using System.Text.Json;
using System.Text.Json.Serialization;
using AcDream.Platform;

namespace AcDream.Launcher.Core.Profiles;

/// <summary>
/// Load/save/CRUD owner for <c>launcher-profiles.json</c> (Campaign LA
/// spec §5) — the launcher's ONLY credential/profile store, and the
/// binding surface the Avalonia UI (slice LA4) mutates directly.
///
/// <para>
/// A store instance holds the current in-memory <see cref="Document"/>
/// after <see cref="Load"/>; every CRUD method mutates that document in
/// place so callers can chain <c>store.AddServer(...); store.Save();</c>
/// without re-threading a returned document through every call.
/// </para>
/// </summary>
public sealed class LauncherProfileStore
{
    internal const int CurrentVersion = 1;

    private static readonly JsonSerializerOptions SerializerOptions = new()
    {
        AllowTrailingCommas = false,
        PropertyNamingPolicy = JsonNamingPolicy.CamelCase,
        PropertyNameCaseInsensitive = false,
        ReadCommentHandling = JsonCommentHandling.Disallow,
        UnmappedMemberHandling = JsonUnmappedMemberHandling.Disallow,
        WriteIndented = true,
        Converters =
        {
            new JsonStringEnumConverter(
                JsonNamingPolicy.CamelCase,
                allowIntegerValues: false),
        },
    };

    public LauncherProfileStore(string filePath)
    {
        ArgumentException.ThrowIfNullOrWhiteSpace(filePath);
        FilePath = Path.GetFullPath(filePath);
        Document = new LauncherProfileDocument();
    }

    /// <summary>Resolve the store at the canonical location under
    /// <see cref="ApplicationPathSet.ConfigDirectory"/>
    /// (<c>%APPDATA%\acdream\launcher-profiles.json</c> /
    /// <c>~/.config/acdream/launcher-profiles.json</c>).</summary>
    public static LauncherProfileStore ForApplicationPaths(ApplicationPathSet paths)
    {
        ArgumentNullException.ThrowIfNull(paths);
        return new LauncherProfileStore(
            Path.Combine(paths.ConfigDirectory, "launcher-profiles.json"));
    }

    public string FilePath { get; }

    public LauncherProfileDocument Document { get; private set; }

    /// <summary>
    /// Loads <see cref="Document"/> from <see cref="FilePath"/>. A
    /// missing file is not an error — it resolves to a fresh empty
    /// document (version 1, no servers), matching a never-launched
    /// installation. Returns true when a file was actually read.
    /// </summary>
    public bool Load()
    {
        if (!File.Exists(FilePath))
        {
            Document = new LauncherProfileDocument();
            return false;
        }

        LauncherProfileDocument? document;
        using (FileStream stream = File.OpenRead(FilePath))
        {
            try
            {
                document = JsonSerializer.Deserialize<LauncherProfileDocument>(
                    stream,
                    SerializerOptions);
            }
            catch (JsonException ex)
            {
                throw new LauncherProfileException(
                    $"'{FilePath}' is not a valid launcher profile document.",
                    ex);
            }
        }

        if (document is null)
        {
            throw new LauncherProfileException($"'{FilePath}' is empty.");
        }

        if (document.Version != CurrentVersion)
        {
            throw new LauncherProfileException(
                $"Unsupported launcher-profiles version {document.Version}; "
                + $"expected {CurrentVersion}.");
        }

        Document = document;
        return true;
    }

    /// <summary>
    /// Persists <see cref="Document"/> to <see cref="FilePath"/> via a
    /// write-then-atomic-rename so a crash mid-write never leaves a
    /// truncated credentials file. On Linux, restricts the final file to
    /// owner read/write (0600) per Campaign LA's plaintext-credential
    /// decision (spec §5, decisions log).
    /// </summary>
    public void Save()
    {
        string? directory = Path.GetDirectoryName(FilePath);
        if (!string.IsNullOrEmpty(directory))
        {
            Directory.CreateDirectory(directory);
        }

        string tempPath = FilePath + ".tmp";
        using (FileStream stream = File.Create(tempPath))
        {
            JsonSerializer.Serialize(stream, Document, SerializerOptions);
        }

        File.Move(tempPath, FilePath, overwrite: true);

        if (OperatingSystem.IsLinux())
        {
            File.SetUnixFileMode(
                FilePath,
                UnixFileMode.UserRead | UnixFileMode.UserWrite);
        }
    }

    // --- Server CRUD -----------------------------------------------

    public ServerProfile AddServer(string name, string host, int port)
    {
        ArgumentException.ThrowIfNullOrWhiteSpace(name);
        ArgumentException.ThrowIfNullOrWhiteSpace(host);
        RequireValidPort(port);

        if (FindServer(name) is not null)
        {
            throw new LauncherProfileException(
                $"A server named '{name}' already exists.");
        }

        var server = new ServerProfile { Name = name, Host = host, Port = port };
        Document.Servers.Add(server);
        return server;
    }

    public void EditServer(
        string name,
        string? newName = null,
        string? newHost = null,
        int? newPort = null)
    {
        ServerProfile server = FindServerOrThrow(name);

        if (newName is not null)
        {
            ArgumentException.ThrowIfNullOrWhiteSpace(newName);
            if (!string.Equals(newName, server.Name, StringComparison.Ordinal)
                && FindServer(newName) is not null)
            {
                throw new LauncherProfileException(
                    $"A server named '{newName}' already exists.");
            }

            server.Name = newName;
        }

        if (newHost is not null)
        {
            ArgumentException.ThrowIfNullOrWhiteSpace(newHost);
            server.Host = newHost;
        }

        if (newPort is not null)
        {
            RequireValidPort(newPort.Value);
            server.Port = newPort.Value;
        }
    }

    public void RemoveServer(string name)
    {
        ServerProfile server = FindServerOrThrow(name);
        Document.Servers.Remove(server);
    }

    // --- Account CRUD ------------------------------------------------

    public AccountProfile AddAccount(string serverName, string account, string password)
    {
        ArgumentException.ThrowIfNullOrWhiteSpace(account);
        ArgumentNullException.ThrowIfNull(password);
        ServerProfile server = FindServerOrThrow(serverName);

        if (FindAccount(server, account) is not null)
        {
            throw new LauncherProfileException(
                $"Account '{account}' already exists on server '{serverName}'.");
        }

        var profile = new AccountProfile { Account = account, Password = password };
        server.Accounts.Add(profile);
        return profile;
    }

    public void EditAccount(
        string serverName,
        string account,
        string? newAccount = null,
        string? newPassword = null)
    {
        ServerProfile server = FindServerOrThrow(serverName);
        AccountProfile profile = FindAccountOrThrow(server, account);

        if (newAccount is not null)
        {
            ArgumentException.ThrowIfNullOrWhiteSpace(newAccount);
            if (!string.Equals(newAccount, profile.Account, StringComparison.Ordinal)
                && FindAccount(server, newAccount) is not null)
            {
                throw new LauncherProfileException(
                    $"Account '{newAccount}' already exists on server '{serverName}'.");
            }

            profile.Account = newAccount;
        }

        if (newPassword is not null)
        {
            profile.Password = newPassword;
        }
    }

    public void RemoveAccount(string serverName, string account)
    {
        ServerProfile server = FindServerOrThrow(serverName);
        AccountProfile profile = FindAccountOrThrow(server, account);
        server.Accounts.Remove(profile);
    }

    // --- Character settings (roster-driven add/remove; user-edited settings) ---

    /// <summary>
    /// Edits the user-owned settings of an existing character row. There
    /// is no manual add/remove for characters — the roster (
    /// <see cref="MergeRoster"/>) is the only source of new rows, per
    /// spec §5/§6.
    /// </summary>
    public void EditCharacter(
        string serverName,
        string account,
        string characterName,
        LaunchMode? launchMode = null,
        IReadOnlyList<string>? plugins = null,
        IReadOnlyList<string>? loginCommands = null)
    {
        ServerProfile server = FindServerOrThrow(serverName);
        AccountProfile profile = FindAccountOrThrow(server, account);
        CharacterProfile character = FindCharacterOrThrow(profile, characterName);

        if (launchMode is not null)
        {
            character.LaunchMode = launchMode.Value;
        }

        if (plugins is not null)
        {
            character.Plugins = [.. plugins];
        }

        if (loginCommands is not null)
        {
            character.LoginCommands = [.. loginCommands];
        }
    }

    /// <summary>
    /// Folds a reported character roster into an account's
    /// <see cref="AccountProfile.Characters"/> (Campaign LA spec §3/§5/
    /// §6): every roster entry either updates the name of an existing
    /// row (matched by <see cref="CharacterProfile.Id"/>) while
    /// PRESERVING that row's user settings (<see cref="LaunchMode"/>,
    /// <see cref="CharacterProfile.Plugins"/>,
    /// <see cref="CharacterProfile.LoginCommands"/>), or is inserted as a
    /// new row with default settings (<see cref="LaunchMode.GuiSelect"/>,
    /// no plugins, no login commands). Existing rows absent from the
    /// roster are RETAINED unchanged — they may simply be pending-delete
    /// (ACE keeps deleted characters queryable during the grace window)
    /// or the roster snapshot may be partial; this store never deletes a
    /// character row on the caller's behalf.
    /// </summary>
    public void MergeRoster(
        string serverName,
        string account,
        IReadOnlyList<CharacterRosterEntry> roster)
    {
        ArgumentNullException.ThrowIfNull(roster);
        ServerProfile server = FindServerOrThrow(serverName);
        AccountProfile profile = FindAccountOrThrow(server, account);

        foreach (CharacterRosterEntry entry in roster)
        {
            string idText = CharacterIdFormat.ToHexString(entry.Id);
            CharacterProfile? existing = profile.Characters.Find(
                character => string.Equals(
                    character.Id,
                    idText,
                    StringComparison.OrdinalIgnoreCase));

            // Defensive fallback for a hand-edited file where a character
            // row was added with a name but no id yet.
            existing ??= profile.Characters.Find(
                character => character.Id is null
                    && string.Equals(
                        character.Name,
                        entry.Name,
                        StringComparison.Ordinal));

            if (existing is not null)
            {
                existing.Id = idText;
                existing.Name = entry.Name;
                continue;
            }

            profile.Characters.Add(new CharacterProfile
            {
                Id = idText,
                Name = entry.Name,
                LaunchMode = LaunchMode.GuiSelect,
                Plugins = [],
                LoginCommands = [],
            });
        }
    }

    // --- Lookups -------------------------------------------------------

    private ServerProfile? FindServer(string name) =>
        Document.Servers.Find(
            server => string.Equals(server.Name, name, StringComparison.Ordinal));

    private ServerProfile FindServerOrThrow(string name)
    {
        ArgumentException.ThrowIfNullOrWhiteSpace(name);
        return FindServer(name)
            ?? throw new LauncherProfileException($"No server named '{name}'.");
    }

    private static AccountProfile? FindAccount(ServerProfile server, string account) =>
        server.Accounts.Find(
            candidate => string.Equals(candidate.Account, account, StringComparison.Ordinal));

    private static AccountProfile FindAccountOrThrow(ServerProfile server, string account)
    {
        ArgumentException.ThrowIfNullOrWhiteSpace(account);
        return FindAccount(server, account)
            ?? throw new LauncherProfileException(
                $"No account '{account}' on server '{server.Name}'.");
    }

    private static CharacterProfile FindCharacterOrThrow(
        AccountProfile profile,
        string characterName)
    {
        ArgumentException.ThrowIfNullOrWhiteSpace(characterName);
        return profile.Characters.Find(
                character => string.Equals(
                    character.Name,
                    characterName,
                    StringComparison.Ordinal))
            ?? throw new LauncherProfileException(
                $"No character '{characterName}' on account '{profile.Account}'.");
    }

    private static void RequireValidPort(int port)
    {
        if (port is < 1 or > 65535)
        {
            throw new LauncherProfileException(
                $"Port {port} is outside the valid 1-65535 range.");
        }
    }
}