function workflow = buildReducedImddWorkflow(scenario)
%BUILDREDUCEDIMDDWORKFLOW Build a reduced deterministic IM/DD workflow.
%
% The helper keeps the stage order aligned with the project workflow while
% allowing tests to switch between representative scenarios:
%   - "minimal": reduced regression baseline
%   - "no-impairment": near-ideal baseline with impairment knobs neutralized
%   - "baseline": reference point for monotonicity checks
%   - "impaired": intentionally degraded variant for monotonicity checks

arguments
    scenario (1, 1) string = "minimal"
end

params = scenarioParameters(scenario);
workflow = runReducedWorkflow(params, scenario);
end

function workflow = runReducedWorkflow(params, scenario)
    % -------------------- TX --------------------
    txPulse = Pulseformer( ...
        "fsym", params.fsym, ...
        "fdac", params.fdac, ...
        "pulse", "rrc", ...
        "pulselength", params.pulseLength, ...
        "alpha", params.rcalpha);

    [digiSig, symbols, txBits] = PAMsource( ...
        "fsym", params.fsym, ...
        "M", params.M, ...
        "order", params.sourceOrder, ...
        "useprbs", false, ...
        "fs_out", params.fdac, ...
        "applyclipping", false, ...
        "applypulseform", true, ...
        "pulseformer", txPulse, ...
        "randkey", params.randomKey, ...
        "duobinary_mode", db_mode.no_db, ...
        "mrds_code", 0).process();

    elSig = AWG( ...
        "fdac", params.fdac, ...
        "f_cutoff", params.fsym, ...
        "lpf_active", params.awgLpfActive, ...
        "kover", params.kover, ...
        "bit_resolution", params.awgBitResolution, ...
        "upsampling_method", params.awgUpsamplingMethod, ...
        "precomp_sinc_rolloff", params.awgPrecompSincRolloff, ...
        "normalize2dac", params.awgNormalize2dac).process(digiSig);

    elSig = elSig.normalize("mode", "oneone");
    elSig = elSig .* params.driverScaling;

    % -------------------- Optical Channel --------------------
    optSigTx = EML( ...
        "mode", eml_mode.im_cosinus, ...
        "power", params.opticalPowerDbm, ...
        "fsimu", elSig.fs, ...
        "lambda", params.laserWavelengthNm, ...
        "bias", params.vbias, ...
        "u_pi", params.uPi, ...
        "linewidth", 0, ...
        "randomkey", params.randomKey + 1, ...
        "alpha", 0).process(elSig);

    optSig = Fiber( ...
        "fsimu", optSigTx.fs, ...
        "fiber_length", params.linkLengthKm, ...
        "alpha", params.fiberAlphaDbPerKm, ...
        "D", 0, ...
        "lambda0", 1310, ...
        "gamma", 0, ...
        "Dslope", 0.07).process(optSigTx);

    rxOptSig = Amplifier( ...
        "amp_mode", "ideal_no_noise", ...
        "gain_mode", "output_power", ...
        "amplification_db", params.ropDbm).process(optSig);

    rxSigAfterPd = Photodiode( ...
        "fsimu", params.fdac * params.kover, ...
        "dark_current", 0, ...
        "responsivity", 1, ...
        "temperature", 20, ...
        "nep", 0, ...
        "randomkey", params.randomKey + 2).process(rxOptSig);

    rxSigFiltered = Filter( ...
        "active", params.rxFilterActive, ...
        "filterType", filtertypes.butterworth, ...
        "f_cutoff", params.rxElectricalBandwidthHz, ...
        "fs", params.fdac * params.kover, ...
        "signal_length", 0, ...
        "filtdegree", 4, ...
        "lowpass", 1).process(rxSigAfterPd);

    scopeLpf = Filter( ...
        "active", params.scopeLpfActive, ...
        "filterType", filtertypes.butterworth, ...
        "f_cutoff", params.scopeBandwidthHz, ...
        "fs", params.fadc, ...
        "signal_length", 0, ...
        "filtdegree", 4, ...
        "lowpass", 1);

    scpeSigPreMf = Scope( ...
        "fsimu", params.fdac * params.kover, ...
        "fadc", params.fadc, ...
        "adcresolution", params.scopeAdcResolution, ...
        "quantbuffer", params.scopeQuantBuffer, ...
        "delay", 0, ...
        "fixed_delay", 0, ...
        "filtertype", filtertypes.butterworth, ...
        "samplingdelay", 0, ...
        "rand_samplingdelay", 0, ...
        "freq_offset", 0, ...
        "samp_jitter", 0, ...
        "block_dc", 1, ...
        "lpf_active", params.scopeLpfActive, ...
        "H_lpf", scopeLpf).process(rxSigFiltered);

    rxMatchedFilter = Pulseformer( ...
        "fsym", params.fsym, ...
        "fdac", 2 * params.fsym, ...
        "pulse", "rrc", ...
        "pulselength", params.pulseLength, ...
        "alpha", params.rcalpha, ...
        "matched", 1);
    scpeSig = rxMatchedFilter.process(scpeSigPreMf);

    [syncedSig, ~] = scpeSig.tsynch( ...
        "reference", symbols, ...
        "fs_ref", params.fsym, ...
        "debug_plots", 0);
    syncedCenteredSig = syncedSig - mean(syncedSig.signal);
    syncedSig = syncedCenteredSig;
    syncedSig.signal = syncedSig.signal(1 : 2 * length(symbols));

    % -------------------- DSP --------------------
    ffeEq = FFE( ...
        "epochs_tr", 2, ...
        "epochs_dd", 1, ...
        "len_tr", params.lenTr, ...
        "mu_dd", 1e-4, ...
        "mu_tr", 1e-2, ...
        "order", 21, ...
        "sps", 2, ...
        "decide", 0, ...
        "adaption_technique", adaption_method.nlms, ...
        "dd_mode", 1);

    ffeResults = ffe( ...
        ffeEq, ...
        params.M, ...
        syncedSig, ...
        symbols, ...
        txBits, ...
        "precode_mode", db_mode.no_db, ...
        "showAnalysis", 0, ...
        "postFFE", [], ...
        "eth_style_symbol_mapping", 0);

    mlseEq = FFE( ...
        "epochs_tr", 2, ...
        "epochs_dd", 1, ...
        "len_tr", params.lenTr, ...
        "mu_dd", 1e-4, ...
        "mu_tr", 1e-2, ...
        "order", 21, ...
        "sps", 2, ...
        "decide", 0, ...
        "adaption_technique", adaption_method.nlms, ...
        "dd_mode", 1);
    postfilter = Postfilter("ncoeff", 1, "useBurg", 1);
    mlse = MLSE( ...
        "duobinary_output", 0, ...
        "M", params.M, ...
        "trellis_states", PAMmapper(params.M, 0).levels);

    [vnleResults, mlseResults] = vnle_postfilter_mlse( ...
        mlseEq, ...
        postfilter, ...
        mlse, ...
        params.M, ...
        syncedSig, ...
        symbols, ...
        txBits, ...
        "precode_mode", db_mode.no_db, ...
        "showAnalysis", 0, ...
        "postFFE", [], ...
        "eth_style_symbol_mapping", 0);

    workflow = struct();
    workflow.scenario = scenario;
    workflow.params = params;
    workflow.Digi_sig = digiSig;
    workflow.Symbols = symbols;
    workflow.Tx_bits = txBits;
    workflow.El_sig = elSig;
    workflow.Opt_sig_tx = optSigTx;
    workflow.Opt_sig = optSig;
    workflow.Rx_sig_after_pd = rxSigAfterPd;
    workflow.Rx_sig_filtered = rxSigFiltered;
    workflow.Scpe_sig_pre_mf = scpeSigPreMf;
    workflow.Scpe_sig = scpeSig;
    workflow.Synced_sig_centered = syncedCenteredSig;
    workflow.Synced_sig = syncedSig;
    workflow.ffe_results = ffeResults;
    workflow.vnle_results = vnleResults;
    workflow.mlse_results = mlseResults;
end

function params = scenarioParameters(scenario)
    params = commonParameters();

    switch lower(string(scenario))
        case "minimal"
            params.ropDbm = 0;
            params.rxElectricalBandwidthHz = 40e9;
            params.scopeBandwidthHz = 25e9;

        case "no-impairment"
            params.randomKey = 11;
            params.linkLengthKm = 0;
            params.fiberAlphaDbPerKm = 0;
            params.ropDbm = 3;
            params.rxElectricalBandwidthHz = 200e9;
            params.scopeBandwidthHz = 200e9;
            params.rxFilterActive = false;
            params.scopeLpfActive = false;
            params.scopeAdcResolution = 24;
            params.scopeQuantBuffer = 0.05;
            params.awgLpfActive = false;
            params.awgBitResolution = 12;
            params.awgUpsamplingMethod = upsampling_mode.resample;
            params.awgNormalize2dac = true;

        case "baseline"
            params.ropDbm = 0;
            params.rxElectricalBandwidthHz = 40e9;
            params.scopeBandwidthHz = 25e9;

        case "impaired"
            params.ropDbm = -15;
            params.rxElectricalBandwidthHz = 12e9;
            params.scopeBandwidthHz = 12e9;

        otherwise
            error("buildReducedImddWorkflow:UnknownScenario", ...
                "Unknown reduced IM/DD scenario '%s'.", scenario);
    end
end

function params = commonParameters()
    params = struct();

    params.M = 4;
    params.fsym = 16e9;
    params.fdac = 64e9;
    params.fadc = 64e9;
    params.kover = 2;
    params.randomKey = 1;
    params.sourceOrder = 12;
    params.rcalpha = 0.05;
    params.pulseLength = 12;
    params.lenTr = 256;

    params.uPi = 3;
    params.vbiasRel = 0.5;
    params.vbias = -params.vbiasRel * params.uPi;
    params.driverScaling = 0.6 * (params.uPi / 2 - abs(params.vbias - params.uPi / 2));

    params.laserWavelengthNm = 1293;
    params.opticalPowerDbm = 3;
    params.linkLengthKm = 1;
    params.fiberAlphaDbPerKm = 0.3;

    params.ropDbm = 0;
    params.rxElectricalBandwidthHz = 40e9;
    params.scopeBandwidthHz = 25e9;
    params.rxFilterActive = true;
    params.scopeLpfActive = true;
    params.scopeAdcResolution = 8;
    params.scopeQuantBuffer = 0.1;
    params.awgLpfActive = false;
    params.awgBitResolution = 8;
    params.awgUpsamplingMethod = upsampling_mode.samplehold;
    params.awgPrecompSincRolloff = 1;
    params.awgNormalize2dac = false;
end