using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text.Json;
using OpenNest.Geometry;
using OpenNest.IO;

namespace OpenNest.Benchmark
{
    /// <summary>
    /// Builds a BenchmarkJob from a JSON manifest that lists DXF files and the
    /// quantity of each to nest. DXF paths resolve relative to the manifest.
    /// Sheet sizes come from the manifest or the caller's override; unlike a
    /// .nest file there is no plate to inherit them from, so a job with none is
    /// an error. Sheet sizes must use the same units as the DXFs.
    /// </summary>
    public static class DxfManifestLoader
    {
        /// <summary>Suffix a manifest needs to be picked up when scanning a folder.</summary>
        public const string FolderSuffix = ".manifest.json";

        private static readonly JsonSerializerOptions JsonOptions = new()
        {
            PropertyNameCaseInsensitive = true,
            ReadCommentHandling = JsonCommentHandling.Skip,
            AllowTrailingCommas = true,
        };

        public static BenchmarkJob Load(
            string manifestPath,
            IReadOnlyList<Size> sheetSizeOverrides = null,
            double? partSpacingOverride = null
        )
        {
            var manifest = ReadManifest(manifestPath);
            var baseDir = Path.GetDirectoryName(Path.GetFullPath(manifestPath));

            if (manifest.Parts == null || manifest.Parts.Count == 0)
                throw new InvalidOperationException(
                    $"Manifest '{manifestPath}' has no parts. Add entries to \"parts\"."
                );

            var sizes = ResolveSheetSizes(manifest, sheetSizeOverrides, manifestPath);
            var requests = manifest.Parts.Select(p => BuildRequest(p, baseDir)).ToList();

            return new BenchmarkJob
            {
                SourceFile = manifestPath,
                CandidateSizes = sizes,
                EdgeSpacing = new Spacing(manifest.EdgeSpacing, manifest.EdgeSpacing),
                PartSpacing = partSpacingOverride ?? manifest.Spacing,
                Quadrant = manifest.Quadrant,
                Requests = requests,
                OffcutCut = OffcutCut(manifest.OffcutCut, manifestPath),
            };
        }

        /// <summary>"horizontal" or "vertical" (any case); absent counts every edge strip.
        /// </summary>
        private static CutOffAxis? OffcutCut(string value, string manifestPath) =>
            value?.ToLowerInvariant() switch
            {
                null => null,
                "horizontal" => CutOffAxis.Horizontal,
                "vertical" => CutOffAxis.Vertical,
                _ => throw new InvalidOperationException(
                    $"Manifest '{manifestPath}' has offcutCut \"{value}\"; "
                        + "use \"horizontal\" or \"vertical\"."
                ),
            };

        private static Manifest ReadManifest(string manifestPath)
        {
            try
            {
                return JsonSerializer.Deserialize<Manifest>(
                        File.ReadAllText(manifestPath),
                        JsonOptions
                    ) ?? throw new InvalidOperationException("The manifest is empty.");
            }
            catch (JsonException ex)
            {
                throw new InvalidOperationException(
                    $"Manifest '{manifestPath}' is not valid JSON: {ex.Message}",
                    ex
                );
            }
        }

        private static List<Size> ResolveSheetSizes(
            Manifest manifest,
            IReadOnlyList<Size> overrides,
            string manifestPath
        )
        {
            if (overrides != null && overrides.Count > 0)
                return overrides.ToList();

            var sizes = new List<Size>();

            foreach (var text in manifest.SheetSizes ?? new List<string>())
            {
                if (!JobLoader.TryParseSheetSize(text, out var size))
                    throw new InvalidOperationException(
                        $"Manifest '{manifestPath}': could not parse sheet size '{text}' (expected e.g. \"48x96\")."
                    );

                sizes.Add(size);
            }

            if (sizes.Count == 0)
                throw new InvalidOperationException(
                    $"Manifest '{manifestPath}' has no sheet sizes. Set \"sheetSizes\" or pass --sheet-sizes."
                );

            return sizes.Distinct().ToList();
        }

        private static DrawingRequest BuildRequest(ManifestPart part, string baseDir)
        {
            if (string.IsNullOrWhiteSpace(part.Dxf))
                throw new InvalidOperationException("A manifest part is missing \"dxf\".");

            if (part.Quantity <= 0)
                throw new InvalidOperationException(
                    $"Manifest part '{part.Dxf}': quantity must be greater than 0 (was {part.Quantity})."
                );

            var dxfPath = Path.GetFullPath(Path.Combine(baseDir, part.Dxf));

            if (!File.Exists(dxfPath))
                throw new FileNotFoundException($"DXF file not found: {dxfPath}", dxfPath);

            Drawing drawing;

            try
            {
                drawing = CadImporter.ImportDrawing(
                    dxfPath,
                    new CadImportOptions { Quantity = part.Quantity }
                );
            }
            catch (Exception ex)
            {
                throw new InvalidOperationException($"Failed to import DXF: {dxfPath}", ex);
            }

            if (drawing.Program == null || drawing.Program.Codes.Count == 0)
                throw new InvalidOperationException($"Failed to import DXF: {dxfPath}");

            // A zero legacy step means automatic rotation to DrawingJobMapper, so lock it explicitly.
            // Quarter turns are a 90° sweep from 0 to 270°; automatic rotation allows any angle.
            var rotations = RotationSet(part);
            if (rotations != RotationChoice.Any)
            {
                var quarter = rotations == RotationChoice.QuarterTurns;
                drawing.Constraints ??= new NestConstraints();
                drawing.Constraints.StepAngle = quarter
                    ? OpenNest.Math.Angle.HalfPI
                    : OpenNest.Math.Angle.TwoPI;
                drawing.Constraints.StartAngle = 0;
                drawing.Constraints.EndAngle = quarter ? 3 * OpenNest.Math.Angle.HalfPI : 0;
                drawing.Constraints.Allow180Equivalent = rotations == RotationChoice.HalfTurns;
            }

            var constraints = drawing.Constraints;

            return new DrawingRequest
            {
                Drawing = drawing,
                Quantity = part.Quantity,
                Priority = drawing.Priority,
                StepAngle = constraints?.StepAngle ?? 0,
                RotationStart = constraints?.StartAngle ?? 0,
                RotationEnd = constraints?.EndAngle ?? 0,
            };
        }

        private enum RotationChoice
        {
            None,
            HalfTurns,
            QuarterTurns,
            Any,
        }

        /// <summary>
        /// A part's "rotations" (degrees) must be {0}, {0, 180} or {0, 90, 180, 270}; without it,
        /// "allowRotation" picks any angle (true, the default: automatic rotation) or none.
        /// </summary>
        private static RotationChoice RotationSet(ManifestPart part)
        {
            if (part.Rotations == null)
                return part.AllowRotation ? RotationChoice.Any : RotationChoice.None;
            if (!part.AllowRotation)
                throw new InvalidOperationException(
                    $"Manifest part '{part.Dxf}': set \"rotations\" or \"allowRotation\", not both."
                );

            var set = part.Rotations
                .Select(degrees => ((degrees % 360) + 360) % 360)
                .Distinct()
                .OrderBy(degrees => degrees)
                .ToArray();
            if (set.SequenceEqual(new[] { 0.0 }))
                return RotationChoice.None;
            if (set.SequenceEqual(new[] { 0.0, 180.0 }))
                return RotationChoice.HalfTurns;
            if (set.SequenceEqual(new[] { 0.0, 90.0, 180.0, 270.0 }))
                return RotationChoice.QuarterTurns;
            throw new InvalidOperationException(
                $"Manifest part '{part.Dxf}': \"rotations\" must be [0], [0, 180] or "
                    + $"[0, 90, 180, 270] (was [{string.Join(", ", part.Rotations)}])."
            );
        }

        private class Manifest
        {
            public List<string> SheetSizes { get; set; }
            public double Spacing { get; set; }
            public double EdgeSpacing { get; set; }
            public int Quadrant { get; set; } = 1;
            public string OffcutCut { get; set; }
            public List<ManifestPart> Parts { get; set; }
        }

        private class ManifestPart
        {
            public string Dxf { get; set; }
            public int Quantity { get; set; }
            public bool AllowRotation { get; set; } = true;
            public List<double> Rotations { get; set; }
        }
    }
}