using Microsoft.AspNetCore.Authorization;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Azure.Functions.Worker;
using Microsoft.Extensions.Logging;
using Registration.Data;
using System.Security.Claims;
using System.Text.Json;

namespace Registration.Functions;

/// <summary>
/// Registration HTTP endpoints.
///
/// ENDPOINTS:
///   POST /api/registration/register             — Public; requires Bearer token (CIAM JWT).
///                                                 entraSubjectId is extracted from the validated
///                                                 token — the client never supplies it.
///
///   GET  /api/registration/pending              — Admin; requires Function key.
///   GET  /api/registration/item/{id}            — Admin; requires Function key.
///   POST /api/registration/action/{id}/reject   — Admin; requires Function key.
///   POST /api/registration/action/{id}/complete — Admin; requires Function key.
///   GET  /api/health                            — Anonymous.
/// </summary>
public class RegistrationFunctions
{
    private readonly IRegistrationDataService _data;
    private readonly ILogger<RegistrationFunctions> _log;

    private static readonly JsonSerializerOptions JsonOpts = new()
    {
        PropertyNamingPolicy = JsonNamingPolicy.CamelCase,
        PropertyNameCaseInsensitive = true,
        DefaultIgnoreCondition = System.Text.Json.Serialization.JsonIgnoreCondition.WhenWritingNull
    };

    public RegistrationFunctions(IRegistrationDataService data, ILogger<RegistrationFunctions> log)
    {
        _data = data;
        _log = log;
    }

    // ── Helpers ──────────────────────────────────────────────────────────

    /// <summary>
    /// Extract the Entra Object ID from a validated CIAM JWT.
    /// The OID claim is stable across sessions and providers (Google, Apple, Microsoft).
    /// </summary>
    private static string? GetEntraSubjectId(ClaimsPrincipal user) =>
        user.FindFirst("oid")?.Value
        ?? user.FindFirst("http://schemas.microsoft.com/identity/claims/objectidentifier")?.Value
        ?? user.FindFirst("sub")?.Value;

    // ── Public: Register ─────────────────────────────────────────────────

    /// <summary>
    /// Register a new prospect.
    ///
    /// AuthorizationLevel.Anonymous at the trigger allows any caller with a valid
    /// Bearer token — no Function key required from the browser.
    /// The [Authorize] attribute ensures the JWT is present and valid before
    /// the function body runs. entraSubjectId is extracted from token claims only.
    /// </summary>
    [Function("Register")]
    [Authorize]
    public async Task<IActionResult> Register(
        [HttpTrigger(AuthorizationLevel.Anonymous, "post", Route = "registration/register")] HttpRequest req,
        CancellationToken ct)
    {
        // Identity comes from the validated JWT — never from the request body
        var entraSubjectId = GetEntraSubjectId(req.HttpContext.User);

        if (string.IsNullOrEmpty(entraSubjectId))
        {
            _log.LogWarning("[Registration] Register called without a valid token OID claim");
            return new UnauthorizedObjectResult(new { ok = false, error = "Valid authentication required" });
        }

        RegisterRequest? request;
        try
        {
            request = await JsonSerializer.DeserializeAsync<RegisterRequest>(req.Body, JsonOpts, ct);
        }
        catch
        {
            return new BadRequestObjectResult(new { ok = false, error = "Invalid JSON body" });
        }

        if (request == null || string.IsNullOrWhiteSpace(request.BusinessName))
            return new BadRequestObjectResult(new { ok = false, error = "businessName is required" });

        // Stamp the server-validated identity — client-supplied value is ignored
        request.EntraSubjectId = entraSubjectId;

        _log.LogInformation("[Registration] POST register: {Name} by entra={EntraId}",
            request.BusinessName, entraSubjectId);

        var result = await _data.RegisterAsync(request, ct);

        if (!result.Ok)
            return new BadRequestObjectResult(result);

        return new OkObjectResult(result);
    }

    // ── Admin: List pending ───────────────────────────────────────────────

    /// <summary>List all pending registrations. Called by Management API with Function key.</summary>
    [Function("GetPending")]
    public async Task<IActionResult> GetPending(
        [HttpTrigger(AuthorizationLevel.Anonymous, "get", Route = "registration/pending")] HttpRequest req,
        CancellationToken ct)
    {
        _log.LogInformation("[Registration] GET pending");
        var result = await _data.GetPendingAsync(ct);
        return new OkObjectResult(result);
    }

    // ── Admin: Get by ID ─────────────────────────────────────────────────

    /// <summary>Get a single applicant by registration ID. Called by Management API.</summary>
    [Function("GetById")]
    public async Task<IActionResult> GetById(
        [HttpTrigger(AuthorizationLevel.Anonymous, "get", Route = "registration/item/{registrationId}")] HttpRequest req,
        string registrationId,
        CancellationToken ct)
    {
        _log.LogInformation("[Registration] GET {Id}", registrationId);

        var applicant = await _data.GetByIdAsync(registrationId, ct);
        if (applicant == null)
            return new NotFoundObjectResult(new { ok = false, error = "Registration not found" });

        return new OkObjectResult(new { ok = true, applicant });
    }

    // ── Admin: Reject ────────────────────────────────────────────────────

    /// <summary>Reject a pending applicant. Called by Management after admin clicks Reject.</summary>
    [Function("Reject")]
    public async Task<IActionResult> Reject(
        [HttpTrigger(AuthorizationLevel.Anonymous, "post", Route = "registration/action/{registrationId}/reject")] HttpRequest req,
        string registrationId,
        CancellationToken ct)
    {
        RejectBody? body = null;
        try { body = await JsonSerializer.DeserializeAsync<RejectBody>(req.Body, JsonOpts, ct); }
        catch { /* optional body */ }

        _log.LogInformation("[Registration] POST reject: {Id} reason={Reason}",
            registrationId, body?.Reason);

        var result = await _data.RejectAsync(registrationId, body?.Reason, body?.RejectedBy, ct);

        if (!result.Ok)
            return new BadRequestObjectResult(result);

        return new OkObjectResult(result);
    }

    // ── Admin: Complete (approved) ────────────────────────────────────────

    /// <summary>
    /// Mark a registration as approved/completed.
    /// Called by Management after spClientManagement.create succeeds.
    /// Receives the platformClientId to link the registration to the platform record.
    /// </summary>
    [Function("Complete")]
    public async Task<IActionResult> Complete(
        [HttpTrigger(AuthorizationLevel.Anonymous, "post", Route = "registration/action/{registrationId}/complete")] HttpRequest req,
        string registrationId,
        CancellationToken ct)
    {
        CompleteBody? body = null;
        try { body = await JsonSerializer.DeserializeAsync<CompleteBody>(req.Body, JsonOpts, ct); }
        catch { /* optional body */ }

        _log.LogInformation("[Registration] POST complete: {Id} → platform client {PlatformId}",
            registrationId, body?.PlatformClientId);

        var result = await _data.CompleteAsync(registrationId, body?.PlatformClientId, ct);

        if (!result.Ok)
            return new BadRequestObjectResult(result);

        return new OkObjectResult(result);
    }

    // ── Health ───────────────────────────────────────────────────────────

    /// <summary>Health check — anonymous, no auth required.</summary>
    [Function("Health")]
    public IActionResult Health(
        [HttpTrigger(AuthorizationLevel.Anonymous, "get", Route = "health")] HttpRequest req)
    {
        return new OkObjectResult(new
        {
            ok = true,
            service = "registration",
            mode = _data is Registration.Mock.MockDataService ? "mock" : "database",
            timestamp = DateTime.UtcNow
        });
    }
}

// ── Request / Response Bodies ─────────────────────────────────────────────

internal sealed class RejectBody
{
    public string? Reason { get; set; }
    public string? RejectedBy { get; set; }
}

internal sealed class CompleteBody
{
    public string? PlatformClientId { get; set; }
}