using System.Security.Cryptography;
using System.Text;
using System.Text.RegularExpressions;

namespace Lskj.AgentPet.Host.Core.Configuration;

public sealed class HostConfiguration
{
    private static readonly Regex SessionId = new(
        "^[A-Za-z0-9_.:-]{8,128}$",
        RegexOptions.Compiled | RegexOptions.CultureInvariant);
    private static readonly Regex ProcessBoundSessionId = new(
        "^lserp-pet-p(?<pid>[1-9][0-9]{0,9})-s(?<started>[0-9]{9,12})-c(?<scope>[a-f0-9]{32})-[A-Fa-f0-9]{32}$",
        RegexOptions.Compiled | RegexOptions.CultureInvariant);

    private HostConfiguration()
    {
    }

    public required Uri AstrBotBaseUri { get; init; }
    public required string AstrBotApiKey { get; init; }
    public required string AstrBotSessionId { get; init; }
    public required string BridgeClientSessionId { get; init; }
    public int? BridgeProcessId { get; init; }
    public long? BridgeProcessStartedAtUnixSeconds { get; init; }
    public required ErpSessionScopeBinding ExpectedSessionScope { get; init; }
    public required string SpritePath { get; init; }
    public required string BridgeDiscoveryDirectory { get; init; }
    public TimeSpan BridgeTimeout { get; init; } = TimeSpan.FromMinutes(3);
    public TimeSpan ChatTimeout { get; init; } = TimeSpan.FromMinutes(5);
    public TimeSpan AttachmentUploadTimeout { get; init; } = TimeSpan.FromMinutes(2);
    public int MaximumAttachmentCount { get; init; } = 3;
    public long MaximumAttachmentFileBytes { get; init; } = 12 * 1024 * 1024;
    public long MaximumAttachmentTotalBytes { get; init; } = 36 * 1024 * 1024;

    public static HostConfiguration Load(
        IReadOnlyDictionary<string, string?> environment,
        string applicationDirectory)
    {
        ArgumentNullException.ThrowIfNull(environment);
        if (string.IsNullOrWhiteSpace(applicationDirectory))
            throw new HostError("application_directory_missing", "桌宠程序目录无效。");

        string baseUrl = Value(environment, "LSERP_ASTRBOT_BASE_URL")
            ?? "http://127.0.0.1:6185";
        if (!Uri.TryCreate(baseUrl, UriKind.Absolute, out Uri? baseUri)
            || (baseUri.Scheme != Uri.UriSchemeHttps && baseUri.Scheme != Uri.UriSchemeHttp))
        {
            throw new HostError("astrbot_url_invalid", "AstrBot 地址必须是有效的 HTTP/HTTPS 地址。");
        }
        if (!baseUri.IsLoopback)
        {
            throw new HostError(
                "astrbot_loopback_required",
                "当前桌宠只支持与 ERP 同机、同一 Windows 用户边界内的 AstrBot；远程模式必须使用尚未启用的 Agent Gateway。");
        }
        if (!string.IsNullOrEmpty(baseUri.UserInfo)
            || !string.IsNullOrEmpty(baseUri.Query)
            || !string.IsNullOrEmpty(baseUri.Fragment))
        {
            throw new HostError(
                "astrbot_url_invalid",
                "AstrBot 地址不得包含用户信息、查询参数或片段。");
        }

        string apiKey = Value(environment, "LSERP_ASTRBOT_API_KEY") ?? string.Empty;
        if (apiKey.Length < 16 || apiKey.Length > 512)
            throw new HostError("astrbot_api_key_missing", "未配置有效的 AstrBot chat + file scope API Key。");

        string? configuredSessionId = Value(
            environment,
            "LSERP_ASTRBOT_SESSION_ID");
        if (configuredSessionId is null)
        {
            throw new HostError(
                "astrbot_session_process_binding_required",
                "必须由商用启动器传入绑定 ERP PID 和启动时间的 AstrBot 会话。");
        }
        string sessionId = configuredSessionId;
        if (!SessionId.IsMatch(sessionId))
            throw new HostError("astrbot_session_invalid", "AstrBot 会话 ID 格式无效。");
        if (!ProcessBoundSessionId.IsMatch(sessionId))
        {
            throw new HostError(
                "astrbot_session_process_binding_required",
                "AstrBot 会话必须精确绑定 ERP PID、进程启动时间和随机会话值。");
        }
        int? sessionProcessId = ProcessIdFromSession(sessionId);
        int? configuredProcessId = OptionalProcessId(environment, "LSERP_AGENT_BRIDGE_PROCESS_ID");
        if (!configuredProcessId.HasValue)
        {
            throw new HostError(
                "bridge_process_id_required",
                "必须由商用启动器显式传入目标 ERP 进程 ID。");
        }
        if (!sessionProcessId.HasValue
            || sessionProcessId.Value != configuredProcessId.Value)
        {
            throw new HostError(
                "bridge_process_id_mismatch",
                "AstrBot 会话绑定的 ERP 进程与显式配置不一致。");
        }
        ErpSessionScopeBinding expectedScope = ErpSessionScopeBinding.Create(
            RequiredValue(environment, "LSERP_AGENT_EXPECTED_DATABASE_SCOPE_FINGERPRINT"),
            RequiredValue(environment, "LSERP_AGENT_EXPECTED_USER_ID"),
            RequiredValue(environment, "LSERP_AGENT_EXPECTED_USER_NAME"),
            RequiredValue(environment, "LSERP_AGENT_EXPECTED_ACCOUNT_BOOK"),
            RequiredValue(environment, "LSERP_AGENT_EXPECTED_SUBSYSTEM_ID"),
            RequiredBoolean(
                environment,
                "LSERP_AGENT_EXPECTED_IS_ADMINISTRATOR"));
        string configuredScopeToken = ErpSessionScopeBinding.ValidateToken(
            RequiredValue(environment, "LSERP_AGENT_EXPECTED_SESSION_SCOPE_TOKEN"));
        string? sessionScopeToken = SessionScopeTokenFromSession(sessionId);
        if (sessionScopeToken is null
            || !ErpSessionScopeBinding.TokenEquals(expectedScope.Token, configuredScopeToken)
            || !ErpSessionScopeBinding.TokenEquals(expectedScope.Token, sessionScopeToken))
        {
            throw new HostError(
                "bridge_session_scope_token_mismatch",
                "AstrBot 会话绑定的 ERP 用户身份、账套、子系统或数据库与显式配置不一致。");
        }

        string sprite = FullPath(
            Value(environment, "LSERP_PET_SPRITE_PATH")
                ?? Path.Combine(
                    Environment.GetFolderPath(Environment.SpecialFolder.UserProfile),
                    ".codex", "pets", "guga", "spritesheet.webp"),
            "pet_sprite_path_invalid");
        string discovery = FullPath(
            Value(environment, "LSERP_AGENT_BRIDGE_DISCOVERY")
                ?? Path.Combine(
                    Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData),
                    "Langsu", "Lserp", "AgentBridge"),
            "bridge_discovery_path_invalid");

        int maximumCount = Integer(environment, "LSERP_ATTACHMENT_MAX_COUNT", 3, 1, 3);
        int maximumFileMb = Integer(environment, "LSERP_ATTACHMENT_MAX_FILE_MB", 12, 1, 12);
        int maximumTotalMb = Integer(
            environment,
            "LSERP_ATTACHMENT_MAX_TOTAL_MB",
            maximumCount * maximumFileMb,
            maximumFileMb,
            maximumCount * maximumFileMb);
        return new HostConfiguration
        {
            AstrBotBaseUri = EnsureTrailingSlash(baseUri),
            AstrBotApiKey = apiKey,
            AstrBotSessionId = sessionId,
            BridgeClientSessionId = CreateBridgeClientSessionId(sessionId),
            BridgeProcessId = configuredProcessId,
            BridgeProcessStartedAtUnixSeconds = ProcessStartedAtFromSession(sessionId),
            ExpectedSessionScope = expectedScope,
            SpritePath = sprite,
            BridgeDiscoveryDirectory = discovery,
            BridgeTimeout = Milliseconds(environment, "LSERP_AGENT_BRIDGE_TIMEOUT_MS", 180_000, 1_000, 300_000),
            ChatTimeout = Milliseconds(environment, "LSERP_ASTRBOT_TIMEOUT_MS", 300_000, 5_000, 600_000),
            AttachmentUploadTimeout = Milliseconds(environment, "LSERP_ATTACHMENT_UPLOAD_TIMEOUT_MS", 120_000, 5_000, 300_000),
            MaximumAttachmentCount = maximumCount,
            MaximumAttachmentFileBytes = maximumFileMb * 1024L * 1024L,
            MaximumAttachmentTotalBytes = maximumTotalMb * 1024L * 1024L
        };
    }

    public static string CreateBridgeClientSessionId(string astrBotSessionId)
    {
        if (string.IsNullOrWhiteSpace(astrBotSessionId)
            || !SessionId.IsMatch(astrBotSessionId))
        {
            throw new HostError("astrbot_session_invalid", "AstrBot 会话 ID 格式无效。");
        }
        byte[] digest = SHA256.HashData(Encoding.UTF8.GetBytes(astrBotSessionId));
        return "astrbot-" + Convert.ToHexString(digest).ToLowerInvariant()[..32];
    }

    public static int? ProcessIdFromSession(string astrBotSessionId)
    {
        if (string.IsNullOrWhiteSpace(astrBotSessionId)
            || !SessionId.IsMatch(astrBotSessionId))
        {
            throw new HostError("astrbot_session_invalid", "AstrBot 会话 ID 格式无效。");
        }
        Match match = ProcessBoundSessionId.Match(astrBotSessionId);
        if (!match.Success) return null;
        if (!int.TryParse(match.Groups["pid"].Value, out int processId)
            || processId <= 0)
        {
            throw new HostError("bridge_process_id_invalid", "ERP 进程 ID 格式无效。");
        }
        return processId;
    }

    public static long? ProcessStartedAtFromSession(string astrBotSessionId)
    {
        if (string.IsNullOrWhiteSpace(astrBotSessionId)
            || !SessionId.IsMatch(astrBotSessionId))
        {
            throw new HostError("astrbot_session_invalid", "AstrBot 会话 ID 格式无效。");
        }
        Match match = ProcessBoundSessionId.Match(astrBotSessionId);
        if (!match.Success || !match.Groups["started"].Success) return null;
        if (!long.TryParse(match.Groups["started"].Value, out long startedAt)
            || startedAt <= 0
            || startedAt > 253402300799L)
        {
            throw new HostError("bridge_process_start_invalid", "ERP 进程启动时间指纹无效。");
        }
        return startedAt;
    }

    public static string? SessionScopeTokenFromSession(string astrBotSessionId)
    {
        if (string.IsNullOrWhiteSpace(astrBotSessionId)
            || !SessionId.IsMatch(astrBotSessionId))
        {
            throw new HostError("astrbot_session_invalid", "AstrBot 会话 ID 格式无效。");
        }
        Match match = ProcessBoundSessionId.Match(astrBotSessionId);
        if (!match.Success || !match.Groups["scope"].Success) return null;
        return ErpSessionScopeBinding.ValidateToken(match.Groups["scope"].Value);
    }

    public byte[] ValidateFiles()
    {
        return WebpAtlasValidator.ReadValidatedBytes(SpritePath);
    }

    private static string? Value(IReadOnlyDictionary<string, string?> values, string name)
    {
        return values.TryGetValue(name, out string? value) && !string.IsNullOrWhiteSpace(value)
            ? value.Trim()
            : null;
    }

    private static string RequiredValue(
        IReadOnlyDictionary<string, string?> values,
        string name)
    {
        return Value(values, name) ?? throw new HostError(
            "expected_erp_session_scope_required",
            "商用启动器必须传入完整的预期 ERP 会话作用域。");
    }

    private static bool RequiredBoolean(
        IReadOnlyDictionary<string, string?> values,
        string name)
    {
        string value = RequiredValue(values, name);
        if (string.Equals(value, "true", StringComparison.OrdinalIgnoreCase))
            return true;
        if (string.Equals(value, "false", StringComparison.OrdinalIgnoreCase))
            return false;
        throw new HostError(
            "expected_erp_session_scope_invalid",
            "预期 ERP 管理员状态必须是 true 或 false。");
    }

    private static string FullPath(string value, string errorCode)
    {
        try
        {
            return Path.GetFullPath(value);
        }
        catch (Exception error) when (error is ArgumentException or NotSupportedException or PathTooLongException)
        {
            throw new HostError(errorCode, "桌宠路径配置无效。", error);
        }
    }

    private static TimeSpan Milliseconds(
        IReadOnlyDictionary<string, string?> values,
        string name,
        int defaultValue,
        int minimum,
        int maximum)
    {
        string? raw = Value(values, name);
        if (raw is null) return TimeSpan.FromMilliseconds(defaultValue);
        if (!int.TryParse(raw, out int value) || value < minimum || value > maximum)
            throw new HostError("timeout_invalid", name + " 超出允许范围。");
        return TimeSpan.FromMilliseconds(value);
    }

    private static int Integer(
        IReadOnlyDictionary<string, string?> values,
        string name,
        int defaultValue,
        int minimum,
        int maximum)
    {
        string? raw = Value(values, name);
        if (raw is null) return defaultValue;
        if (!int.TryParse(raw, out int value) || value < minimum || value > maximum)
            throw new HostError("attachment_limit_invalid", name + " 超出允许范围。");
        return value;
    }

    private static int? OptionalProcessId(
        IReadOnlyDictionary<string, string?> values,
        string name)
    {
        string? raw = Value(values, name);
        if (raw is null) return null;
        if (!int.TryParse(raw, out int value) || value <= 0)
            throw new HostError("bridge_process_id_invalid", name + " 必须是有效的 ERP 进程 ID。");
        return value;
    }

    private static Uri EnsureTrailingSlash(Uri value)
    {
        string text = value.AbsoluteUri.EndsWith("/", StringComparison.Ordinal)
            ? value.AbsoluteUri
            : value.AbsoluteUri + "/";
        return new Uri(text, UriKind.Absolute);
    }
}