using System.Text.Json;
using System.Text.Json.Serialization;
using Chessistics.Engine.Model;

namespace Chessistics.Engine.Loading;

public static class LevelLoader
{
    private static readonly JsonSerializerOptions Options = new()
    {
        PropertyNameCaseInsensitive = true,
        Converters = { new JsonStringEnumConverter(JsonNamingPolicy.CamelCase) }
    };

    public static LevelDef Load(string json)
    {
        var dto = JsonSerializer.Deserialize<LevelDto>(json, Options)
            ?? throw new JsonException("Failed to deserialize level JSON.");

        Validate(dto);

        return new LevelDef
        {
            Id = dto.Id,
            Name = dto.Name,
            Description = dto.Description ?? "",
            Width = dto.Width,
            Height = dto.Height,
            Productions = dto.Productions.Select(p => new ProductionDef(
                new Coords(p.Col, p.Row), p.Name, ParseCargo(p.Cargo), p.Amount
            )).ToList(),
            Demands = dto.Demands.Select(d => new DemandDef(
                new Coords(d.Col, d.Row), d.Name, ParseCargo(d.Cargo), d.Amount, d.Deadline
            )).ToList(),
            Walls = dto.Walls?.Select(w => new Coords(w.Col, w.Row)).ToList() ?? [],
            Stock = dto.Stock.Select(s => new PieceStock(ParseKind(s.Kind), s.Count, s.Level)).ToList()
        };
    }

    public static LevelDef LoadFromFile(string path)
    {
        var json = File.ReadAllText(path);
        return Load(json);
    }

    private static CargoType ParseCargo(string cargo) => cargo.ToLowerInvariant() switch
    {
        "wood" => CargoType.Wood,
        "stone" => CargoType.Stone,
        _ => throw new JsonException($"Unknown cargo type: '{cargo}'")
    };

    private static PieceKind ParseKind(string kind) => kind.ToLowerInvariant() switch
    {
        "pawn" => PieceKind.Pawn,
        "rook" => PieceKind.Rook,
        "bishop" => PieceKind.Bishop,
        "knight" => PieceKind.Knight,
        _ => throw new JsonException($"Unknown piece kind: '{kind}'")
    };

    private static void Validate(LevelDto dto)
    {
        if (string.IsNullOrWhiteSpace(dto.Name))
            throw new JsonException("Level name is required.");
        if (dto.Width <= 0 || dto.Height <= 0)
            throw new JsonException("Level dimensions must be positive.");
        if (dto.Productions.Count == 0)
            throw new JsonException("Level must have at least one production.");
        if (dto.Demands.Count == 0)
            throw new JsonException("Level must have at least one demand.");
        if (dto.Stock.Count == 0)
            throw new JsonException("Level must have at least one piece in stock.");
    }

    // DTOs for JSON deserialization
    private class LevelDto
    {
        public int Id { get; set; }
        public string Name { get; set; } = "";
        public string? Description { get; set; }
        public int Width { get; set; }
        public int Height { get; set; }
        public List<ProductionDto> Productions { get; set; } = [];
        public List<DemandDto> Demands { get; set; } = [];
        public List<CoordsDto>? Walls { get; set; }
        public List<StockDto> Stock { get; set; } = [];
    }

    private class ProductionDto
    {
        public int Col { get; set; }
        public int Row { get; set; }
        public string Name { get; set; } = "";
        public string Cargo { get; set; } = "";
        public int Amount { get; set; } = 1;
    }

    private class DemandDto
    {
        public int Col { get; set; }
        public int Row { get; set; }
        public string Name { get; set; } = "";
        public string Cargo { get; set; } = "";
        public int Amount { get; set; }
        public int Deadline { get; set; }
    }

    private class CoordsDto
    {
        public int Col { get; set; }
        public int Row { get; set; }
    }

    private class StockDto
    {
        public string Kind { get; set; } = "";
        public int Count { get; set; }
        public int Level { get; set; } = 1;
    }
}