using System;
using System.Collections.Generic;
using System.Text.Json.Nodes;

namespace Penumbra.CrashHandler.Buffers;

/// <summary> Only expose the write interface for the buffer. </summary>
public interface IModdedFileBufferWriter
{
    /// <summary> Write a line into the buffer with the given data. </summary>
    /// <param name="characterAddress"> The address of the related character, if known. </param>
    /// <param name="characterName"> The name of the related character, anonymized or relying on index if unavailable, if known. </param>
    /// <param name="collectionId"> The GUID of the associated collection. </param>
    /// <param name="requestedFileName"> The file name as requested by the game. </param>
    /// <param name="actualFileName"> The actual modded file name loaded. </param>
    public void WriteLine(nint characterAddress, ReadOnlySpan<byte> characterName, Guid collectionId, ReadOnlySpan<byte> requestedFileName,
        ReadOnlySpan<byte> actualFileName);
}

/// <summary> The full crash entry for a loaded modded file. </summary>
public record struct ModdedFileLoadedEntry(
    double Age,
    DateTimeOffset Timestamp,
    int ThreadId,
    string CharacterName,
    string CharacterAddress,
    Guid CollectionId,
    string RequestedFileName,
    string ActualFileName) : ICrashDataEntry;

internal sealed class ModdedFileBuffer : MemoryMappedBuffer, IModdedFileBufferWriter, IBufferReader
{
    private const int    _version      = 1;
    private const int    _lineCount    = 128;
    private const int    _lineCapacity = 1024;
    private const string _name         = "Penumbra.ModdedFile";

    public void WriteLine(nint characterAddress, ReadOnlySpan<byte> characterName, Guid collectionId, ReadOnlySpan<byte> requestedFileName,
        ReadOnlySpan<byte> actualFileName)
    {
        var accessor = GetCurrentLineLocking();
        lock (accessor)
        {
            accessor.Write(0,  DateTimeOffset.UtcNow.ToUnixTimeMilliseconds());
            accessor.Write(8,  Environment.CurrentManagedThreadId);
            accessor.Write(12, characterAddress);
            var span = GetSpan(accessor, 20, 16);
            collectionId.TryWriteBytes(span);
            accessor.SafeMemoryMappedViewHandle.ReleasePointer();
            span = GetSpan(accessor, 36, 80);
            WriteSpan(characterName, span);
            accessor.SafeMemoryMappedViewHandle.ReleasePointer();
            span = GetSpan(accessor, 116, 260);
            WriteSpan(requestedFileName, span);
            accessor.SafeMemoryMappedViewHandle.ReleasePointer();
            span = GetSpan(accessor, 376);
            WriteSpan(actualFileName, span);
            accessor.SafeMemoryMappedViewHandle.ReleasePointer();
        }
    }

    public uint TotalCount
        => TotalWrittenLines;

    public IEnumerable<JsonObject> GetLines(DateTimeOffset crashTime)
    {
        var lineCount = (int)CurrentLineCount;
        for (var i = lineCount - 1; i >= 0; --i)
        {
            var line              = GetLine(i);
            var timestamp         = DateTimeOffset.FromUnixTimeMilliseconds(BitConverter.ToInt64(line));
            var thread            = BitConverter.ToInt32(line[8..]);
            var address           = BitConverter.ToUInt64(line[12..]);
            var collectionId      = new Guid(line[20..36]);
            var characterName     = ReadString(line[36..]);
            var requestedFileName = ReadString(line[116..]);
            var actualFileName    = ReadString(line[376..]);
            yield return new JsonObject()
            {
                [nameof(ModdedFileLoadedEntry.Age)]               = (crashTime - timestamp).TotalSeconds,
                [nameof(ModdedFileLoadedEntry.Timestamp)]         = timestamp,
                [nameof(ModdedFileLoadedEntry.ThreadId)]          = thread,
                [nameof(ModdedFileLoadedEntry.CharacterName)]     = characterName,
                [nameof(ModdedFileLoadedEntry.CharacterAddress)]  = address.ToString("X"),
                [nameof(ModdedFileLoadedEntry.CollectionId)]      = collectionId,
                [nameof(ModdedFileLoadedEntry.RequestedFileName)] = requestedFileName,
                [nameof(ModdedFileLoadedEntry.ActualFileName)]    = actualFileName,
            };
        }
    }

    public static IBufferReader CreateReader(int pid)
        => new ModdedFileBuffer(false, pid);

    public static IModdedFileBufferWriter CreateWriter(int pid)
        => new ModdedFileBuffer(pid);

    private ModdedFileBuffer(bool writer, int pid)
        : base($"{_name}_{pid}_{_version}", _version)
    { }

    private ModdedFileBuffer(int pid)
        : base($"{_name}_{pid}_{_version}", _version, _lineCount, _lineCapacity)
    { }
}