/**
 * Agent discovery and configuration
 */

import * as fs from "node:fs";
import * as path from "node:path";
import { fileURLToPath } from "node:url";
import { getAgentDir, parseFrontmatter } from "@earendil-works/pi-coding-agent";
import { getAgentThinkingLevelFromFrontmatter, type AgentThinkingLevel } from "./thinking.ts";

export type AgentScope = "user" | "project" | "both";

export interface AgentConfig {
	name: string;
	description: string;
	tools?: string[];
	model?: string;
	thinkingLevel?: AgentThinkingLevel;
	systemPrompt: string;
	source: "user" | "project";
	filePath: string;
}

export interface AgentDiscoveryResult {
	agents: AgentConfig[];
	projectAgentsDir: string | null;
}
function loadAgentsFromDir(dir: string, source: "user" | "project"): AgentConfig[] {
	const agents: AgentConfig[] = [];

	if (!fs.existsSync(dir)) {
		return agents;
	}

	let entries: fs.Dirent[];
	try {
		entries = fs.readdirSync(dir, { withFileTypes: true });
	} catch {
		return agents;
	}

	for (const entry of entries) {
		if (!entry.name.endsWith(".md")) continue;
		if (!entry.isFile() && !entry.isSymbolicLink()) continue;

		const filePath = path.join(dir, entry.name);
		let content: string;
		try {
			content = fs.readFileSync(filePath, "utf-8");
		} catch {
			continue;
		}

		const { frontmatter, body } = parseFrontmatter<Record<string, unknown>>(content);

		const configuredName = typeof frontmatter.name === "string" ? frontmatter.name : undefined;
		const description = typeof frontmatter.description === "string" ? frontmatter.description : undefined;
		const name = configuredName || path.basename(entry.name, ".md");
		if (!name || !description) {
			continue;
		}

		const tools = typeof frontmatter.tools === "string"
			? frontmatter.tools
					.split(",")
					.map((tool) => tool.trim())
					.filter(Boolean)
			: undefined;
		const model = typeof frontmatter.model === "string" ? frontmatter.model.trim() || undefined : undefined;

		agents.push({
			name,
			description,
			tools: tools && tools.length > 0 ? tools : undefined,
			model,
			thinkingLevel: getAgentThinkingLevelFromFrontmatter(frontmatter),
			systemPrompt: body,
			source,
			filePath,
		});
	}

	return agents;
}

function isDirectory(p: string): boolean {
	try {
		return fs.statSync(p).isDirectory();
	} catch {
		return false;
	}
}

function getExtensionAgentsDir(): string | null {
	const dir = path.join(path.dirname(fileURLToPath(import.meta.url)), "agents");
	return isDirectory(dir) ? dir : null;
}

export function discoverAgents(cwd: string, scope: AgentScope): AgentDiscoveryResult {
	void cwd;
	const userDir = path.join(getAgentDir(), "agents");
	const projectAgentsDir = getExtensionAgentsDir();

	const userAgents = scope === "project" ? [] : loadAgentsFromDir(userDir, "user");
	const projectAgents = scope === "user" || !projectAgentsDir ? [] : loadAgentsFromDir(projectAgentsDir, "project");

	const agentMap = new Map<string, AgentConfig>();

	if (scope === "both") {
		for (const agent of userAgents) agentMap.set(agent.name.toLowerCase(), agent);
		for (const agent of projectAgents) agentMap.set(agent.name.toLowerCase(), agent);
	} else if (scope === "user") {
		for (const agent of userAgents) agentMap.set(agent.name.toLowerCase(), agent);
	} else {
		for (const agent of projectAgents) agentMap.set(agent.name.toLowerCase(), agent);
	}

	return { agents: Array.from(agentMap.values()), projectAgentsDir };
}

export function findAgentByName(agents: AgentConfig[], name: string): AgentConfig | undefined {
	const normalized = name.trim().toLowerCase();
	return agents.find((agent) => agent.name.toLowerCase() === normalized);
}

export function formatAgentList(agents: AgentConfig[], maxItems: number): { text: string; remaining: number } {
	if (agents.length === 0) return { text: "none", remaining: 0 };
	const listed = agents.slice(0, maxItems);
	const remaining = agents.length - listed.length;
	return {
		text: listed.map((a) => `${a.name} (${a.source}): ${a.description}`).join("; "),
		remaining,
	};
}