module history.model;

import std.datetime.systime;

/**
 * A history containing a series of items, which all usually pertain to a
 * certain target entity.
 */
struct History {
    immutable ulong id;
}

/**
 * The type of history item. This can be used as a discriminator value to treat
 * different history types separately.
 */
enum HistoryItemType : string {
    TEXT = "TEXT"
}

HistoryItemType getHistoryItemType(string text) {
    import std.traits;
    static foreach (t; EnumMembers!HistoryItemType) {
        if (text == t) return t;
    }
    throw new Exception("Unknown history item type: " ~ text);
}

/**
 * A single item in a history. It has a UTC timestamp and a type. From the type,
 * one can get more specific information.
 */
struct HistoryItem {
    immutable ulong id;
    immutable ulong historyId;
    immutable SysTime timestamp;
    immutable HistoryItemType type;
}

/**
 * Additional data for history items with the TEXT type.
 */
struct HistoryItemText {
    immutable ulong itemId;
    immutable string content;
}