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 =16;
end
% There are a total of 6 entries in each of the rate and state variable arrays.
% There are a total of 23 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 environment (second)');
    LEGEND_ALGEBRAIC(:,1) = strpad('q_L_B1_init in component environment (fmol)');
    LEGEND_CONSTANTS(:,1) = strpad('q_R_B1_init in component environment (fmol)');
    LEGEND_CONSTANTS(:,2) = strpad('q_Gs_init in component environment (fmol)');
    LEGEND_CONSTANTS(:,3) = strpad('q_LR_B1_init in component environment (fmol)');
    LEGEND_CONSTANTS(:,4) = strpad('q_R_B1Gs_init in component environment (fmol)');
    LEGEND_CONSTANTS(:,5) = strpad('q_LR_B1Gs_init in component environment (fmol)');
    LEGEND_CONSTANTS(:,6) = strpad('stimSt in component environment (second)');
    LEGEND_CONSTANTS(:,7) = strpad('stimDur in component environment (second)');
    LEGEND_CONSTANTS(:,8) = strpad('tR in component environment (second)');
    LEGEND_CONSTANTS(:,9) = strpad('stimMag in component environment (fmol)');
    LEGEND_CONSTANTS(:,10) = strpad('stimHolding in component environment (fmol)');
    LEGEND_CONSTANTS(:,23) = strpad('m in component environment (fmol_per_sec)');
    LEGEND_ALGEBRAIC(:,2) = strpad('q_L_B1 in component environment (fmol)');
    LEGEND_ALGEBRAIC(:,3) = strpad('q_R_B1 in component environment (fmol)');
    LEGEND_ALGEBRAIC(:,4) = strpad('q_Gs in component environment (fmol)');
    LEGEND_ALGEBRAIC(:,5) = strpad('q_LR_B1 in component environment (fmol)');
    LEGEND_ALGEBRAIC(:,6) = strpad('q_R_B1Gs in component environment (fmol)');
    LEGEND_ALGEBRAIC(:,7) = strpad('q_LR_B1Gs in component environment (fmol)');
    LEGEND_STATES(:,1) = strpad('q_L_B1 in component LRGbinding_B1AR (fmol)');
    LEGEND_STATES(:,2) = strpad('q_R_B1 in component LRGbinding_B1AR (fmol)');
    LEGEND_STATES(:,3) = strpad('q_Gs in component LRGbinding_B1AR (fmol)');
    LEGEND_STATES(:,4) = strpad('q_LR_B1 in component LRGbinding_B1AR (fmol)');
    LEGEND_STATES(:,5) = strpad('q_R_B1Gs in component LRGbinding_B1AR (fmol)');
    LEGEND_STATES(:,6) = strpad('q_LR_B1Gs in component LRGbinding_B1AR (fmol)');
    LEGEND_CONSTANTS(:,11) = strpad('kappa_R_C_B1 in component LRGbinding_B1AR_parameters (fmol_per_sec)');
    LEGEND_CONSTANTS(:,12) = strpad('kappa_R_R_B1 in component LRGbinding_B1AR_parameters (fmol_per_sec)');
    LEGEND_CONSTANTS(:,13) = strpad('kappa_R_L_B1 in component LRGbinding_B1AR_parameters (fmol_per_sec)');
    LEGEND_CONSTANTS(:,14) = strpad('K_L_B1 in component LRGbinding_B1AR_parameters (per_fmol)');
    LEGEND_CONSTANTS(:,15) = strpad('K_R_B1 in component LRGbinding_B1AR_parameters (per_fmol)');
    LEGEND_CONSTANTS(:,16) = strpad('K_Gs in component LRGbinding_B1AR_parameters (per_fmol)');
    LEGEND_CONSTANTS(:,17) = strpad('K_LR_B1 in component LRGbinding_B1AR_parameters (per_fmol)');
    LEGEND_CONSTANTS(:,18) = strpad('K_R_B1Gs in component LRGbinding_B1AR_parameters (per_fmol)');
    LEGEND_CONSTANTS(:,19) = strpad('K_LR_B1Gs in component LRGbinding_B1AR_parameters (per_fmol)');
    LEGEND_CONSTANTS(:,20) = strpad('R in component constants (J_per_K_per_mol)');
    LEGEND_CONSTANTS(:,21) = strpad('T in component constants (kelvin)');
    LEGEND_ALGEBRAIC(:,8) = strpad('mu_L_B1 in component LRGbinding_B1AR (J_per_mol)');
    LEGEND_ALGEBRAIC(:,9) = strpad('mu_R_B1 in component LRGbinding_B1AR (J_per_mol)');
    LEGEND_ALGEBRAIC(:,10) = strpad('mu_Gs in component LRGbinding_B1AR (J_per_mol)');
    LEGEND_ALGEBRAIC(:,11) = strpad('mu_LR_B1 in component LRGbinding_B1AR (J_per_mol)');
    LEGEND_ALGEBRAIC(:,12) = strpad('mu_R_B1Gs in component LRGbinding_B1AR (J_per_mol)');
    LEGEND_ALGEBRAIC(:,13) = strpad('mu_LR_B1Gs in component LRGbinding_B1AR (J_per_mol)');
    LEGEND_ALGEBRAIC(:,14) = strpad('v_R_C_B1 in component LRGbinding_B1AR (fmol_per_sec)');
    LEGEND_ALGEBRAIC(:,15) = strpad('v_R_R_B1 in component LRGbinding_B1AR (fmol_per_sec)');
    LEGEND_ALGEBRAIC(:,16) = strpad('v_R_L_B1 in component LRGbinding_B1AR (fmol_per_sec)');
    LEGEND_CONSTANTS(:,22) = strpad('F in component constants (C_per_mol)');
    LEGEND_RATES(:,1) = strpad('d/dt q_L_B1 in component LRGbinding_B1AR (fmol)');
    LEGEND_RATES(:,2) = strpad('d/dt q_R_B1 in component LRGbinding_B1AR (fmol)');
    LEGEND_RATES(:,3) = strpad('d/dt q_Gs in component LRGbinding_B1AR (fmol)');
    LEGEND_RATES(:,4) = strpad('d/dt q_LR_B1 in component LRGbinding_B1AR (fmol)');
    LEGEND_RATES(:,5) = strpad('d/dt q_R_B1Gs in component LRGbinding_B1AR (fmol)');
    LEGEND_RATES(:,6) = strpad('d/dt q_LR_B1Gs in component LRGbinding_B1AR (fmol)');
    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) = 0.0004579000;
    CONSTANTS(:,2) = 0.1455400000;
    CONSTANTS(:,3) = 0;
    CONSTANTS(:,4) = 0;
    CONSTANTS(:,5) = 0;
    CONSTANTS(:,6) = 3.1;
    CONSTANTS(:,7) = 0.5e1;
    CONSTANTS(:,8) = 0.3e1;
    CONSTANTS(:,9) = 1e-7;
    CONSTANTS(:,10) = 1e-8;
    STATES(:,1) = 1e-16;
    STATES(:,2) = 1e-16;
    STATES(:,3) = 1e-16;
    STATES(:,4) = 1e-16;
    STATES(:,5) = 1e-16;
    STATES(:,6) = 1e-16;
    CONSTANTS(:,11) = 5573.84;
    CONSTANTS(:,12) = 641.71;
    CONSTANTS(:,13) = 1143.57;
    CONSTANTS(:,14) = 0.885956;
    CONSTANTS(:,15) = 0.834078;
    CONSTANTS(:,16) = 0.18177;
    CONSTANTS(:,17) = 7.24472;
    CONSTANTS(:,18) = 172.108;
    CONSTANTS(:,19) = 2.80863;
    CONSTANTS(:,20) = 8.31;
    CONSTANTS(:,21) = 310;
    CONSTANTS(:,22) = 96485;
    CONSTANTS(:,23) = CONSTANTS(:,9)./CONSTANTS(:,8);
    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(:,3) = STATES(:,2)+CONSTANTS(:,1);
    ALGEBRAIC(:,9) =  CONSTANTS(:,20).*CONSTANTS(:,21).*log( CONSTANTS(:,15).*ALGEBRAIC(:,3));
    ALGEBRAIC(:,4) = STATES(:,3)+CONSTANTS(:,2);
    ALGEBRAIC(:,10) =  CONSTANTS(:,20).*CONSTANTS(:,21).*log( CONSTANTS(:,16).*ALGEBRAIC(:,4));
    ALGEBRAIC(:,6) = STATES(:,5)+CONSTANTS(:,4);
    ALGEBRAIC(:,12) =  CONSTANTS(:,20).*CONSTANTS(:,21).*log( CONSTANTS(:,18).*ALGEBRAIC(:,6));
    ALGEBRAIC(:,14) =  CONSTANTS(:,11).*exp((ALGEBRAIC(:,9)+ALGEBRAIC(:,10))./( CONSTANTS(:,20).*CONSTANTS(:,21))) - exp(ALGEBRAIC(:,12)./( CONSTANTS(:,20).*CONSTANTS(:,21)));
    RATES(:,5) = ALGEBRAIC(:,14);
    ALGEBRAIC(:,5) = STATES(:,4)+CONSTANTS(:,3);
    ALGEBRAIC(:,11) =  CONSTANTS(:,20).*CONSTANTS(:,21).*log( CONSTANTS(:,17).*ALGEBRAIC(:,5));
    ALGEBRAIC(:,7) = STATES(:,6)+CONSTANTS(:,5);
    ALGEBRAIC(:,13) =  CONSTANTS(:,20).*CONSTANTS(:,21).*log( CONSTANTS(:,19).*ALGEBRAIC(:,7));
    ALGEBRAIC(:,15) =  CONSTANTS(:,12).*exp((ALGEBRAIC(:,11)+ALGEBRAIC(:,10))./( CONSTANTS(:,20).*CONSTANTS(:,21))) - exp(ALGEBRAIC(:,13)./( CONSTANTS(:,20).*CONSTANTS(:,21)));
    RATES(:,3) =  - ALGEBRAIC(:,14) - ALGEBRAIC(:,15);
    RATES(:,6) = ALGEBRAIC(:,15);
    ALGEBRAIC(:,1) = piecewise({VOI<CONSTANTS(:,6)&VOI>CONSTANTS(:,6) - CONSTANTS(:,8), CONSTANTS(:,10)+ CONSTANTS(:,23).*((VOI - CONSTANTS(:,6))+CONSTANTS(:,8)) , VOI>=CONSTANTS(:,6)&VOI<CONSTANTS(:,6)+CONSTANTS(:,7), CONSTANTS(:,9)+CONSTANTS(:,10) , VOI<CONSTANTS(:,6)+CONSTANTS(:,8)+CONSTANTS(:,7)&VOI>=CONSTANTS(:,6)+CONSTANTS(:,7), CONSTANTS(:,10)+  - CONSTANTS(:,23).*(((VOI - CONSTANTS(:,6)) - CONSTANTS(:,8)) - CONSTANTS(:,7)) }, CONSTANTS(:,10));
    ALGEBRAIC(:,2) = STATES(:,1)+ALGEBRAIC(:,1);
    ALGEBRAIC(:,8) =  CONSTANTS(:,20).*CONSTANTS(:,21).*log( CONSTANTS(:,14).*ALGEBRAIC(:,2));
    ALGEBRAIC(:,16) =  CONSTANTS(:,13).*exp((ALGEBRAIC(:,9)+ALGEBRAIC(:,8))./( CONSTANTS(:,20).*CONSTANTS(:,21))) - exp(ALGEBRAIC(:,11)./( CONSTANTS(:,20).*CONSTANTS(:,21)));
    RATES(:,1) =  - ALGEBRAIC(:,16);
    RATES(:,2) =  - ALGEBRAIC(:,14) - ALGEBRAIC(:,16);
    RATES(:,4) =  - ALGEBRAIC(:,15)+ALGEBRAIC(:,16);
   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(:,3) = STATES(:,2)+CONSTANTS(:,1);
    ALGEBRAIC(:,9) =  CONSTANTS(:,20).*CONSTANTS(:,21).*log( CONSTANTS(:,15).*ALGEBRAIC(:,3));
    ALGEBRAIC(:,4) = STATES(:,3)+CONSTANTS(:,2);
    ALGEBRAIC(:,10) =  CONSTANTS(:,20).*CONSTANTS(:,21).*log( CONSTANTS(:,16).*ALGEBRAIC(:,4));
    ALGEBRAIC(:,6) = STATES(:,5)+CONSTANTS(:,4);
    ALGEBRAIC(:,12) =  CONSTANTS(:,20).*CONSTANTS(:,21).*log( CONSTANTS(:,18).*ALGEBRAIC(:,6));
    ALGEBRAIC(:,14) =  CONSTANTS(:,11).*exp((ALGEBRAIC(:,9)+ALGEBRAIC(:,10))./( CONSTANTS(:,20).*CONSTANTS(:,21))) - exp(ALGEBRAIC(:,12)./( CONSTANTS(:,20).*CONSTANTS(:,21)));
    ALGEBRAIC(:,5) = STATES(:,4)+CONSTANTS(:,3);
    ALGEBRAIC(:,11) =  CONSTANTS(:,20).*CONSTANTS(:,21).*log( CONSTANTS(:,17).*ALGEBRAIC(:,5));
    ALGEBRAIC(:,7) = STATES(:,6)+CONSTANTS(:,5);
    ALGEBRAIC(:,13) =  CONSTANTS(:,20).*CONSTANTS(:,21).*log( CONSTANTS(:,19).*ALGEBRAIC(:,7));
    ALGEBRAIC(:,15) =  CONSTANTS(:,12).*exp((ALGEBRAIC(:,11)+ALGEBRAIC(:,10))./( CONSTANTS(:,20).*CONSTANTS(:,21))) - exp(ALGEBRAIC(:,13)./( CONSTANTS(:,20).*CONSTANTS(:,21)));
    ALGEBRAIC(:,1) = piecewise({VOI<CONSTANTS(:,6)&VOI>CONSTANTS(:,6) - CONSTANTS(:,8), CONSTANTS(:,10)+ CONSTANTS(:,23).*((VOI - CONSTANTS(:,6))+CONSTANTS(:,8)) , VOI>=CONSTANTS(:,6)&VOI<CONSTANTS(:,6)+CONSTANTS(:,7), CONSTANTS(:,9)+CONSTANTS(:,10) , VOI<CONSTANTS(:,6)+CONSTANTS(:,8)+CONSTANTS(:,7)&VOI>=CONSTANTS(:,6)+CONSTANTS(:,7), CONSTANTS(:,10)+  - CONSTANTS(:,23).*(((VOI - CONSTANTS(:,6)) - CONSTANTS(:,8)) - CONSTANTS(:,7)) }, CONSTANTS(:,10));
    ALGEBRAIC(:,2) = STATES(:,1)+ALGEBRAIC(:,1);
    ALGEBRAIC(:,8) =  CONSTANTS(:,20).*CONSTANTS(:,21).*log( CONSTANTS(:,14).*ALGEBRAIC(:,2));
    ALGEBRAIC(:,16) =  CONSTANTS(:,13).*exp((ALGEBRAIC(:,9)+ALGEBRAIC(:,8))./( CONSTANTS(:,20).*CONSTANTS(:,21))) - exp(ALGEBRAIC(:,11)./( CONSTANTS(:,20).*CONSTANTS(:,21)));
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