using System.Text.Json;
using System.Text.Json.Serialization;
using AcDream.Launcher.Core.Profiles;
using AcDream.Platform;

namespace AcDream.Launcher.Core.Launching;

/// <summary>The composed session-config document plus the per-launch
/// paths derived from the session id, per Campaign LA spec §6.
/// <see cref="StderrLogPath"/> is launcher-internal (fix #406 sibling
/// gap) — it never appears in the written <c>session.json</c>, only in
/// the <see cref="Launching.LauncherProcessSpec"/> the launcher spawns the
/// child with.</summary>
public sealed record ComposedSessionConfig(
    string SessionId,
    string ConfigFilePath,
    string StatusFilePath,
    string StderrLogPath,
    SessionConfigDocument Document);

/// <summary>
/// Injectable composition/write seam used by the canonical launcher
/// orchestrator. Production delegates to <see cref="SessionConfigComposer"/>;
/// tests can capture the exact request without writing a file or starting a
/// client process.
/// </summary>
public interface ILauncherSessionConfigService
{
    ComposedSessionConfig ComposeAndWrite(
        ServerProfile server,
        AccountProfile account,
        CharacterProfile character,
        LauncherInstallRecord install,
        ApplicationPathSet paths,
        string sessionId,
        int? loginCommandDelayMs = null);

    ComposedSessionConfig ComposeProbeAndWrite(
        ServerProfile server,
        AccountProfile account,
        LauncherInstallRecord install,
        ApplicationPathSet paths,
        string sessionId);
}

public sealed class LauncherSessionConfigService : ILauncherSessionConfigService
{
    public ComposedSessionConfig ComposeAndWrite(
        ServerProfile server,
        AccountProfile account,
        CharacterProfile character,
        LauncherInstallRecord install,
        ApplicationPathSet paths,
        string sessionId,
        int? loginCommandDelayMs = null) =>
        SessionConfigComposer.ComposeAndWrite(
            server,
            account,
            character,
            install,
            paths,
            sessionId,
            loginCommandDelayMs);

    public ComposedSessionConfig ComposeProbeAndWrite(
        ServerProfile server,
        AccountProfile account,
        LauncherInstallRecord install,
        ApplicationPathSet paths,
        string sessionId) =>
        SessionConfigComposer.ComposeProbeAndWrite(
            server,
            account,
            install,
            paths,
            sessionId);
}

/// <summary>
/// Builds the per-launch <see cref="SessionConfigDocument"/> from a
/// profile character + install record (Campaign LA spec §6). Passwords
/// NEVER appear in the composed document — the credential is always the
/// <c>standardInput</c> provider; the launcher feeds the password to the
/// child process's stdin separately (<see cref="LauncherProcessSupervisor"/>).
/// </summary>
public static class SessionConfigComposer
{
    internal static readonly JsonSerializerOptions SerializerOptions = new()
    {
        PropertyNamingPolicy = JsonNamingPolicy.CamelCase,
        DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingNull,
        WriteIndented = true,
    };

    /// <summary>
    /// Builds the document and the paths it would be written to under
    /// <c>&lt;CacheDirectory&gt;/launcher/sessions/&lt;sessionId&gt;/</c>,
    /// without touching disk. <paramref name="sessionId"/> is caller-
    /// supplied so composition stays a pure function of its inputs
    /// (golden-file tests pass a fixed id).
    /// </summary>
    public static ComposedSessionConfig Compose(
        ServerProfile server,
        AccountProfile account,
        CharacterProfile character,
        LauncherInstallRecord install,
        ApplicationPathSet paths,
        string sessionId,
        int? loginCommandDelayMs = null)
    {
        ArgumentNullException.ThrowIfNull(server);
        ArgumentNullException.ThrowIfNull(account);
        ArgumentNullException.ThrowIfNull(character);
        ArgumentNullException.ThrowIfNull(install);
        ArgumentNullException.ThrowIfNull(paths);
        ArgumentException.ThrowIfNullOrWhiteSpace(sessionId);

        (string configFilePath, string statusFilePath, string stderrLogPath) =
            BuildSessionPaths(paths, sessionId);

        SessionCharacterSelector? selector = character.LaunchMode == LaunchMode.GuiSelect
            ? null
            : BuildSelector(character);

        SessionPolicyDescriptor? policy = character.LaunchMode == LaunchMode.Headless
            ? new SessionPolicyDescriptor()
            : null;

        var descriptor = new SessionDescriptor
        {
            Id = sessionId,
            Endpoint = new SessionEndpointDescriptor
            {
                Host = server.Host,
                Port = server.Port,
            },
            Account = account.Account,
            Character = selector,
            Policy = policy,
            Credential = new SessionCredentialDescriptor(),
            Plugins = ComposePluginAllowList(character.Plugins),
            LoginCommands = character.LoginCommands.Count > 0
                ? [.. character.LoginCommands]
                : null,
            LoginCommandDelayMs = loginCommandDelayMs,
            StatusFile = statusFilePath,
        };

        var document = new SessionConfigDocument
        {
            Process = new SessionProcessSettings
            {
                Content = new SessionContentDescriptor
                {
                    DatDirectory = install.DatDirectory,
                    PreparedAssetPath = install.PreparedAssetPath,
                },
            },
            Sessions = [descriptor],
        };

        return new ComposedSessionConfig(
            sessionId,
            configFilePath,
            statusFilePath,
            stderrLogPath,
            document);
    }

    /// <summary>
    /// Builds a probe session-config document (Campaign LA plan §LA2/
    /// §LA3 review finding F2): the session carries <c>mode: "probe"</c>,
    /// no <c>character</c> selector, and no <c>policy</c> — the host
    /// reports the account's character roster over the status stream and
    /// exits without entering the world. Probes carry an explicit empty
    /// <c>plugins</c> allow-list so a plugin installed on the machine cannot
    /// run merely because the probe has no character-level plugin settings.
    /// </summary>
    public static ComposedSessionConfig ComposeProbe(
        ServerProfile server,
        AccountProfile account,
        LauncherInstallRecord install,
        ApplicationPathSet paths,
        string sessionId)
    {
        ArgumentNullException.ThrowIfNull(server);
        ArgumentNullException.ThrowIfNull(account);
        ArgumentNullException.ThrowIfNull(install);
        ArgumentNullException.ThrowIfNull(paths);
        ArgumentException.ThrowIfNullOrWhiteSpace(sessionId);

        (string configFilePath, string statusFilePath, string stderrLogPath) =
            BuildSessionPaths(paths, sessionId);

        var descriptor = new SessionDescriptor
        {
            Id = sessionId,
            Mode = "probe",
            Endpoint = new SessionEndpointDescriptor
            {
                Host = server.Host,
                Port = server.Port,
            },
            Account = account.Account,
            Character = null,
            Policy = null,
            Credential = new SessionCredentialDescriptor(),
            Plugins = [],
            LoginCommands = null,
            LoginCommandDelayMs = null,
            StatusFile = statusFilePath,
        };

        var document = new SessionConfigDocument
        {
            Process = new SessionProcessSettings
            {
                Content = new SessionContentDescriptor
                {
                    DatDirectory = install.DatDirectory,
                    PreparedAssetPath = install.PreparedAssetPath,
                },
            },
            Sessions = [descriptor],
        };

        return new ComposedSessionConfig(
            sessionId,
            configFilePath,
            statusFilePath,
            stderrLogPath,
            document);
    }

    /// <summary>Composes and writes <c>session.json</c> to
    /// <see cref="ComposedSessionConfig.ConfigFilePath"/>, creating the
    /// per-session directory. The status file itself is created by the
    /// launched host, not the launcher.</summary>
    public static ComposedSessionConfig ComposeAndWrite(
        ServerProfile server,
        AccountProfile account,
        CharacterProfile character,
        LauncherInstallRecord install,
        ApplicationPathSet paths,
        string sessionId,
        int? loginCommandDelayMs = null)
    {
        ComposedSessionConfig composed = Compose(
            server,
            account,
            character,
            install,
            paths,
            sessionId,
            loginCommandDelayMs);

        return Write(composed);
    }

    /// <summary>Probe counterpart to <see cref="ComposeAndWrite"/>. It
    /// writes the pinned <c>mode: "probe"</c> document and never includes
    /// a character selector, policy, plugin set, login commands, or password.
    /// </summary>
    public static ComposedSessionConfig ComposeProbeAndWrite(
        ServerProfile server,
        AccountProfile account,
        LauncherInstallRecord install,
        ApplicationPathSet paths,
        string sessionId) =>
        Write(ComposeProbe(server, account, install, paths, sessionId));

    /// <summary>
    /// Maps a character's configured plugin ids to the session config's
    /// allow-list.
    /// </summary>
    /// <remarks>
    /// <para>
    /// LA5 distinguishes an OMITTED allow-list (load every discovered plugin)
    /// from an explicit EMPTY one (load none). A brand-new character profile
    /// starts with an empty list, which meant a client that ships plugins
    /// loaded none of them until the user typed an id — "ships with the
    /// client" and "works out of the box" were different things, and the
    /// difference was invisible: nothing was logged, the panel simply never
    /// appeared.
    /// </para>
    /// <para>
    /// So "nothing configured" now maps to omitted — plugins are on by
    /// default, including ones installed later. The opt-out is kept, because
    /// losing it would be a real regression for anyone running a stripped
    /// session: the literal id <c>none</c> maps to the explicit empty list.
    /// </para>
    /// </remarks>
    private static List<string>? ComposePluginAllowList(IReadOnlyList<string> configured)
    {
        if (configured.Count == 0)
            return null;                                   // default: load all

        if (configured.Count == 1
            && string.Equals(configured[0], "none", StringComparison.OrdinalIgnoreCase))
        {
            return [];                                     // explicit: load none
        }

        return [.. configured];
    }

    private static ComposedSessionConfig Write(ComposedSessionConfig composed)
    {
        string? directory = Path.GetDirectoryName(composed.ConfigFilePath);
        if (!string.IsNullOrEmpty(directory))
        {
            Directory.CreateDirectory(directory);
        }

        using FileStream stream = File.Create(composed.ConfigFilePath);
        JsonSerializer.Serialize(stream, composed.Document, SerializerOptions);

        return composed;
    }

    /// <summary>Serializes the composed document exactly as
    /// <see cref="ComposeAndWrite"/> would write it — used by golden-file
    /// tests that assert on the JSON text without touching disk.</summary>
    public static string Serialize(SessionConfigDocument document) =>
        JsonSerializer.Serialize(document, SerializerOptions);

    private static (string ConfigFilePath, string StatusFilePath, string StderrLogPath)
        BuildSessionPaths(
            ApplicationPathSet paths,
            string sessionId)
    {
        string sessionDirectory = Path.Combine(
            paths.CacheDirectory,
            "launcher",
            "sessions",
            sessionId);

        return (
            Path.Combine(sessionDirectory, "session.json"),
            Path.Combine(sessionDirectory, "status.jsonl"),
            // fix #406 sibling gap: lives beside status.jsonl in the same
            // per-session directory.
            Path.Combine(sessionDirectory, "client.err.log"));
    }

    private static SessionCharacterSelector BuildSelector(CharacterProfile character)
    {
        // A parsed id of 0 is not a usable selector — both host loaders
        // (App/Headless) reject `id: 0` outright, so falling through to
        // the name selector here is the only shape that reaches a real
        // character (Campaign LA plan §LA3 review finding F10).
        if (CharacterIdFormat.TryParse(character.Id, out uint id) && id != 0)
        {
            return new SessionCharacterSelector { Id = id };
        }

        if (!string.IsNullOrWhiteSpace(character.Name))
        {
            return new SessionCharacterSelector { Name = character.Name };
        }

        throw new InvalidOperationException(
            "Character has neither a usable id nor a name to select by.");
    }
}