import crypto from "node:crypto";

import { resolveUserTimezone } from "../../agents/date-time.js";
import { buildWorkspaceSkillSnapshot } from "../../agents/skills.js";
import { ensureSkillsWatcher, getSkillsSnapshotVersion } from "../../agents/skills/refresh.js";
import type { ClawdbotConfig } from "../../config/config.js";
import { type SessionEntry, updateSessionStore } from "../../config/sessions.js";
import { buildChannelSummary } from "../../infra/channel-summary.js";
import { getRemoteSkillEligibility } from "../../infra/skills-remote.js";
import { drainSystemEventEntries } from "../../infra/system-events.js";

export async function prependSystemEvents(params: {
  cfg: ClawdbotConfig;
  sessionKey: string;
  isMainSession: boolean;
  isNewSession: boolean;
  prefixedBodyBase: string;
}): Promise<string> {
  const compactSystemEvent = (line: string): string | null => {
    const trimmed = line.trim();
    if (!trimmed) return null;
    const lower = trimmed.toLowerCase();
    if (lower.includes("reason periodic")) return null;
    if (lower.includes("heartbeat")) return null;
    if (trimmed.startsWith("Node:")) {
      return trimmed.replace(/ · last input [^·]+/i, "").trim();
    }
    return trimmed;
  };

  const resolveExplicitTimezone = (value: string): string | undefined => {
    try {
      new Intl.DateTimeFormat("en-US", { timeZone: value }).format(new Date());
      return value;
    } catch {
      return undefined;
    }
  };

  const resolveSystemEventTimezone = (cfg: ClawdbotConfig) => {
    const raw = cfg.agents?.defaults?.envelopeTimezone?.trim();
    if (!raw) return { mode: "local" as const };
    const lowered = raw.toLowerCase();
    if (lowered === "utc" || lowered === "gmt") return { mode: "utc" as const };
    if (lowered === "local" || lowered === "host") return { mode: "local" as const };
    if (lowered === "user") {
      return {
        mode: "iana" as const,
        timeZone: resolveUserTimezone(cfg.agents?.defaults?.userTimezone),
      };
    }
    const explicit = resolveExplicitTimezone(raw);
    return explicit ? { mode: "iana" as const, timeZone: explicit } : { mode: "local" as const };
  };

  const formatUtcTimestamp = (date: Date): string => {
    const yyyy = String(date.getUTCFullYear()).padStart(4, "0");
    const mm = String(date.getUTCMonth() + 1).padStart(2, "0");
    const dd = String(date.getUTCDate()).padStart(2, "0");
    const hh = String(date.getUTCHours()).padStart(2, "0");
    const min = String(date.getUTCMinutes()).padStart(2, "0");
    const sec = String(date.getUTCSeconds()).padStart(2, "0");
    return `${yyyy}-${mm}-${dd}T${hh}:${min}:${sec}Z`;
  };

  const formatZonedTimestamp = (date: Date, timeZone?: string): string | undefined => {
    const parts = new Intl.DateTimeFormat("en-US", {
      timeZone,
      year: "numeric",
      month: "2-digit",
      day: "2-digit",
      hour: "2-digit",
      minute: "2-digit",
      second: "2-digit",
      hourCycle: "h23",
      timeZoneName: "short",
    }).formatToParts(date);
    const pick = (type: string) => parts.find((part) => part.type === type)?.value;
    const yyyy = pick("year");
    const mm = pick("month");
    const dd = pick("day");
    const hh = pick("hour");
    const min = pick("minute");
    const sec = pick("second");
    const tz = [...parts]
      .reverse()
      .find((part) => part.type === "timeZoneName")
      ?.value?.trim();
    if (!yyyy || !mm || !dd || !hh || !min || !sec) return undefined;
    return `${yyyy}-${mm}-${dd} ${hh}:${min}:${sec}${tz ? ` ${tz}` : ""}`;
  };

  const formatSystemEventTimestamp = (ts: number, cfg: ClawdbotConfig) => {
    const date = new Date(ts);
    if (Number.isNaN(date.getTime())) return "unknown-time";
    const zone = resolveSystemEventTimezone(cfg);
    if (zone.mode === "utc") return formatUtcTimestamp(date);
    if (zone.mode === "local") return formatZonedTimestamp(date) ?? "unknown-time";
    return formatZonedTimestamp(date, zone.timeZone) ?? "unknown-time";
  };

  const systemLines: string[] = [];
  const queued = drainSystemEventEntries(params.sessionKey);
  systemLines.push(
    ...queued
      .map((event) => {
        const compacted = compactSystemEvent(event.text);
        if (!compacted) return null;
        return `[${formatSystemEventTimestamp(event.ts, params.cfg)}] ${compacted}`;
      })
      .filter((v): v is string => Boolean(v)),
  );
  if (params.isMainSession && params.isNewSession) {
    const summary = await buildChannelSummary(params.cfg);
    if (summary.length > 0) systemLines.unshift(...summary);
  }
  if (systemLines.length === 0) return params.prefixedBodyBase;

  const block = systemLines.map((l) => `System: ${l}`).join("\n");
  return `${block}\n\n${params.prefixedBodyBase}`;
}

export async function ensureSkillSnapshot(params: {
  sessionEntry?: SessionEntry;
  sessionStore?: Record<string, SessionEntry>;
  sessionKey?: string;
  storePath?: string;
  sessionId?: string;
  isFirstTurnInSession: boolean;
  workspaceDir: string;
  cfg: ClawdbotConfig;
  /** If provided, only load skills with these names (for per-channel skill filtering) */
  skillFilter?: string[];
}): Promise<{
  sessionEntry?: SessionEntry;
  skillsSnapshot?: SessionEntry["skillsSnapshot"];
  systemSent: boolean;
}> {
  const {
    sessionEntry,
    sessionStore,
    sessionKey,
    storePath,
    sessionId,
    isFirstTurnInSession,
    workspaceDir,
    cfg,
    skillFilter,
  } = params;

  let nextEntry = sessionEntry;
  let systemSent = sessionEntry?.systemSent ?? false;
  const remoteEligibility = getRemoteSkillEligibility();
  const snapshotVersion = getSkillsSnapshotVersion(workspaceDir);
  ensureSkillsWatcher({ workspaceDir, config: cfg });
  const shouldRefreshSnapshot =
    snapshotVersion > 0 && (nextEntry?.skillsSnapshot?.version ?? 0) < snapshotVersion;

  if (isFirstTurnInSession && sessionStore && sessionKey) {
    const current = nextEntry ??
      sessionStore[sessionKey] ?? {
        sessionId: sessionId ?? crypto.randomUUID(),
        updatedAt: Date.now(),
      };
    const skillSnapshot =
      isFirstTurnInSession || !current.skillsSnapshot || shouldRefreshSnapshot
        ? buildWorkspaceSkillSnapshot(workspaceDir, {
            config: cfg,
            skillFilter,
            eligibility: { remote: remoteEligibility },
            snapshotVersion,
          })
        : current.skillsSnapshot;
    nextEntry = {
      ...current,
      sessionId: sessionId ?? current.sessionId ?? crypto.randomUUID(),
      updatedAt: Date.now(),
      systemSent: true,
      skillsSnapshot: skillSnapshot,
    };
    sessionStore[sessionKey] = { ...sessionStore[sessionKey], ...nextEntry };
    if (storePath) {
      await updateSessionStore(storePath, (store) => {
        store[sessionKey] = { ...store[sessionKey], ...nextEntry };
      });
    }
    systemSent = true;
  }

  const skillsSnapshot = shouldRefreshSnapshot
    ? buildWorkspaceSkillSnapshot(workspaceDir, {
        config: cfg,
        skillFilter,
        eligibility: { remote: remoteEligibility },
        snapshotVersion,
      })
    : (nextEntry?.skillsSnapshot ??
      (isFirstTurnInSession
        ? undefined
        : buildWorkspaceSkillSnapshot(workspaceDir, {
            config: cfg,
            skillFilter,
            eligibility: { remote: remoteEligibility },
            snapshotVersion,
          })));
  if (
    skillsSnapshot &&
    sessionStore &&
    sessionKey &&
    !isFirstTurnInSession &&
    (!nextEntry?.skillsSnapshot || shouldRefreshSnapshot)
  ) {
    const current = nextEntry ?? {
      sessionId: sessionId ?? crypto.randomUUID(),
      updatedAt: Date.now(),
    };
    nextEntry = {
      ...current,
      sessionId: sessionId ?? current.sessionId ?? crypto.randomUUID(),
      updatedAt: Date.now(),
      skillsSnapshot,
    };
    sessionStore[sessionKey] = { ...sessionStore[sessionKey], ...nextEntry };
    if (storePath) {
      await updateSessionStore(storePath, (store) => {
        store[sessionKey] = { ...store[sessionKey], ...nextEntry };
      });
    }
  }

  return { sessionEntry: nextEntry, skillsSnapshot, systemSent };
}

export async function incrementCompactionCount(params: {
  sessionEntry?: SessionEntry;
  sessionStore?: Record<string, SessionEntry>;
  sessionKey?: string;
  storePath?: string;
  now?: number;
  /** Token count after compaction - if provided, updates session token counts */
  tokensAfter?: number;
}): Promise<number | undefined> {
  const {
    sessionEntry,
    sessionStore,
    sessionKey,
    storePath,
    now = Date.now(),
    tokensAfter,
  } = params;
  if (!sessionStore || !sessionKey) return undefined;
  const entry = sessionStore[sessionKey] ?? sessionEntry;
  if (!entry) return undefined;
  const nextCount = (entry.compactionCount ?? 0) + 1;
  // Build update payload with compaction count and optionally updated token counts
  const updates: Partial<SessionEntry> = {
    compactionCount: nextCount,
    updatedAt: now,
  };
  // If tokensAfter is provided, update the cached token counts to reflect post-compaction state
  if (tokensAfter != null && tokensAfter > 0) {
    updates.totalTokens = tokensAfter;
    // Clear input/output breakdown since we only have the total estimate after compaction
    updates.inputTokens = undefined;
    updates.outputTokens = undefined;
  }
  sessionStore[sessionKey] = {
    ...entry,
    ...updates,
  };
  if (storePath) {
    await updateSessionStore(storePath, (store) => {
      store[sessionKey] = {
        ...store[sessionKey],
        ...updates,
      };
    });
  }
  return nextCount;
}