/**
 * @file test_server.js
 * @brief Server Test Suite
 */

const http = require('http');
const fs = require('fs');
const path = require('path');
const ChunkServer = require('../server/server');

const PORT = 18080;
const TEST_DIR = path.join(__dirname, 'test_files');

let passed = 0;
let failed = 0;

function assert(cond, msg) {
    if (cond) {
        console.log(`[PASS] ${msg}`);
        passed++;
    } else {
        console.log(`[FAIL] ${msg}`);
        failed++;
    }
}

/**
 * HTTP GET helper
 */
function httpRequest(options, expectedStatus = 200) {
    return new Promise((resolve, reject) => {
        const req = http.request(options, (res) => {
            let data = Buffer.alloc(0);
            res.on('data', chunk => {
                data = Buffer.concat([data, chunk]);
            });
            res.on('end', () => {
                resolve({
                    statusCode: res.statusCode,
                    headers: res.headers,
                    body: data
                });
            });
        });
        req.on('error', reject);
        req.end();
    });
}

/**
 * Setup test files
 */
function setupTestFiles() {
    if (!fs.existsSync(TEST_DIR)) {
        fs.mkdirSync(TEST_DIR);
    }
    
    // Create test file: 3072 bytes (3 chunks of 1024)
    const testData = Buffer.alloc(3072);
    for (let i = 0; i < 3072; i++) {
        testData[i] = i % 256;
    }
    fs.writeFileSync(path.join(TEST_DIR, 'test.bin'), testData);
    
    // Create small file: 100 bytes
    const smallData = Buffer.alloc(100);
    for (let i = 0; i < 100; i++) {
        smallData[i] = 0x42;
    }
    fs.writeFileSync(path.join(TEST_DIR, 'small.bin'), smallData);
}

/**
 * Cleanup test files
 */
function cleanupTestFiles() {
    try {
        fs.rmSync(TEST_DIR, { recursive: true, force: true });
    } catch (e) {
        // Ignore
    }
}

/**
 * Test suite
 */
async function runTests() {
    console.log("========================================");
    console.log(" Chunk Server Test Suite");
    console.log("========================================\n");
    
    // Setup
    setupTestFiles();
    
    const server = new ChunkServer({
        port: PORT,
        rootPath: TEST_DIR,
        chunkSize: 1024
    });
    
    await server.start();
    console.log("\n--- Server Tests ---");
    
    try {
        // Test 1: Get first chunk
        const res1 = await httpRequest({
            hostname: 'localhost',
            port: PORT,
            path: '/ota?file=test.bin',
            method: 'GET'
        });
        
        assert(res1.statusCode === 200, "First chunk returns 200");
        assert(res1.headers['content-type'] === 'application/octet-stream', "Content-Type is octet-stream");
        assert(res1.headers['x-file-size'] === '3072', "X-File-Size header present");
        assert(res1.headers['x-total-chunks'] === '3', "X-Total-Chunks header present");
        assert(res1.body.length === 2 + 1024 + 4, "First chunk size correct (header + payload + crc)");
        
        // Verify chunk index in payload
        assert(res1.body.readUInt16LE(0) === 0, "Chunk index is 0");
        
        // Test 2: Get second chunk
        const res2 = await httpRequest({
            hostname: 'localhost',
            port: PORT,
            path: '/ota?file=test.bin&chunk=1',
            method: 'GET'
        });
        
        assert(res2.statusCode === 206, "Second chunk returns 206");
        assert(res2.body.readUInt16LE(0) === 1, "Chunk index is 1");
        assert(res2.body.length === 2 + 1024 + 4, "Second chunk size correct");
        
        // Test 3: Get last chunk (smaller)
        const res3 = await httpRequest({
            hostname: 'localhost',
            port: PORT,
            path: '/ota?file=test.bin&chunk=2',
            method: 'GET'
        });
        
        assert(res3.statusCode === 206, "Last chunk returns 206");
        assert(res3.body.readUInt16LE(0) === 2, "Chunk index is 2");
        assert(res3.body.length === 2 + 1024 + 4, "Last chunk size correct");
        
        // Test 4: Invalid chunk index
        const res4 = await httpRequest({
            hostname: 'localhost',
            port: PORT,
            path: '/ota?file=test.bin&chunk=10',
            method: 'GET'
        });
        
        assert(res4.statusCode === 416, "Invalid chunk returns 416");
        
        // Test 5: File not found
        const res5 = await httpRequest({
            hostname: 'localhost',
            port: PORT,
            path: '/ota?file=nonexistent.bin',
            method: 'GET'
        });
        
        assert(res5.statusCode === 404, "Missing file returns 404");
        
        // Test 6: Missing file parameter
        const res6 = await httpRequest({
            hostname: 'localhost',
            port: PORT,
            path: '/ota',
            method: 'GET'
        });
        
        assert(res6.statusCode === 400, "Missing file param returns 400");
        
        // Test 7: Small file (single chunk)
        const res7 = await httpRequest({
            hostname: 'localhost',
            port: PORT,
            path: '/ota?file=small.bin',
            method: 'GET'
        });
        
        assert(res7.statusCode === 200, "Small file returns 200");
        assert(res7.headers['x-total-chunks'] === '1', "Small file has 1 chunk");
        assert(res7.body.length === 2 + 100 + 4, "Small file chunk size correct");
        
        // Test 8: Verify CRC32
        const payload = res1.body.slice(2, 2 + 1024);
        const receivedCrc = res1.body.readUInt32LE(2 + 1024);
        const calculatedCrc = ChunkServer.crc32(payload);
        console.log(`Received CRC:  ${receivedCrc.toString(16)}`);
        console.log(`Calculated CRC: ${calculatedCrc.toString(16)}`);
        console.log(`Calculated >>>0: ${(calculatedCrc >>> 0).toString(16)}`);
        assert(receivedCrc === (calculatedCrc >>> 0), "CRC32 verification passed");
        
    } catch (err) {
        console.error("Test error:", err);
        failed++;
    } finally {
        await server.stop();
        cleanupTestFiles();
    }
    
    console.log("\n========================================");
    console.log(` Results: ${passed} passed, ${failed} failed`);
    console.log("========================================");
    
    process.exit(failed === 0 ? 0 : 1);
}

runTests().catch(err => {
    console.error("Fatal error:", err);
    process.exit(1);
});