function pred = load_predicates(plant)
% LOAD_PREDICATES  Read predicates.json and resolve rhs_expr into numbers.
%
%  Returns:
%    pred.constants              - struct with T_c0, T_cold0, T_f0, T_standby
%    pred.operational_deadbands  - struct of predicates (each: A_poly, b_poly, meaning)
%    pred.safety_limits          - struct of halfspace limits (each: A_poly, b_poly, meaning)
%    pred.mode_invariants        - struct mapping mode-invariant name to
%                                    its conjoined (A_poly, b_poly, components)
%
%  Each halfspace is of the form { x : A_poly * x <= b_poly }.  Conjunctions
%  (polytopes) stack rows into A_poly / b_poly.
%
%  Usage:
%    plant = pke_params();
%    pred  = load_predicates(plant);
%    inv2  = pred.mode_invariants.inv2_holds;
%    is_in = all(inv2.A_poly * x <= inv2.b_poly);

    here = fileparts(mfilename('fullpath'));
    raw  = fileread(fullfile(here, 'predicates.json'));
    J    = jsondecode(raw);

    % --- Constants used in rhs_expr evaluations ---
    T_c0     = plant.T_c0;                                       %#ok<NASGU>
    T_f0     = plant.T_f0;                                       %#ok<NASGU>
    T_cold0  = plant.T_cold0;                                    %#ok<NASGU>
    T_standby_offset_C = J.derived.T_standby_offset_C;
    T_standby = T_c0 + T_standby_offset_C;                       %#ok<NASGU>

    pred.constants = struct( ...
        'T_c0',               plant.T_c0, ...
        'T_f0',               plant.T_f0, ...
        'T_cold0',            plant.T_cold0, ...
        'T_standby',          T_standby, ...
        'T_standby_offset_C', T_standby_offset_C, ...
        'T_standby_offset_F', J.derived.T_standby_offset_F, ...
        't_avg_in_range_halfwidth_C', J.derived.t_avg_in_range_halfwidth_C, ...
        'p_above_crit_threshold_n',   J.derived.p_above_crit_threshold_n, ...
        'T_fuel_limit_C',     J.derived.T_fuel_limit_C, ...
        'T_c_high_trip_C',    J.derived.T_c_high_trip_C, ...
        'n_high_trip',        J.derived.n_high_trip);

    % --- operational_deadbands ---
    pred.operational_deadbands = parse_group(J.operational_deadbands, ...
        T_c0, T_f0, T_cold0, T_standby);

    % --- safety_limits ---
    pred.safety_limits = parse_group(J.safety_limits, ...
        T_c0, T_f0, T_cold0, T_standby);

    % --- mode_invariants: conjunctions of safety_limits entries ---
    inv_names = fieldnames(J.mode_invariants);
    for k = 1:numel(inv_names)
        name = inv_names{k};
        if startsWith(name, '_') || startsWith(name, 'x_'), continue, end
        entry = J.mode_invariants.(name);
        if ~isstruct(entry) || ~isfield(entry, 'conjunction_of'), continue, end
        components = entry.conjunction_of;
        if ischar(components), components = {components}; end
        A_all = [];
        b_all = [];
        for i = 1:numel(components)
            comp = components{i};
            A_all = [A_all; pred.safety_limits.(comp).A_poly];  %#ok<AGROW>
            b_all = [b_all; pred.safety_limits.(comp).b_poly];  %#ok<AGROW>
        end
        pred.mode_invariants.(name).A_poly     = A_all;
        pred.mode_invariants.(name).b_poly     = b_all;
        pred.mode_invariants.(name).meaning    = entry.meaning;
        pred.mode_invariants.(name).components = components;
    end
end

function group_out = parse_group(group_in, T_c0, T_f0, T_cold0, T_standby)
    names = fieldnames(group_in);
    group_out = struct();
    for k = 1:numel(names)
        name = names{k};
        % MATLAB jsondecode renames "_comment" -> "x_comment" and similar
        if startsWith(name, '_') || startsWith(name, 'x_'), continue, end
        entry = group_in.(name);
        if ~isstruct(entry) || ~isfield(entry, 'halfspaces'), continue, end
        hs_list = entry.halfspaces;
        if iscell(hs_list)
            n_hs = numel(hs_list);
            get_hs = @(i) hs_list{i};
        else
            n_hs = numel(hs_list);
            get_hs = @(i) hs_list(i);
        end
        A_poly = zeros(n_hs, 10);
        b_poly = zeros(n_hs, 1);
        for i = 1:n_hs
            hs = get_hs(i);
            A_poly(i, hs.state_index) = hs.coeff;
            b_poly(i) = evalin_context(hs.rhs_expr, T_c0, T_f0, T_cold0, T_standby);
        end
        group_out.(name).A_poly  = A_poly;
        group_out.(name).b_poly  = b_poly;
        group_out.(name).meaning = entry.meaning;
    end
end

function val = evalin_context(expr, T_c0, T_f0, T_cold0, T_standby)       %#ok<INUSD>
    val = eval(expr);
end