/**
 * Company Context Extension
 *
 * WHAT: On session start, loads config/company.json (the single source of
 *       truth). If `remoteConfigUrl` is set, tries to fetch a fresh config
 *       from there with a short timeout and falls back silently to the local
 *       file on any error. Renders a short corporate context from
 *       `company-context.md` and injects it into the system prompt. Also
 *       registers the `/kit-config` command for debugging effective values.
 *
 * CONFIGURE: Edit config/company.json (gitHost, trackerUrl, docsUrl, repoMap,
 *       rules, remoteConfigUrl). Edit the wording in company-context.md —
 *       non-programmers can safely change text between the {{placeholders}}.
 *
 * DISABLE: Remove/rename this file from the package `extensions/` folder,
 *       or exclude it via the package manifest / settings.
 */

import * as fs from "node:fs";
import * as path from "node:path";
import { fileURLToPath } from "node:url";
import type { ExtensionAPI } from "@earendil-works/pi-coding-agent";

interface CompanyConfig {
	gitHost: string;
	trackerUrl: string;
	docsUrl: string;
	repoMap: string;
	rules: string[];
	remoteConfigUrl: string | null;
}

const HERE = path.dirname(fileURLToPath(import.meta.url));
const CONFIG_PATH = path.join(HERE, "..", "config", "company.json");
const TEMPLATE_PATH = path.join(HERE, "company-context.md");
const REMOTE_TIMEOUT_MS = 2500;
const MAX_CONTEXT_LINES = 40;

const DEFAULT_CONFIG: CompanyConfig = {
	gitHost: "TODO",
	trackerUrl: "TODO",
	docsUrl: "TODO",
	repoMap: "TODO",
	rules: [],
	remoteConfigUrl: null,
};

/** Read and validate the local config file, falling back to defaults. */
function readLocalConfig(): CompanyConfig {
	try {
		const raw = JSON.parse(fs.readFileSync(CONFIG_PATH, "utf8"));
		return normalize(raw);
	} catch {
		return { ...DEFAULT_CONFIG };
	}
}

/** Keep only known keys and coerce types, so junk in remote/local JSON is ignored. */
function normalize(raw: Record<string, unknown>): CompanyConfig {
	const str = (v: unknown, d: string) => (typeof v === "string" ? v : d);
	return {
		gitHost: str(raw.gitHost, DEFAULT_CONFIG.gitHost),
		trackerUrl: str(raw.trackerUrl, DEFAULT_CONFIG.trackerUrl),
		docsUrl: str(raw.docsUrl, DEFAULT_CONFIG.docsUrl),
		repoMap: str(raw.repoMap, DEFAULT_CONFIG.repoMap),
		rules: Array.isArray(raw.rules) ? raw.rules.filter((r): r is string => typeof r === "string") : [],
		remoteConfigUrl: typeof raw.remoteConfigUrl === "string" ? raw.remoteConfigUrl : null,
	};
}

/** Try to fetch a fresh config from a URL. Returns null on any failure. */
async function fetchRemoteConfig(url: string): Promise<CompanyConfig | null> {
	try {
		const res = await fetch(url, { signal: AbortSignal.timeout(REMOTE_TIMEOUT_MS) });
		if (!res.ok) return null;
		const raw = (await res.json()) as Record<string, unknown>;
		return normalize(raw);
	} catch {
		return null; // network error, timeout, bad JSON — fall back silently
	}
}

/** Load the context template once; fall back to a minimal inline template. */
function loadTemplate(): string {
	try {
		return fs.readFileSync(TEMPLATE_PATH, "utf8");
	} catch {
		return [
			"# Корпоративный контекст",
			"git-хост: {{gitHost}}",
			"трекер: {{trackerUrl}}",
			"документация: {{docsUrl}}",
			"репозитории: {{repoMap}}",
			"правила:",
			"{{rules}}",
		].join("\n");
	}
}

/** Render the corporate context from the template + effective config. */
function renderContext(template: string, cfg: CompanyConfig): string {
	const rulesBlock = cfg.rules.length > 0 ? cfg.rules.map((r) => `- ${r}`).join("\n") : "- (правила не заданы)";
	const rendered = template
		.replaceAll("{{gitHost}}", cfg.gitHost)
		.replaceAll("{{trackerUrl}}", cfg.trackerUrl)
		.replaceAll("{{docsUrl}}", cfg.docsUrl)
		.replaceAll("{{repoMap}}", cfg.repoMap)
		.replaceAll("{{rules}}", rulesBlock);
	// Safety cap: never inject more than MAX_CONTEXT_LINES lines.
	return rendered.split("\n").slice(0, MAX_CONTEXT_LINES).join("\n").trimEnd();
}

export default function companyContextExtension(pi: ExtensionAPI) {
	const template = loadTemplate();

	// Effective config and where it came from. Refreshed on every session start.
	let effective: CompanyConfig = readLocalConfig();
	let source: "local" | "remote" = "local";

	pi.on("session_start", async (_event, ctx) => {
		effective = readLocalConfig();
		source = "local";

		if (effective.remoteConfigUrl) {
			const remote = await fetchRemoteConfig(effective.remoteConfigUrl);
			if (remote) {
				// Remote wins, but keep the local remoteConfigUrl so a bad remote
				// value can't orphan future refreshes.
				effective = { ...remote, remoteConfigUrl: effective.remoteConfigUrl };
				source = "remote";
			}
		}

		if (ctx.hasUI) {
			ctx.ui.notify(`pi-kit: корпоративный контекст загружен (источник: ${source})`, "info");
		}
	});

	pi.on("before_agent_start", async (event) => {
		const rendered = renderContext(template, effective);
		if (!rendered) return undefined;
		return { systemPrompt: `${event.systemPrompt}\n\n${rendered}` };
	});

	pi.registerCommand("kit-config", {
		description: "Показать действующие корпоративные значения pi-kit и их источник",
		handler: async (_args, ctx) => {
			const origin =
				source === "remote"
					? `remote (${effective.remoteConfigUrl})`
					: `local (${CONFIG_PATH})`;
			const lines = [
				`Источник: ${origin}`,
				"",
				`gitHost:    ${effective.gitHost}`,
				`trackerUrl: ${effective.trackerUrl}`,
				`docsUrl:    ${effective.docsUrl}`,
				`repoMap:    ${effective.repoMap}`,
				`remoteConfigUrl: ${effective.remoteConfigUrl ?? "(не задан)"}`,
				"rules:",
				...(effective.rules.length > 0 ? effective.rules.map((r) => `  - ${r}`) : ["  (нет)"]),
			];

			if (ctx.hasUI) {
				await ctx.ui.select("Действующая конфигурация pi-kit", lines);
			} else {
				ctx.ui.notify(lines.join("\n"), "info");
			}
		},
	});
}