import {
	createBashToolDefinition,
	getAgentDir,
	type ExtensionAPI,
} from "@earendil-works/pi-coding-agent";
import { loadConfig, type PwshNativeConfig } from "./config.ts";
import { createPowerShellOperations } from "./operations.ts";
import { resolvePowerShellRuntime, type PowerShellRuntime } from "./runtime.ts";

const DISCOVERY_TOOLS = ["ls", "find", "grep"] as const;

function errorMessage(error: unknown): string {
	return error instanceof Error ? error.message : String(error);
}

export function selectActiveTools(
	activeTools: readonly string[],
	preserveDiscoveryTools: boolean,
	pwshAvailable: boolean,
): string[] {
	const disabled = new Set<string>(["bash", "pwsh"]);
	if (!preserveDiscoveryTools) {
		for (const name of DISCOVERY_TOOLS) disabled.add(name);
	}
	const selected = activeTools.filter((name) => !disabled.has(name));
	if (pwshAvailable) selected.push("pwsh");
	return [...new Set(selected)];
}

export const PWSH_TOOL_DESCRIPTION =
	"Execute native PowerShell 7 on Windows. Output is tail-truncated to 2,000 lines or 50 KB; full output is saved to a temporary file. Optional timeout is in seconds.";

export function createPromptGuidelines(config: PwshNativeConfig): string[] {
	return [
		"Use pwsh only when a shell is needed; use native PowerShell syntax and $env:NAME for environment variables.",
		"Prefer dedicated file and search tools over pwsh; otherwise bound recursive output and prefer rg or fd when available.",
		config.elevationGuidance
			? "In pwsh, elevation guidance is enabled, but elevate only after an explicit user request."
			: "Do not elevate from pwsh unless the user explicitly requests it.",
	];
}

function unavailableUserCommand(reason: string) {
	return {
		result: {
			output: `pi-pwsh-native is unavailable: ${reason}`,
			exitCode: 1,
			cancelled: false,
			truncated: false,
		},
	};
}

export default function piPwshNative(pi: ExtensionAPI): void {
	if (process.platform !== "win32") {
		pi.on("session_start", (_event, ctx) => {
			ctx.ui.notify("pi-pwsh-native is Windows-only; no tools were changed.", "warning");
		});
		return;
	}

	let config: PwshNativeConfig | undefined;
	let runtime: PowerShellRuntime | undefined;
	let operations: ReturnType<typeof createPowerShellOperations> | undefined;
	let setupError: string | undefined;
	try {
		config = loadConfig({ agentDir: getAgentDir() }).config;
	} catch (error) {
		setupError = errorMessage(error);
	}

	pi.on("session_start", (_event, ctx) => {
		if (!setupError && config && !runtime) {
			try {
				runtime = resolvePowerShellRuntime(config);
				operations = createPowerShellOperations(runtime, config);
			} catch (error) {
				setupError = errorMessage(error);
			}
		}

		if (setupError || !config || !runtime || !operations) {
			const reason = setupError ?? "unknown setup failure";
			pi.setActiveTools(selectActiveTools(pi.getActiveTools(), true, false));
			ctx.ui.notify(`pi-pwsh-native: ${reason} Bash was disabled; no shell fallback was activated.`, "error");
			return;
		}

		const definition = createBashToolDefinition(ctx.cwd, { operations });
		pi.registerTool({
			...definition,
			name: "pwsh",
			label: "pwsh",
			description: PWSH_TOOL_DESCRIPTION,
			promptSnippet: "Execute native PowerShell 7 commands",
			promptGuidelines: createPromptGuidelines(config),
		});
		pi.setActiveTools(
			selectActiveTools(pi.getActiveTools(), config.preserveDiscoveryTools, true),
		);
	});

	const replaceUserBash = config?.replaceUserBash ?? true;
	if (replaceUserBash) {
		pi.on("user_bash", () =>
			operations
				? { operations }
				: unavailableUserCommand(setupError ?? "PowerShell has not been initialized"),
		);
	}
}