using System.Collections.Generic;
using System.Linq;
using Prefab.Shared.Catalog.Products;

namespace Prefab.Web.Client.Models.Catalog;

/// <summary>
/// UI-facing projection of the catalog product detail configuration payload.
/// </summary>
public sealed class ProductDisplayModel
{
    public Guid Id { get; init; }

    public string Slug { get; init; } = string.Empty;

    public string Name { get; init; } = string.Empty;

    public string? Description { get; init; }

    public decimal? BasePrice { get; init; }

    public string? Sku { get; init; }

    public IReadOnlyList<CategoryRef> Categories { get; init; } = Array.Empty<CategoryRef>();

    public IReadOnlyList<OptionDefinition> Options { get; init; } = Array.Empty<OptionDefinition>();

    public IReadOnlyList<Spec> Specs { get; init; } = Array.Empty<Spec>();

    public IReadOnlyDictionary<string, string>? GenericAttributes { get; init; }

    public sealed record OptionDefinition(
        Guid Id,
        string Code,
        string Name,
        int DataType,
        bool IsVariantAxis,
        string? Unit,
        decimal? Min,
        decimal? Max,
        decimal? Step,
        decimal? PricePerUnit,
        IReadOnlyList<Tier> Tiers,
        IReadOnlyList<OptionValue> Values);

    public sealed record OptionValue(
        Guid Id,
        string Code,
        string Label,
        decimal? PriceDelta,
        int PriceDeltaKind);

    public sealed record Tier(
        decimal FromInclusive,
        decimal? ToInclusive,
        decimal UnitRate,
        decimal? FlatDelta);

    public sealed record Spec(
        string Name,
        string? Value,
        decimal? NumericValue,
        string? UnitCode);

    public sealed record CategoryRef(
        Guid Id,
        string Name,
        string Slug);

    public static ProductDisplayModel From(GetProductDetail.ProductDetailDto product)
    {
        ArgumentNullException.ThrowIfNull(product);

        var options = product.Options?
            .Select(option => new OptionDefinition(
                option.Id,
                option.Code,
                option.Name,
                option.DataType,
                option.IsVariantAxis,
                option.Unit,
                option.Min,
                option.Max,
                option.Step,
                option.PricePerUnit,
                option.Tiers?
                    .Select(tier => new Tier(
                        tier.FromInclusive,
                        tier.ToInclusive,
                        tier.UnitRate,
                        tier.FlatDelta))
                    .ToList() ?? new List<Tier>(),
                option.Values?
                    .Select(value => new OptionValue(
                        value.Id,
                        value.Code,
                        value.Label,
                        value.PriceDelta,
                        value.PriceDeltaKind))
                    .ToList() ?? new List<OptionValue>()))
            .ToList() ?? new List<OptionDefinition>();

        var specs = product.Specs?
            .Select(spec => new Spec(
                spec.Name,
                spec.Value,
                spec.NumericValue,
                spec.UnitCode))
            .ToList() ?? new List<Spec>();

        var categories = product.Categories?
            .Select(category => new CategoryRef(
                category.Id,
                category.Name,
                category.Slug))
            .ToList() ?? new List<CategoryRef>();

        return new ProductDisplayModel
        {
            Id = product.Id,
            Slug = product.Slug,
            Name = product.Name,
            Description = product.Description,
            BasePrice = product.Price,
            Sku = product.Sku,
            Categories = categories,
            Options = options,
            Specs = specs,
            GenericAttributes = product.GenericAttributes
        };
    }
}