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

namespace Chessistics.Engine.Loading;

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

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

        Validate(dto);

        return new CampaignDef
        {
            Name = dto.Name,
            InitialWidth = dto.InitialWidth,
            InitialHeight = dto.InitialHeight,
            Missions = dto.Missions.Select(ParseMission).ToList()
        };
    }

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

    private static MissionDef ParseMission(MissionDto m)
    {
        var patch = new TerrainPatch
        {
            NewWidth = m.TerrainPatch.NewWidth,
            NewHeight = m.TerrainPatch.NewHeight,
            Cells = m.TerrainPatch.Cells.Select(ParsePatchCell).ToList()
        };

        return new MissionDef
        {
            Id = m.Id,
            Name = m.Name,
            Description = m.Description ?? "",
            Flavor = m.Flavor ?? "",
            TerrainPatch = patch,
            Stock = m.Stock?.Select(s => new PieceStock(ParseKind(s.Kind), s.Count, s.Level)).ToList() ?? [],
            UnlockedPieces = m.UnlockedPieces?.Select(ParseKind).ToList() ?? [],
            UnlockedLevels = m.UnlockedLevels?.Select(u => new PieceUpgrade(ParseKind(u.Kind), u.Level)).ToList() ?? []
        };
    }

    private static PatchCell ParsePatchCell(CellDto c)
    {
        var cellType = c.Type.ToLowerInvariant() switch
        {
            "empty" => CellType.Empty,
            "wall" => CellType.Wall,
            "production" => CellType.Production,
            "demand" => CellType.Demand,
            "transformer" => CellType.Transformer,
            _ => throw new JsonException($"Unknown cell type: '{c.Type}'")
        };

        ProductionDef? prod = null;
        if (cellType == CellType.Production && c.Production != null)
        {
            prod = new ProductionDef(new Coords(c.Col, c.Row), c.Production.Name, ParseCargo(c.Production.Cargo), c.Production.Amount);
        }

        DemandDef? demand = null;
        if (cellType == CellType.Demand && c.Demand != null)
        {
            demand = new DemandDef(new Coords(c.Col, c.Row), c.Demand.Name, ParseCargo(c.Demand.Cargo), c.Demand.Amount);
        }

        TransformerDef? transformer = null;
        if (cellType == CellType.Transformer && c.Transformer != null)
        {
            transformer = new TransformerDef(
                new Coords(c.Col, c.Row), c.Transformer.Name,
                ParseCargo(c.Transformer.InputCargo), c.Transformer.InputRequired,
                ParseCargo(c.Transformer.OutputCargo), c.Transformer.OutputAmount);
        }

        return new PatchCell
        {
            Col = c.Col,
            Row = c.Row,
            Type = cellType,
            Production = prod,
            Demand = demand,
            Transformer = transformer
        };
    }

    private static CargoType ParseCargo(string cargo) => cargo.ToLowerInvariant() switch
    {
        "wood" => CargoType.Wood,
        "stone" => CargoType.Stone,
        "tools" => CargoType.Tools,
        "arms" => CargoType.Arms,
        "gold" => CargoType.Gold,
        _ => 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,
        "queen" => PieceKind.Queen,
        _ => throw new JsonException($"Unknown piece kind: '{kind}'")
    };

    private static void Validate(CampaignDto dto)
    {
        if (string.IsNullOrWhiteSpace(dto.Name))
            throw new JsonException("Campaign name is required.");
        if (dto.InitialWidth <= 0 || dto.InitialHeight <= 0)
            throw new JsonException("Campaign dimensions must be positive.");
        if (dto.Missions.Count == 0)
            throw new JsonException("Campaign must have at least one mission.");

        int prevWidth = dto.InitialWidth;
        int prevHeight = dto.InitialHeight;
        foreach (var mission in dto.Missions)
        {
            if (mission.TerrainPatch.NewWidth < prevWidth || mission.TerrainPatch.NewHeight < prevHeight)
                throw new JsonException($"Mission '{mission.Name}': terrain cannot shrink (was {prevWidth}x{prevHeight}, got {mission.TerrainPatch.NewWidth}x{mission.TerrainPatch.NewHeight}).");
            prevWidth = mission.TerrainPatch.NewWidth;
            prevHeight = mission.TerrainPatch.NewHeight;
        }
    }

    // DTOs
    private class CampaignDto
    {
        public string Name { get; set; } = "";
        public int InitialWidth { get; set; }
        public int InitialHeight { get; set; }
        public List<MissionDto> Missions { get; set; } = [];
    }

    private class MissionDto
    {
        public int Id { get; set; }
        public string Name { get; set; } = "";
        public string? Description { get; set; }
        public string? Flavor { get; set; }
        public TerrainPatchDto TerrainPatch { get; set; } = new();
        public List<StockDto>? Stock { get; set; }
        public List<string>? UnlockedPieces { get; set; }
        public List<UpgradeDto>? UnlockedLevels { get; set; }
    }

    private class TerrainPatchDto
    {
        public int NewWidth { get; set; }
        public int NewHeight { get; set; }
        public List<CellDto> Cells { get; set; } = [];
    }

    private class CellDto
    {
        public int Col { get; set; }
        public int Row { get; set; }
        public string Type { get; set; } = "empty";
        public ProductionDto? Production { get; set; }
        public DemandDto? Demand { get; set; }
        public TransformerDto? Transformer { get; set; }
    }

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

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

    private class TransformerDto
    {
        public string Name { get; set; } = "";
        public string InputCargo { get; set; } = "";
        public int InputRequired { get; set; } = 1;
        public string OutputCargo { get; set; } = "";
        public int OutputAmount { get; set; } = 1;
    }

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

    private class UpgradeDto
    {
        public string Kind { get; set; } = "";
        public int Level { get; set; }
    }
}