namespace AIStudio.Tools.ToolCallingSystem;

/// <summary>
/// Builds the schema describing a tool's settings.
/// </summary>
/// <remarks>
/// Settings are stored as text throughout, so there is no field type to choose here. What a
/// field declares instead is whether it must be set, whether it holds a secret, and whether it
/// offers a fixed choice.<br/><br/>
/// Titles and descriptions are deliberately absent: they come from the implementation, which can
/// translate them. See the settings field label and description hooks on the tool interface.
/// </remarks>
public sealed class ToolSettingsSchemaBuilder
{
    private readonly Dictionary<string, ToolSettingsFieldDefinition> properties = new(StringComparer.Ordinal);
    private readonly HashSet<string> requiredNames = new(StringComparer.Ordinal);

    private string currentGroup = string.Empty;

    public static ToolSettingsSchemaBuilder Create() => new();

    /// <summary>
    /// Puts every field declared after this call into one group.
    /// </summary>
    /// <remarks>
    /// Call it again with another name to start the next group, or with an empty name to
    /// leave grouping behind. Groups are shown in the order in which they first appear here,
    /// and so are the fields within them.
    /// </remarks>
    public ToolSettingsSchemaBuilder InGroup(string groupKey)
    {
        this.currentGroup = groupKey;
        return this;
    }

    /// <summary>
    /// A field the tool cannot work without.
    /// </summary>
    /// <remarks>
    /// The tool counts as unconfigured while a required field is empty, which keeps it out of the
    /// model's reach instead of letting it run and fail.
    /// </remarks>
    public ToolSettingsSchemaBuilder Required(string name) => this.Add(name, isRequired: true);

    public ToolSettingsSchemaBuilder Optional(string name) => this.Add(name, isRequired: false);

    /// <summary>
    /// A required field whose value is picked from one of the app's option lists.
    /// </summary>
    public ToolSettingsSchemaBuilder RequiredChoice(string name, string optionSource) => this.Add(name, isRequired: true, optionSource: optionSource);

    public ToolSettingsSchemaBuilder OptionalChoice(string name, string optionSource) => this.Add(name, isRequired: false, optionSource: optionSource);

    /// <summary>
    /// An optional field whose value is picked from a short list the tool spells out itself.
    /// </summary>
    /// <remarks>
    /// Use this for values only one tool knows, such as the markets a single search service
    /// offers. Anything the app maintains elsewhere belongs in an option source instead, which
    /// also gives the user a translated name rather than the raw value.
    /// </remarks>
    public ToolSettingsSchemaBuilder OptionalEnum(string name, params string[] values) => this.Add(name, isRequired: false, enumValues: values);

    /// <summary>
    /// A field kept in the operating system's keyring rather than in the settings file.
    /// </summary>
    public ToolSettingsSchemaBuilder OptionalSecret(string name) => this.Add(name, isRequired: false, isSecret: true);

    public ToolSettingsSchemaBuilder RequiredSecret(string name) => this.Add(name, isRequired: true, isSecret: true);

    public ToolSettingsSchema Build() => new()
    {
        Properties = new(this.properties, StringComparer.Ordinal),
        Required = [..this.requiredNames],
    };

    private ToolSettingsSchemaBuilder Add(string name, bool isRequired, string optionSource = "", bool isSecret = false, IReadOnlyList<string>? enumValues = null)
    {
        this.properties[name] = new ToolSettingsFieldDefinition
        {
            OptionSource = optionSource,
            EnumValues = enumValues?.ToList() ?? [],
            Secret = isSecret,
            Group = this.currentGroup,
        };

        if (isRequired)
            this.requiredNames.Add(name);

        return this;
    }
}