/**
 * Main extension entrypoint.
 *
 * Wires together request patching, remote compaction, runtime state
 * reconstruction, session lifecycle cleanup, and Pi-native HTTP request patching.
 */
import type { ExtensionAPI } from "@earendil-works/pi-coding-agent";
import type { AgentMessage } from "@earendil-works/pi-agent-core";
import { isRecord, loadConfig } from "./config.ts";
import {
  applyRemoteHistoryPayloadPatch,
  extractResponsesReasoningConfig,
  extractResponsesTextConfig,
  isOpenAICodexResponsesModel,
  looksLikeResponsesPayload,
  messageMatchesModel,
  modelKey,
  supportsRemoteCompactionModel,
  thinkingLevelToResponsesReasoning,
} from "./openai.ts";
import {
  buildCompactionSummaryText,
  buildRemoteCompactionDetails,
  buildToolsPayload,
  callRemoteCompactionEndpoint,
  generateBestEffortLocalSummary,
  messageToResponseItems,
  messagesToResponseItems,
  normalizeResponseItemsForPrompt,
  reconstructRemoteCompactionStateFromBranch,
} from "./remote-compaction.ts";
import {
  clearAllRuntimeState,
  clearRemoteCompactionState,
  clearResponsesRequestShapeState,
  getRemoteCompactionState,
  getResponsesRequestShapeState,
  setRemoteCompactionState,
  setResponsesRequestShapeState,
} from "./state.ts";

type TargetModel = Parameters<typeof modelKey>[0];

type BranchEntry = {
  type: string;
  id: string;
  details?: unknown;
  message?: unknown;
  thinkingLevel?: unknown;
};

type SessionContextLike = {
  sessionManager: {
    getSessionId(): string;
    getBranch(): BranchEntry[];
  };
};

function getSessionId(ctx: SessionContextLike): string {
  return ctx.sessionManager.getSessionId();
}

function getBranchMessages(branchEntries: BranchEntry[]): AgentMessage[] {
  return branchEntries.flatMap((entry) =>
    entry.type === "message" && entry.message ? [entry.message as AgentMessage] : [],
  );
}

function getBranchThinkingLevel(branchEntries: BranchEntry[]): string | undefined {
  for (let index = branchEntries.length - 1; index >= 0; index--) {
    const entry = branchEntries[index];
    if (entry?.type !== "thinking_level_change") continue;
    return typeof entry.thinkingLevel === "string" ? entry.thinkingLevel : undefined;
  }
  return undefined;
}

function clearSessionRuntimeState(sessionId: string | undefined): void {
  clearRemoteCompactionState(sessionId);
  clearResponsesRequestShapeState(sessionId);
}

function syncRemoteState(ctx: SessionContextLike): void {
  const sessionId = getSessionId(ctx);
  const branchEntries = ctx.sessionManager.getBranch() as Array<{
    type: string;
    id: string;
    details?: unknown;
    message?: AgentMessage;
  }>;
  const state = reconstructRemoteCompactionStateFromBranch({ branchEntries });
  if (state) {
    setRemoteCompactionState(sessionId, state);
  } else {
    clearRemoteCompactionState(sessionId);
  }
}

function getMatchingRemoteState(
  sessionId: string,
  model: TargetModel | undefined,
): ReturnType<typeof getRemoteCompactionState> {
  if (!model) return undefined;
  const remoteState = getRemoteCompactionState(sessionId);
  return remoteState && remoteState.modelKey === modelKey(model) ? remoteState : undefined;
}

function extendRemoteHistoryIfCompatible(params: {
  sessionId: string;
  model: TargetModel | undefined;
  message: AgentMessage;
}): void {
  const remoteState = getMatchingRemoteState(params.sessionId, params.model);
  if (!remoteState || !params.model) return;
  if (params.message.role === "assistant" && !messageMatchesModel(params.message, params.model)) {
    return;
  }

  const items = messageToResponseItems(params.message);
  if (items.length === 0) return;

  setRemoteCompactionState(params.sessionId, {
    ...remoteState,
    explicitHistory: [...remoteState.explicitHistory, ...items],
  });
}

function maybeNotifyRequestFeatures(params: {
  notifiedModels: Set<string>;
  hasUI: boolean;
  notify: boolean;
  ui: { notify(message: string, level: "info" | "warning"): void };
  model: TargetModel;
  features: string[];
}): void {
  if (!params.notify || !params.hasUI || params.features.length === 0) return;

  const key = `${String(params.model.provider)}/${String(params.model.id)}`;
  const noticeKey = `${key}:${params.features.join(",")}`;
  if (params.notifiedModels.has(noticeKey)) return;

  params.notifiedModels.add(noticeKey);
  params.ui.notify(`OpenAI compaction active for ${key} (${params.features.join(", ")})`, "info");
}

export default function openaiServerCompactionExtension(pi: ExtensionAPI) {
  const notifiedModels = new Set<string>();

  pi.on("session_start", (_event, ctx) => {
    const sessionId = getSessionId(ctx);
    clearResponsesRequestShapeState(sessionId);
    syncRemoteState(ctx);
  });

  const clearBeforeSessionChange = (_event: unknown, ctx: SessionContextLike): void => {
    clearSessionRuntimeState(getSessionId(ctx));
  };
  pi.on("session_before_switch", clearBeforeSessionChange);
  pi.on("session_before_fork", clearBeforeSessionChange);
  pi.on("session_before_tree", clearBeforeSessionChange);

  const syncAfterSessionChange = (_event: unknown, ctx: SessionContextLike): void => {
    syncRemoteState(ctx);
  };
  pi.on("session_tree", syncAfterSessionChange);
  pi.on("session_compact", syncAfterSessionChange);

  pi.on("model_select", (_event, ctx) => {
    clearResponsesRequestShapeState(getSessionId(ctx));
  });

  pi.on("session_shutdown", () => {
    clearAllRuntimeState();
  });

  pi.on("session_before_compact", async (event, ctx) => {
    const cfg = loadConfig(ctx.cwd);
    const model = ctx.model;
    if (!cfg.enabled || !model || !supportsRemoteCompactionModel(model)) return undefined;

    const auth = await ctx.modelRegistry.getApiKeyAndHeaders(model);
    if (!auth.ok || !auth.apiKey) return undefined;

    const tools = buildToolsPayload(pi.getAllTools(), pi.getActiveTools());
    const sessionId = getSessionId(ctx);
    const branchEntries = event.branchEntries as BranchEntry[];
    const remoteState = getMatchingRemoteState(sessionId, model);
    const observedRequestShape = getResponsesRequestShapeState(sessionId);
    const fullBranchMessages = getBranchMessages(branchEntries);
    const responseItems = remoteState
      ? remoteState.explicitHistory
      : messagesToResponseItems(fullBranchMessages);
    const promptResponseItems = normalizeResponseItemsForPrompt(responseItems, model);
    const thinkingLevel = pi.getThinkingLevel();
    const fallbackReasoning = model.reasoning
      ? thinkingLevelToResponsesReasoning(thinkingLevel ?? getBranchThinkingLevel(branchEntries))
      : undefined;
    const reasoning = observedRequestShape?.reasoning ?? fallbackReasoning;
    const text = observedRequestShape?.text;

    const [localResult, remoteResult] = await Promise.allSettled([
      generateBestEffortLocalSummary({
        preparation: event.preparation,
        messages: fullBranchMessages,
        model,
        apiKey: auth.apiKey,
        headers: auth.headers,
        customInstructions: event.customInstructions,
        signal: event.signal,
        thinkingLevel,
        firstKeptEntryId: event.preparation.firstKeptEntryId,
        tokensBefore: event.preparation.tokensBefore,
      }),
      callRemoteCompactionEndpoint({
        model,
        apiKey: auth.apiKey,
        headers: auth.headers,
        sessionId,
        input: promptResponseItems,
        instructions: ctx.getSystemPrompt(),
        tools,
        parallelToolCalls: true,
        reasoning,
        text,
        signal: event.signal,
      }),
    ]);

    if (remoteResult.status !== "fulfilled") {
      if (localResult.status === "fulfilled") {
        return { compaction: localResult.value };
      }
      if (!event.signal.aborted && ctx.hasUI) {
        const message =
          remoteResult.reason instanceof Error
            ? remoteResult.reason.message
            : String(remoteResult.reason);
        ctx.ui.notify(
          `OpenAI remote compaction failed; falling back to default compaction. ${message}`,
          "warning",
        );
      }
      return undefined;
    }

    const remoteDetails = buildRemoteCompactionDetails(
      model,
      remoteResult.value.output,
      remoteResult.value.usage,
    );
    const localSummary =
      localResult.status === "fulfilled"
        ? localResult.value
        : {
            summary: buildCompactionSummaryText(model),
            firstKeptEntryId: event.preparation.firstKeptEntryId,
            tokensBefore: event.preparation.tokensBefore,
          };

    return {
      compaction: {
        summary: localSummary.summary,
        firstKeptEntryId: localSummary.firstKeptEntryId,
        tokensBefore: localSummary.tokensBefore,
        details: {
          ...(localSummary.details !== undefined
            ? { localSummaryDetails: localSummary.details }
            : {}),
          remoteCompaction: remoteDetails,
        },
      },
    };
  });

  pi.on("message_end", (event, ctx) => {
    const sessionId = getSessionId(ctx);
    const model = ctx.model;

    extendRemoteHistoryIfCompatible({
      sessionId,
      model,
      message: event.message,
    });
  });

  pi.on("before_provider_request", (event, ctx) => {
    const cfg = loadConfig(ctx.cwd);
    if (!cfg.enabled) return undefined;

    const model = ctx.model;
    if (
      !model ||
      !supportsRemoteCompactionModel(model) ||
      !isRecord(event.payload) ||
      !looksLikeResponsesPayload(event.payload)
    ) {
      return undefined;
    }

    const sessionId = getSessionId(ctx);
    setResponsesRequestShapeState(sessionId, {
      updatedAt: Date.now(),
      reasoning: extractResponsesReasoningConfig(event.payload),
      text: extractResponsesTextConfig(event.payload),
    });
    const remoteState = getMatchingRemoteState(sessionId, model);

    if (isOpenAICodexResponsesModel(model)) {
      if (!remoteState) return undefined;
      const payload = applyRemoteHistoryPayloadPatch({
        payload: event.payload,
        explicitHistory: normalizeResponseItemsForPrompt(
          remoteState.explicitHistory,
          model,
        ) as unknown[],
      });
      maybeNotifyRequestFeatures({
        notifiedModels,
        hasUI: ctx.hasUI,
        notify: cfg.notify,
        ui: ctx.ui,
        model,
        features: ["remote_compaction_history"],
      });
      return payload;
    }

    if (!remoteState) return undefined;

    const payload = applyRemoteHistoryPayloadPatch({
      payload: event.payload,
      explicitHistory: normalizeResponseItemsForPrompt(
        remoteState.explicitHistory,
        model,
      ) as unknown[],
    });
    maybeNotifyRequestFeatures({
      notifiedModels,
      hasUI: ctx.hasUI,
      notify: cfg.notify,
      ui: ctx.ui,
      model,
      features: ["remote_compaction_history", "native_http"],
    });

    return payload;
  });
}