/**
 * Copyright (c) 2026, Salesforce, Inc.,
 * All rights reserved.
 * For full license text, see the LICENSE.txt file
 */

import crypto from "node:crypto";
import fs from "node:fs";
import os from "node:os";
import path from "node:path";

/**
 * Resolves the graphiti home directory at call time. Re-reads
 * `GRAPHITI_HOME` on every call so tests that mutate the env var after
 * module load (or fixtures that set it before each call) see the current
 * value rather than a frozen snapshot from import time.
 *
 * Single source of truth for every graphiti file/directory path: schema
 * cache, sessions, ObjectInfo cache, the active-session pointer.
 */
export function graphitiHome(): string {
	return process.env.GRAPHITI_HOME ?? path.join(os.homedir(), ".graphiti");
}

/**
 * Write `text` to `finalPath` atomically. Writes to a sibling
 * `<base>.tmp.<pid>.<timestamp>.<rand>` file, then renames over the final
 * path. Concurrent readers see either the old contents or the fully-written
 * new contents — never a partial. The temp file is unlinked if the rename
 * fails, so failure paths do not leak partial files.
 */
export function atomicWriteText(finalPath: string, text: string): void {
	fs.mkdirSync(path.dirname(finalPath), { recursive: true });
	const tmp = `${finalPath}.tmp.${process.pid}.${Date.now()}.${crypto.randomBytes(4).toString("hex")}`;
	fs.writeFileSync(tmp, text, "utf-8");
	try {
		fs.renameSync(tmp, finalPath);
	} catch (e) {
		try {
			fs.unlinkSync(tmp);
		} catch {
			// best-effort cleanup
		}
		throw e;
	}
}

/** Write JSON to `finalPath` atomically (pretty-printed). See {@link atomicWriteText}. */
export function atomicWriteJson(finalPath: string, payload: unknown): void {
	atomicWriteText(finalPath, JSON.stringify(payload, null, 2));
}