#include "FilamentMixer.hpp"

#include <algorithm>
#include <cassert>
#include <cctype>
#include <cmath>
#include <cstdio>
#include <limits>
#include <set>
#include <sstream>
#include <numeric>

#include <boost/log/trivial.hpp>

#include "ColorDecomposeRecipe.hpp"
#include "FilamentMixerModel.hpp"
#include "LocalesUtils.hpp"

namespace Slic3r {
namespace {

inline float clamp01(float x)
{
    return std::max(0.0f, std::min(1.0f, x));
}

inline float srgb_to_linear(float x)
{
    return (x >= 0.04045f) ? std::pow((x + 0.055f) / 1.055f, 2.4f) : x / 12.92f;
}

inline float linear_to_srgb(float x)
{
    return (x >= 0.0031308f) ? (1.055f * std::pow(x, 1.0f / 2.4f) - 0.055f) : (12.92f * x);
}

inline unsigned char to_u8(float x)
{
    const float clamped = clamp01(x);
    return static_cast<unsigned char>(clamped * 255.0f + 0.5f);
}

inline float to_f01(unsigned char x)
{
    return static_cast<float>(x) / 255.0f;
}

} // namespace

void filament_mixer_lerp(unsigned char r1, unsigned char g1, unsigned char b1,
                         unsigned char r2, unsigned char g2, unsigned char b2,
                         float t,
                         unsigned char* out_r, unsigned char* out_g, unsigned char* out_b)
{
    ::filament_mixer::lerp(r1, g1, b1, r2, g2, b2, t, out_r, out_g, out_b);
}

void filament_mixer_lerp_float(float r1, float g1, float b1,
                               float r2, float g2, float b2,
                               float t,
                               float* out_r, float* out_g, float* out_b)
{
    unsigned char ur = 0, ug = 0, ub = 0;
    filament_mixer_lerp(to_u8(r1), to_u8(g1), to_u8(b1),
                        to_u8(r2), to_u8(g2), to_u8(b2),
                        t, &ur, &ug, &ub);
    *out_r = to_f01(ur);
    *out_g = to_f01(ug);
    *out_b = to_f01(ub);
}

void filament_mixer_lerp_linear_float(float r1, float g1, float b1,
                                      float r2, float g2, float b2,
                                      float t,
                                      float* out_r, float* out_g, float* out_b)
{
    const float sr1 = linear_to_srgb(clamp01(r1));
    const float sg1 = linear_to_srgb(clamp01(g1));
    const float sb1 = linear_to_srgb(clamp01(b1));
    const float sr2 = linear_to_srgb(clamp01(r2));
    const float sg2 = linear_to_srgb(clamp01(g2));
    const float sb2 = linear_to_srgb(clamp01(b2));

    float out_sr = 0.0f, out_sg = 0.0f, out_sb = 0.0f;
    filament_mixer_lerp_float(sr1, sg1, sb1, sr2, sg2, sb2, t, &out_sr, &out_sg, &out_sb);

    *out_r = srgb_to_linear(clamp01(out_sr));
    *out_g = srgb_to_linear(clamp01(out_sg));
    *out_b = srgb_to_linear(clamp01(out_sb));
}

static bool parse_hex(const std::string &hex, unsigned char &r, unsigned char &g, unsigned char &b)
{
    if (hex.size() < 7 || hex[0] != '#') return false;
    unsigned rv = 0, gv = 0, bv = 0;
    if (std::sscanf(hex.c_str(), "#%02x%02x%02x", &rv, &gv, &bv) != 3) return false;
    r = (unsigned char)rv; g = (unsigned char)gv; b = (unsigned char)bv;
    return true;
}

std::string blend_color(const std::string& hex_a, const std::string& hex_b, float ratio_b)
{
    unsigned char r1 = 128, g1 = 128, b1 = 128;
    unsigned char r2 = 128, g2 = 128, b2 = 128;
    parse_hex(hex_a, r1, g1, b1);
    parse_hex(hex_b, r2, g2, b2);

    unsigned char mr = 0, mg = 0, mb = 0;
    filament_mixer_lerp(r1, g1, b1, r2, g2, b2, ratio_b, &mr, &mg, &mb);

    char buf[8];
    std::snprintf(buf, sizeof(buf), "#%02X%02X%02X", mr, mg, mb);
    return std::string(buf);
}

std::string blend_color_multi(const std::vector<std::string> &hex_colors,
                              const std::vector<int> &weights)
{
    if (hex_colors.size() >= 2 && hex_colors.size() == weights.size()) {
        std::string measured = lookup_measured_blend_color(hex_colors, weights);
        if (!measured.empty())
            return measured;
    }

    if (hex_colors.empty())
        return "#000000";
    if (hex_colors.size() == 1) {
        unsigned char cr = 128, cg = 128, cb = 128;
        parse_hex(hex_colors.front(), cr, cg, cb);
        char buf[8];
        std::snprintf(buf, sizeof(buf), "#%02X%02X%02X", cr, cg, cb);
        return std::string(buf);
    }

    assert(hex_colors.size() == weights.size());

    unsigned char r = 128, g = 128, b = 128;
    int accumulated = 0;

    for (size_t i = 0; i < hex_colors.size() && i < weights.size(); ++i) {
        if (weights[i] <= 0)
            continue;
        unsigned char cr = 128, cg = 128, cb = 128;
        parse_hex(hex_colors[i], cr, cg, cb);
        if (accumulated == 0) {
            r = cr; g = cg; b = cb;
            accumulated = weights[i];
        } else {
            const int new_total = accumulated + weights[i];
            const float t = static_cast<float>(weights[i]) / static_cast<float>(new_total);
            filament_mixer_lerp(r, g, b, cr, cg, cb, t, &r, &g, &b);
            accumulated = new_total;
        }
    }

    if (accumulated == 0)
        return "#000000";

    char buf[8];
    std::snprintf(buf, sizeof(buf), "#%02X%02X%02X", r, g, b);
    return std::string(buf);
}

std::vector<unsigned int> parse_mixed_components(const std::string &str)
{
    std::vector<unsigned int> components;
    if (str.empty())
        return components;
    std::istringstream ss(str);
    std::string token;
    while (std::getline(ss, token, ',')) {
        try {
            int val = std::stoi(token);
            if (val >= 0)
                components.push_back(static_cast<unsigned int>(val));
        } catch (...) {}
    }
    return components;
}

namespace {

// Parse a token that may represent a finite double or "use default" (empty / "nan").
// Returns NaN on either explicit sentinel or any parse error.
inline double parse_tangent_token(const std::string& tok)
{
    if (tok.empty()) return std::numeric_limits<double>::quiet_NaN();
    std::string lower(tok.size(), '\0');
    std::transform(tok.begin(), tok.end(), lower.begin(),
                   [](unsigned char c) { return static_cast<char>(std::tolower(c)); });
    if (lower == "nan") return std::numeric_limits<double>::quiet_NaN();
    try {
        const double v = std::stod(tok);
        if (!std::isfinite(v)) return std::numeric_limits<double>::quiet_NaN();
        return v;
    } catch (...) {
        return std::numeric_limits<double>::quiet_NaN();
    }
}

// Split a "a,b,c,d" segment on commas, preserving empty tokens (so "0.5,0.4,," yields
// {"0.5","0.4","",""}). Used by the gradient-curve parser to distinguish NaN tangents
// from a malformed segment.
inline std::vector<std::string> split_commas(const std::string& seg)
{
    std::vector<std::string> out;
    size_t start = 0;
    while (true) {
        const size_t comma = seg.find(',', start);
        if (comma == std::string::npos) {
            out.emplace_back(seg.substr(start));
            return out;
        }
        out.emplace_back(seg.substr(start, comma - start));
        start = comma + 1;
    }
}

} // namespace

// Default Fritsch-Carlson PCHIP tangents for a sorted-by-x anchor list. m has size n
// matching the anchor count; for n == 1 the tangent is 0; for n == 2 both endpoint
// tangents equal the single secant (degenerates to linear).
std::vector<double> compute_pchip_default_tangents(const std::vector<GradientAnchor>& pts)
{
    const size_t n = pts.size();
    std::vector<double> m(n, 0.0);
    if (n < 2) return m;

    std::vector<double> d(n - 1);
    for (size_t i = 0; i + 1 < n; ++i) {
        const double h = std::max(1e-12, pts[i + 1].x - pts[i].x);
        d[i] = (pts[i + 1].y - pts[i].y) / h;
    }

    m[0]     = d[0];
    m[n - 1] = d[n - 2];
    for (size_t i = 1; i + 1 < n; ++i)
        m[i] = 0.5 * (d[i - 1] + d[i]);

    // Fritsch-Carlson monotonic guard: kill flats then rescale steep tangents so the
    // resulting cubic never overshoots [min, max] of the surrounding anchors.
    for (size_t i = 0; i + 1 < n; ++i) {
        if (d[i] == 0.0) {
            m[i]     = 0.0;
            m[i + 1] = 0.0;
            continue;
        }
        const double a = m[i]     / d[i];
        const double b = m[i + 1] / d[i];
        const double s = a * a + b * b;
        if (s > 9.0) {
            const double tau = 3.0 / std::sqrt(s);
            m[i]     = tau * a * d[i];
            m[i + 1] = tau * b * d[i];
        }
    }
    return m;
}

GradientCurve parse_gradient_curve(const std::string& s)
{
    GradientCurve curve;
    if (s.empty())
        return curve;

    CNumericLocalesSetter c_locale_setter;
    std::istringstream ss(s);
    std::string segment;
    while (std::getline(ss, segment, '|')) {
        if (segment.empty())
            continue;
        const auto fields = split_commas(segment);
        // 2-field legacy form -> (x, y), tangents stay NaN.
        // 4-field form -> (x, y, m_in, m_out), empty / "nan" tokens preserved as NaN.
        if (fields.size() != 2 && fields.size() != 4) {
            BOOST_LOG_TRIVIAL(warning) << "parse_gradient_curve: ignoring malformed segment \""
                                       << segment << "\" (expected 2 or 4 comma-separated fields, got "
                                       << fields.size() << ")";
            continue;
        }
        try {
            double x = std::stod(fields[0]);
            double y = std::stod(fields[1]);
            x = std::max(0.0, std::min(1.0, x));
            y = std::max(kGradientMinRatio, std::min(kGradientMaxRatio, y));
            GradientAnchor a;
            a.x = x;
            a.y = y;
            if (fields.size() == 4) {
                a.m_in  = parse_tangent_token(fields[2]);
                a.m_out = parse_tangent_token(fields[3]);
            }
            curve.points.push_back(a);
        } catch (const std::exception& e) {
            BOOST_LOG_TRIVIAL(warning) << "parse_gradient_curve: ignoring unparseable segment \""
                                       << segment << "\": " << e.what();
        }
    }

    if (curve.points.size() < 2) {
        if (!curve.points.empty())
            BOOST_LOG_TRIVIAL(warning) << "parse_gradient_curve: only "
                << curve.points.size() << " valid point(s), need at least 2; discarding";
        curve.points.clear();
        return curve;
    }

    std::sort(curve.points.begin(), curve.points.end(),
              [](const GradientAnchor& a, const GradientAnchor& b) {
                  return a.x < b.x;
              });
    return curve;
}

std::string serialize_gradient_curve(const GradientCurve& c)
{
    if (c.points.empty())
        return std::string{};

    CNumericLocalesSetter c_locale_setter;
    std::string out;
    char buf[128];
    for (size_t i = 0; i < c.points.size(); ++i) {
        if (i > 0) out += '|';
        const auto& a = c.points[i];
        const bool has_in  = std::isfinite(a.m_in);
        const bool has_out = std::isfinite(a.m_out);
        if (has_in || has_out) {
            // Emit empty tokens for NaN slots so the legacy parser would still split
            // four fields; the new parser interprets empty tokens as "use PCHIP default".
            char in_buf[32]  = {0};
            char out_buf[32] = {0};
            if (has_in)  std::snprintf(in_buf,  sizeof(in_buf),  "%.4f", a.m_in);
            if (has_out) std::snprintf(out_buf, sizeof(out_buf), "%.4f", a.m_out);
            std::snprintf(buf, sizeof(buf), "%.4f,%.4f,%s,%s",
                          a.x, a.y, in_buf, out_buf);
        } else {
            // 4-field form is only emitted when at least one tangent is finite; the
            // 2-field form is emitted otherwise so the JSON payload stays minimal
            // and remains readable by older clients that only know (x, y) pairs.
            std::snprintf(buf, sizeof(buf), "%.4f,%.4f", a.x, a.y);
        }
        out += buf;
    }
    return out;
}

double sample_gradient_curve(const GradientCurve& c, double t)
{
    const auto& pts = c.points;
    if (pts.size() < 2)
        return 0.5;
    if (t <= pts.front().x)
        return pts.front().y;
    if (t >= pts.back().x)
        return pts.back().y;

    // PCHIP defaults are computed for every call; control point counts are typically
    // tiny (< 16) so the allocation cost is negligible compared to any actual rendering
    // or G-code work that drives the sampler.
    const std::vector<double> m_def = compute_pchip_default_tangents(pts);
    const size_t n = pts.size();

    // Linear scan to locate the interval [pts[i].x, pts[i+1].x] containing t. Cheap
    // and avoids the upper_bound boilerplate; n is small.
    for (size_t i = 1; i < n; ++i) {
        const double x0 = pts[i - 1].x;
        const double x1 = pts[i].x;
        if (t > x1) continue;

        const double y0 = pts[i - 1].y;
        const double y1 = pts[i].y;
        const double h  = std::max(1e-12, x1 - x0);
        const double m_left  = std::isfinite(pts[i - 1].m_out) ? pts[i - 1].m_out : m_def[i - 1];
        const double m_right = std::isfinite(pts[i].m_in)      ? pts[i].m_in      : m_def[i];

        const double u   = (t - x0) / h;
        const double u2  = u * u;
        const double u3  = u2 * u;
        const double h00 =  2.0 * u3 - 3.0 * u2 + 1.0;
        const double h10 =        u3 - 2.0 * u2 + u;
        const double h01 = -2.0 * u3 + 3.0 * u2;
        const double h11 =        u3 -       u2;
        double y = h00 * y0 + h10 * h * m_left
                 + h01 * y1 + h11 * h * m_right;
        // Defensive clamp in case tangent overrides on legacy curves push the
        // single-segment Hermite slightly outside the anchor band.
        if (y < kGradientMinRatio) y = kGradientMinRatio;
        if (y > kGradientMaxRatio) y = kGradientMaxRatio;
        return y;
    }
    return pts.back().y;
}

std::vector<double> parse_mixed_ratios(const std::string &str, size_t n_components)
{
    CNumericLocalesSetter c_locale_setter;
    std::vector<double> ratios;
    if (!str.empty()) {
        std::istringstream ss(str);
        std::string token;
        while (std::getline(ss, token, ',')) {
            try {
                double val = std::stod(token);
                if (val > 0.0)
                    ratios.push_back(val);
            } catch (...) {}
        }
    }

    if (ratios.size() != n_components || n_components == 0) {
        ratios.assign(n_components, n_components > 0 ? 1.0 / n_components : 0.0);
        return ratios;
    }

    double sum = std::accumulate(ratios.begin(), ratios.end(), 0.0);
    if (sum > 0.0 && std::abs(sum - 1.0) > 1e-6) {
        for (double &r : ratios)
            r /= sum;
    }
    return ratios;
}

bool has_any_mixed_filament(const std::vector<unsigned char> &is_mixed)
{
    for (unsigned char v : is_mixed)
        if (v) return true;
    return false;
}

std::vector<size_t> check_mixed_filament_integrity(
    const std::vector<unsigned char> &is_mixed,
    const std::vector<std::string>   &comp_strs,
    size_t num_physical)
{
    std::vector<size_t> broken;
    for (size_t i = 0; i < is_mixed.size(); ++i) {
        if (!is_mixed[i]) continue;
        if (i >= comp_strs.size() || comp_strs[i].empty()) {
            broken.push_back(i);
            continue;
        }
        auto comps = parse_mixed_components(comp_strs[i]);
        if (comps.size() < 2) {
            broken.push_back(i);
            continue;
        }
        for (unsigned int c : comps) {
            if (c < 1 || c > num_physical) {
                broken.push_back(i);
                break;
            }
        }
    }
    return broken;
}

std::vector<unsigned int> expand_mixed_filaments(
    const std::vector<unsigned int> &extruders_0based,
    const std::vector<unsigned char> &is_mixed,
    const std::vector<std::string>  &comp_strs)
{
    std::vector<unsigned int> result;
    for (unsigned int ext : extruders_0based) {
        if (ext < is_mixed.size() && is_mixed[ext] && ext < comp_strs.size()) {
            auto comps = parse_mixed_components(comp_strs[ext]);
            for (unsigned int c : comps)
                if (c >= 1) result.push_back(c - 1);
        } else {
            result.push_back(ext);
        }
    }
    std::sort(result.begin(), result.end());
    result.erase(std::unique(result.begin(), result.end()), result.end());
    return result;
}

void remap_mixed_components_on_delete(
    const std::vector<unsigned char> &is_mixed,
    std::vector<std::string>         &comp_strs,
    unsigned int                      del_1based)
{
    for (size_t i = 0; i < is_mixed.size(); ++i) {
        if (!is_mixed[i]) continue;
        if (i >= comp_strs.size() || comp_strs[i].empty()) continue;

        auto comps = parse_mixed_components(comp_strs[i]);
        std::ostringstream ss;
        for (size_t j = 0; j < comps.size(); ++j) {
            if (j > 0) ss << ',';
            if (comps[j] == del_1based)
                ss << 0;
            else if (comps[j] > del_1based)
                ss << (comps[j] - 1);
            else
                ss << comps[j];
        }
        comp_strs[i] = ss.str();
    }
}

std::vector<size_t> check_mixed_filament_type_consistency(
    const std::vector<unsigned char> &is_mixed,
    const std::vector<std::string>   &comp_strs,
    const std::vector<std::string>   &filament_types)
{
    std::vector<size_t> result;
    for (size_t i = 0; i < is_mixed.size(); ++i) {
        if (!is_mixed[i]) continue;
        if (i >= comp_strs.size() || comp_strs[i].empty()) continue;
        auto comps = parse_mixed_components(comp_strs[i]);
        if (comps.size() < 2) continue;

        std::string ref_type;
        bool mismatch = false;
        for (unsigned int c : comps) {
            if (c == 0) continue; // sentinel for deleted component
            size_t idx = static_cast<size_t>(c) - 1; // 1-based -> 0-based
            if (idx >= filament_types.size()) continue;
            if (ref_type.empty())
                ref_type = filament_types[idx];
            else if (filament_types[idx] != ref_type) {
                mismatch = true;
                break;
            }
        }
        if (mismatch)
            result.push_back(i);
    }
    return result;
}

void expand_mixed_slots_in_unprintables(
    std::vector<std::set<int>>        &unprintables,
    const std::vector<unsigned char>  &is_mixed,
    const std::vector<std::string>    &comp_strs)
{
    for (auto &unprintable_set : unprintables) {
        std::set<int> expanded;
        for (int fid : unprintable_set) {
            if (fid >= 0 && (size_t)fid < is_mixed.size() && is_mixed[fid]
                && (size_t)fid < comp_strs.size()) {
                auto comps = parse_mixed_components(comp_strs[fid]);
                for (unsigned int c : comps)
                    if (c >= 1) expanded.insert((int)(c - 1));
            } else {
                expanded.insert(fid);
            }
        }
        unprintable_set = std::move(expanded);
    }
}

void sanitize_mixed_gradient_curve_array(std::vector<std::string>& vals)
{
    for (size_t i = 0; i < vals.size(); ++i) {
        if (vals[i].empty())
            continue;
        // parse_gradient_curve returns empty for both "empty input" and "<2 valid points";
        // we already skipped empty, so an empty result means a corrupted single-point slot.
        if (parse_gradient_curve(vals[i]).empty()) {
            BOOST_LOG_TRIVIAL(warning) << "sanitize_mixed_gradient_curve_array: slot "
                << i << " curve \"" << vals[i]
                << "\" has fewer than 2 valid points; clearing to linear";
            vals[i].clear();
        }
    }
}

bool try_parse_mixed_components_strict(const std::string &str,
                                       std::vector<unsigned int> &components,
                                       std::string &err)
{
    components.clear();
    if (str.empty()) {
        err = "empty component list";
        return false;
    }
    std::istringstream ss(str);
    std::string token;
    while (std::getline(ss, token, ',')) {
        if (token.empty()) {
            err = "empty component index";
            return false;
        }
        try {
            const long val = std::stol(token);
            if (val < 1) {
                err = "component index must be >= 1 (got " + token + ")";
                return false;
            }
            components.push_back(static_cast<unsigned int>(val));
        } catch (...) {
            err = "invalid component index \"" + token + "\"";
            return false;
        }
    }
    if (components.size() < 2) {
        err = "at least 2 components required (got " + std::to_string(components.size()) + ")";
        return false;
    }
    std::set<unsigned int> seen;
    for (unsigned int c : components) {
        if (!seen.insert(c).second) {
            err = "duplicate component index " + std::to_string(c);
            return false;
        }
    }
    return true;
}

bool try_parse_mixed_ratios_strict(const std::string &str,
                                   size_t n_components,
                                   std::string &err)
{
    if (str.empty())
        return true;

    CNumericLocalesSetter c_locale_setter;
    std::vector<double> ratios;
    std::istringstream ss(str);
    std::string token;
    while (std::getline(ss, token, ',')) {
        if (token.empty()) {
            err = "empty ratio value";
            return false;
        }
        try {
            const double val = std::stod(token);
            if (!(val > 0.0)) {
                err = "ratio must be positive (got " + token + ")";
                return false;
            }
            ratios.push_back(val);
        } catch (...) {
            err = "invalid ratio \"" + token + "\"";
            return false;
        }
    }
    if (ratios.size() != n_components) {
        err = "expected " + std::to_string(n_components) + " ratio(s), got "
            + std::to_string(ratios.size());
        return false;
    }
    return true;
}

bool validate_gradient_range_strict(const std::string &str, std::string &err)
{
    if (str.empty())
        return true;

    CNumericLocalesSetter c_locale_setter;
    float v0 = 0.f, v1 = 0.f;
    if (std::sscanf(str.c_str(), "%f,%f", &v0, &v1) != 2) {
        err = "expected two comma-separated floats, e.g. \"0.10,0.90\"";
        return false;
    }
    if (!(v0 > 0.f && v0 < 1.f && v1 > 0.f && v1 < 1.f)) {
        err = "start and end ratios must be in (0, 1)";
        return false;
    }
    return true;
}

static void append_error(std::map<std::string, std::string> &errors,
                         const std::string &key,
                         const std::string &msg)
{
    auto it = errors.find(key);
    if (it == errors.end())
        errors.emplace(key, msg);
    else
        it->second += "; " + msg;
}

static bool has_mixed_sub_params_specified(
    const std::vector<std::string>   &comp_strs,
    const std::vector<std::string>   &ratio_strs,
    const std::vector<unsigned char> &gradient_flags)
{
    for (const std::string &s : comp_strs)
        if (!s.empty()) return true;
    for (const std::string &s : ratio_strs)
        if (!s.empty()) return true;
    for (unsigned char g : gradient_flags)
        if (g) return true;
    return false;
}

static bool mixed_string_array_was_specified(const std::vector<std::string> &vals)
{
    for (const std::string &s : vals)
        if (!s.empty())
            return true;
    return false;
}

static bool mixed_bool_array_was_specified(const std::vector<unsigned char> &vals)
{
    for (unsigned char v : vals)
        if (v)
            return true;
    return false;
}

static void check_mixed_array_size_required(std::map<std::string, std::string> &errors,
                                            const std::string &opt_key,
                                            size_t actual_size,
                                            size_t expected_size)
{
    if (actual_size != expected_size) {
        append_error(errors, opt_key,
            "array size " + std::to_string(actual_size)
            + " does not match filament slot count " + std::to_string(expected_size));
    }
}

std::map<std::string, std::string> validate_mixed_filament_params(
    const std::vector<unsigned char> &is_mixed,
    const std::vector<std::string>   &comp_strs,
    const std::vector<std::string>   &ratio_strs,
    const std::vector<unsigned char> &gradient_flags,
    const std::vector<std::string>   &gradient_range_strs,
    const std::vector<std::string>   &gradient_curve_strs)
{
    std::map<std::string, std::string> errors;

    if (has_mixed_sub_params_specified(comp_strs, ratio_strs, gradient_flags)
        && !has_any_mixed_filament(is_mixed)) {
        append_error(errors, "filament_is_mixed",
            "must be set when mixed filament parameters are specified");
        return errors;
    }

    if (!has_any_mixed_filament(is_mixed))
        return errors;

    const size_t slot_count = is_mixed.size();

    // Rule 1: mixed filament model → components & ratios arrays must cover every slot.
    check_mixed_array_size_required(errors, "filament_mixed_components", comp_strs.size(), slot_count);
    check_mixed_array_size_required(errors, "filament_mixed_sublayer_ratios", ratio_strs.size(), slot_count);

    // Rule 2: gradient passed (any slot true) → gradient & range arrays must cover every slot.
    const bool gradient_specified = mixed_bool_array_was_specified(gradient_flags);
    if (gradient_specified) {
        check_mixed_array_size_required(errors, "filament_mixed_gradient", gradient_flags.size(), slot_count);
        check_mixed_array_size_required(errors, "filament_mixed_gradient_range", gradient_range_strs.size(), slot_count);
    }

    // Rule 3: curve passed (any non-empty entry) → curve array must cover every slot.
    const bool curve_specified = mixed_string_array_was_specified(gradient_curve_strs);
    if (curve_specified)
        check_mixed_array_size_required(errors, "filament_mixed_gradient_curve", gradient_curve_strs.size(), slot_count);

    size_t num_physical = 0;
    for (unsigned char v : is_mixed)
        if (!v) ++num_physical;

    for (size_t i = 0; i < is_mixed.size(); ++i) {
        if (!is_mixed[i])
            continue;

        const std::string slot = "slot " + std::to_string(i + 1);
        const std::string comp_str = i < comp_strs.size() ? comp_strs[i] : "";

        std::vector<unsigned int> components;
        std::string comp_err;
        if (!try_parse_mixed_components_strict(comp_str, components, comp_err)) {
            append_error(errors, "filament_mixed_components", slot + ": " + comp_err);
            continue;
        }

        for (unsigned int c : components) {
            if (c > num_physical) {
                append_error(errors, "filament_mixed_components",
                       slot + ": component " + std::to_string(c)
                       + " out of range (max physical filament index is "
                       + std::to_string(num_physical) + ")");
                break;
            }
            if (c == i + 1) {
                append_error(errors, "filament_mixed_components",
                       slot + ": cannot reference itself as a component");
                break;
            }
            const size_t idx0 = static_cast<size_t>(c - 1);
            if (idx0 < is_mixed.size() && is_mixed[idx0]) {
                append_error(errors, "filament_mixed_components",
                       slot + ": component " + std::to_string(c)
                       + " references a mixed filament slot");
                break;
            }
        }

        std::string ratio_err;
        const std::string ratio_str = i < ratio_strs.size() ? ratio_strs[i] : "";
        if (!try_parse_mixed_ratios_strict(ratio_str, components.size(), ratio_err))
            append_error(errors, "filament_mixed_sublayer_ratios", slot + ": " + ratio_err);

        const bool gradient_on = i < gradient_flags.size() && gradient_flags[i];
        if (gradient_on) {
            if (components.size() != 2) {
                append_error(errors, "filament_mixed_gradient",
                       slot + ": gradient requires exactly 2 components");
            }

            if (gradient_specified) {
                std::string range_err;
                const std::string range_str = i < gradient_range_strs.size() ? gradient_range_strs[i] : "";
                if (!validate_gradient_range_strict(range_str, range_err))
                    append_error(errors, "filament_mixed_gradient_range", slot + ": " + range_err);
            }

            if (curve_specified) {
                const std::string curve_str = i < gradient_curve_strs.size() ? gradient_curve_strs[i] : "";
                if (!curve_str.empty() && parse_gradient_curve(curve_str).empty())
                    append_error(errors, "filament_mixed_gradient_curve",
                           slot + ": invalid curve (need at least 2 valid control points)");
            }
        }
    }

    return errors;
}

} // namespace Slic3r