import { existsSync, readFileSync } from "fs";
import { homedir } from "os";
import { dirname, join, resolve } from "path";
import { fileURLToPath } from "url";

// =============================================================================
// Package Detection
// =============================================================================

const __filename = fileURLToPath(import.meta.url);
const __dirname = dirname(__filename);

/**
 * Detect if we're running as a Bun compiled binary.
 * Bun binaries have import.meta.url containing "$bunfs" (Bun's virtual filesystem path)
 */
export const isBunBinary = import.meta.url.includes("$bunfs");

// =============================================================================
// Package Asset Paths (shipped with executable)
// =============================================================================

/**
 * Get the base directory for resolving package assets (themes, package.json, README.md, CHANGELOG.md).
 * - For Bun binary: returns the directory containing the executable
 * - For Node.js (dist/): returns __dirname (the dist/ directory)
 * - For tsx (src/): returns parent directory (the package root)
 */
export function getPackageDir(): string {
	if (isBunBinary) {
		// Bun binary: process.execPath points to the compiled executable
		return dirname(process.execPath);
	}
	// Node.js: check if package.json exists in __dirname (dist/) or parent (src/ case)
	if (existsSync(join(__dirname, "package.json"))) {
		return __dirname;
	}
	// Running from src/ via tsx - go up one level to package root
	return dirname(__dirname);
}

/**
 * Get path to built-in themes directory (shipped with package)
 * - For Bun binary: theme/ next to executable
 * - For Node.js (dist/): dist/theme/
 * - For tsx (src/): src/theme/
 */
export function getThemesDir(): string {
	if (isBunBinary) {
		return join(dirname(process.execPath), "theme");
	}
	// __dirname is either dist/ or src/ - theme is always a subdirectory
	return join(__dirname, "theme");
}

/** Get path to package.json */
export function getPackageJsonPath(): string {
	return join(getPackageDir(), "package.json");
}

/** Get path to README.md */
export function getReadmePath(): string {
	return resolve(join(getPackageDir(), "README.md"));
}

/** Get path to CHANGELOG.md */
export function getChangelogPath(): string {
	return resolve(join(getPackageDir(), "CHANGELOG.md"));
}

// =============================================================================
// App Config (from package.json piConfig)
// =============================================================================

const pkg = JSON.parse(readFileSync(getPackageJsonPath(), "utf-8"));

export const APP_NAME: string = pkg.piConfig?.name || "pi";
export const CONFIG_DIR_NAME: string = pkg.piConfig?.configDir || ".pi";
export const VERSION: string = pkg.version;

// e.g., PI_CODING_AGENT_DIR or TAU_CODING_AGENT_DIR
export const ENV_AGENT_DIR = `${APP_NAME.toUpperCase()}_CODING_AGENT_DIR`;

// =============================================================================
// User Config Paths (~/.pi/agent/*)
// =============================================================================

/** Get the agent config directory (e.g., ~/.pi/agent/) */
export function getAgentDir(): string {
	return process.env[ENV_AGENT_DIR] || join(homedir(), CONFIG_DIR_NAME, "agent");
}

/** Get path to user's custom themes directory */
export function getCustomThemesDir(): string {
	return join(getAgentDir(), "themes");
}

/** Get path to models.json */
export function getModelsPath(): string {
	return join(getAgentDir(), "models.json");
}

/** Get path to oauth.json */
export function getOAuthPath(): string {
	return join(getAgentDir(), "oauth.json");
}

/** Get path to settings.json */
export function getSettingsPath(): string {
	return join(getAgentDir(), "settings.json");
}

/** Get path to tools directory */
export function getToolsDir(): string {
	return join(getAgentDir(), "tools");
}

/** Get path to slash commands directory */
export function getCommandsDir(): string {
	return join(getAgentDir(), "commands");
}

/** Get path to sessions directory */
export function getSessionsDir(): string {
	return join(getAgentDir(), "sessions");
}

/** Get path to debug log file */
export function getDebugLogPath(): string {
	return join(getAgentDir(), `${APP_NAME}-debug.log`);
}