/**
 * Hamekara POS Bridge (PEC_PCPOS file-drop)
 * -----------------------------------------
 * Exposes HTTP endpoints your app can call to trigger POS operations.
 * It writes a request .txt into C:\Users\Public\PEC_PCPOS\request
 * and waits for a response .txt in C:\Users\Public\PEC_PCPOS\response,
 * which are handled by the Parsian Windows service (PEC_PCPOS).
 *
 * Endpoints:
 *   POST /pos/sale    -> { amount, invoice? }
 *   POST /pos/cancel  -> { invoice? , traceNo? }  // only if your PEC supports it
 *   GET  /pos/health  -> service folders + POS config status
 *
 * Environment Variables (optional):
 *   PORT=9090
 *   POS_IP=192.168.100.90
 *   POS_PORT=2020
 *   PEC_REQ_DIR=C:\Users\Public\PEC_PCPOS\request
 *   PEC_RES_DIR=C:\Users\Public\PEC_PCPOS\response
 *   PEC_CANCEL_OP=CANCEL    // or ABORT or whatever your build requires
 *   SALE_TIMEOUT_MS=90000
 *   CANCEL_TIMEOUT_MS=30000
 *8696814046000
 * 
 * Dependencies: express, cors
 *   npm install express cors
 */

const express = require('express');
const cors = require('cors');
const fs = require('fs');
const path = require('path');

// -----------------------------
// Configuration
// -----------------------------
const PORT = parseInt(process.env.PORT || '9090', 10);

// POS network
const POS_IP = process.env.POS_IP || '192.168.100.90';
const POS_PORT = parseInt(process.env.POS_PORT || '2020', 10);

// PEC file-drop directories
const REQ_DIR = process.env.PEC_REQ_DIR || 'C:\\Users\\Public\\PEC_PCPOS\\request';
const RES_DIR = process.env.PEC_RES_DIR || 'C:\\Users\\Public\\PEC_PCPOS\\response';

// Ops / timeouts
const SALE_TIMEOUT_MS = parseInt(process.env.SALE_TIMEOUT_MS || '90000', 10);
const CANCEL_TIMEOUT_MS = parseInt(process.env.CANCEL_TIMEOUT_MS || '30000', 10);
const CANCEL_OP = (process.env.PEC_CANCEL_OP || 'CANCEL').trim().toUpperCase();

// basic polling cadence (ms)
const POLL_MS = 100;
const FS_STABILIZE_MS = 50;

// -----------------------------
// Utilities
// -----------------------------

// Ensure directories exist (creates if missing)
for (const d of [REQ_DIR, RES_DIR]) {
    try {
        if (!fs.existsSync(d)) fs.mkdirSync(d, { recursive: true });
    } catch (e) {
        // If these are truly managed by the PEC installer, creation might fail on locked systems; it's ok.
    }
}

// Simple process-wide mutex to serialize device access
let busy = false;
function lock() {
    return new Promise(resolve => {
        const tryEnter = () => (!busy ? ((busy = true), resolve()) : setTimeout(tryEnter, 40));
        tryEnter();
    });
}
function unlock() { busy = false; }

// Atomic write helper (write .part then rename)
function writeAtomic(filePath, content) {
    const tmp = filePath + '.part';
    fs.writeFileSync(tmp, content, 'utf8');
    fs.renameSync(tmp, filePath);
}

// Parse key=value text file into object
function parseKV(text) {
    const out = {};
    String(text || '')
        .split(/\r?\n/)
        .forEach(line => {
            const i = line.indexOf('=');
            if (i > 0) {
                const k = line.slice(0, i).trim();
                const v = line.slice(i + 1).trim();
                if (k) out[k] = v;
            }
        });
    return out;
}

// Generate a unique safe tag for paired req/resp files
function makeTag(prefix) {
    const stamp = new Date().toISOString().replace(/[:]/g, '-');
    const rnd = Math.floor(1000 + Math.random() * 9000);
    return `${prefix}_${stamp}_${rnd}`;
}

// Wait until a specific file appears or timeout
async function waitForFile(filePath, timeoutMs) {
    const start = Date.now();
    while (Date.now() - start < timeoutMs) {
        if (fs.existsSync(filePath)) {
            // tiny delay to let PEC finish writing file fully
            await new Promise(r => setTimeout(r, FS_STABILIZE_MS));
            try {
                return fs.readFileSync(filePath, 'utf8');
            } catch (_) {
                // in case of transient file-lock, brief wait then retry
            }
        }
        await new Promise(r => setTimeout(r, POLL_MS));
    }
    throw new Error('POS timeout');
}

// Clean a few old files with same tag (safety; not strictly required)
function safeCleanup(filePath) {
    try { if (fs.existsSync(filePath)) fs.unlinkSync(filePath); } catch (_) {}
    try { if (fs.existsSync(filePath + '.part')) fs.unlinkSync(filePath + '.part'); } catch (_) {}
}

// -----------------------------
// Core POS Ops (via PEC file-drop)
// -----------------------------

async function doSale(amountRial, invoice, timeoutMs = SALE_TIMEOUT_MS) {
    if (!fs.existsSync(REQ_DIR) || !fs.existsSync(RES_DIR)) {
        throw new Error('POS folders not found. Ensure PEC_PCPOS Windows component is installed and running.');
    }

    const tag = makeTag('SALE');
    const reqFile = path.join(REQ_DIR, `${tag}.txt`);
    const resFile = path.join(RES_DIR, `${tag}.txt`);

    // Build request payload (keys expected by your PEC build)
    const payloadLines = [
        'TYPE=LAN',
        `IP=${POS_IP}`,
        `PORT=${POS_PORT}`,
        'OP=SALE',
        `AMOUNT=${amountRial}`,
        `INVOICE=${invoice}`
    ];
    const payload = payloadLines.join('\r\n') + '\r\n';

    // Clean any leftovers and write request
    safeCleanup(reqFile);
    safeCleanup(resFile);
    writeAtomic(reqFile, payload);

    // Wait for matching response
    const raw = await waitForFile(resFile, timeoutMs);
    const kv = parseKV(raw);

    // Normalize common fields
    const code = String(kv.ResponseCode || kv.CODE || kv.Code || '');
    return {
        ok: code === '0',
        code,
        message: kv.Message || kv.Msg || '',
        amount: Number(amountRial),
        invoice,
        rrn: kv.RRN || kv.RefNo || '',
        stan: kv.STAN || '',
        traceNo: kv.TraceNo || kv.TRACE || '',
        cardMasked: kv.PAN || kv.CardNo || '',
        authCode: kv.AuthCode || kv.Auth || '',
        raw
    };
}

// Optional cancel/abort operation (only if your PEC build supports it)
// Many builds require TRACE or INVOICE; OP name may differ (CANCEL/ABORT/VOID)
async function doCancel({ invoice, traceNo, timeoutMs = CANCEL_TIMEOUT_MS, op = CANCEL_OP }) {
    if (!fs.existsSync(REQ_DIR) || !fs.existsSync(RES_DIR)) {
        throw new Error('POS folders not found. Ensure PEC_PCPOS Windows component is installed and running.');
    }

    const tag = makeTag('CANCEL');
    const reqFile = path.join(REQ_DIR, `${tag}.txt`);
    const resFile = path.join(RES_DIR, `${tag}.txt`);

    const lines = [
        'TYPE=LAN',
        `IP=${POS_IP}`,
        `PORT=${POS_PORT}`,
        `OP=${op}`,
    ];
    if (invoice) lines.push(`INVOICE=${String(invoice).slice(0, 40)}`);
    if (traceNo) lines.push(`TRACE=${String(traceNo).slice(0, 40)}`);

    const payload = lines.join('\r\n') + '\r\n';

    safeCleanup(reqFile);
    safeCleanup(resFile);
    writeAtomic(reqFile, payload);

    const raw = await waitForFile(resFile, timeoutMs);
    const kv = parseKV(raw);
    const code = String(kv.ResponseCode || kv.CODE || kv.Code || '');
    return {
        ok: code === '0',
        code,
        message: kv.Message || kv.Msg || '',
        invoice: invoice || '',
        traceNo: traceNo || '',
        raw,
        kv
    };
}

// -----------------------------
// HTTP Server
// -----------------------------
const app = express();

app.use(express.json({ limit: '64kb' }));
app.use(cors({
    origin: [
        'https://hamekara.com',
        'https://admin.hamekara.com',
        'http://localhost',
        'http://127.0.0.1'
    ],
    credentials: false
}));

// Health check (folders + current POS config)
app.get('/pos/health', (req, res) => {
    const okReq = fs.existsSync(REQ_DIR);
    const okRes = fs.existsSync(RES_DIR);
    res.json({
        ok: okReq && okRes,
        reqDir: { path: REQ_DIR, exists: okReq },
        resDir: { path: RES_DIR, exists: okRes },
        pos: { ip: POS_IP, port: POS_PORT },
        timeouts: { saleMs: SALE_TIMEOUT_MS, cancelMs: CANCEL_TIMEOUT_MS },
        cancelOp: CANCEL_OP
    });
});

// SALE endpoint
app.post('/pos/sale', async (req, res) => {
    await lock();
    const startedAt = Date.now();
    try {
        const rawAmount = String(req.body.amount ?? '').trim();
        const amount = rawAmount.replace(/\D/g, ''); // keep digits only
        const invoice = String(req.body.invoice || `INV-${Date.now()}`).slice(0, 40);

        if (!amount || amount === '0') {
            return res.status(422).json({ ok: false, code: 'INVALID', message: 'Invalid amount' });
        }

        console.log(`[SALE] amount=${amount} invoice=${invoice} -> ${POS_IP}:${POS_PORT}`);
        const result = await doSale(amount, invoice);
        const ms = Date.now() - startedAt;
        console.log(`[SALE] done in ${ms}ms ok=${result.ok} code=${result.code} rrn=${result.rrn || '-'} trace=${result.traceNo || '-'}`);
        res.json(result);
    } catch (e) {
        const msg = e && e.message ? e.message : String(e);
        console.error(`[SALE] ERROR: ${msg}`);
        res.status(/timeout/i.test(msg) ? 504 : 500).json({ ok: false, code: 'ERR', message: msg });
    } finally {
        unlock();
    }
});

// CANCEL endpoint (works only if PEC build supports OP name + fields)
app.post('/pos/cancel', async (req, res) => {
    await lock();
    const startedAt = Date.now();
    try {
        const invoice = req.body.invoice ? String(req.body.invoice).slice(0, 40) : '';
        const traceNo = req.body.traceNo ? String(req.body.traceNo).slice(0, 40) : '';
        if (!invoice && !traceNo) {
            return res.status(422).json({ ok: false, code: 'INVALID', message: 'invoice or traceNo required' });
        }
        console.log(`[CANCEL] op=${CANCEL_OP} invoice=${invoice || '-'} trace=${traceNo || '-'} -> ${POS_IP}:${POS_PORT}`);
        const out = await doCancel({ invoice, traceNo });
        const ms = Date.now() - startedAt;
        console.log(`[CANCEL] done in ${ms}ms ok=${out.ok} code=${out.code}`);
        res.json(out);
    } catch (e) {
        const msg = e && e.message ? e.message : String(e);
        console.error(`[CANCEL] ERROR: ${msg}`);
        res.status(/timeout/i.test(msg) ? 504 : 500).json({ ok: false, code: 'ERR', message: msg });
    } finally {
        unlock();
    }
});

// Root (tiny help)
app.get('/', (req, res) => {
    res.type('text/plain').send(
        `Hamekara POS Bridge is running.

POST /pos/sale    { "amount": 120000, "invoice": "INV-123" }
POST /pos/cancel  { "invoice": "INV-123" } or { "traceNo": "000123" }   // if supported
GET  /pos/health

Config:
  PORT=${PORT}
  POS_IP=${POS_IP}
  POS_PORT=${POS_PORT}
  REQ_DIR=${REQ_DIR}
  RES_DIR=${RES_DIR}
  SALE_TIMEOUT_MS=${SALE_TIMEOUT_MS}
  CANCEL_TIMEOUT_MS=${CANCEL_TIMEOUT_MS}
  PEC_CANCEL_OP=${CANCEL_OP}
`);
});

// -----------------------------
// Start server
// -----------------------------
app.listen(PORT, () => {
    console.log(`POS bridge on http://localhost:${PORT}`);
    console.log(`Using POS ${POS_IP}:${POS_PORT}`);
    console.log(`ReqDir: ${REQ_DIR}`);
    console.log(`ResDir: ${RES_DIR}`);
});