using System.Security.Claims;
using System.Text.Json;
using Microsoft.AspNetCore.Authentication;
using Microsoft.AspNetCore.Authentication.Cookies;
using Microsoft.AspNetCore.Authorization;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Routing;
using ZB.MOM.WW.OtOpcUa.Security.Jwt;
using ZB.MOM.WW.OtOpcUa.Security.Ldap;

namespace ZB.MOM.WW.OtOpcUa.Security.Endpoints;

public static class AuthEndpoints
{
    /// <summary>JSON body schema for API-side login callers (kept stable for tests).</summary>
    public sealed record LoginRequest(string Username, string Password);

    public sealed record TokenResponse(string Token);

    public static IEndpointRouteBuilder MapOtOpcUaAuth(this IEndpointRouteBuilder app)
    {
        // The login endpoint serves two callers with different ergonomics:
        //   - Browser form POST (application/x-www-form-urlencoded) → redirect dance
        //   - API JSON POST (application/json) → 204 / 401 / 503 status codes
        // DisableAntiforgery: the login form is the entry point — anonymous by definition,
        // no prior session, so XSRF doesn't apply. AllowAnonymous: override the
        // AddOtOpcUaAuth fallback policy that would otherwise 401 the request.
        app.MapPost("/auth/login", (Delegate)LoginAsync).AllowAnonymous().DisableAntiforgery();
        app.MapGet("/auth/ping", (Delegate)Ping).AllowAnonymous();
        app.MapPost("/auth/token", (Delegate)IssueToken).RequireAuthorization();
        app.MapPost("/auth/logout", (Delegate)LogoutAsync).RequireAuthorization();
        return app;
    }

    private static async Task<IResult> LoginAsync(
        HttpContext http,
        ILdapAuthService ldap,
        CancellationToken ct)
    {
        var isForm = http.Request.HasFormContentType;
        string username, password, returnUrl;

        if (isForm)
        {
            var form = await http.Request.ReadFormAsync(ct);
            username = form["username"].ToString();
            password = form["password"].ToString();
            returnUrl = form["returnUrl"].ToString();
        }
        else
        {
            var body = await JsonSerializer.DeserializeAsync<LoginRequest>(
                http.Request.Body,
                new JsonSerializerOptions(JsonSerializerDefaults.Web),
                ct);
            username = body?.Username ?? string.Empty;
            password = body?.Password ?? string.Empty;
            returnUrl = string.Empty;
        }

        LdapAuthResult result;
        try
        {
            result = await ldap.AuthenticateAsync(username, password, ct);
        }
        catch (Exception)
        {
            return Results.StatusCode(StatusCodes.Status503ServiceUnavailable);
        }

        if (!result.Success)
        {
            if (!isForm) return Results.Unauthorized();

            var qs = $"?error={Uri.EscapeDataString(result.Error ?? "Invalid credentials")}";
            if (!string.IsNullOrWhiteSpace(returnUrl))
                qs += $"&returnUrl={Uri.EscapeDataString(returnUrl)}";
            return Results.Redirect("/login" + qs);
        }

        var claims = new List<Claim>
        {
            new(ClaimTypes.NameIdentifier, result.Username ?? username),
            new(JwtTokenService.UsernameClaimType, result.Username ?? username),
            new(JwtTokenService.DisplayNameClaimType, result.DisplayName ?? username),
        };
        foreach (var role in result.Roles)
            claims.Add(new Claim(ClaimTypes.Role, role));

        var identity = new ClaimsIdentity(claims, CookieAuthenticationDefaults.AuthenticationScheme);
        var principal = new ClaimsPrincipal(identity);

        await http.SignInAsync(CookieAuthenticationDefaults.AuthenticationScheme, principal);

        if (!isForm) return Results.NoContent();
        return Results.Redirect(string.IsNullOrWhiteSpace(returnUrl) ? "/" : returnUrl);
    }

    private static IResult Ping(HttpContext http) =>
        http.User.Identity?.IsAuthenticated == true ? Results.Ok() : Results.Unauthorized();

    private static IResult IssueToken(HttpContext http, JwtTokenService jwt)
    {
        var user = http.User;
        var username = user.FindFirst(JwtTokenService.UsernameClaimType)?.Value
                       ?? user.Identity?.Name
                       ?? string.Empty;
        var displayName = user.FindFirst(JwtTokenService.DisplayNameClaimType)?.Value ?? username;
        var roles = user.FindAll(ClaimTypes.Role).Select(c => c.Value).ToArray();

        return Results.Ok(new TokenResponse(jwt.Issue(displayName, username, roles)));
    }

    private static async Task<IResult> LogoutAsync(HttpContext http)
    {
        await http.SignOutAsync(CookieAuthenticationDefaults.AuthenticationScheme);

        // Browser form POST → redirect to /login so the user lands somewhere visible.
        // API callers that prefer the status-only contract should hit the endpoint with
        // Accept: application/json and we'll hand them a 204 instead.
        var wantsJson = http.Request.Headers.Accept.Any(v =>
            v?.Contains("application/json", StringComparison.OrdinalIgnoreCase) == true);
        if (wantsJson) return Results.NoContent();
        return Results.Redirect("/login");
    }
}