#include "algo/VolumeBuilder.hpp"

#include <algorithm>
#include <cmath>
#include <cstddef>
#include <limits>
#include <stdexcept>

#include "algo/IdwInterpolator.hpp"

namespace geopro::core {

namespace {
// 某轴：优先用 cell 间距；若包络 ext 过大致格数超 kMaxVolumeDim，则**放大间距**使 maxDim 格跨满 ext
//   （分辨率降低，但**不截断**——否则跨 TM 多剖面相距 > maxDim×cell 时，远端剖面落网格外、丢失）。
void fitAxis(double ext, double cell, double& outCell, int& outN) {
    if (!(ext > 0.0) || !(cell > 0.0)) { outCell = (cell > 0.0 ? cell : 1.0); outN = 1; return; }
    int n = static_cast<int>(ext / cell) + 1;
    if (n <= kMaxVolumeDim) {
        outCell = cell;
        outN = (n < 1) ? 1 : n;
        return;
    }
    outN = kMaxVolumeDim;
    outCell = ext / static_cast<double>(kMaxVolumeDim - 1);  // maxDim 格覆盖全 ext
}
}  // namespace

BuiltVolume buildVolume(const PointSet& pts, double cellXY, double cellZ,
                        double power, double maxDist) {
    if (pts.v.empty()) {
        throw std::invalid_argument("buildVolume: empty point set");
    }

    // 1) 点集包络。
    double minx = pts.x[0], maxx = pts.x[0];
    double miny = pts.y[0], maxy = pts.y[0];
    double minz = pts.z[0], maxz = pts.z[0];
    for (std::size_t i = 1; i < pts.v.size(); ++i) {
        minx = std::min(minx, pts.x[i]); maxx = std::max(maxx, pts.x[i]);
        miny = std::min(miny, pts.y[i]); maxy = std::max(maxy, pts.y[i]);
        minz = std::min(minz, pts.z[i]); maxz = std::max(maxz, pts.z[i]);
    }

    // 2) GridSpec（角点对齐 = 原点取包络最小角）。间距优先用 cell；包络过大时放大间距以覆盖全程
    //    （fitAxis），避免跨 TM 多剖面相距过远时远端被截断。
    GridSpec spec{};
    spec.ox = minx; spec.oy = miny; spec.oz = minz;
    fitAxis(maxx - minx, cellXY, spec.dx, spec.nx);
    fitAxis(maxy - miny, cellXY, spec.dy, spec.ny);
    fitAxis(maxz - minz, cellZ, spec.dz, spec.nz);
    spec.power = power;
    spec.maxDist = maxDist;

    // 3) IDW（maxDist 外 NaN 留空）。
    const IdwInterpolator idw;
    ScalarVolume vol = idw.interpolate(pts, spec);

    // 4) 数据实测值域（仅有限值）。无有限值 → 退化 {0,1}。
    double vmin = std::numeric_limits<double>::infinity();
    double vmax = -std::numeric_limits<double>::infinity();
    for (double v : vol.data()) {
        if (std::isnan(v)) continue;
        vmin = std::min(vmin, v); vmax = std::max(vmax, v);
    }
    if (!(vmin < vmax)) { vmin = 0.0; vmax = 1.0; }

    return BuiltVolume{std::move(vol), spec, vmin, vmax};
}

}  // namespace geopro::core