/**
 * @author jackice
 * @date 2026-08-10
 *
 * pi-handoff：把当前会话的上下文交接给新会话。
 * 移植自 omp（oh-my-pi）的 SessionHandoff，核心差异：
 * - 生成 handoff 文档后先经编辑器确认，再注入新会话
 * - 可选：压缩前自动生成 handoff 文档存盘（默认关闭）
 */

import { dirname, join } from "node:path";
import { fileURLToPath } from "node:url";
import { readFileSync } from "node:fs";
import * as os from "node:os";
import type { Message } from "@earendil-works/pi-ai";
import { uuidv7 } from "@earendil-works/pi-ai";
import type { ExtensionAPI, ExtensionCommandContext, ExtensionContext } from "@earendil-works/pi-coding-agent";
import { BorderedLoader, convertToLlm } from "@earendil-works/pi-coding-agent";
import {
	getHandoffMessages,
	isAutoSaveEnabled,
	renderHandoffPrompt,
	saveHandoffDocumentTo,
	shouldSkipAutoSave,
	wrapHandoffContext,
} from "./lib.js";

// ── 资源路径 ──────────────────────────────────────────────────────────

const MODULE_DIR = dirname(fileURLToPath(import.meta.url));
const TEMPLATE_PATH = join(MODULE_DIR, "handoff-document.md");
const CONFIG_PATH = join(os.homedir(), ".pi", "handoff.json");

function loadTemplate(): string {
	return readFileSync(TEMPLATE_PATH, "utf8");
}

interface HandoffConfig {
	autoSaveOnCompact?: boolean;
}

function loadConfig(): HandoffConfig {
	try {
		return JSON.parse(readFileSync(CONFIG_PATH, "utf8")) as HandoffConfig;
	} catch {
		return {};
	}
}

// ── handoff 文档生成 ───────────────────────────────────────────────────

function isTextContent(content: Message["content"][number]): content is { type: "text"; text: string } {
	return typeof content === "object" && content !== null && content.type === "text";
}

/**
 * 用一次 oneshot LLM 调用生成 handoff 文档。
 * 与 omp 一致：完整会话历史 + handoff 模板作为最后一条 user 消息，
 * systemPrompt 沿用主会话的语境。返回 null 表示取消/失败。
 */
async function generateHandoffDocument(
	ctx: ExtensionContext,
	goal: string | undefined,
	signal: AbortSignal | undefined,
): Promise<string | null> {
	if (!ctx.model) return null;

	const messages = getHandoffMessages(ctx.sessionManager.getBranch());
	if (messages.length === 0) return null;

	const handoffPrompt = renderHandoffPrompt(loadTemplate(), goal);
	const requestMessages: Message[] = [
		...convertToLlm(messages),
		{
			role: "user",
			content: [{ type: "text", text: handoffPrompt }],
			timestamp: Date.now(),
		},
	];

	const systemPrompt = ctx.getSystemPrompt();
	const response = await ctx.modelRegistry.complete(
		ctx.model,
		{ systemPrompt: systemPrompt || undefined, messages: requestMessages },
		{
			signal,
			cacheRetention: "none",
			sessionId: uuidv7(),
		},
	);

	if (response.stopReason === "aborted") return null;
	return response.content.filter(isTextContent).map((c) => c.text).join("\n");
}

/** 把 handoff 文档保存到会话 artifacts 目录（与 omp 存盘位置一致）。 */
function saveHandoffDocument(ctx: ExtensionContext, document: string): string | null {
	return saveHandoffDocumentTo(ctx.sessionManager.getSessionFile(), document);
}

// ── 扩展入口 ───────────────────────────────────────────────────────────

export default function handoffExtension(pi: ExtensionAPI): void {
	pi.registerFlag("handoff-auto-save", {
		type: "boolean",
		description: "压缩前自动生成 handoff 文档保存到会话 artifacts 目录",
	});

	// 手动交接：/handoff [目标指令]
	pi.registerCommand("handoff", {
		description: "把当前会话上下文交接给新会话（生成 handoff 文档 → 确认 → 注入新会话）",
		handler: async (args, ctx) => {
			if (!ctx.hasUI) {
				ctx.ui.notify("/handoff 需要交互模式", "error");
				return;
			}
			if (!ctx.model) {
				ctx.ui.notify("未选择模型", "error");
				return;
			}

			const goal = args.trim() || undefined;

			// 带加载动画生成（可 abort）
			const document = await ctx.ui.custom<string | null>((tui, theme, _kb, done) => {
				const loader = new BorderedLoader(tui, theme, "生成 handoff 文档...");
				loader.onAbort = () => done(null);

				generateHandoffDocument(ctx, goal, loader.signal)
					.then(done)
					.catch((err) => {
						console.error("Handoff 生成失败:", err);
						done(null);
					});

				return loader;
			});

			if (document === null) {
				ctx.ui.notify("已取消", "info");
				return;
			}

			// 编辑器确认（undefined = 取消）
			const confirmed = await ctx.ui.editor("编辑 handoff 文档", document);
			if (confirmed === undefined) {
				ctx.ui.notify("已取消", "info");
				return;
			}

			// 开新会话，把 handoff 文档作为首条上下文消息注入
			const currentSessionFile = ctx.sessionManager.getSessionFile();
			const result = await ctx.newSession({
				parentSession: currentSessionFile,
				setup: async (sm) => {
					sm.appendCustomMessageEntry("handoff", wrapHandoffContext(confirmed), true);
				},
				withSession: async (replacementCtx) => {
					replacementCtx.ui.notify("Handoff 就绪，在新会话中继续", "info");
				},
			});

			if (result.cancelled) {
				ctx.ui.notify("新会话已取消", "info");
			}
		},
	});

	// 自动留存：压缩前生成 handoff 文档存盘（默认关闭，不切换会话）
	pi.on("session_before_compact", async (event, ctx) => {
		const flagValue = pi.getFlag("handoff-auto-save");
		// boolean flag：CLI 未传时为 undefined，此时回落到配置文件
		const flag = typeof flagValue === "boolean" ? flagValue : undefined;
		const autoSave = isAutoSaveEnabled(flag, loadConfig().autoSaveOnCompact);
		if (!autoSave) return;
		// overflow 恢复会重试被中断的回合，跳过以免干扰
		if (shouldSkipAutoSave(event.willRetry)) return;

		try {
			const document = await generateHandoffDocument(ctx, undefined, event.signal);
			if (!document) return;
			const filePath = saveHandoffDocument(ctx, document);
			if (filePath) {
				ctx.ui.notify(`Handoff 已保存: ${filePath}`, "info");
			}
		} catch {
			// 静默失败：不阻塞压缩流程
		}
	});
}