using Microsoft.AspNetCore.Mvc;
using Campus_live_rewrite.api.server;

namespace Campus_live_rewrite.Controllers
{
    // Patch handshake. CampusPatch (the DLL) POSTs here once at startup (main.cpp) with the
    // shared secret in the X-Campus-Patch header. The SERVER holds the real secret and compares:
    // a match answers 200, anything else answers 403. A DLL with the wrong/absent header is
    // denied here, and main.cpp aborts on a non-200 so that client never connects.
    //
    // The secret lives ONLY on the server (ConfigCampus.PatchSignature) - the DLL just echoes
    // what it was built with; the server is what decides.
    [ApiController]
    public class PatchController : ControllerBase
    {
        public const string HeaderName = "X-Campus-Patch";

        [HttpPost("/api/patch/verify")]
        [HttpGet("/api/patch/verify")]
        public IActionResult Verify()
        {
            string sent = Request.Headers[HeaderName].FirstOrDefault() ?? "";
            string expected = ConfigCampus.PatchSignature ?? "";

            string ip = Request.Headers["CF-Connecting-IP"].FirstOrDefault()
                        ?? Request.Headers["X-Forwarded-For"].FirstOrDefault()
                        ?? HttpContext.Connection.RemoteIpAddress?.ToString()
                        ?? "?";

            bool ok = !string.IsNullOrEmpty(expected) && FixedTimeEquals(sent, expected);

            if (!ok)
            {
                Console.WriteLine($"[patchverify] DENIED {ip} - signature {(string.IsNullOrEmpty(sent) ? "absent" : "mismatch")}");
                return StatusCode(StatusCodes.Status403Forbidden, new { ok = false });
            }

            // Just a friendly startup check for the DLL - real enforcement is the per-request
            // X-Campus-Patch header validated in PatchGateMiddleware. No whitelist is kept.
            Console.WriteLine($"[patchverify] OK {ip}");
            return Ok(new { ok = true });
        }

        // Constant-time compare so the secret can't be brute-forced a byte at a time by timing.
        private static bool FixedTimeEquals(string a, string b)
        {
            var ab = System.Text.Encoding.UTF8.GetBytes(a ?? "");
            var bb = System.Text.Encoding.UTF8.GetBytes(b ?? "");
            return System.Security.Cryptography.CryptographicOperations.FixedTimeEquals(ab, bb);
        }
    }
}