using System;
using System.Collections.Generic;
using System.IO;
using System.Text;
using System.Windows.Media;
using System.Windows.Media.Media3D;
using STPViewer.Services;
using IOPath = System.IO.Path; // CADability.GeoObject.Path（曲線）撞名

namespace SmokeTest;

/// <summary>
/// STL 匯出驗證（無 UI）：
/// 1) binary — 已知立方體網格寫出 → 解析 header/三角形數/座標範圍比對（含縮放）
/// 2) ASCII — facet 數與 solid/endsolid 結構
/// 3) 退化三角形（零面積）自動濾除
/// </summary>
public static class StlExportTest
{
    public static int Run(string? stepPath = null)
    {
        Console.WriteLine("=== StlExportTest ===");
        int failed = 0;
        string dir = IOPath.Combine(IOPath.GetTempPath(), "stpviewer_stl_test");
        Directory.CreateDirectory(dir);

        MeshGeometry3D cube = BuildCube(10); // 10×10×10 mm、12 三角形

        // 1) binary：三角形數 + 縮放後座標範圍
        {
            string f = IOPath.Combine(dir, "cube_bin.stl");
            double scale = 1.0 / 25.4; // mm → inch
            int written = StlExportService.Write(f, new[] { cube }, ascii: false, scale);
            (uint count, float min, float max) = ReadBinary(f);
            bool ok = written == 12 && count == 12
                      && Math.Abs(min - 0f) < 1e-5 && Math.Abs(max - 10f / 25.4f) < 1e-4;
            Report(ref failed, ok, $"binary 寫出/回讀 12 三角形、inch 縮放範圍 [{min:F4}, {max:F4}]");
        }

        // 2) ASCII：facet 數 + 結構
        {
            string f = IOPath.Combine(dir, "cube_ascii.stl");
            int written = StlExportService.Write(f, new[] { cube }, ascii: true, scale: 1.0);
            string text = File.ReadAllText(f);
            int facets = CountOccurrences(text, "facet normal");
            bool ok = written == 12 && facets == 12
                      && text.StartsWith("solid ", StringComparison.Ordinal)
                      && text.Contains("endsolid");
            Report(ref failed, ok, $"ASCII 結構完整、facet = {facets}");
        }

        // 3) 退化三角形濾除：加一個零面積三角形 → 仍是 12
        {
            var degenerate = new MeshGeometry3D();
            degenerate.Positions.Add(new Point3D(0, 0, 0));
            degenerate.Positions.Add(new Point3D(1, 1, 1));
            degenerate.Positions.Add(new Point3D(2, 2, 2)); // 共線 → 面積 0
            degenerate.TriangleIndices.Add(0);
            degenerate.TriangleIndices.Add(1);
            degenerate.TriangleIndices.Add(2);
            degenerate.Freeze();

            string f = IOPath.Combine(dir, "cube_degen.stl");
            int written = StlExportService.Write(f, new[] { cube, degenerate }, ascii: false, scale: 1.0);
            (uint count, _, _) = ReadBinary(f);
            bool ok = written == 12 && count == 12;
            Report(ref failed, ok, $"退化三角形濾除（寫出 {written}）");
        }

        // 4)（可選）真實 STEP：B-rep 精細重新三角化 → 寫 binary STL 驗證
        //（不測「較粗」：CADability GetTriangulation 對比快取粗的精度回傳既有快取，粗化無效 → 功能已移除）
        if (stepPath is not null)
        {
            var data = new StepImportService().Import(stepPath);
            var geos = Collect(data.Root).ToList();
            int importTris = data.Root.TriangleCount;
            Console.WriteLine($"  來源 {IOPath.GetFileName(stepPath)}：{geos.Count} 個 B-rep 物件、匯入網格 {importTris:N0} 三角形");

            var meshes = StlExportService.Tessellate(
                geos, StlExportService.PrecisionFactor(StlMeshQuality.Fine));
            string f = IOPath.Combine(dir, "step_fine.stl");
            int written = StlExportService.Write(f, meshes, ascii: false, scale: 1.0);
            (uint count, _, _) = ReadBinary(f);
            Report(ref failed, meshes.Count > 0 && written > 0 && count == written,
                $"精細重新三角化 {meshes.Count} 面 → {written:N0} 三角形");
            // CADability 三角形數對精度非單調（0.4× 反而比 1× 少），Fine=0.15× 實測明顯更細
            Report(ref failed, written > importTris,
                $"精細（{written:N0}）> 匯入預設（{importTris:N0}）");
        }

        Console.WriteLine(failed == 0 ? "StlExportTest: PASS" : $"StlExportTest: FAIL（{failed} 項）");
        return failed;
    }

    private static IEnumerable<CADability.GeoObject.IGeoObject> Collect(ImportedNode n)
    {
        foreach (CADability.GeoObject.IGeoObject g in n.SourceGeos) yield return g;
        foreach (ImportedNode c in n.Children)
            foreach (CADability.GeoObject.IGeoObject g in Collect(c))
                yield return g;
    }

    private static void Report(ref int failed, bool ok, string what)
    {
        Console.WriteLine($"  [{(ok ? "PASS" : "FAIL")}] {what}");
        if (!ok) failed++;
    }

    /// <summary>0..size 的軸對齊立方體，12 個三角形（法向不講究，STL 寫出時自算）</summary>
    private static MeshGeometry3D BuildCube(double s)
    {
        var m = new MeshGeometry3D();
        Point3D[] v =
        {
            new(0, 0, 0), new(s, 0, 0), new(s, s, 0), new(0, s, 0),
            new(0, 0, s), new(s, 0, s), new(s, s, s), new(0, s, s),
        };
        foreach (Point3D p in v) m.Positions.Add(p);
        int[] quads = { 0,3,2,1,  4,5,6,7,  0,1,5,4,  1,2,6,5,  2,3,7,6,  3,0,4,7 };
        for (int q = 0; q < quads.Length; q += 4)
        {
            m.TriangleIndices.Add(quads[q]); m.TriangleIndices.Add(quads[q + 1]); m.TriangleIndices.Add(quads[q + 2]);
            m.TriangleIndices.Add(quads[q]); m.TriangleIndices.Add(quads[q + 2]); m.TriangleIndices.Add(quads[q + 3]);
        }
        m.Freeze();
        return m;
    }

    private static (uint Count, float Min, float Max) ReadBinary(string path)
    {
        using var br = new BinaryReader(File.OpenRead(path));
        byte[] header = br.ReadBytes(80);
        if (Encoding.ASCII.GetString(header, 0, 5) == "solid")
            throw new InvalidDataException("binary STL header 不可以 solid 開頭");
        uint count = br.ReadUInt32();
        float min = float.MaxValue, max = float.MinValue;
        for (uint t = 0; t < count; t++)
        {
            br.ReadBytes(12); // normal
            for (int k = 0; k < 9; k++)
            {
                float f = br.ReadSingle();
                min = Math.Min(min, f);
                max = Math.Max(max, f);
            }
            br.ReadUInt16(); // attribute
        }
        return (count, min, max);
    }

    private static int CountOccurrences(string text, string token)
    {
        int n = 0;
        for (int i = text.IndexOf(token, StringComparison.Ordinal); i >= 0;
             i = text.IndexOf(token, i + token.Length, StringComparison.Ordinal)) n++;
        return n;
    }
}