function h = plot_measurements_gpt(T, cfg)
% Versatile plotting from your DB table (with cbrewer2 'Paired' palette).
%
% Usage:
%   h = plot_measurements_flex(dataTable, cfg)

%% ---- Defaults
if nargin < 2, cfg = struct; end
defaults = struct( ...
    'x_axis'      , 'symbolrate', ...
    'y_axis'      , 'BER', ...
    'y_scale'     , 'auto', ...
    'group_by'    , {{'equalizer_structure','pre_emph'}}, ...
    'filters'     , struct, ...
    'agg'         , 'mean', ...
    'outlier'     , 'auto', ...
    'mad_z'       , 3, ...
    'pct_limits'  , [2.5 97.5], ...
    'min_pts_x'   , 3, ...
    'show_raw'    , true, ...
    'show_precoded', [], ...
    'show_spread' , 'none', ...
    'fec_lines'   , [2.2e-4 4.85e-3 2e-2], ...
    'plot', struct() ...
);
cfg = filldefaults(cfg, defaults);

% ---- Plot defaults (new)
plotdefs = struct( ...
    'use_cbrewer2'          , true, ...
    'colormap'              , 'Paired', ...     % ColorBrewer 'Paired'
    'paired_dark_first'     , true, ...         % dark for lines, light for scatter
    'lineWidth'             , 1.8, ...
    'errWidth'              , 1.0, ...
    'scatterSize'           , 14, ...
    'scatterAlpha'          , 0.35, ...
    'marker'                , 'o', ...
    'marker_precoded'       , 's', ...
    'lineStyle_pre_emph_on' , '--', ...
    'lineStyle_pre_emph_off', '-', ...
    'legendLocation'        , 'best', ...
    'fecLineWidth'          , 2.2, ...          % thicker FEC limits
    'fecColor'              , [0.25 0.25 0.25], ...
    'capSize'               , 6, ...
    'lineStyle_default'      , '-', ...
    'use_pre_emph_styling'   , true ...
);
cfg.plot = filldefaults(cfg.plot, plotdefs);

%% ---- Derived/prep columns
if ~ismember('pre_emph', T.Properties.VariableNames)
    if ~ismember('db_mode', T.Properties.VariableNames)
        error('Missing column "db_mode" for pre_emph derivation.');
    end
    T.pre_emph = T.db_mode == 0;
end
if ~ismember(cfg.y_axis, T.Properties.VariableNames)
    error('y_axis "%s" not found in table.', cfg.y_axis);
end

isBER = startsWith(cfg.y_axis, "BER", 'IgnoreCase', true);
if strcmpi(cfg.y_scale,'auto'), cfg.y_scale = tern(isBER, 'log', 'linear'); end
if strcmpi(cfg.outlier,'auto'), cfg.outlier = tern(isBER, 'mad', 'none'); end
if isempty(cfg.show_precoded)
    cfg.show_precoded = isBER && ismember('BER_precoded', T.Properties.VariableNames);
end

%% ---- Filters
T = applyFilters(T, cfg.filters);
[x_raw, x_label] = computeX(T, cfg.x_axis);
y_raw = T.(cfg.y_axis);

validXY = isfinite(x_raw) & isfinite(y_raw);
T   = T(validXY, :);
x_raw = x_raw(validXY);
y_raw = y_raw(validXY);

if cfg.show_precoded && ismember('BER_precoded', T.Properties.VariableNames)
    y_raw_p = T.BER_precoded(validXY);
else
    y_raw_p = [];
end

%% ---- Grouping
group_by = cfg.group_by;
if ~all(ismember(group_by, T.Properties.VariableNames))
    error('Some group_by columns are missing in table.');
end
[G, grpTbl] = findgroups(T(:, group_by));
nG = max(G);

% ==== Colors (cbrewer2 'Paired' with dark/ light pairs) ====
[cols_line, cols_scatter] = buildGroupColors(nG, cfg.plot);

%% ---- Plotting
figure; hold on; grid on;
h.lines   = gobjects(nG,1);
h.err     = gobjects(nG,1);
h.scat    = gobjects(nG,1);
h.lines_p = gobjects(nG,1);

for gi = 1:nG
    idx = (G==gi);
    Ti  = T(idx,:);
    xi  = x_raw(idx);
    yi  = y_raw(idx);

    % Aggregate per unique x
    [xu, ia, iu] = unique(xi);
    yu   = nan(size(xu));
    ylo  = nan(size(xu));
    yhi  = nan(size(xu));

    for k = 1:numel(xu)
        bin = (iu==k);
        yy  = yi(bin);
        yy  = yy(isfinite(yy));
        if isempty(yy), continue; end
        km = outlierMask(yy, cfg, strcmpi(cfg.y_scale,'log'));
        if nnz(km) < cfg.min_pts_x, km = true(size(yy)); end
        yy = yy(km);

        if strcmpi(cfg.agg,'median'), yu(k)=median(yy,'omitnan'); elseif strcmpi(cfg.agg,'mean'), yu(k)=mean(yy,'omitnan'); elseif strcmpi(cfg.agg,'min'), yu(k)=min(yy); end
        if strcmpi(cfg.show_spread,'iqr')
            q = prctile(yy,[25 75]);
            ylo(k) = max(yu(k)-q(1), eps);
            yhi(k) = max(q(2)-yu(k), eps);
        end
    end

    % sort
    [xu, ord] = sort(xu);
    yu  = yu(ord); ylo = ylo(ord); yhi = yhi(ord);

    % Styles
    % Decide if we style by pre_emph
    canStyleByPre = cfg.plot.use_pre_emph_styling && ismember('pre_emph', T.Properties.VariableNames);

    if canStyleByPre
        if any(strcmp(group_by,'pre_emph'))
            % pre_emph is an explicit grouping key -> take it from the group table
            pre = logical(grpTbl.pre_emph(gi));
        else
            % pre_emph not grouped, but available in the rows -> infer from the members of this group
            pre = logical(mode(T.pre_emph(G==gi)));
        end
        ls = tern(pre, cfg.plot.lineStyle_pre_emph_on, cfg.plot.lineStyle_pre_emph_off);
    else
        % no pre-emph styling → use a single default style
        ls = cfg.plot.lineStyle_default;
    end

    lbl = buildLabel(grpTbl(gi,:), group_by);

    % Main line (dark)
    colL = cols_line(gi,:);
    h.lines(gi) = plot(xu, yu, ...
        'LineWidth', cfg.plot.lineWidth, ...
        'Marker', cfg.plot.marker, 'MarkerSize', 5, ...
        'Color', colL, 'LineStyle', ls, ...
        'DisplayName', char(lbl));

    % Spread (IQR) in line color
    if strcmpi(cfg.show_spread,'iqr') && any(isfinite(ylo)) && any(isfinite(yhi))
        h.err(gi) = errorbar(xu, yu, ylo, yhi, 'LineStyle','none', ...
            'Color', colL, 'CapSize', cfg.plot.capSize, 'HandleVisibility','off');
        h.err(gi).LineWidth = cfg.plot.errWidth;
    end

    % Raw kept scatter (light)
    if cfg.show_raw
        keep_all = false(size(yi));
        for k = 1:numel(xu)
            bin = (iu==k);
            yy  = yi(bin);
            km  = outlierMask(yy, cfg, strcmpi(cfg.y_scale,'log'));
            if nnz(km) < cfg.min_pts_x, km = true(size(yy)); end
            keep_all(bin) = km;
        end
        colS = cols_scatter(gi,:);
        scatter(xi(keep_all), yi(keep_all), cfg.plot.scatterSize, colS, 'filled', ...
            'MarkerFaceAlpha', cfg.plot.scatterAlpha, 'MarkerEdgeAlpha', cfg.plot.scatterAlpha, ...
            'HandleVisibility','off');
    end

    % Precoded overlay (dotted, squares), in line color
    if cfg.show_precoded && ~isempty(y_raw_p) && strcmpi(cfg.y_axis,'BER')
        ypi = y_raw_p(idx);
        ypu = nan(size(xu));
        for k = 1:numel(xu)
            bin = (iu==k);
            yy  = ypi(bin);
            yy  = yy(isfinite(yy));
            if isempty(yy), continue; end
            km = outlierMask(yy, cfg, true);
            if nnz(km) < cfg.min_pts_x, km = true(size(yy)); end
            yy = yy(km);
            if strcmpi(cfg.agg,'median'), ypu(k)=median(yy,'omitnan'); elseif strcmpi(cfg.agg,'mean'), ypu(k)=mean(yy,'omitnan'); elseif strcmpi(cfg.agg,'min'), ypu(k)=min(yy); end
        end
        h.lines_p(gi) = plot(xu, ypu, ...
            'LineWidth', max(1.2, cfg.plot.lineWidth-0.2), ...
            'Marker', cfg.plot.marker_precoded, 'MarkerSize', 5, ...
            'Color', colL, 'LineStyle', ':', ...
            'DisplayName', [char(lbl) ' (precoded)']);
    end
end

%% ---- Axes / Labels / FEC
ylabel(cfg.y_axis, 'Interpreter','none');
xlabel(x_label,    'Interpreter','none');
set(gca, 'YScale', cfg.y_scale, 'FontSize', 11);
legend('Location', cfg.plot.legendLocation); box on;

if startsWith(cfg.y_axis,"BER",'IgnoreCase',true)
    for v = cfg.fec_lines
        yline(v, '--', 'Color', cfg.plot.fecColor, ...
            'LineWidth', cfg.plot.fecLineWidth, 'HandleVisibility','off');
    end
    ylim([1e-4, 0.3]);
end

end % ===== main =====


%% ===================== Helpers =====================

function cfg = filldefaults(cfg, defs)
fn = fieldnames(defs);
for i = 1:numel(fn)
    f = fn{i};
    if ~isfield(cfg, f) || isempty(cfg.(f))
        cfg.(f) = defs.(f);
    elseif isstruct(defs.(f)) && isstruct(cfg.(f))
        cfg.(f) = filldefaults(cfg.(f), defs.(f)); % recursive for structs
    end
end
end

function out = tern(cond, a, b)
if cond, out = a; else, out = b; end
end

function T2 = applyFilters(T, filters)
if isempty(filters), T2 = T; return; end
keep = true(height(T),1);
fns  = fieldnames(filters);
for i = 1:numel(fns)
    name = fns{i};
    if ~ismember(name, T.Properties.VariableNames)
        warning('Filter column "%s" not found. Ignored.', name); %#ok<*WNTAG>
        continue
    end
    val = filters.(name);
    col = T.(name);
    if isa(val,'function_handle')
        m = val(col);
        if ~islogical(m) || ~isequal(size(m), size(col))
            error('Filter for %s must return logical mask of same size.', name);
        end
        keep = keep & m;
    else
        keep = keep & ismember(col, val);
    end
end
T2 = T(keep,:);
end

function [x, label] = computeX(T, whichX)
switch lower(whichX)
    case {'symbolrate','baudrate'}
        x = T.symbolrate * 1e-9;
        label = 'Symbol rate [GBd]';
    case 'bitrate'
        if ~ismember('pam_level', T.Properties.VariableNames)
            error('bitrate requires "pam_level" column.');
        end
        bits = log2(double(T.pam_level));
        x = (T.symbolrate .* bits) * 1e-9;
        label = 'Bitrate [Gb/s]';
    otherwise
        if ~ismember(whichX, T.Properties.VariableNames)
            error('x_axis "%s" not found in table.', whichX);
        end
        x = T.(whichX);
        label = whichX;
end
x = double(x(:));
end

function keep = outlierMask(y, cfg, useLog)
if isempty(y), keep = false(size(y)); return; end
y = y(:);
switch lower(cfg.outlier)
    case 'none'
        keep = true(size(y)); return
    case 'mad'
        z = tern(useLog, log10(y), y);
        med = median(z,'omitnan');
        madv = median(abs(z-med),'omitnan');
        if ~(isfinite(madv) && madv>0)
            keep = true(size(y)); return
        end
        sigma = 1.4826*madv;
        zz = tern(useLog, log10(y), y);
        keep = abs(zz - med) <= cfg.mad_z*sigma;
    case 'pctl'
        pr = prctile(y, cfg.pct_limits);
        keep = (y >= pr(1)) & (y <= pr(2));
    otherwise
        error('Unknown outlier mode "%s".', cfg.outlier);
end
end

function s = buildLabel(grpRow, group_by)
parts = strings(1, numel(group_by));
for i = 1:numel(group_by)
    key = group_by{i};
    val = grpRow.(key);
    if iscell(val), val = val{1}; end
    if islogical(val), val = tern(val,'pre-emph on','pre-emph off'); end
    parts(i) = sprintf('%s=%s', key, string(val));
end
s = strjoin(parts, ', ');
end

function [cols_line, cols_scatter] = buildGroupColors(nG, plotcfg)
% Build paired colors (dark for lines, light for scatter) using cbrewer2('Paired')
useBrewer = plotcfg.use_cbrewer2 && exist('cbrewer2','file')==2;
if useBrewer
    N = max(2*nG, 12); % ensure pairs available
    C = cbrewer2(plotcfg.colormap, N);
    cols_line    = zeros(nG,3);
    cols_scatter = zeros(nG,3);
    for i = 1:nG
        if plotcfg.paired_dark_first
            dark = C(2*i-1, :); light = C(2*i, :);
        else
            light = C(2*i-1, :); dark = C(2*i, :);
        end
        cols_line(i,:)    = dark;
        cols_scatter(i,:) = light;
    end
else
    % Fallback: lines() + lightened scatter
    C = lines(max(nG,7));
    cols_line    = C(1:nG,:);
    cols_scatter = zeros(nG,3);
    for i = 1:nG
        cols_scatter(i,:) = lightenColor(cols_line(i,:), 0.5); % 50% toward white
    end
end
end

function c2 = lightenColor(c, fracTowardWhite)
c = c(:).';
c2 = (1-fracTowardWhite)*c + fracTowardWhite*1;
end