using System.Text.Json;
using Microsoft.EntityFrameworkCore;
using Tiku.Application.Auth;
using Tiku.Application.Tenancy;
using Tiku.Domain.Identity;
using Tiku.Domain.Tenancy;
using Tiku.Infrastructure.Persistence;

namespace Tiku.Infrastructure.Auth;

public sealed class AuthService(
    TikuDbContext dbContext,
    IPasswordHasher passwordHasher,
    ISmsVerificationService smsVerificationService,
    ISessionService sessionService,
    IWechatOAuthClient wechatOAuthClient,
    ITenantExternalProviderConfigService providerConfigService) : IAuthService
{
    private const string PasswordProvider = "password";
    private const string SmsProvider = "sms";
    private const string WechatWebProvider = "wechat_web";
    private const string WechatMiniAppProvider = "wechat_miniapp";
    private static readonly string[] WechatWebProviderAliases = ["wechat_web", "wechat-web", "wechat"];
    private static readonly string[] WechatMiniAppProviderAliases = ["wechat-miniapp", "wechat_miniapp", "wechat-mini", "wechatMiniapp"];
    private static readonly string[] WechatIdentityProviders = ["wechat_web", "wechat-web", "wechat", "wechat-miniapp", "wechat_miniapp", "wechat-mini", "wechatMiniapp"];

    public async Task<AuthenticatedUser> LoginWithPasswordAsync(
        PasswordLoginRequest request,
        CancellationToken cancellationToken = default)
    {
        var phone = SmsCodeHashing.NormalizePhone(request.Phone);
        var user = await dbContext.Users
            .SingleOrDefaultAsync(entity => entity.Phone == phone, cancellationToken);
        var identity = user is null
            ? null
            : await dbContext.UserIdentities
                .SingleOrDefaultAsync(
                    entity =>
                        entity.UserId == user.Id &&
                        entity.Provider == PasswordProvider &&
                        entity.ProviderSubject == phone,
                    cancellationToken);

        if (user is null ||
            identity is null ||
            !TryGetPasswordHash(identity.SecretPayload, out var passwordHash) ||
            !passwordHasher.Verify(request.Password, passwordHash))
        {
            await AddLoginEventAsync(
                request.TenantId,
                user?.Id,
                PasswordProvider,
                phone,
                AuthLoginResult.Failed,
                "invalid_credentials",
                request.IpAddress,
                request.UserAgent,
                cancellationToken);
            throw new InvalidCredentialsException();
        }

        return await CompleteSuccessfulLoginAsync(
            request.TenantId,
            user,
            PasswordProvider,
            phone,
            request.IpAddress,
            request.UserAgent,
            cancellationToken);
    }

    public async Task<AuthenticatedUser> LoginWithSmsAsync(
        SmsLoginRequest request,
        CancellationToken cancellationToken = default)
    {
        var phone = SmsCodeHashing.NormalizePhone(request.Phone);
        var user = await dbContext.Users
            .SingleOrDefaultAsync(entity => entity.Phone == phone, cancellationToken);

        try
        {
            await smsVerificationService.VerifyCodeAsync(
                request.TenantId,
                phone,
                SmsPurpose.Login,
                request.Code,
                cancellationToken);
        }
        catch (InvalidCredentialsException exception)
        {
            await AddLoginEventAsync(
                request.TenantId,
                user?.Id,
                SmsProvider,
                phone,
                AuthLoginResult.Failed,
                exception.Code,
                request.IpAddress,
                request.UserAgent,
                cancellationToken);
            throw;
        }

        if (user is null)
        {
            await AddLoginEventAsync(
                request.TenantId,
                null,
                SmsProvider,
                phone,
                AuthLoginResult.Failed,
                "user_not_found",
                request.IpAddress,
                request.UserAgent,
                cancellationToken);
            throw new InvalidCredentialsException();
        }

        return await CompleteSuccessfulLoginAsync(
            request.TenantId,
            user,
            SmsProvider,
            phone,
            request.IpAddress,
            request.UserAgent,
            cancellationToken);
    }

    public Task<AuthenticatedUser> LoginWithWechatWebAsync(
        WechatLoginRequest request,
        CancellationToken cancellationToken = default)
    {
        return LoginWithWechatAsync(
            request,
            WechatWebProvider,
            WechatWebProviderAliases,
            (options, code, token) => wechatOAuthClient.ExchangeWebCodeAsync(options, code, token),
            cancellationToken);
    }

    public Task<AuthenticatedUser> LoginWithWechatMiniAppAsync(
        WechatLoginRequest request,
        CancellationToken cancellationToken = default)
    {
        return LoginWithWechatAsync(
            request,
            WechatMiniAppProvider,
            WechatMiniAppProviderAliases,
            (options, code, token) => wechatOAuthClient.ExchangeMiniAppCodeAsync(options, code, token),
            cancellationToken);
    }

    public async Task<AuthTokenPair> RefreshAsync(
        RefreshSessionRequest request,
        CancellationToken cancellationToken = default)
    {
        if (!sessionService.TryParseRefreshToken(request.RefreshToken, out var locator))
        {
            throw new SessionRevokedException();
        }

        var tokenHash = sessionService.HashRefreshToken(request.RefreshToken);
        var now = DateTimeOffset.UtcNow;
        var session = await dbContext.AuthSessions
            .SingleOrDefaultAsync(entity =>
                entity.Id == locator.SessionId &&
                entity.TenantId == locator.TenantId &&
                entity.TokenHash == tokenHash,
                cancellationToken);

        if (session is null || session.RevokedAt is not null || session.ExpiresAt <= now)
        {
            throw new SessionRevokedException();
        }

        var user = await dbContext.Users.FindAsync([session.UserId], cancellationToken)
            ?? throw new SessionRevokedException();
        var membership = await FindActiveMembershipAsync(session.TenantId, session.UserId, cancellationToken)
            ?? throw new TenantAccessDeniedException();

        session.RevokedAt = now;
        await AddLoginEventAsync(
            session.TenantId,
            session.UserId,
            "refresh",
            user.Phone ?? user.Email,
            AuthLoginResult.Success,
            null,
            request.IpAddress,
            request.UserAgent,
            cancellationToken);

        return await sessionService.IssueAsync(
            user.Id,
            user.Phone,
            user.Email,
            membership,
            "refresh",
            request.IpAddress,
            request.UserAgent,
            cancellationToken);
    }

    public async Task LogoutAsync(
        LogoutSessionRequest request,
        CancellationToken cancellationToken = default)
    {
        if (!sessionService.TryParseRefreshToken(request.RefreshToken, out var locator))
        {
            return;
        }

        var tokenHash = sessionService.HashRefreshToken(request.RefreshToken);
        var session = await dbContext.AuthSessions
            .SingleOrDefaultAsync(entity =>
                entity.Id == locator.SessionId &&
                entity.TenantId == locator.TenantId &&
                entity.TokenHash == tokenHash,
                cancellationToken);

        if (session is null || session.RevokedAt is not null)
        {
            return;
        }

        session.RevokedAt = DateTimeOffset.UtcNow;
        await AddLoginEventAsync(
            session.TenantId,
            session.UserId,
            "logout",
            null,
            AuthLoginResult.Success,
            null,
            null,
            null,
            cancellationToken);
    }

    private async Task<AuthenticatedUser> CompleteSuccessfulLoginAsync(
        Guid tenantId,
        User user,
        string provider,
        string identifier,
        string? ipAddress,
        string? userAgent,
        CancellationToken cancellationToken)
    {
        var membership = await FindActiveMembershipAsync(tenantId, user.Id, cancellationToken);
        if (membership is null)
        {
            await AddLoginEventAsync(
                tenantId,
                user.Id,
                provider,
                identifier,
                AuthLoginResult.Failed,
                "tenant_access_denied",
                ipAddress,
                userAgent,
                cancellationToken);
            throw new TenantAccessDeniedException();
        }

        var tenant = await dbContext.Tenants.FindAsync([tenantId], cancellationToken)
            ?? throw new TenantAccessDeniedException();
        var tokens = await sessionService.IssueAsync(
            user.Id,
            user.Phone,
            user.Email,
            membership,
            provider,
            ipAddress,
            userAgent,
            cancellationToken);

        await AddLoginEventAsync(
            tenantId,
            user.Id,
            provider,
            identifier,
            AuthLoginResult.Success,
            null,
            ipAddress,
            userAgent,
            cancellationToken);

        return new AuthenticatedUser(
            user.Id,
            user.Phone,
            user.Email,
            user.Name,
            new TenantMembershipSummary(
                tenant.Id,
                tenant.Name,
                membership.Role,
                membership.Status),
            tokens);
    }

    private async Task<AuthenticatedUser> LoginWithWechatAsync(
        WechatLoginRequest request,
        string provider,
        IReadOnlyList<string> providerAliases,
        Func<WechatProviderOptions, string, CancellationToken, Task<WechatIdentity>> exchangeCodeAsync,
        CancellationToken cancellationToken)
    {
        var config = await LoadWechatProviderOptionsAsync(
            request.TenantId,
            provider,
            providerAliases,
            cancellationToken);

        WechatIdentity identity;
        try
        {
            identity = await exchangeCodeAsync(config, request.Code, cancellationToken);
        }
        catch (AuthException exception)
        {
            await AddLoginEventAsync(
                request.TenantId,
                null,
                provider,
                null,
                AuthLoginResult.Failed,
                exception.Code,
                request.IpAddress,
                request.UserAgent,
                cancellationToken);
            throw;
        }

        var providerSubject = $"{config.AppId}:{identity.OpenId}";
        var user = await UpsertWechatUserAsync(
            provider,
            providerSubject,
            config.AppId,
            identity,
            cancellationToken);
        await EnsureTenantMembershipAsync(
            request.TenantId,
            user.Id,
            cancellationToken);

        return await CompleteSuccessfulLoginAsync(
            request.TenantId,
            user,
            provider,
            identity.OpenId,
            request.IpAddress,
            request.UserAgent,
            cancellationToken);
    }

    private async Task<WechatProviderOptions> LoadWechatProviderOptionsAsync(
        Guid tenantId,
        string provider,
        IReadOnlyList<string> aliases,
        CancellationToken cancellationToken)
    {
        TenantExternalProviderAccount? account = null;
        foreach (var alias in aliases)
        {
            try
            {
                account = await providerConfigService.GetActiveProviderAsync(
                    tenantId,
                    TenantExternalProviderCapability.Identity,
                    alias,
                    cancellationToken);
                break;
            }
            catch (TenantExternalProviderException)
            {
            }
        }

        if (account is null)
        {
            throw new AuthProviderNotConfiguredException(provider);
        }

        var appId = GetJsonString(account.ConfigPublic, "appId", "clientId");
        var appSecret = GetJsonString(account.SecretPayload, "appSecret", "clientSecret", "secret");
        if (string.IsNullOrWhiteSpace(appId) || string.IsNullOrWhiteSpace(appSecret))
        {
            throw new AuthProviderNotConfiguredException(provider);
        }

        return new WechatProviderOptions(appId, appSecret);
    }

    private async Task<User> UpsertWechatUserAsync(
        string provider,
        string providerSubject,
        string appId,
        WechatIdentity wechatIdentity,
        CancellationToken cancellationToken)
    {
        var existingIdentity = await dbContext.UserIdentities
            .SingleOrDefaultAsync(
                identity =>
                    identity.Provider == provider &&
                    identity.ProviderSubject == providerSubject,
                cancellationToken);
        var user = existingIdentity is null
            ? await FindUserByWechatUnionIdAsync(wechatIdentity.UnionId, cancellationToken)
            : await dbContext.Users.FindAsync([existingIdentity.UserId], cancellationToken);

        if (user is null)
        {
            user = new User
            {
                Name = wechatIdentity.Nickname,
                AvatarUrl = wechatIdentity.AvatarUrl,
                PrimaryRole = "student",
                RawProfile = CreateWechatRawProfile(wechatIdentity)
            };
            dbContext.Users.Add(user);
        }
        else
        {
            user.Name = string.IsNullOrWhiteSpace(user.Name) ? wechatIdentity.Nickname : user.Name;
            user.AvatarUrl = string.IsNullOrWhiteSpace(user.AvatarUrl) ? wechatIdentity.AvatarUrl : user.AvatarUrl;
        }

        if (existingIdentity is null)
        {
            existingIdentity = new UserIdentity
            {
                UserId = user.Id,
                Provider = provider,
                ProviderSubject = providerSubject
            };
            dbContext.UserIdentities.Add(existingIdentity);
        }

        existingIdentity.UserId = user.Id;
        existingIdentity.OpenId = wechatIdentity.OpenId;
        existingIdentity.UnionId = wechatIdentity.UnionId;
        existingIdentity.SecretPayload = CreateWechatSecretPayload(appId, wechatIdentity);
        await dbContext.SaveChangesAsync(cancellationToken);

        return user;
    }

    private async Task<User?> FindUserByWechatUnionIdAsync(
        string? unionId,
        CancellationToken cancellationToken)
    {
        if (string.IsNullOrWhiteSpace(unionId))
        {
            return null;
        }

        var identity = await dbContext.UserIdentities
            .Where(entity =>
                entity.UnionId == unionId &&
                WechatIdentityProviders.Contains(entity.Provider))
            .OrderBy(entity => entity.CreatedAt)
            .FirstOrDefaultAsync(cancellationToken);

        return identity is null
            ? null
            : await dbContext.Users.FindAsync([identity.UserId], cancellationToken);
    }

    private async Task EnsureTenantMembershipAsync(
        Guid tenantId,
        Guid userId,
        CancellationToken cancellationToken)
    {
        var activeMembershipExists = await dbContext.TenantMemberships.AnyAsync(
            membership =>
                membership.TenantId == tenantId &&
                membership.UserId == userId &&
                membership.Status == MembershipStatus.Active,
            cancellationToken);

        if (activeMembershipExists)
        {
            return;
        }

        var studentMembership = await dbContext.TenantMemberships
            .FirstOrDefaultAsync(
                membership =>
                    membership.TenantId == tenantId &&
                    membership.UserId == userId &&
                    membership.Role == TenantRole.Student,
                cancellationToken);
        if (studentMembership is null)
        {
            dbContext.TenantMemberships.Add(new TenantMembership
            {
                TenantId = tenantId,
                UserId = userId,
                Role = TenantRole.Student,
                Status = MembershipStatus.Active
            });
        }
        else
        {
            studentMembership.Status = MembershipStatus.Active;
        }

        await dbContext.SaveChangesAsync(cancellationToken);
    }

    private async Task<TenantMembership?> FindActiveMembershipAsync(
        Guid tenantId,
        Guid userId,
        CancellationToken cancellationToken)
    {
        return await dbContext.TenantMemberships
            .Where(entity =>
                entity.TenantId == tenantId &&
                entity.UserId == userId &&
                entity.Status == MembershipStatus.Active)
            .OrderBy(entity => entity.Role)
            .FirstOrDefaultAsync(cancellationToken);
    }

    private async Task AddLoginEventAsync(
        Guid tenantId,
        Guid? userId,
        string provider,
        string? identifier,
        AuthLoginResult result,
        string? failureCode,
        string? ipAddress,
        string? userAgent,
        CancellationToken cancellationToken)
    {
        dbContext.AuthLoginEvents.Add(new AuthLoginEvent
        {
            TenantId = tenantId,
            UserId = userId,
            Provider = provider,
            Identifier = identifier,
            Result = result,
            FailureCode = failureCode,
            IpAddress = ipAddress,
            UserAgent = userAgent
        });

        await dbContext.SaveChangesAsync(cancellationToken);
    }

    private static bool TryGetPasswordHash(JsonElement secretPayload, out string passwordHash)
    {
        passwordHash = string.Empty;
        return secretPayload.ValueKind == JsonValueKind.Object &&
               secretPayload.TryGetProperty("passwordHash", out var property) &&
               property.ValueKind == JsonValueKind.String &&
               !string.IsNullOrWhiteSpace(passwordHash = property.GetString() ?? string.Empty);
    }

    private static string? GetJsonString(JsonElement element, params string[] names)
    {
        if (element.ValueKind != JsonValueKind.Object)
        {
            return null;
        }

        foreach (var name in names)
        {
            if (element.TryGetProperty(name, out var property) &&
                property.ValueKind == JsonValueKind.String &&
                !string.IsNullOrWhiteSpace(property.GetString()))
            {
                return property.GetString()!.Trim();
            }
        }

        return null;
    }

    private static JsonElement CreateWechatRawProfile(WechatIdentity identity)
    {
        using var document = JsonDocument.Parse(identity.RawJson);
        return document.RootElement.Clone();
    }

    private static JsonElement CreateWechatSecretPayload(string appId, WechatIdentity identity)
    {
        var payload = new
        {
            appId,
            sessionKey = identity.SessionKey,
            raw = JsonSerializer.Deserialize<JsonElement>(identity.RawJson),
            updatedAt = DateTimeOffset.UtcNow
        };
        return JsonSerializer.SerializeToElement(payload);
    }
}