using System;
using System.Buffers.Binary;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Security.Cryptography;
using OpenNest.Bending;
using OpenNest.Breakoffs;
using OpenNest.Converters;
using OpenNest.Dimensions;
using OpenNest.Geometry;
using OpenNest.IO.Bending;
using OpenNest.Math;
using OpenNest.TabbedCutouts;

namespace OpenNest.IO
{
    /// <summary>
    /// Shared service that converts a CAD source file into a fully-populated
    /// <see cref="Drawing"/>. Used by the UI, console, MCP, API, and training
    /// tools so all code paths produce identical drawings.
    /// </summary>
    public static class CadImporter
    {
        /// <summary>
        /// Load a DXF file, run bend detection, and return a mutable result
        /// ready for interactive editing or direct conversion to a Drawing.
        /// </summary>
        public static CadImportResult Import(string path, CadImportOptions options = null)
        {
            options ??= CadImportOptions.Default;

            var dxf = Svg.IsSvg(path)
                ? Svg.Import(path, options)
                : Dxf.Import(path, preserveRepairMarks: options.BendRepair != null);

            var cleanup =
                options.BendRepair == null
                    ? dxf.Entities
                    : dxf.Entities.Where(e => !IsRepairMark(e)).ToList();
            RemoveDuplicateArcs(cleanup);
            RemoveZeroSweepArcs(cleanup);
            GeometryOptimizer.JoinFullCircles(cleanup);
            if (options.BendRepair != null)
            {
                dxf.Entities.RemoveAll(e => !IsRepairMark(e) && !cleanup.Contains(e));
                dxf.Entities.AddRange(cleanup.Where(e => !dxf.Entities.Contains(e)).ToList());
            }

            var bends = new List<Bend>();
            if (options.DetectBends && dxf.Document != null)
            {
                bends =
                    options.BendDetectorName == null
                        ? BendDetectorRegistry.AutoDetect(dxf.Document)
                        : BendDetectorRegistry
                            .GetByName(options.BendDetectorName)
                            ?.DetectBends(dxf.Document)
                            ?? new List<Bend>();
            }

            var repairReports = new List<BendRepairReport>();
            if (options.BendRepair == null)
                Bend.UpdateEtchEntities(dxf.Entities, bends);
            else
            {
                // Unitless DXFs require the explicit caller declaration. Never override a conflicting header.
                var headerUnits = (int)(dxf.Document?.Header.InsUnits ?? 0);
                var requestedUnits =
                    options.BendRepair.DrawingUnits == BendRepairUnits.Inches ? 1 : 4;
                if (headerUnits != 0 && headerUnits != requestedUnits)
                    repairReports = bends
                        .Select(
                            (b, i) =>
                                new BendRepairReport(
                                    i,
                                    "Skipped",
                                    "DXF insertion units conflict with the declared repair units or are unsupported.",
                                    b.StartPoint,
                                    b.EndPoint,
                                    b.StartPoint,
                                    b.EndPoint
                                )
                        )
                        .ToList();
                else
                    repairReports = BendRepair.Apply(dxf.Entities, bends, options.BendRepair);
            }

            AssignFileIds(path, dxf.Entities);

            return new CadImportResult
            {
                Entities = dxf.Entities,
                RawEntities = dxf.RawEntities,
                Bends = bends,
                BendRepairReports = repairReports,
                Bounds = dxf.Entities.GetBoundingBox(),
                SourcePath = path,
                Name = options.Name ?? Path.GetFileNameWithoutExtension(path),
                Document = dxf.Document,
                Warnings = dxf.Warnings,
            };
        }

        /// <summary>
        /// Gives each imported entity an id derived from the file's bytes and the entity's
        /// position in the import, so importing an unchanged file again yields the same ids
        /// (and the same library package), while any change to the file yields entirely new
        /// ids: ids key suppression, roles and edge selections, so one must never move to
        /// another entity.
        /// </summary>
        private static void AssignFileIds(string path, IList<Entity> entities)
        {
            Span<byte> input = stackalloc byte[32 + 4];
            Span<byte> digest = stackalloc byte[32];
            using (var stream = SharedFile.OpenRead(path))
                SHA256.HashData(stream, input[..32]);

            for (var i = 0; i < entities.Count; i++)
            {
                BinaryPrimitives.WriteInt32LittleEndian(input[32..], i);
                SHA256.HashData(input, digest);
                // RFC 9562 version 8 (custom) layout.
                digest[7] = (byte)((digest[7] & 0x0F) | 0x80);
                digest[8] = (byte)((digest[8] & 0x3F) | 0x80);
                entities[i].Id = new Guid(digest[..16]);
            }
        }

        /// <summary>
        /// Convenience for headless callers: Import a file and build a Drawing
        /// in a single call, using all loaded entities and detected bends.
        /// </summary>
        public static Drawing ImportDrawing(string path, CadImportOptions options = null)
        {
            options ??= CadImportOptions.Default;
            var result = Import(path, options);
            return BuildDrawing(
                result,
                result.Entities,
                result.Bends,
                options.Quantity,
                options.Customer,
                editedProgram: null
            );
        }

        /// <summary>
        /// Build a fully-populated <see cref="Drawing"/> from an import result plus
        /// the caller's current entity and bend state. UI callers pass the currently
        /// visible subset; headless callers pass the full lists.
        ///
        /// The produced drawing has:
        /// - Program generated from the visible entities, with its first rapid moved
        ///   to the origin and the pierce location stored in Source.Offset
        /// - SourceEntities containing all non-bend-source entities from the result
        /// - SuppressedEntityIds containing entities whose layer or IsVisible is false
        /// - Bends copied from the provided list
        /// - Customer, Quantity, Source.Path from options / result
        /// </summary>
        /// <param name="result">Import result from <see cref="Import"/>.</param>
        /// <param name="entities">
        /// Entities to build the program from. Typically the currently visible subset.
        /// </param>
        /// <param name="bends">Bends to attach to the drawing.</param>
        /// <param name="quantity">Required quantity.</param>
        /// <param name="customer">Customer name, or null.</param>
        /// <param name="editedProgram">
        /// When non-null, replaces the generated program (used by the UI to honor
        /// in-place G-code edits). Source.Offset is still populated from the
        /// generated program so round-trips stay consistent.
        /// </param>
        /// <param name="breakoffs">
        /// Breakoffs to merge into the program and keep on the drawing; ones that cannot be
        /// resolved against <paramref name="entities"/> are kept but not applied.
        /// </param>
        /// <param name="tabbedCutouts">
        /// Tabbed cutouts to merge into the program (after breakoffs) and keep on the drawing;
        /// ones that cannot be resolved are kept but not applied.
        /// </param>
        /// <param name="entityRoles">
        /// Per-entity role overrides keyed by source entity ID, applied before breakoffs and kept
        /// on the drawing; display-only entities stay out of the program.
        /// </param>
        /// <param name="dimensions">Dimensions to keep on the drawing; they never affect the program.</param>
        public static Drawing BuildDrawing(
            CadImportResult result,
            IEnumerable<Entity> entities,
            IEnumerable<Bend> bends,
            int quantity,
            string customer,
            OpenNest.CNC.Program editedProgram,
            IReadOnlyList<Breakoff> breakoffs = null,
            IReadOnlyList<TabbedCutout> tabbedCutouts = null,
            IReadOnlyDictionary<System.Guid, EntityRole> entityRoles = null,
            IReadOnlyList<DrawingDimension> dimensions = null
        )
        {
            var visible = entityRoles is { Count: > 0 }
                ? EntityRoles.ForProgram(entities, entityRoles)
                : entities as IList<Entity> ?? new List<Entity>(entities);
            var bendList = bends as IList<Bend> ?? new List<Bend>(bends);

            var cut = breakoffs is { Count: > 0 }
                ? BreakoffBuilder.Apply(visible.ToList(), breakoffs, out _)
                : visible;
            if (tabbedCutouts is { Count: > 0 })
                cut = TabbedCutoutBuilder.Apply(cut.ToList(), tabbedCutouts, out _);
            var normalized = ShapeProfile.NormalizeEntities(cut);
            var pgm = ConvertGeometry.ToProgram(normalized);

            var offset = Vector.Zero;
            if (
                pgm != null
                && pgm.Codes.Count > 0
                && pgm[0].Type == OpenNest.CNC.CodeType.RapidMove
            )
            {
                var rapid = (OpenNest.CNC.RapidMove)pgm[0];
                offset = rapid.EndPoint;
                pgm.Offset(-offset);
            }

            var drawing = new Drawing(result.Name)
            {
                Color = Drawing.GetNextColor(),
                Customer = customer,
            };
            drawing.Source.Path = result.SourcePath;
            drawing.Source.Offset = offset;
            drawing.Quantity.Required = quantity;
            drawing.Bends.AddRange(bendList);
            drawing.Breakoffs = breakoffs?.Select(b => b.Clone()).ToList() ?? new List<Breakoff>();
            drawing.TabbedCutouts = tabbedCutouts?.Select(c => c.Clone()).ToList() ?? new List<TabbedCutout>();
            drawing.Dimensions = dimensions?.Select(d => d.Clone()).ToList() ?? new List<DrawingDimension>();
            drawing.Program = editedProgram ?? pgm;

            var bendSources = new HashSet<Entity>(
                bendList.Where(b => b.SourceEntity != null).Select(b => b.SourceEntity)
            );

            drawing.SourceEntities = result.Entities.Where(e => !bendSources.Contains(e)).ToList();

            drawing.SuppressedEntityIds = new HashSet<System.Guid>(
                drawing
                    .SourceEntities.Where(e =>
                        !(e.Layer != null && e.Layer.IsVisible && e.IsVisible)
                    )
                    .Select(e => e.Id)
            );

            var sourceIds = new HashSet<System.Guid>(drawing.SourceEntities.Select(e => e.Id));
            drawing.EntityRoles = entityRoles?
                .Where(r => sourceIds.Contains(r.Key))
                .ToDictionary(r => r.Key, r => r.Value) ?? new Dictionary<System.Guid, EntityRole>();

            return drawing;
        }

        /// <summary>
        /// The entities an editor shows for an existing drawing, in its source frame: the stored
        /// source entities with their suppression applied to <see cref="Entity.IsVisible"/>, or
        /// for older drawings without them, the program geometry moved back by
        /// <c>Source.Offset</c> without rapids.
        /// </summary>
        public static List<Entity> EditableEntities(Drawing drawing)
        {
            if (drawing.SourceEntities != null)
            {
                // Use stored entities with stable GUIDs; apply suppression state
                var entities = new List<Entity>(drawing.SourceEntities);

                foreach (var entity in entities)
                    entity.IsVisible = !drawing.SuppressedEntityIds.Contains(entity.Id);

                return entities;
            }

            var derived = ConvertProgram.ToGeometry(drawing.Program);

            // Re-apply source offset so entities appear in their natural position
            if (drawing.Source?.Offset != null && drawing.Source.Offset != Vector.Zero)
            {
                foreach (var entity in derived)
                    entity.Offset(drawing.Source.Offset);
            }

            // Remove rapid traversals — they aren't part of the cut geometry
            derived.RemoveAll(e => e.Layer == SpecialLayers.Rapid);
            return derived;
        }

        /// <summary>
        /// Applies an edited rebuild of <paramref name="existing"/> in place, so placed parts keep
        /// their drawing reference. Geometry, source, customer, quantity and bends are taken from
        /// <paramref name="edited"/>; the library link and cut pins stay, since pins live in the
        /// source frame and are resolved against the new program when used.
        /// </summary>
        public static void ApplyEdit(Drawing existing, Drawing edited)
        {
            existing.Program = edited.Program;
            existing.SourceEntities = edited.SourceEntities;
            existing.SuppressedEntityIds = edited.SuppressedEntityIds;
            existing.EntityRoles = edited.EntityRoles;
            existing.Source = edited.Source;
            existing.Customer = edited.Customer;
            existing.Quantity.Required = edited.Quantity.Required;
            existing.Bends.Clear();
            existing.Bends.AddRange(edited.Bends);
            existing.Breakoffs = edited.Breakoffs;
            existing.TabbedCutouts = edited.TabbedCutouts;
            existing.Dimensions = edited.Dimensions;
        }

        private static bool IsRepairMark(Entity e) =>
            string.Equals(e.Layer?.Name, "ETCH", System.StringComparison.OrdinalIgnoreCase)
            || string.Equals(e.Layer?.Name, "SCRIBE", System.StringComparison.OrdinalIgnoreCase);

        internal static void RemoveZeroSweepArcs(List<Entity> entities)
        {
            entities.RemoveAll(e =>
                e is Arc arc && arc.StartAngle.IsEqualTo(arc.EndAngle, Tolerance.ChainTolerance)
            );
        }

        internal static void RemoveDuplicateArcs(List<Entity> entities)
        {
            var circles = entities.OfType<Circle>().ToList();
            var arcs = entities.OfType<Arc>().ToList();
            var arcsToRemove = new List<Arc>();

            foreach (var arc in arcs)
            {
                foreach (var circle in circles)
                {
                    if (arc.Layer?.Name != circle.Layer?.Name)
                        continue;

                    if (!arc.Center.DistanceTo(circle.Center).IsEqualTo(0))
                        continue;

                    if (!arc.Radius.IsEqualTo(circle.Radius))
                        continue;

                    arcsToRemove.Add(arc);
                    break;
                }
            }

            foreach (var arc in arcsToRemove)
                entities.Remove(arc);
        }
    }
}