/**
 * System Info Extension
 *
 * Injects host environment details into the system prompt:
 * - OS (Windows / Linux / macOS)
 * - Terminal / shell environment
 * - Local IPv4 addresses
 * - Common programming language toolchains
 *
 * Auto-discovered from .sproutclaw/agent/extensions/system-info/
 */

import { spawnSync } from "node:child_process";
import os from "node:os";
import { basename } from "node:path";
import type { ExtensionAPI } from "@earendil-works/pi-coding-agent";

interface ToolchainEntry {
	label: string;
	version: string;
	path: string;
}

interface SystemInfoSnapshot {
	os: string;
	platform: string;
	arch: string;
	hostname: string;
	terminal: string;
	shell: string;
	ipAddresses: string[];
	toolchains: ToolchainEntry[];
	capturedAt: string;
}

const NULL = "NULL";

interface ToolchainProbe {
	label: string;
	bins: string[];
	args: string[];
}

const TOOLCHAIN_PROBES: ToolchainProbe[] = [
	{ label: "Python", bins: ["python3", "python"], args: ["--version"] },
	{ label: "Java", bins: ["java"], args: ["-version"] },
	{ label: "Node.js", bins: ["node"], args: ["--version"] },
	{ label: "Bun", bins: ["bun"], args: ["--version"] },
	{ label: "Rust", bins: ["rustc"], args: ["--version"] },
	{ label: "Clang", bins: ["clang"], args: ["--version"] },
	{ label: "Golang", bins: ["go"], args: ["version"] },
	{ label: "GCC", bins: ["gcc"], args: ["--version"] },
];

function isIPv4(family: string | number): boolean {
	return family === "IPv4" || family === 4;
}

function getOsLabel(): string {
	switch (process.platform) {
		case "win32":
			return "Windows";
		case "linux":
			return "Linux";
		case "darwin":
			return "macOS";
		default:
			return process.platform;
	}
}

function describeShell(): string {
	if (process.platform === "win32") {
		if (process.env.PSModulePath || /powershell/i.test(process.env.SHELL ?? "")) {
			return "PowerShell";
		}
		const comspec = process.env.ComSpec;
		return comspec ? basename(comspec) : "unknown";
	}

	const shell = process.env.SHELL;
	return shell ? basename(shell) : "unknown";
}

function describeTerminal(): string {
	const parts: string[] = [];

	if (process.env.TERM_PROGRAM) {
		const version = process.env.TERM_PROGRAM_VERSION;
		parts.push(version ? `${process.env.TERM_PROGRAM} ${version}` : process.env.TERM_PROGRAM);
	} else if (process.env.WT_SESSION) {
		parts.push("Windows Terminal");
	} else if (process.env.CURSOR_TRACE_ID || process.env.CURSOR_AGENT) {
		parts.push("Cursor");
	} else if (process.env.VSCODE_PID || process.env.TERM_PROGRAM === "vscode") {
		parts.push("VS Code Integrated Terminal");
	} else if (process.env.TERM) {
		parts.push(`TERM=${process.env.TERM}`);
	}

	const shell = describeShell();
	if (shell !== "unknown") {
		parts.push(`shell=${shell}`);
	}

	return parts.length > 0 ? parts.join(", ") : "unknown";
}

function getLocalIpAddresses(): string[] {
	const addresses: string[] = [];

	for (const [interfaceName, entries] of Object.entries(os.networkInterfaces())) {
		if (!entries) continue;
		for (const entry of entries) {
			if (entry.internal || !isIPv4(entry.family)) continue;
			addresses.push(`${interfaceName}: ${entry.address}`);
		}
	}

	return addresses;
}

function firstNonEmptyLine(text: string): string {
	return (
		text
			.split(/\r?\n/)
			.map((line) => line.trim())
			.find((line) => line.length > 0) ?? ""
	);
}

function findExecutable(candidates: string[]): string | null {
	for (const candidate of candidates) {
		if (process.platform === "win32") {
			const result = spawnSync("where.exe", [candidate], { encoding: "utf8", timeout: 5000 });
			const line = firstNonEmptyLine(result.stdout ?? "");
			if (result.status === 0 && line) {
				return line;
			}
			continue;
		}

		const result = spawnSync("sh", ["-lc", `command -v ${candidate} 2>/dev/null`], {
			encoding: "utf8",
			timeout: 5000,
		});
		const line = firstNonEmptyLine(result.stdout ?? "");
		if (result.status === 0 && line) {
			return line;
		}
	}

	return null;
}

function runVersionCommand(executable: string, args: string[]): string {
	const result = spawnSync(executable, args, {
		encoding: "utf8",
		timeout: 5000,
		windowsHide: true,
	});

	const output = firstNonEmptyLine(`${result.stdout ?? ""}\n${result.stderr ?? ""}`);
	return output;
}

function probeToolchain(probe: ToolchainProbe): ToolchainEntry {
	const executable = findExecutable(probe.bins);
	if (!executable) {
		return { label: probe.label, version: NULL, path: NULL };
	}

	const version = runVersionCommand(executable, probe.args);
	return {
		label: probe.label,
		version: version || NULL,
		path: executable,
	};
}

function collectToolchains(): ToolchainEntry[] {
	return TOOLCHAIN_PROBES.map((probe) => probeToolchain(probe));
}

function collectSystemInfo(): SystemInfoSnapshot {
	return {
		os: getOsLabel(),
		platform: process.platform,
		arch: process.arch,
		hostname: os.hostname(),
		terminal: describeTerminal(),
		shell: describeShell(),
		ipAddresses: getLocalIpAddresses(),
		toolchains: collectToolchains(),
		capturedAt: new Date().toISOString(),
	};
}

function formatToolchainLine(entry: ToolchainEntry): string {
	if (entry.version === NULL && entry.path === NULL) {
		return `- ${entry.label}: version=${NULL}, path=${NULL}`;
	}
	return `- ${entry.label}: version=${entry.version}, path=${entry.path}`;
}

function formatSystemInfoSection(info: SystemInfoSnapshot): string {
	const ipLines =
		info.ipAddresses.length > 0
			? info.ipAddresses.map((address) => `- ${address}`).join("\n")
			: "- (no non-loopback IPv4 address found)";

	const toolchainLines = info.toolchains.map((entry) => formatToolchainLine(entry)).join("\n");

	return `
## Host Environment

The following reflects the machine where SproutClaw is running. Use it when choosing commands, paths, or network assumptions.

- OS: ${info.os} (${info.platform}/${info.arch})
- Hostname: ${info.hostname}
- Terminal: ${info.terminal}
- Shell: ${info.shell}
- Local IPv4:
${ipLines}
- Toolchains:
${toolchainLines}
- Captured at: ${info.capturedAt}
`.trimEnd();
}

function formatSummary(info: SystemInfoSnapshot): string {
	const ips = info.ipAddresses.length > 0 ? info.ipAddresses.join(", ") : "none";
	const toolchainSummary = info.toolchains
		.map((entry) => {
			if (entry.version === NULL) {
				return `${entry.label}: ${NULL}`;
			}
			return `${entry.label}: ${entry.version}`;
		})
		.join("\n");

	return [
		`OS: ${info.os}`,
		`Terminal: ${info.terminal}`,
		`Shell: ${info.shell}`,
		`IPv4: ${ips}`,
		"",
		toolchainSummary,
	].join("\n");
}

export default function systemInfoExtension(pi: ExtensionAPI) {
	let systemInfo = collectSystemInfo();

	function refreshSystemInfo(): SystemInfoSnapshot {
		systemInfo = collectSystemInfo();
		return systemInfo;
	}

	pi.on("session_start", async () => {
		refreshSystemInfo();
	});

	pi.on("before_agent_start", async (event) => {
		const section = formatSystemInfoSection(systemInfo);
		if (event.systemPrompt.includes("## Host Environment")) {
			return undefined;
		}
		return {
			systemPrompt: `${event.systemPrompt}\n\n${section}`,
		};
	});

	pi.registerCommand("system-info", {
		description: "Show or refresh injected host environment details",
		handler: async (_args, ctx) => {
			const info = refreshSystemInfo();
			ctx.ui.notify(formatSummary(info), "info");
		},
	});
}