRun, hydratedRunIds: availableRunIds, terminalHydratedRunIds: availableTerminalRunIds, retry,
    isInitialHydrating: nativeRuns.some((run) => !availableRunIds.has(run.id)),
  };
}