using System.Linq;
using System.Reactive.Linq;
using System.Text;
using Intromat.Model.Compiler;
using Intromat.Model.Compiler.Error;
using ReactiveUI;

namespace Intromat.ViewModels
{
    public class CodePreviewViewModel : ReactiveObject
    {
        private readonly ObservableAsPropertyHelper<string> _compiledCode;

        private IStatement? _code;

        private string? _compilerError;

        public CodePreviewViewModel()
        {
            this.WhenAnyValue(vm => vm.Code).Where(c => c != null)
                .Select(Compile)
                .ToProperty(this, vm => vm.CompiledCode, out _compiledCode);
        }

        public IStatement? Code
        {
            get => _code;
            set => this.RaiseAndSetIfChanged(ref _code, value);
        }

        public string? CompilerError
        {
            get => _compilerError;
            set => this.RaiseAndSetIfChanged(ref _compilerError, value);
        }

        public string CompiledCode => _compiledCode.Value;

        private string Compile(IStatement? c)
        {
            if (c == null)
            {
                CompilerError = "No code provided";
                return string.Empty;
            }

            CompilerError = string.Empty;
            CompilerContext ctx = new();
            var sb = new StringBuilder();
            try
            {
                c.CompileHeader(ctx, sb);
                c.Compile(ctx, sb);
                return sb.ToString();
            }
            catch (CompilerException e)
            {
                string trace = string.Join("\n", ctx.VariablesScopesStack.Select(s => s.Identifier));
                CompilerError = e.Message + "\nProblem is near:\n" + trace;
                return string.Empty;
            }
        }
    }
}