using System.Text.Json;
using HSchool.Content;
using HSchool.People;
using HSchool.Schedule;
using HSchool.Simulation;
using Microsoft.Extensions.Options;

namespace HSchool.Server.Game;

/// <summary>On-disk record of one school. Extra JSON fields are ignored so later slices can grow it.</summary>
internal sealed class SchoolSave
{
    public int Format { get; init; }

    public int Id { get; init; }

    public string Name { get; init; } = "";

    public DateTime GameTime { get; init; }

    public bool Running { get; init; }

    public int SpeedIndex { get; init; }

    public IReadOnlyList<string>? ModIds { get; init; }

    public MapLayout? Map { get; init; }

    public string? CountryId { get; init; }

    public string? ClimatePresetId { get; init; }

    public string? NativeLanguage { get; init; }

    public IReadOnlyList<PresenceSnapshot>? Presence { get; init; }

    public SchoolDressRules? DressRules { get; init; }

    /// <summary>Normalized player name. Missing or blank means ownerless.</summary>
    public string? Owner { get; init; }

    /// <summary>Portrait presets copied at create. Generation reads this, not the global template.</summary>
    public SwarmUiConfigFile? PortraitSettings { get; init; }
}

/// <summary>Allocates school ids that survive a process restart.</summary>
internal sealed record SchoolSaveIndex(int NextId);

/// <summary>
/// JSON files under <see cref="SimulationOptions.SavesDirectory"/>. The worker of a school is the
/// only writer of that school's file; the supervisor reads the directory at start and on reload.
/// </summary>
internal sealed class SchoolStore
{
    public const int CurrentFormat = 3;

    private const string IndexFileName = "index.json";

    private static readonly JsonSerializerOptions Json = new()
    {
        PropertyNamingPolicy = JsonNamingPolicy.CamelCase,
        PropertyNameCaseInsensitive = true,
        WriteIndented = true,
    };

    private readonly ILogger<SchoolStore> _logger;

    public SchoolStore(IOptions<SimulationOptions> options, IHostEnvironment environment, ILogger<SchoolStore> logger)
    {
        _logger = logger;

        var configured = options.Value.SavesDirectory;
        DirectoryPath = Path.IsPathRooted(configured)
            ? configured
            : Path.GetFullPath(Path.Combine(environment.ContentRootPath, configured));

        Directory.CreateDirectory(DirectoryPath);
        logger.LogInformation("School saves directory is {Directory}.", DirectoryPath);
    }

    public string DirectoryPath { get; }

    public int ReadNextId()
    {
        var path = IndexPath();
        if (!File.Exists(path))
        {
            return 1;
        }

        try
        {
            var json = File.ReadAllText(path);
            var index = JsonSerializer.Deserialize<SchoolSaveIndex>(json, Json);
            return index is { NextId: > 0 } ? index.NextId : 1;
        }
        catch (Exception ex)
        {
            _logger.LogWarning(ex, "Could not read {Path}; school ids will start from the files on disk.", path);
            return 1;
        }
    }

    public void WriteNextId(int nextId)
    {
        WriteAtomic(IndexPath(), new SchoolSaveIndex(nextId));
    }

    public IReadOnlyList<SchoolSave> LoadAll()
    {
        var saves = new List<SchoolSave>();

        // The id inside the file decides which school this is and which file it is saved back to,
        // so two files claiming the same id would give the menu two cards over one worker and then
        // overwrite each other on the next save.
        var claimed = new Dictionary<int, string>();

        foreach (var path in Directory.EnumerateFiles(DirectoryPath, "*.json"))
        {
            var fileName = Path.GetFileName(path);
            if (string.Equals(fileName, IndexFileName, StringComparison.OrdinalIgnoreCase)
                || fileName.EndsWith(".people.json", StringComparison.OrdinalIgnoreCase)
                || fileName.EndsWith(".timetable.json", StringComparison.OrdinalIgnoreCase))
            {
                continue;
            }

            try
            {
                var json = File.ReadAllText(path);
                var save = JsonSerializer.Deserialize<SchoolSave>(json, Json);
                if (save is null)
                {
                    _logger.LogWarning("Save {Path} deserialized to nothing; leaving the file in place.", path);
                    continue;
                }

                if (save.Id <= 0)
                {
                    _logger.LogWarning(
                        "Save {Path} has id {Id}; ids start at 1. Leaving the file in place.",
                        path,
                        save.Id);
                    continue;
                }

                if (!GameClock.IsValidStartDate(save.GameTime))
                {
                    _logger.LogWarning(
                        "Save {Path} has a game time outside the supported range; leaving the file in place.",
                        path);
                    continue;
                }

                // Claimed last, so a file rejected above does not reserve an id a good file needs.
                if (!claimed.TryAdd(save.Id, path))
                {
                    _logger.LogWarning(
                        "Save {Path} claims id {Id}, already taken by {Owner}; leaving the file in place.",
                        path,
                        save.Id,
                        claimed[save.Id]);
                    continue;
                }

                saves.Add(new SchoolSave
                {
                    Format = save.Format,
                    Id = save.Id,
                    Name = save.Name,
                    GameTime = DateTime.SpecifyKind(save.GameTime, DateTimeKind.Utc),
                    Running = save.Running,
                    SpeedIndex = save.SpeedIndex,
                    ModIds = save.ModIds,
                    Map = save.Map,
                    CountryId = save.CountryId,
                    ClimatePresetId = save.ClimatePresetId,
                    NativeLanguage = save.NativeLanguage,
                    Presence = save.Presence,
                    DressRules = save.DressRules,
                    Owner = save.Owner,
                    PortraitSettings = save.PortraitSettings,
                });
            }
            catch (Exception ex)
            {
                _logger.LogWarning(ex, "Could not read save {Path}; leaving the file in place.", path);
            }
        }

        saves.Sort((left, right) => left.Id.CompareTo(right.Id));
        return saves;
    }

    /// <summary>Older and newer files stay on disk for the menu to delete; they never start.</summary>
    public static bool CanStart(SchoolSave save) =>
        save.Format == CurrentFormat && !string.IsNullOrWhiteSpace(save.CountryId);

    public void Save(SchoolSave save)
    {
        WriteAtomic(SchoolPath(save.Id), save);
    }

    public void Delete(int id)
    {
        var path = SchoolPath(id);
        if (File.Exists(path))
        {
            File.Delete(path);
        }

        var people = PeoplePath(id);
        if (File.Exists(people))
        {
            File.Delete(people);
        }

        var timetable = TimetablePath(id);
        if (File.Exists(timetable))
        {
            File.Delete(timetable);
        }

        var portraits = PortraitsDirectory(id);
        if (Directory.Exists(portraits))
        {
            Directory.Delete(portraits, recursive: true);
        }
    }

    public bool HasPortrait(int schoolId, string personId, PortraitKind kind) =>
        File.Exists(PortraitPath(schoolId, personId, kind));

    public (bool HasAvatar, bool HasCustom, bool HasFullBody) PortraitFlags(int schoolId, string personId)
    {
        var directory = PortraitsDirectory(schoolId);
        if (!Directory.Exists(directory))
        {
            return (false, false, false);
        }

        return (
            HasPortrait(schoolId, personId, PortraitKind.Avatar),
            HasPortrait(schoolId, personId, PortraitKind.Custom),
            HasPortrait(schoolId, personId, PortraitKind.Full));
    }

    public string CustomPortraitPromptPath(int schoolId, string personId)
    {
        var safeId = SanitizePersonId(personId);
        return Path.Combine(PortraitsDirectory(schoolId), $"{safeId}.custom.prompt.txt");
    }

    public string? TryReadCustomPortraitPrompt(int schoolId, string personId)
    {
        var path = CustomPortraitPromptPath(schoolId, personId);
        return File.Exists(path) ? File.ReadAllText(path) : null;
    }

    public string PortraitPath(int schoolId, string personId, PortraitKind kind)
    {
        var safeId = SanitizePersonId(personId);
        var suffix = PortraitKindParser.ToApiValue(kind);
        return Path.Combine(PortraitsDirectory(schoolId), $"{safeId}.{suffix}.png");
    }

    public void SavePortrait(int schoolId, string personId, PortraitKind kind, ReadOnlySpan<byte> png, string? customPrompt = null)
    {
        var path = PortraitPath(schoolId, personId, kind);
        Directory.CreateDirectory(Path.GetDirectoryName(path)!);
        var temp = path + ".tmp";
        File.WriteAllBytes(temp, png);
        File.Move(temp, path, overwrite: true);

        if (kind == PortraitKind.Custom && customPrompt is not null)
        {
            var promptPath = CustomPortraitPromptPath(schoolId, personId);
            var promptTemp = promptPath + ".tmp";
            File.WriteAllText(promptTemp, customPrompt);
            File.Move(promptTemp, promptPath, overwrite: true);
        }
    }

    private static string SanitizePersonId(string personId)
    {
        foreach (var ch in personId)
        {
            if (ch is not (>= 'a' and <= 'z' or >= 'A' and <= 'Z' or >= '0' and <= '9' or '.' or '-' or '_'))
            {
                throw new ArgumentException("The person id contains invalid characters.", nameof(personId));
            }
        }

        return personId;
    }

    public RosterDocument? TryReadPeople(int id)
    {
        var path = PeoplePath(id);
        if (!File.Exists(path))
        {
            return null;
        }

        try
        {
            return RosterJson.Parse(File.ReadAllText(path));
        }
        catch (Exception ex)
        {
            throw new SchoolContentUnavailableException(
                $"School {id} people file could not be read.",
                ex);
        }
    }

    public void SavePeople(int id, RosterDocument document)
    {
        WriteAtomic(PeoplePath(id), document, RosterJson.Options);
    }

    public Timetable? TryReadTimetable(int id)
    {
        var path = TimetablePath(id);
        if (!File.Exists(path))
        {
            return null;
        }

        try
        {
            var json = File.ReadAllText(path);
            return JsonSerializer.Deserialize<Timetable>(json, Json);
        }
        catch (Exception ex)
        {
            throw new SchoolContentUnavailableException(
                $"School {id} timetable file could not be read.",
                ex);
        }
    }

    public void SaveTimetable(int id, Timetable table)
    {
        WriteAtomic(TimetablePath(id), table);
    }

    private string SchoolPath(int id) => Path.Combine(DirectoryPath, $"{id}.json");

    private string PeoplePath(int id) => Path.Combine(DirectoryPath, $"{id}.people.json");

    private string TimetablePath(int id) => Path.Combine(DirectoryPath, $"{id}.timetable.json");

    private string PortraitsDirectory(int id) => Path.Combine(DirectoryPath, $"{id}.portraits");

    private string IndexPath() => Path.Combine(DirectoryPath, IndexFileName);

    private static void WriteAtomic<T>(string path, T value, JsonSerializerOptions? options = null)
    {
        var json = JsonSerializer.Serialize(value, options ?? Json);
        var temp = path + ".tmp";
        File.WriteAllText(temp, json);
        File.Move(temp, path, overwrite: true);
    }
}