const { canBindTcpPort } = require('./jlinkPortCheck.cjs');

/** Preferred ports per session (dynamic fallback if busy). */
const JLINK_PORTS_BY_SESSION = {
    receiver: {
        gdb: 29021,
        swo: 29022,
        rtt: 19021,
    },
    transmitter: {
        gdb: 29031,
        swo: 29032,
        rtt: 19022,
    },
};

const GDB_PORT_RANGE = { min: 29000, max: 29199 };
const SWO_PORT_RANGE = { min: 29000, max: 29199 };
const RTT_PORT_RANGE = { min: 19020, max: 19199 };

const portCandidates = (preferred, min, max) => {
    const ordered = [preferred];
    for (let port = min; port <= max; port++) {
        if (port !== preferred) ordered.push(port);
    }
    return ordered;
};

const pickTcpPort = async (preferred, range, reserved) => {
    for (const port of portCandidates(preferred, range.min, range.max)) {
        if (reserved.has(port)) continue;
        if (await canBindTcpPort('127.0.0.1', port)) {
            reserved.add(port);
            return port;
        }
    }

    throw new Error(
        `사용 가능한 TCP 포트가 없습니다 (선호 ${preferred}, 범위 ${range.min}-${range.max}). JLinkGDBServerCL을 모두 종료한 뒤 다시 시도하세요.`
    );
};

const allocateSessionPorts = async (sessionId, reserved = new Set()) => {
    const preferred = JLINK_PORTS_BY_SESSION[sessionId];
    if (!preferred) {
        throw new Error(`Unknown session for port allocation: ${sessionId}`);
    }

    return {
        gdb: await pickTcpPort(preferred.gdb, GDB_PORT_RANGE, reserved),
        swo: await pickTcpPort(preferred.swo, SWO_PORT_RANGE, reserved),
        rtt: await pickTcpPort(preferred.rtt, RTT_PORT_RANGE, reserved),
    };
};

module.exports = {
    JLINK_PORTS_BY_SESSION,
    allocateSessionPorts,
};