classdef MLSE_test < IMDDTestCase
    methods (Test, TestTags = {'unit', 'fast', 'dsp', 'mlse'})
        function constructorStoresConfiguration(testCase)
            mlse = MLSE( ...
                "M", 4, ...
                "DIR", [1 0.35], ...
                "trellis_states", [-3 -1 1 3], ...
                "duobinary_output", false, ...
                "trellis_state_mode", 2, ...
                "trellis_exclusion", 0, ...
                "scale_mode", 0, ...
                "debug", 0);

            testCase.verifyEqual(mlse.M, 4);
            testCase.verifyEqual(mlse.DIR, [1 0.35]);
            testCase.verifyEqual(mlse.trellis_states, [-3 -1 1 3]);
            testCase.verifyFalse(mlse.duobinary_output);
            testCase.verifyEqual(mlse.trellis_state_mode, 2);
            testCase.verifyEqual(mlse.trellis_exclusion, 0);
            testCase.verifyEqual(mlse.scale_mode, 0);
            testCase.verifyEqual(mlse.debug, 0);
        end

        function processRecoversKnownPAM4Sequence(testCase)
            [txBits, txSymbols, rxSymbols, mlse] = makePam4Fixture();

            txSignal = Informationsignal(txSymbols, "fs", 1);
            rxSignal = Signal(rxSymbols, "fs", 1);

            hdSignal = mlse.process(rxSignal, txSignal);
            rxBits = PAMmapper(4, 0).demap(hdSignal);

            testCase.verifyClass(hdSignal, "Signal");
            testCase.verifyEqual(hdSignal.fs, rxSignal.fs);
            testCase.verifyEqual(rxBits.signal, txBits, ...
                "MLSE should recover the transmitted PAM-4 bits on the deterministic fixture.");
        end

        function processReturnsExpectedShapesAndFiniteMetric(testCase)
            [txBits, txSymbols, rxSymbols, mlse] = makePam4Fixture();

            [viterbiSymbols, llr, gmi] = mlse.process_(rxSymbols, txSymbols);
            rxBits = PAMmapper(4, 0).demap(viterbiSymbols(:));
            expectedSymbols = txSymbols(:) ./ rms(txSymbols(:));

            testCase.verifyEqual(numel(viterbiSymbols), numel(rxSymbols));
            testCase.verifyEqual(size(llr), [numel(rxSymbols), 2]);
            testCase.verifyTrue(isfinite(gmi));
            testCase.verifyEqual(viterbiSymbols(:), expectedSymbols, "AbsTol", 1e-12);
            testCase.verifyEqual(rxBits, txBits, ...
                "Lower-level MLSE output should decode the same deterministic fixture.");
        end
    end
end

function [txBits, txSymbols, rxSymbols, mlse] = makePam4Fixture()
    txBits = [ ...
        0 0; ...
        0 1; ...
        1 1; ...
        1 0; ...
        0 1; ...
        1 0; ...
        0 0; ...
        1 1];

    mapper = PAMmapper(4, 0);
    txSignal = Informationsignal(txBits);
    txSymbols = mapper.map(txSignal).signal;

    channel = [1 0.35];
    rxSymbols = filter(channel, 1, txSymbols);
    rxSymbols = rxSymbols + 0.01 * [0; 1; -1; 2; -2; 1; -1; 0];

    mlse = MLSE( ...
        "M", 4, ...
        "DIR", channel, ...
        "trellis_states", mapper.levels, ...
        "duobinary_output", false, ...
        "trellis_state_mode", 2, ...
        "trellis_exclusion", 0, ...
        "scale_mode", 0, ...
        "debug", 0);
end