using System.Text.Json.Serialization;

namespace Elternbeirat.Contracts;

/// <summary>
///     A single question and answer of the FAQ, as stored in PocketBase.
/// </summary>
/// <remarks>
///     On the FAQ page, entries are grouped by their <see cref="Topic"/>. The topic is
///     a PocketBase relation; <see cref="Topic"/> is the resolved topic record, present
///     only when the query expanded the relation (see <see cref="FaqExpand"/>).
/// </remarks>
public record Faq
{
    /// <summary>
    ///     Gets the PocketBase record id.
    /// </summary>
    /// <remarks>
    ///     <see langword="required"/>: every stored record has an id. Modeling it as
    ///     required states which fields a record must carry, independent of the store,
    ///     so a future data source has to supply them too.
    /// </remarks>
    [JsonPropertyName("id")]
    public required string Id { get; init; }

    /// <summary>
    ///     Gets the question as a parent would phrase it.
    /// </summary>
    /// <remarks>
    ///     <see langword="required"/>: a FAQ entry without a question is incomplete, and
    ///     the field is required in PocketBase.
    /// </remarks>
    [JsonPropertyName("question")]
    public required string Question { get; init; }

    /// <summary>
    ///     Gets the answer as Markdown.
    /// </summary>
    /// <remarks>
    ///     <see langword="required"/>: a FAQ entry exists to answer its question, so an
    ///     entry without an answer is incomplete. The field is required in PocketBase.
    /// </remarks>
    [JsonPropertyName("answer")]
    public required string Answer { get; init; }

    /// <summary>
    ///     Gets the expanded relations returned by PocketBase, or <see langword="null"/>
    ///     when the query did not expand any.
    /// </summary>
    [JsonPropertyName("expand")]
    public FaqExpand? Expand { get; init; }

    /// <summary>
    ///     Gets the resolved topic this entry is grouped under, or <see langword="null"/>
    ///     when the query did not expand the topic relation.
    /// </summary>
    /// <remarks>
    ///     Convenience over <see cref="Expand"/>: the FAQ page reads the grouping
    ///     heading from here. It is <see langword="null"/> unless the entry was loaded
    ///     with the topic relation expanded.
    /// </remarks>
    [JsonIgnore]
    public FaqTopic? Topic => Expand?.Topic;
}

/// <summary>
///     The relations of a <see cref="Faq"/> that PocketBase returns under
///     <c>expand</c> when the query asks for them.
/// </summary>
/// <remarks>
///     One property per expandable relation, named after its PocketBase field, so the
///     JSON <c>expand</c> object maps straight onto it. <see cref="Faq.Topic"/> reads
///     through this.
/// </remarks>
public record FaqExpand
{
    /// <summary>
    ///     Gets the expanded topic of the <c>topic</c> relation, if it was expanded.
    /// </summary>
    [JsonPropertyName("topic")]
    public FaqTopic? Topic { get; init; }
}