function [VOI, STATES, ALGEBRAIC, CONSTANTS] = mainFunction()
    % This is the "main function".  In Matlab, things work best if you rename this function to match the filename.
   [VOI, STATES, ALGEBRAIC, CONSTANTS] = solveModel();
end

function [algebraicVariableCount] = getAlgebraicVariableCount() 
    % Used later when setting a global variable with the number of algebraic variables.
    % Note: This is not the "main method".  
    algebraicVariableCount =6;
end
% There are a total of 4 entries in each of the rate and state variable arrays.
% There are a total of 17 entries in the constant variable array.
%

function [VOI, STATES, ALGEBRAIC, CONSTANTS] = solveModel()
    % Create ALGEBRAIC of correct size
    global algebraicVariableCount;  algebraicVariableCount = getAlgebraicVariableCount();
    % Initialise constants and state variables
    [INIT_STATES, CONSTANTS] = initConsts;

    % Set timespan to solve over 
    tspan = [0, 10];

    % Set numerical accuracy options for ODE solver
    options = odeset('RelTol', 1e-06, 'AbsTol', 1e-06, 'MaxStep', 1);

    % Solve model with ODE solver
    [VOI, STATES] = ode15s(@(VOI, STATES)computeRates(VOI, STATES, CONSTANTS), tspan, INIT_STATES, options);

    % Compute algebraic variables
    [RATES, ALGEBRAIC] = computeRates(VOI, STATES, CONSTANTS);
    ALGEBRAIC = computeAlgebraic(ALGEBRAIC, CONSTANTS, STATES, VOI);

    % Plot state variables against variable of integration
    [LEGEND_STATES, LEGEND_ALGEBRAIC, LEGEND_VOI, LEGEND_CONSTANTS] = createLegends();
    figure();
    plot(VOI, STATES);
    xlabel(LEGEND_VOI);
    l = legend(LEGEND_STATES);
    set(l,'Interpreter','none');
end

function [LEGEND_STATES, LEGEND_ALGEBRAIC, LEGEND_VOI, LEGEND_CONSTANTS] = createLegends()
    LEGEND_STATES = ''; LEGEND_ALGEBRAIC = ''; LEGEND_VOI = ''; LEGEND_CONSTANTS = '';
    LEGEND_VOI = strpad('time in component temporalExistence (second)');
    LEGEND_CONSTANTS(:,1) = strpad('alphaTF in component Device_TFgenerator (uM_per_second)');
    LEGEND_CONSTANTS(:,15) = strpad('JTF in component Device_TFgenerator (uM_per_second)');
    LEGEND_STATES(:,1) = strpad('TFS in component BioEnv_TFSAssociation (uM)');
    LEGEND_ALGEBRAIC(:,6) = strpad('Jgain_TF in component BioEnv_TFSAssociation_interface (uM_per_second)');
    LEGEND_CONSTANTS(:,16) = strpad('Jgain_TFS in component BioEnv_TFSAssociation_interface (uM_per_second)');
    LEGEND_ALGEBRAIC(:,4) = strpad('JTF in component Device_PhzMSgenerator (uM_per_second)');
    LEGEND_STATES(:,2) = strpad('TF in component BioEnv_TFSAssociation (uM)');
    LEGEND_CONSTANTS(:,2) = strpad('s in component BioEnv_TFSAssociation (uM)');
    LEGEND_CONSTANTS(:,3) = strpad('betaTFS in component BioEnv_TFSAssociation (per_uM_per_second)');
    LEGEND_CONSTANTS(:,4) = strpad('kd in component BioEnv_TFSAssociation (per_second)');
    LEGEND_CONSTANTS(:,5) = strpad('deltaTFS in component BioEnv_TFSAssociation (per_second)');
    LEGEND_CONSTANTS(:,6) = strpad('deltaTF in component BioEnv_TFSAssociation (per_second)');
    LEGEND_ALGEBRAIC(:,1) = strpad('Jassociation in component BioEnv_TFSAssociation (uM_per_second)');
    LEGEND_CONSTANTS(:,7) = strpad('gammaPhzMS in component Device_PhzMSgenerator (uM)');
    LEGEND_CONSTANTS(:,8) = strpad('betaPhzMS in component Device_PhzMSgenerator (uM_per_second)');
    LEGEND_ALGEBRAIC(:,2) = strpad('JPhzMS in component Device_PhzMSgenerator (uM_per_second)');
    LEGEND_CONSTANTS(:,9) = strpad('gammaTF in component Device_PhzMSgenerator (uM)');
    LEGEND_CONSTANTS(:,10) = strpad('betaTF in component Device_PhzMSgenerator (uM_per_second)');
    LEGEND_CONSTANTS(:,11) = strpad('feedbackOn in component Device_PhzMSgenerator (dimensionless)');
    LEGEND_ALGEBRAIC(:,5) = strpad('Jgain_PhzMS in component BioEnv_PhzMStoPYO_interface (uM_per_second)');
    LEGEND_CONSTANTS(:,17) = strpad('Jgain_PYO in component BioEnv_PhzMStoPYO_interface (uM_per_second)');
    LEGEND_STATES(:,3) = strpad('PhzMS in component BioEnv_PhzMStoPYO (uM)');
    LEGEND_STATES(:,4) = strpad('PYO in component BioEnv_PhzMStoPYO (uM)');
    LEGEND_CONSTANTS(:,12) = strpad('deltaPhzMS in component BioEnv_PhzMStoPYO (per_second)');
    LEGEND_CONSTANTS(:,13) = strpad('alphaPYO in component BioEnv_PhzMStoPYO (per_second)');
    LEGEND_CONSTANTS(:,14) = strpad('deltaPYO in component BioEnv_PhzMStoPYO (per_second)');
    LEGEND_ALGEBRAIC(:,3) = strpad('JPYOformation in component BioEnv_PhzMStoPYO (uM_per_second)');
    LEGEND_RATES(:,2) = strpad('d/dt TF in component BioEnv_TFSAssociation (uM)');
    LEGEND_RATES(:,1) = strpad('d/dt TFS in component BioEnv_TFSAssociation (uM)');
    LEGEND_RATES(:,3) = strpad('d/dt PhzMS in component BioEnv_PhzMStoPYO (uM)');
    LEGEND_RATES(:,4) = strpad('d/dt PYO in component BioEnv_PhzMStoPYO (uM)');
    LEGEND_STATES  = LEGEND_STATES';
    LEGEND_ALGEBRAIC = LEGEND_ALGEBRAIC';
    LEGEND_RATES = LEGEND_RATES';
    LEGEND_CONSTANTS = LEGEND_CONSTANTS';
end

function [STATES, CONSTANTS] = initConsts()
    VOI = 0; CONSTANTS = []; STATES = []; ALGEBRAIC = [];
    CONSTANTS(:,1) = 0.05;
    STATES(:,1) = 0;
    STATES(:,2) = 8.6207;
    CONSTANTS(:,2) = 5;
    CONSTANTS(:,3) = 1e6;
    CONSTANTS(:,4) = 4e6;
    CONSTANTS(:,5) = 3.851e-4;
    CONSTANTS(:,6) = 5.8e-3;
    CONSTANTS(:,7) = 5;
    CONSTANTS(:,8) = 0.1;
    CONSTANTS(:,9) = 4;
    CONSTANTS(:,10) = 0.07;
    CONSTANTS(:,11) = 1;
    STATES(:,3) = 0;
    STATES(:,4) = 0;
    CONSTANTS(:,12) = 8.0225e-6;
    CONSTANTS(:,13) = 1.3;
    CONSTANTS(:,14) = 5.8e-1;
    CONSTANTS(:,15) = CONSTANTS(:,1);
    CONSTANTS(:,16) = 0.00000;
    CONSTANTS(:,17) = 0.00000;
    if (isempty(STATES)), warning('Initial values for states not set');, end
end

function [RATES, ALGEBRAIC] = computeRates(VOI, STATES, CONSTANTS)
    global algebraicVariableCount;
    statesSize = size(STATES);
    statesColumnCount = statesSize(2);
    if ( statesColumnCount == 1)
        STATES = STATES';
        ALGEBRAIC = zeros(1, algebraicVariableCount);
        utilOnes = 1;
    else
        statesRowCount = statesSize(1);
        ALGEBRAIC = zeros(statesRowCount, algebraicVariableCount);
        RATES = zeros(statesRowCount, statesColumnCount);
        utilOnes = ones(statesRowCount, 1);
    end
    ALGEBRAIC(:,1) =  CONSTANTS(:,3).*CONSTANTS(:,2).*STATES(:,2) -  CONSTANTS(:,4).*STATES(:,1);
    RATES(:,1) = (ALGEBRAIC(:,1) -  CONSTANTS(:,5).*STATES(:,1))+CONSTANTS(:,16);
    ALGEBRAIC(:,3) =  CONSTANTS(:,13).*STATES(:,3);
    RATES(:,4) = (CONSTANTS(:,17) -  CONSTANTS(:,14).*STATES(:,4))+ALGEBRAIC(:,3);
    ALGEBRAIC(:,2) = ( CONSTANTS(:,8).*STATES(:,1))./(CONSTANTS(:,7)+STATES(:,1));
    ALGEBRAIC(:,5) = ALGEBRAIC(:,2);
    RATES(:,3) = ALGEBRAIC(:,5) -  CONSTANTS(:,12).*STATES(:,3);
    ALGEBRAIC(:,4) = piecewise({CONSTANTS(:,11) ~= 0.00000, ( CONSTANTS(:,10).*STATES(:,1))./(CONSTANTS(:,9)+STATES(:,1)) }, 0.00000);
    ALGEBRAIC(:,6) = CONSTANTS(:,15)+ALGEBRAIC(:,4);
    RATES(:,2) = ( - ALGEBRAIC(:,1)+ALGEBRAIC(:,6)) -  CONSTANTS(:,6).*STATES(:,2);
   RATES = RATES';
end

% Calculate algebraic variables
function ALGEBRAIC = computeAlgebraic(ALGEBRAIC, CONSTANTS, STATES, VOI)
    statesSize = size(STATES);
    statesColumnCount = statesSize(2);
    if ( statesColumnCount == 1)
        STATES = STATES';
        utilOnes = 1;
    else
        statesRowCount = statesSize(1);
        utilOnes = ones(statesRowCount, 1);
    end
    ALGEBRAIC(:,1) =  CONSTANTS(:,3).*CONSTANTS(:,2).*STATES(:,2) -  CONSTANTS(:,4).*STATES(:,1);
    ALGEBRAIC(:,3) =  CONSTANTS(:,13).*STATES(:,3);
    ALGEBRAIC(:,2) = ( CONSTANTS(:,8).*STATES(:,1))./(CONSTANTS(:,7)+STATES(:,1));
    ALGEBRAIC(:,5) = ALGEBRAIC(:,2);
    ALGEBRAIC(:,4) = piecewise({CONSTANTS(:,11) ~= 0.00000, ( CONSTANTS(:,10).*STATES(:,1))./(CONSTANTS(:,9)+STATES(:,1)) }, 0.00000);
    ALGEBRAIC(:,6) = CONSTANTS(:,15)+ALGEBRAIC(:,4);
end

% Compute result of a piecewise function
function x = piecewise(cases, default)
    set = [0];
    for i = 1:2:length(cases)
        if (length(cases{i+1}) == 1)
            x(cases{i} & ~set,:) = cases{i+1};
        else
            x(cases{i} & ~set,:) = cases{i+1}(cases{i} & ~set);
        end
        set = set | cases{i};
        if(set), break, end
    end
    if (length(default) == 1)
        x(~set,:) = default;
    else
        x(~set,:) = default(~set);
    end
end

% Pad out or shorten strings to a set length
function strout = strpad(strin)
    req_length = 160;
    insize = size(strin,2);
    if insize > req_length
        strout = strin(1:req_length);
    else
        strout = [strin, blanks(req_length - insize)];
    end
end