import { createHash, randomUUID } from "node:crypto";
import { Type } from "typebox";
import {
  buildSessionContext,
  convertToLlm,
  estimateTokens,
  generateSummaryWithUsage,
  sessionEntryToContextMessages,
  truncateHead,
  DEFAULT_MAX_BYTES,
  DEFAULT_MAX_LINES,
  type ExtensionAPI,
  type ExtensionContext,
  type SessionEntry,
} from "@earendil-works/pi-coding-agent";
import { DEFAULT_CONFIG, loadConfig } from "./src/config.js";
import {
  applyContextEdits,
  planMasking,
  rebuildMaskedLedger,
  type MaskedLedgerEntry,
} from "./src/masking.js";
import { buildNativeCompactionTransport, isNativeCompactionModel } from "./src/native-provider.js";
import {
  buildCompactionRequestBody,
  buildReplacementHistory,
  buildToolPayload,
  callRemoteCompaction,
  findNativeCheckpoint,
  isJsonObject,
  mergeFeatureHeader,
  messagesToResponseItems,
  modelKey,
  NATIVE_COMPACTION_KIND,
  NATIVE_COMPACTION_VERSION,
  stripInputFromPayload,
  type JsonObject,
  type NativeCompactionDetails,
  type ResponseItem,
} from "./src/native-compaction.js";
import { contentText, SegmentIndex } from "./src/segment-index.js";
import {
  CompactionServiceRegistry,
  publishCompactionService,
  unpublishCompactionService,
} from "./src/service.js";
import { effectiveThreshold } from "./src/token-accounting.js";
import {
  COMPACTION_CUSTOM_TYPE,
  COMPACTION_VERSION,
  QUERY_TOOL_NAME,
  type MaskedResultRecord,
  type PiCompactionConfig,
  type ProjectionSnapshot,
} from "./src/types.js";

interface SessionRuntime {
  index: SegmentIndex;
  config: PiCompactionConfig;
  codexCache?: { fingerprint: string; modelKey: string; toolsHash: string; items: ResponseItem[] };
  masked: Map<string, MaskedLedgerEntry>;
  lastAutoCompactLeafId: string | null;
}

interface CachedPayload {
  modelKey: string;
  payload: JsonObject;
}

function errorMessage(error: unknown): string {
  return error instanceof Error ? error.message : String(error);
}

interface EnvironmentValue {
  hash: string;
  tokens: number;
  contextWindow: number;
}

interface EnvironmentCacheEntry extends EnvironmentValue {
  prompt: string;
  modelIdentity: string;
  activeNames: string[];
  tools: unknown[];
}

function hash(value: string): string {
  return createHash("sha256").update(value).digest("hex").slice(0, 20);
}

function environment(
  pi: ExtensionAPI,
  ctx: ExtensionContext,
  cache: Map<string, EnvironmentCacheEntry>,
): EnvironmentValue {
  const sessionId = ctx.sessionManager.getSessionId();
  const prompt = ctx.getSystemPrompt();
  const activeNames = pi.getActiveTools();
  const active = new Set(activeNames);
  const tools = pi.getAllTools().filter((tool) => active.has(tool.name));
  const contextWindow = ctx.model?.contextWindow ?? 0;
  const modelIdentity = ctx.model ? modelKey(ctx.model) : "none";
  const previous = cache.get(sessionId);
  if (
    previous
    && previous.prompt === prompt
    && previous.contextWindow === contextWindow
    && previous.modelIdentity === modelIdentity
    && previous.activeNames.length === activeNames.length
    && previous.activeNames.every((name, index) => name === activeNames[index])
    && previous.tools.length === tools.length
    && previous.tools.every((tool, index) => tool === tools[index])
  ) return previous;

  const serializedTools = JSON.stringify(tools.map((tool) => ({
    name: tool.name,
    description: tool.description,
    parameters: tool.parameters,
  })));
  const text = `${modelIdentity}\n${prompt}\n${serializedTools}`;
  const value: EnvironmentCacheEntry = {
    prompt,
    modelIdentity,
    activeNames: [...activeNames],
    tools,
    hash: hash(text),
    tokens: Math.ceil(text.length / 4),
    contextWindow,
  };
  cache.set(sessionId, value);
  return value;
}

function portableSummary(messages: readonly any[], maxChars = 24_000): string {
  const sections: string[] = ["Portable context checkpoint generated by pi-compaction."];
  for (const message of messages) {
    if (message?.role === "toolResult") {
      const text = Array.isArray(message.content)
        ? message.content.flatMap((part: any) => part?.type === "text" ? [part.text] : []).join("\n")
        : "";
      if (text) sections.push(`[Tool ${message.toolName ?? "unknown"}] ${text}`);
      continue;
    }
    if (message?.role === "user") {
      const text = typeof message.content === "string"
        ? message.content
        : Array.isArray(message.content)
          ? message.content.flatMap((part: any) => part?.type === "text" ? [part.text] : []).join("\n")
          : "";
      if (text) sections.push(`[User] ${text}`);
      continue;
    }
    if (message?.role === "assistant" && Array.isArray(message.content)) {
      const text = message.content.flatMap((part: any) => part?.type === "text" ? [part.text] : []).join("\n");
      if (text) sections.push(`[Assistant] ${text}`);
    }
  }
  const combined = sections.join("\n\n");
  if (combined.length <= maxChars) return combined;
  const head = Math.floor(maxChars * 0.35);
  const tail = maxChars - head - 32;
  return `${combined.slice(0, head)}\n\n… checkpoint truncated …\n\n${combined.slice(-tail)}`;
}

function asPortableMessage(summary: string): any {
  return {
    role: "user",
    content: [{ type: "text", text: summary }],
    timestamp: Date.now(),
  };
}

function setFeatureHeader(headers: Record<string, string | null>): void {
  const existing = Object.entries(headers).find(([name]) => name.toLowerCase() === "x-codex-beta-features");
  if (existing) headers[existing[0]] = mergeFeatureHeader(existing[1]);
  else headers["x-codex-beta-features"] = mergeFeatureHeader(undefined);
}

function cleanHeaders(headers: Record<string, string | null> | undefined): Record<string, string> | undefined {
  if (!headers) return undefined;
  return Object.fromEntries(Object.entries(headers).filter((entry): entry is [string, string] => typeof entry[1] === "string"));
}

function activeToolsHash(pi: ExtensionAPI): string {
  return hash(pi.getActiveTools().join("\0"));
}

export default function piCompactionExtension(pi: ExtensionAPI): void {
  const runtimes = new Map<string, SessionRuntime>();
  const payloads = new Map<string, CachedPayload>();
  const environments = new Map<string, EnvironmentCacheEntry>();
  const service = new CompactionServiceRegistry();
  publishCompactionService(service);

  const maskedRecords = (sessionId: string, ids: string[]): MaskedResultRecord[] => {
    const masked = runtimes.get(sessionId)?.masked;
    if (!masked) return [];
    return ids.flatMap((id) => {
      const entry = masked.get(id);
      return entry
        ? [{
          toolCallId: id,
          resultTimestamp: entry.resultTimestamp,
          deterministicSummary: entry.placeholder,
        }]
        : [];
    });
  };

  const runtimeFor = (ctx: ExtensionContext): SessionRuntime => {
    const sessionId = ctx.sessionManager.getSessionId();
    let runtime = runtimes.get(sessionId);
    if (!runtime) {
      runtime = {
        index: new SegmentIndex(sessionId),
        config: structuredClone(DEFAULT_CONFIG),
        masked: rebuildLedger(ctx),
        lastAutoCompactLeafId: null,
      };
      runtimes.set(sessionId, runtime);
      service.setSession(sessionId, (ids) => maskedRecords(sessionId, ids));
    }
    return runtime;
  };

  const ledgerStats = (runtime: SessionRuntime): { maskedResults: number; reclaimedTokens: number } => {
    let reclaimedTokens = 0;
    for (const entry of runtime.masked.values()) {
      reclaimedTokens += Math.max(0, entry.originalTokens - entry.placeholderTokens);
    }
    return { maskedResults: runtime.masked.size, reclaimedTokens };
  };

  const projectMessages = (
    ctx: ExtensionContext,
    runtime: SessionRuntime,
    messages: readonly any[],
  ): ProjectionSnapshot => {
    const env = environment(pi, ctx, environments);
    const stats = ledgerStats(runtime);
    const snapshot = runtime.index.project(messages, {
      environmentHash: env.hash,
      environmentTokens: env.tokens,
      contextWindow: env.contextWindow,
      maskedResults: stats.maskedResults,
      reclaimedTokens: stats.reclaimedTokens,
    });
    service.setSnapshot(snapshot);
    return snapshot;
  };

  const rebuildLedger = (ctx: ExtensionContext): Map<string, MaskedLedgerEntry> =>
    rebuildMaskedLedger(
      ctx.sessionManager.getBranch(),
      ctx.sessionManager.getLeafId(),
      (message) => estimateTokens(message as any),
    );

  const hydrateRuntime = (ctx: ExtensionContext, runtime: SessionRuntime): void => {
    runtime.index.hydrate();
    runtime.masked = rebuildLedger(ctx);
    runtime.lastAutoCompactLeafId = null;
    runtime.codexCache = undefined;
  };

  const branchMessages = (
    ctx: ExtensionContext,
    runtime: SessionRuntime,
    branch: SessionEntry[],
    excludeLastAssistantError = false,
  ): { snapshot: ProjectionSnapshot; checkpoint: ReturnType<typeof findNativeCheckpoint> } => {
    const checkpoint = findNativeCheckpoint(branch);
    let messages: any[];
    if (checkpoint.status === "valid") {
      // sessionEntryToContextMessages sees only raw entries; applyContextEdits
      // additionally replays the latest context_edit per target (omissions and
      // placeholder replacements included).
      messages = applyContextEdits(branch.slice(checkpoint.checkpoint.entryIndex + 1));
      if (checkpoint.checkpoint.details.modelKey !== (ctx.model ? modelKey(ctx.model) : "")) {
        messages = [asPortableMessage(checkpoint.checkpoint.details.portableSummary), ...messages];
      }
    } else {
      messages = buildSessionContext(branch).messages;
    }
    if (excludeLastAssistantError) {
      const index = messages.findLastIndex((message) => message.role === "assistant");
      if (index >= 0 && messages[index]?.stopReason === "error") messages = messages.toSpliced(index, 1);
    }
    return { snapshot: projectMessages(ctx, runtime, messages), checkpoint };
  };

  const codexInput = (
    piModel: any,
    runtime: SessionRuntime,
    snapshot: ProjectionSnapshot,
    checkpoint?: NativeCompactionDetails,
  ): ResponseItem[] => {
    const toolsHash = activeToolsHash(pi);
    const key = modelKey(piModel);
    const cached = runtime.codexCache;
    if (cached && cached.fingerprint === snapshot.fingerprint && cached.modelKey === key && cached.toolsHash === toolsHash) {
      return cached.items;
    }
    const tail = messagesToResponseItems(piModel, convertToLlm(snapshot.messages as any), pi.getAllTools());
    const items = checkpoint && checkpoint.modelKey === key
      ? [...structuredClone(checkpoint.replacementHistory), ...tail]
      : tail;
    runtime.codexCache = { fingerprint: snapshot.fingerprint, modelKey: key, toolsHash, items };
    snapshot.codexItems = items;
    return items;
  };

  pi.on("session_start", async (_event, ctx) => {
    publishCompactionService(service);
    const sessionId = ctx.sessionManager.getSessionId();
    const config = await loadConfig();
    const runtime = runtimes.get(sessionId) ?? {
      index: new SegmentIndex(sessionId),
      config,
      masked: new Map<string, MaskedLedgerEntry>(),
      lastAutoCompactLeafId: null,
    };
    runtime.config = config;
    runtime.index.hydrate();
    runtime.masked = rebuildLedger(ctx);
    runtime.lastAutoCompactLeafId = null;
    runtimes.set(sessionId, runtime);
    service.setSession(sessionId, (ids) => maskedRecords(sessionId, ids));
  });

  pi.on("session_shutdown", (_event, ctx) => {
    const sessionId = ctx.sessionManager.getSessionId();
    runtimes.delete(sessionId);
    payloads.delete(sessionId);
    environments.delete(sessionId);
    service.deleteSession(sessionId);
    if (runtimes.size === 0) unpublishCompactionService(service);
  });

  pi.on("session_tree", (_event, ctx) => {
    const runtime = runtimeFor(ctx);
    hydrateRuntime(ctx, runtime);
    service.clearSnapshot(ctx.sessionManager.getSessionId());
  });

  pi.on("session_compact", (_event, ctx) => {
    const runtime = runtimeFor(ctx);
    hydrateRuntime(ctx, runtime);
    service.clearSnapshot(ctx.sessionManager.getSessionId());
    payloads.delete(ctx.sessionManager.getSessionId());
  });

  pi.on("model_select", (_event, ctx) => {
    const sessionId = ctx.sessionManager.getSessionId();
    payloads.delete(sessionId);
    environments.delete(sessionId);
    const runtime = runtimes.get(sessionId);
    if (runtime) runtime.codexCache = undefined;
  });

  pi.on("turn_end", (event, ctx) => {
    const runtime = runtimeFor(ctx);
    if (!runtime.config.enabled) return undefined;

    const previous = runtime.index.getSnapshot();
    const usage = ctx.getContextUsage();
    if (usage?.tokens && previous) {
      const env = environment(pi, ctx, environments);
      runtime.index.recordUsage(
        usage.tokens,
        previous.messageEstimate + estimateTokens(event.message as any),
        env.hash,
      );
    }

    const currentTokens = usage?.tokens
      ?? (event.context?.contextMessages ?? []).reduce((sum, message) => sum + estimateTokens(message as any), 0)
        + environment(pi, ctx, environments).tokens;
    const plan = planMasking({
      contextEntries: event.context?.contextEntries ?? [],
      currentTokens,
      contextWindow: ctx.model?.contextWindow ?? 0,
      masking: runtime.config.masking,
      estimate: (message) => estimateTokens(message as any),
    });
    if (!plan.drafts.length) return undefined;
    for (const result of plan.masked) {
      runtime.masked.set(result.toolCallId, {
        placeholder: result.placeholder,
        originalTokens: result.originalTokens,
        placeholderTokens: result.placeholderTokens,
        resultTimestamp: result.resultTimestamp,
      });
    }
    return { entries: [...(event.entries ?? []), ...plan.drafts] };
  });

  pi.on("agent_settled", (_event, ctx) => {
    const runtime = runtimeFor(ctx);
    if (!runtime.config.enabled || ctx.isIdle?.() === false) return;
    const snapshot = runtime.index.getSnapshot();
    const tokens = ctx.getContextUsage()?.tokens ?? snapshot?.effectiveTokens;
    if (tokens == null) return;
    const contextWindow = ctx.model?.contextWindow ?? snapshot?.contextWindow ?? 0;
    const threshold = effectiveThreshold(
      runtime.config.summary.triggerTokens,
      runtime.config.summary.triggerRatio,
      contextWindow,
    );
    if (tokens < threshold) return;
    const leafId = ctx.sessionManager.getLeafId();
    if (leafId !== null && runtime.lastAutoCompactLeafId === leafId) return;
    runtime.lastAutoCompactLeafId = leafId;
    ctx.compact({
      onError: (error) => {
        if (ctx.hasUI) ctx.ui.notify(`pi-compaction auto summary failed: ${errorMessage(error)}`, "warning");
      },
    });
  });

  pi.on("context", (event, ctx) => {
    const runtime = runtimeFor(ctx);
    const branch = ctx.sessionManager.getBranch() as SessionEntry[];
    const checkpoint = findNativeCheckpoint(branch);
    if (checkpoint.status === "invalid") {
      ctx.abort();
      if (ctx.hasUI) ctx.ui.notify("pi-compaction checkpoint is malformed; request blocked.", "error");
      return { messages: [] };
    }
    if (checkpoint.status === "valid") {
      const projected = branchMessages(ctx, runtime, branch);
      return { messages: projected.snapshot.messages as any };
    }
    // Non-checkpoint path only refreshes the shared snapshot; the message list
    // is returned to Pi unchanged — masking is append-only via context_edit.
    projectMessages(ctx, runtime, event.messages);
    return undefined;
  });

  pi.on("before_provider_headers", (event, ctx) => {
    if (isNativeCompactionModel(ctx.model)) setFeatureHeader(event.headers);
  });

  pi.on("before_provider_request", (event, ctx) => {
    const model = ctx.model;
    if (!model || !isNativeCompactionModel(model) || !isJsonObject(event.payload)) return undefined;
    const runtime = runtimeFor(ctx);
    const sessionId = ctx.sessionManager.getSessionId();
    payloads.set(sessionId, { modelKey: modelKey(model), payload: stripInputFromPayload(event.payload) });
    const checkpoint = findNativeCheckpoint(ctx.sessionManager.getBranch() as SessionEntry[]);
    if (checkpoint.status !== "valid" || checkpoint.checkpoint.details.modelKey !== modelKey(model)) return undefined;
    const snapshot = runtime.index.getSnapshot();
    if (!snapshot) return undefined;
    const payload: JsonObject = {
      ...event.payload,
      input: codexInput(model, runtime, snapshot, checkpoint.checkpoint.details),
    };
    delete payload.messages;
    delete payload.previous_response_id;
    return payload;
  });

  pi.on("session_before_compact", async (event, ctx) => {
    const runtime = runtimeFor(ctx);
    if (!runtime.config.enabled) return undefined;
    const { snapshot, checkpoint } = branchMessages(
      ctx,
      runtime,
      event.branchEntries as SessionEntry[],
      event.reason === "overflow" && event.willRetry,
    );

    const model = ctx.model;
    if (!model) return undefined;
    if (!runtime.config.native.enabled || !isNativeCompactionModel(model)) {
      try {
        const auth = await ctx.modelRegistry.getApiKeyAndHeaders(model);
        if (!auth.ok) return undefined;
        const result = await generateSummaryWithUsage(
          snapshot.messages as any,
          model,
          16_384,
          auth.apiKey,
          cleanHeaders(auth.headers),
          event.signal,
          event.customInstructions,
          undefined,
          runtime.config.summary.thinking,
        );
        return {
          compaction: {
            summary: result.text,
            firstKeptEntryId: event.preparation.firstKeptEntryId,
            tokensBefore: snapshot.effectiveTokens,
            usage: result.usage,
            details: {
              kind: COMPACTION_CUSTOM_TYPE,
              version: COMPACTION_VERSION,
              checkpoint: "portable",
              sourceFingerprint: snapshot.fingerprint,
            },
          },
        };
      } catch (error) {
        if (!event.signal.aborted) console.error("pi-compaction: portable checkpoint failed:", error);
        return undefined;
      }
    }

    try {
      const auth = await ctx.modelRegistry.getApiKeyAndHeaders(model);
      if (!auth.ok) throw new Error(auth.error);
      const currentCheckpoint = checkpoint.status === "valid" ? checkpoint.checkpoint.details : undefined;
      const input = codexInput(model, runtime, snapshot, currentCheckpoint);
      const sessionId = ctx.sessionManager.getSessionId();
      const cached = payloads.get(sessionId);
      const body = buildCompactionRequestBody({
        basePayload: cached?.modelKey === modelKey(model) ? cached.payload : undefined,
        model,
        input,
        instructions: ctx.getSystemPrompt(),
        tools: buildToolPayload(pi.getAllTools(), pi.getActiveTools()),
        sessionId,
      });
      if (ctx.hasUI) ctx.ui.notify(`pi-compaction: creating ${model.provider} native checkpoint...`, "info");
      const remote = await callRemoteCompaction({
        ...buildNativeCompactionTransport({ model, apiKey: auth.apiKey, headers: cleanHeaders(auth.headers), sessionId }),
        body,
        signal: event.signal,
      });
      const details: NativeCompactionDetails = {
        kind: NATIVE_COMPACTION_KIND,
        version: NATIVE_COMPACTION_VERSION,
        checkpoint: "native",
        modelKey: modelKey(model),
        replacementHistory: buildReplacementHistory(
          input,
          remote.compactionItem,
          Math.min(64_000, Math.max(4_096, Math.floor(snapshot.contextWindow * 0.25))),
        ),
        portableSummary: portableSummary(snapshot.messages),
        sourceFingerprint: snapshot.fingerprint,
      };
      return {
        compaction: {
          summary: `Pi native checkpoint ${randomUUID()}`,
          firstKeptEntryId: event.preparation.firstKeptEntryId,
          tokensBefore: snapshot.effectiveTokens,
          usage: remote.usage,
          details,
        },
      };
    } catch (error) {
      if (!event.signal.aborted && ctx.hasUI) {
        ctx.ui.notify(`pi-compaction native checkpoint failed; falling back to Pi: ${errorMessage(error)}`, "warning");
      }
      return undefined;
    }
  });

  pi.on("session_before_tree", async (event, ctx) => {
    const model = ctx.model;
    if (!event.preparation.userWantsSummary || !model) return undefined;
    const runtime = runtimeFor(ctx);
    if (!runtime.config.enabled) return undefined;
    const messages = event.preparation.entriesToSummarize.flatMap((entry) => sessionEntryToContextMessages(entry));
    const snapshot = projectMessages(ctx, runtime, messages);
    try {
      const auth = await ctx.modelRegistry.getApiKeyAndHeaders(model);
      if (!auth.ok) return undefined;
      const result = await generateSummaryWithUsage(
        snapshot.messages as any,
        model,
        16_384,
        auth.apiKey,
        cleanHeaders(auth.headers),
        event.signal,
        event.preparation.customInstructions,
        undefined,
        runtime.config.summary.thinking,
        undefined,
        undefined,
        undefined,
        undefined,
      );
      return {
        summary: {
          summary: result.text,
          usage: result.usage,
          details: {
            kind: COMPACTION_CUSTOM_TYPE,
            version: COMPACTION_VERSION,
            checkpoint: "portable",
            sourceFingerprint: snapshot.fingerprint,
          },
        },
      };
    } catch (error) {
      if (!event.signal.aborted) console.error("pi-compaction: branch summary failed:", error);
      return undefined;
    }
  });

  pi.registerTool({
    name: QUERY_TOOL_NAME,
    label: "Query Compacted Tool History",
    description: "Recover the original output of a tool result that pi-compaction cleared from context, by tool call id.",
    promptSnippet: "Recover original tool output cleared from context",
    promptGuidelines: [
      "Use context_tree_query when you see a \"[pi-compaction] Earlier\" placeholder and still need the original tool output.",
    ],
    parameters: Type.Object({
      toolCallIds: Type.Array(Type.String(), { minItems: 1, maxItems: 20 }),
    }),
    async execute(_id, params, _signal, _update, ctx) {
      const branch = ctx.sessionManager.getBranch() as SessionEntry[];
      const calls = new Map<string, { toolName: string; args: unknown }>();
      const results = new Map<string, any>();
      for (const entry of branch) {
        const message = (entry as any)?.message;
        if ((entry as any)?.type !== "message" || !message) continue;
        if (message.role === "assistant" && Array.isArray(message.content)) {
          for (const block of message.content) {
            if (block?.type === "toolCall" && typeof block.id === "string") {
              calls.set(block.id, {
                toolName: String(block.name ?? "unknown"),
                args: block.arguments ?? block.input ?? block.args ?? {},
              });
            }
          }
        } else if (message.role === "toolResult" && typeof message.toolCallId === "string") {
          results.set(message.toolCallId, message);
        }
      }

      const found: string[] = [];
      const blocks: string[] = [];
      for (const id of params.toolCallIds) {
        const result = results.get(id);
        if (!result) continue;
        found.push(id);
        const call = calls.get(id) ?? { toolName: String(result.toolName ?? "unknown"), args: {} };
        const perResultBytes = Math.max(1_024, Math.floor(DEFAULT_MAX_BYTES / Math.max(1, params.toolCallIds.length)));
        const args = truncateHead(JSON.stringify(call.args ?? {}), { maxLines: 20, maxBytes: 2_048 }).content;
        const rawText = contentText(result.content);
        const truncated = truncateHead(rawText, {
          maxLines: Math.max(20, Math.floor(DEFAULT_MAX_LINES / Math.max(1, params.toolCallIds.length))),
          maxBytes: perResultBytes,
        });
        blocks.push([
          `## ${id}`,
          `Tool: ${call.toolName}`,
          `Args: ${args}`,
          `Status: ${result.isError ? "ERROR" : "OK"}`,
          "",
          truncated.content,
          ...(truncated.truncated ? [`[truncated: ${truncated.outputLines}/${truncated.totalLines} lines]`] : []),
        ].join("\n"));
      }
      const missing = params.toolCallIds.filter((id: string) => !results.has(id));
      for (const id of missing) blocks.push(`## ${id}\n(not found)`);
      return {
        content: [{ type: "text", text: blocks.join("\n\n---\n\n") }],
        details: { toolCallIds: found, missing },
      };
    },
  });

  pi.registerCommand("compaction-status", {
    description: "Show effective/raw context usage and pi-compaction state",
    handler: async (_args, ctx) => {
      const metrics = service.getMetrics(ctx.sessionManager.getSessionId());
      const text = metrics
        ? [
            `Effective: ${metrics.effectiveTokens}/${metrics.contextWindow} (${metrics.percent.toFixed(1)}%, ${metrics.confidence})`,
            `Raw: ${metrics.rawTokens}/${metrics.contextWindow}`,
            `Reclaimed: ${metrics.reclaimedTokens}`,
            `Segments: ${metrics.segmentCount}; masked tool results: ${metrics.maskedResults}; generation: ${metrics.generation}`,
          ].join("\n")
        : "pi-compaction has no projection snapshot yet.";
      if (ctx.hasUI) ctx.ui.notify(text, "info");
      else process.stderr.write(`${text}\n`);
    },
  });
}