import * as fs from 'node:fs/promises';
import { join } from 'node:path';
import { vi } from 'vitest';

/** Read-only agent transport backed by fixture files. Mutations still fail. */
export async function mockAgentFiles() {
    const backend = await import('../../src/lib/server/backends/native.js');
    const { serverDir } = await import('../../src/lib/server/config.js');
    return vi.spyOn(backend, 'nativeRequest').mockImplementation(async (instance, kind, payload = {}) => {
        const path = join(serverDir(instance.server), String(payload.path ?? '.'));
        let result: unknown;
        if (kind === 'files.read') {
            const content = await fs.readFile(path).catch((error: NodeJS.ErrnoException) => { if (error.code === 'ENOENT') return null; throw error; });
            result = { contentBase64: content?.toString('base64') ?? null };
        } else if (kind === 'files.stat') {
            const stat = await fs.stat(path).catch((error: NodeJS.ErrnoException) => { if (error.code === 'ENOENT') return null; throw error; });
            result = stat ? { exists: true, size: stat.size, mtime: stat.mtime.toISOString(), isDirectory: stat.isDirectory(), isFile: stat.isFile() } : null;
        } else if (kind === 'files.list') {
            result = { entries: (await fs.readdir(path, { withFileTypes: true })).map(entry => ({ name: entry.name, isDirectory: entry.isDirectory(), isFile: entry.isFile() })) };
        } else throw new Error(`Unexpected agent command: ${kind}`);
        return result as never;
    });
}