using System.Text.Json;
using System.Text.Json.Serialization;

namespace HSchool.People;

/// <summary>On-disk shape of <c>saves/{id}.people.json</c>. Composition only — needs are not live values.</summary>
public sealed class RosterDocument
{
    public const int CurrentFormat = 1;

    public int Format { get; init; } = CurrentFormat;

    public int Seed { get; init; }

    public required IReadOnlyList<Person> People { get; init; }

    public required IReadOnlyList<Family> Families { get; init; }

    public required IReadOnlyList<SchoolClass> Classes { get; init; }

    public ApplicantPool? Applicants { get; init; }

    public Roster ToRoster() => new(People, Families, Classes);

    public static RosterDocument From(int seed, Roster roster, ApplicantPool? applicants = null) =>
        new()
        {
            Format = CurrentFormat,
            Seed = seed,
            People = roster.People,
            Families = roster.Families,
            Classes = roster.Classes,
            Applicants = applicants,
        };
}

public static class RosterJson
{
    public static JsonSerializerOptions Options { get; } = new()
    {
        PropertyNamingPolicy = JsonNamingPolicy.CamelCase,
        PropertyNameCaseInsensitive = true,
        WriteIndented = true,
        DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingNull,
    };

    public static string Serialize(RosterDocument document) =>
        JsonSerializer.Serialize(document, Options);

    public static RosterDocument Parse(string json)
    {
        var document = JsonSerializer.Deserialize<RosterDocument>(json, Options);
        if (document is null || document.People is null || document.Families is null || document.Classes is null)
        {
            throw new InvalidOperationException("People save deserialized to nothing.");
        }

        return document;
    }
}