using System.Xml; // XmlWriter
using System.Text.Json; // Utf8JsonWriter, JsonWriterOptions
using Packt.Shared; // Category, Product

using static System.IO.Path;
using static System.Environment;

// we want to easily show the difference between outputting
// XML using elements or attributes so we will define a 
// delegate to reference the two different methods.

delegate void WriteDataDelegate(string name, string? value);

partial class Program
{
  static void GenerateXmlFile(
    IQueryable<Category> categories, bool useAttributes = true)
  {
    string which = useAttributes ? "attibutes" : "elements";

    string xmlFile = $"categories-and-products-using-{which}.xml";

    using (FileStream xmlStream = File.Create(
      Combine(CurrentDirectory, xmlFile)))
    {
      using (XmlWriter xml = XmlWriter.Create(xmlStream,
        new XmlWriterSettings { Indent = true }))
      {

        WriteDataDelegate writeMethod;

        if (useAttributes)
        {
          writeMethod = xml.WriteAttributeString;
        }
        else // use elements
        {
          writeMethod = xml.WriteElementString;
        }

        xml.WriteStartDocument();
        xml.WriteStartElement("categories");

        foreach (Category c in categories)
        {
          xml.WriteStartElement("category");
          writeMethod("id", c.CategoryId.ToString());
          writeMethod("name", c.CategoryName);
          writeMethod("desc", c.Description);
          writeMethod("product_count", c.Products.Count.ToString());
          xml.WriteStartElement("products");

          foreach (Product p in c.Products)
          {
            xml.WriteStartElement("product");

            writeMethod("id", p.ProductId.ToString());
            writeMethod("name", p.ProductName);
            writeMethod("cost", p.Cost is null ? "0" : p.Cost.Value.ToString());
            writeMethod("stock", p.Stock.ToString());
            writeMethod("discontinued", p.Discontinued.ToString());

            xml.WriteEndElement(); // </product>
          }
          xml.WriteEndElement(); // </products>
          xml.WriteEndElement(); // </category>
        }
        xml.WriteEndElement(); // </categories>
      }
    }

    WriteLine("{0} contains {1:N0} bytes.",
      arg0: xmlFile,
      arg1: new FileInfo(xmlFile).Length);
  }

  static void GenerateCsvFile(IQueryable<Category> categories)
  {
    string csvFile = "categories-and-products.csv";

    using (FileStream csvStream = File.Create(Combine(CurrentDirectory, csvFile)))
    {
      using (StreamWriter csv = new(csvStream))
      {

        csv.WriteLine("CategoryId,CategoryName,Description,ProductId,ProductName,Cost,Stock,Discontinued");

        foreach (Category c in categories)
        {
          foreach (Product p in c.Products)
          {
            csv.Write("{0},\"{1}\",\"{2}\",",
              arg0: c.CategoryId,
              arg1: c.CategoryName,
              arg2: c.Description);

            csv.Write("{0},\"{1}\",{2},",
              arg0: p.ProductId,
              arg1: p.ProductName,
              arg2: p.Cost is null ? 0 : p.Cost.Value);

            csv.WriteLine("{0},{1}",
              arg0: p.Stock,
              arg1: p.Discontinued);
          }
        }
      }
    }

    WriteLine("{0} contains {1:N0} bytes.",
      arg0: csvFile,
      arg1: new FileInfo(csvFile).Length);
  }

  static void GenerateJsonFile(IQueryable<Category> categories)
  {
    string jsonFile = "categories-and-products.json";

    using (FileStream jsonStream = File.Create(Combine(CurrentDirectory, jsonFile)))
    {
      using (Utf8JsonWriter json = new(jsonStream,
        new JsonWriterOptions { Indented = true }))
      {
        json.WriteStartObject();
        json.WriteStartArray("categories");

        foreach (Category c in categories)
        {
          json.WriteStartObject();

          json.WriteNumber("id", c.CategoryId);
          json.WriteString("name", c.CategoryName);
          json.WriteString("desc", c.Description);
          json.WriteNumber("product_count", c.Products.Count);

          json.WriteStartArray("products");

          foreach (Product p in c.Products)
          {
            json.WriteStartObject();

            json.WriteNumber("id", p.ProductId);
            json.WriteString("name", p.ProductName);
            json.WriteNumber("cost", p.Cost is null ? 0 : p.Cost.Value);
            json.WriteNumber("stock", p.Stock is null ? 0 : p.Stock.Value);
            json.WriteBoolean("discontinued", p.Discontinued);

            json.WriteEndObject(); // product
          }
          json.WriteEndArray(); // products
          json.WriteEndObject(); // category
        }
        json.WriteEndArray(); // categories
        json.WriteEndObject();
      }
    }

    WriteLine("{0} contains {1:N0} bytes.",
      arg0: jsonFile,
      arg1: new FileInfo(jsonFile).Length);
  }
}