using EonaCat.FirstLight.SaveTransfer.VdfGenerator.KeyValue.Models;

namespace EonaCat.FirstLight.SaveTransfer.VdfGenerator.KeyValue;

/// <summary>
/// Provides static methods for deserializing text representations of key-value groups into KvGroup objects.
/// </summary>
public static class KeyValueDeserializer
{
    /// <summary>
    /// Deserializes the specified text into a KvGroup object.
    /// </summary>
    /// <param name="text">The input string containing the serialized representation of a KvGroup. Cannot be null.</param>
    /// <returns>A KvGroup object that represents the data contained in the input text.</returns>
    public static KeyValueGroup Deserialize(string text)
    {
        var tokenizer = new KeyValueTokenizer(text);
        return ParseGroup(tokenizer);
    }

    /// <summary>
    /// Parses a group from the provided tokenizer, including any nested groups or key-value pairs.
    /// </summary>
    /// <param name="t">The tokenizer used to read group names, symbols, and key-value pairs from the input stream. Must not be null and must be positioned at the start of a group.</param>
    /// <param name="k">The optional name of the group to parse. If null, the group name is read from the tokenizer.</param>
    /// <returns>A KvGroup representing the parsed group, including all nested groups and key-value pairs.</returns>
    private static KeyValueGroup ParseGroup(KeyValueTokenizer t, string? k = null)
    {
        // Expect group name
        var groupName = k ?? t.ReadString();
        var group = new KeyValueGroup(groupName);

        t.ReadSymbol('{');

        while (!t.PeekSymbol('}'))
        {
            var key = t.ReadString();

            if (t.PeekSymbol('{'))
            {
                // Nested group
                group.Nodes.Add(ParseGroup(t, key));
            }
            else
            {
                // Key-value pair
                var value = t.ReadString();
                group.Nodes.Add(new Models.KeyValuePair(key, value));
            }
        }

        t.ReadSymbol('}');
        return group;
    }
}