import type { ExtensionAPI, Skill } from "@earendil-works/pi-coding-agent";
import registerPackageChangelog from "./changelog.js";
import { createSkillsTool, prepareSkillsCodeModeInput } from "./src/tool.js";

export { createSkillsTool, prepareSkillsCodeModeInput } from "./src/tool.js";

const REGISTRATION_KEY = Symbol.for(
	"@howaboua/pi-better-skills-tool.registered",
);
const CODE_MODE_PACKAGE = "@howaboua/pi-codex-conversion";
const CODE_MODE_MODULE = `${CODE_MODE_PACKAGE}/code-mode`;

export default async function skillsExtension(pi: ExtensionAPI): Promise<void> {
	registerPackageChangelog(pi);
	const sharedState = pi.events as typeof pi.events & {
		[REGISTRATION_KEY]?: object;
	};
	if (sharedState[REGISTRATION_KEY]) return;
	const owner = {};
	sharedState[REGISTRATION_KEY] = owner;

	let loadedSkills: readonly Skill[] = [];
	pi.on("before_agent_start", (event) => {
		const options = event.systemPromptOptions;
		loadedSkills = [...options.skills];
		// Native /skill: expansion uses Pi's loader, not these prompt fields.
		options.skills = [];
		delete options.sections["skills"];
		delete options.sections["skill_catalog"];
		if (options.forceSystemPrompt !== undefined) {
			// Full-prompt overrides bypass sections. Preserve text outside catalog containers.
			options.forceSystemPrompt = options.forceSystemPrompt.replace(
				/<(skills|skill_catalog)>[\s\S]*?<\/\1>/g,
				"",
			);
		}
	});
	let gpt = false;
	const tool = createSkillsTool({
		getLoadedSkills: () => loadedSkills,
		isGpt: () => gpt,
	});
	const ordinaryGuidelines = tool.promptGuidelines;
	pi.registerTool(tool);
	try {
		const { registerGptPromptMode } = await import(
			"@howaboua/pi-codex-conversion/prompt-mode"
		);
		registerGptPromptMode(pi, (active) => {
			gpt = active;
			if (active)
				tool.promptGuidelines = [
					"skills: List once/session start; before work read always-applicable+task-relevant skills",
				];
			else if (ordinaryGuidelines) tool.promptGuidelines = ordinaryGuidelines;
			else delete tool.promptGuidelines;
			return [tool];
		});
	} catch (error) {
		if (
			!(error instanceof Error) ||
			!("code" in error) ||
			![
				"ERR_MODULE_NOT_FOUND",
				"MODULE_NOT_FOUND",
				"ERR_PACKAGE_PATH_NOT_EXPORTED",
			].includes(String(error.code)) ||
			!error.message.includes(CODE_MODE_PACKAGE)
		)
			throw error;
	}

	const registration = await registerSkillsInCodeMode(pi, tool);
	pi.on("session_shutdown", () => {
		registration?.unregister();
		if (sharedState[REGISTRATION_KEY] === owner)
			delete sharedState[REGISTRATION_KEY];
	});
}

async function registerSkillsInCodeMode(
	pi: ExtensionAPI,
	tool: ReturnType<typeof createSkillsTool>,
) {
	try {
		const { adaptToolForCodeMode, registerCodeModeExtensionTools } =
			await import("@howaboua/pi-codex-conversion/code-mode");
		return registerCodeModeExtensionTools(pi, () => [
			adaptToolForCodeMode(tool, {
				kind: "freeform",
				inputOptional: true,
				prepareInput: prepareSkillsCodeModeInput,
				usage: "await tools.skills() // discover skills and calling syntax",
			}),
		]);
	} catch (error) {
		if (isMissingCodeModeExtension(error)) return undefined;
		if (isOutdatedCodeModeExtension(error)) {
			throw new Error(
				"Update " +
					CODE_MODE_PACKAGE +
					" to 3.0.24 or newer to use Better Skills with it",
				{ cause: error },
			);
		}
		throw error;
	}
}

function isMissingCodeModeExtension(error: unknown): boolean {
	if (
		!error ||
		typeof error !== "object" ||
		!("code" in error) ||
		!("message" in error) ||
		typeof error.message !== "string"
	)
		return false;
	if (
		error.code !== "ERR_MODULE_NOT_FOUND" &&
		error.code !== "MODULE_NOT_FOUND"
	)
		return false;
	const missing = error.message.match(
		/Cannot find (?:package|module) ['"]([^'"]+)['"]/,
	)?.[1];
	return missing === CODE_MODE_PACKAGE || missing === CODE_MODE_MODULE;
}

function isOutdatedCodeModeExtension(error: unknown): boolean {
	if (
		!error ||
		typeof error !== "object" ||
		!("code" in error) ||
		!("message" in error) ||
		typeof error.message !== "string"
	)
		return false;
	return (
		(error.code === "ERR_PACKAGE_PATH_NOT_EXPORTED" ||
			error.code === "ERR_UNSUPPORTED_DIR_IMPORT") &&
		(error.message.includes(CODE_MODE_MODULE) ||
			(error.message.includes("Package subpath './code-mode'") &&
				error.message.includes(CODE_MODE_PACKAGE)))
	);
}