using System.Runtime.CompilerServices;
using System.Text;
using OpenTK.Graphics.OpenGL;
using OpenTK.Mathematics;
using Serilog;

namespace Engine.Renderer.Shader;

public class ShaderProgram : OpenGlObject
{
    private readonly Dictionary<string, int> _uniforms = new();

    public static ShaderProgram CreateFromSource(string source)
    {
        var vertexSource = new StringBuilder();
        var fragmentSource = new StringBuilder();
        var inFragment = false;
        var inVertex = false;

        foreach (var line in source.Split('\n'))
        {
            if (line.StartsWith("#shader vertex"))
            {
                inVertex = true;
                inFragment = false;
            }
            else if (line.StartsWith("#shader fragment"))
            {
                inVertex = false;
                inFragment = true;
            }
            else if (inVertex)
            {
                vertexSource.AppendLine(line);
            }
            else if (inFragment)
            {
                fragmentSource.AppendLine(line);
            }
        }

        return new ShaderProgram(vertexSource.ToString(), fragmentSource.ToString());
    }

    public ShaderProgram(string vertexSource, string fragmentSource)
    {
        var vertexShader = CompileSource(vertexSource, ShaderType.VertexShader);
        var fragmentShader = CompileSource(fragmentSource, ShaderType.FragmentShader);

        Handle = LinkProgram(vertexShader, fragmentShader);
    }

    public void SetUniform<T>(string name, T value, [CallerMemberName] string caller = "")
    {
        try
        {
            var location = GetUniformLocation(name);

            switch (value)
            {
                case bool boolValue:
                    GL.ProgramUniform1(Handle, location, boolValue ? 1 : 0);
                    break;
                case int intValue:
                    GL.ProgramUniform1(Handle, location, intValue);
                    break;
                case float floatValue:
                    GL.ProgramUniform1(Handle, location, floatValue);
                    break;
                case Vector2 vec2:
                    GL.ProgramUniform2(Handle, location, vec2);
                    break;
                case Vector3 vec3:
                    GL.ProgramUniform3(Handle, location, vec3);
                    break;
                case Vector4 vec4:
                    GL.ProgramUniform4(Handle, location, vec4);
                    break;
                case Matrix4 matrix:
                    GL.ProgramUniformMatrix4(Handle, location, false, ref matrix);
                    break;
                default:
                    throw new ArgumentException($"Unsupported uniform type: {typeof(T).Name}");
            }
        }
        catch (Exception ex)
        {
            Log.Error(ex, "Failed to set uniform {UniformName} from {Caller}", name, caller);
            throw;
        }
    }

    internal override void Bind()
    {
        GL.UseProgram(Handle);
    }

    internal override void Unbind()
    {
        GL.UseProgram(0);
    }

    protected override void Destroy()
    {
        GL.DeleteProgram(Handle);
    }

    private int GetUniformLocation(string name)
    {
        if (_uniforms.TryGetValue(name, out var location))
            return location;

        location = GL.GetUniformLocation(Handle, name);
        if (location < 0)
            throw new ArgumentException($"Uniform '{name}' not found in shader program");

        _uniforms.Add(name, location);
        return location;
    }

    private static int CompileSource(string source, ShaderType type)
    {
        var shaderId = GL.CreateShader(type);
        GL.ShaderSource(shaderId, source);
        GL.CompileShader(shaderId);

        GL.GetShader(shaderId, ShaderParameter.CompileStatus, out var status);
        if (status == 0)
        {
            var log = GL.GetShaderInfoLog(shaderId);
            GL.DeleteShader(shaderId);

            throw new ShaderCompilationException(type, log);
        }

        return shaderId;
    }

    private static int LinkProgram(int vertexShader, int fragmentShader)
    {
        var programId = GL.CreateProgram();
        try
        {
            GL.AttachShader(programId, vertexShader);
            GL.AttachShader(programId, fragmentShader);
            GL.LinkProgram(programId);

            GL.GetProgram(programId, GetProgramParameterName.LinkStatus, out var linkStatus);
            if (linkStatus == 0)
            {
                var log = GL.GetProgramInfoLog(programId);
                throw new ShaderLinkException(log);
            }

            GL.ValidateProgram(programId);
            GL.GetProgram(programId, GetProgramParameterName.ValidateStatus, out var validateStatus);
            if (validateStatus == 0)
            {
                var log = GL.GetProgramInfoLog(programId);
                throw new ShaderValidationException(log);
            }
        }
        finally
        {
            GL.DeleteShader(vertexShader);
            GL.DeleteShader(fragmentShader);
        }

        return programId;
    }
}

public class ShaderCompilationException(ShaderType type, string message)
    : Exception($"Failed to compile {type} shader: {message}")
{
    public ShaderType ShaderType { get; } = type;
}

public class ShaderLinkException(string message) : Exception($"Failed to link shader program: {message}");

public class ShaderValidationException(string message) : Exception($"Failed to validate shader program: {message}");