package ins.frontend;

import ins.frontend.utils.RegistrationService;
import ins.frontend.utils.WebApp;
import org.openautonomousconnection.protocol.packets.v1_0_1.beta.web.impl.resource.WebResourceResponsePacket;
import org.openautonomousconnection.protocol.side.web.ProtocolWebServer;
import org.openautonomousconnection.protocol.side.web.managers.SessionManager;
import org.openautonomousconnection.protocol.versions.v1_0_1.beta.WebPacketFlags;
import org.openautonomousconnection.protocol.versions.v1_0_1.beta.WebPacketHeader;
import org.openautonomousconnection.webserver.api.Route;
import org.openautonomousconnection.webserver.api.WebPage;
import org.openautonomousconnection.webserver.api.WebPageContext;
import org.openautonomousconnection.webserver.utils.HeaderMaps;
import org.openautonomousconnection.webserver.utils.Html;

import java.lang.reflect.Method;
import java.nio.charset.StandardCharsets;
import java.util.*;

/**
 * Register page (v1.0.1).
 */
@Route(path = "/register.html")
public final class register implements WebPage {

    private enum ReqMethod { GET, POST, OTHER }

    @Override
    public WebResourceResponsePacket handle(WebPageContext ctx) throws Exception {
        WebApp.init();

        // If a valid session already exists -> go dashboard (keep session)
        if (ctx.session != null && ctx.session.isValid() && ctx.session.getUser() != null) {
            return redirect302(ctx, "dashboard.html", ctx.session.getSessionId());
        }

        ReqMethod method = detectMethod(ctx);
        if (method == ReqMethod.GET) {
            return ok(ctx, renderForm(null));
        }

        if (method != ReqMethod.POST) {
            return text(ctx, 405, "Method Not Allowed");
        }

        String contentType = headerIgnoreCase(ctx.request.getHeaders(), "content-type");
        String ctLower = (contentType == null) ? "" : contentType.toLowerCase(Locale.ROOT);

        if (!ctLower.startsWith("application/x-www-form-urlencoded")) {
            return ok(ctx, renderForm("Unsupported content-type: " + Html.esc(contentType)));
        }

        Map<String, List<String>> form = parseFormUrlEncoded(ctx.request.getBody());
        String username = first(form, "username");
        String password = first(form, "password");

        RegistrationService service = new RegistrationService(WebApp.get().users(), WebApp.get().passwordHasher());
        RegistrationService.Result r = service.register(username, password);

        if (!r.ok()) {
            return ok(ctx, renderForm(r.error()));
        }

        // Create new session (user just registered)
        String ip = resolveIp(ctx);
        String ua = headerIgnoreCase(ctx.request.getHeaders(), "user-agent");
        if (ua == null) ua = "";

        String session = SessionManager.create(
                String.valueOf(r.userId()),
                ip,
                ua,
                (ProtocolWebServer) ctx.client.getServer()
        );

        return redirect302(ctx, "dashboard.html", session);
    }

    private ReqMethod detectMethod(WebPageContext ctx) {
        try {
            Method m = ctx.request.getClass().getMethod("getMethod");
            Object v = m.invoke(ctx.request);
            if (v != null) {
                String s = String.valueOf(v).trim().toUpperCase(Locale.ROOT);
                if ("GET".equals(s)) return ReqMethod.GET;
                if ("POST".equals(s)) return ReqMethod.POST;
                return ReqMethod.OTHER;
            }
        } catch (Exception ignored) {
        }

        byte[] body = ctx.request.getBody();
        if (body != null && body.length > 0) return ReqMethod.POST;
        return ReqMethod.GET;
    }

    private static WebResourceResponsePacket ok(WebPageContext ctx, String html) {
        byte[] body = Html.utf8(html);
        Map<String, String> headers = HeaderMaps.mutable();
        headers.put("content-length", String.valueOf(body.length));
        return new WebResourceResponsePacket(outHeader(ctx), 200, "text/html; charset=utf-8", headers, body, null);
    }

    private static WebResourceResponsePacket text(WebPageContext ctx, int code, String msg) {
        byte[] body = (msg == null ? "" : msg).getBytes(StandardCharsets.UTF_8);
        Map<String, String> headers = HeaderMaps.mutable();
        headers.put("content-length", String.valueOf(body.length));
        return new WebResourceResponsePacket(outHeader(ctx), code, "text/plain; charset=utf-8", headers, body, null);
    }

    private static WebResourceResponsePacket redirect302(WebPageContext ctx, String location, String session) {
        Map<String, String> headers = HeaderMaps.mutable();
        headers.put("Location", location);
        if (session != null && !session.isBlank()) {
            headers.put("Set-Cookie", "session=" + session + "; Path=/; HttpOnly; SameSite=Lax");
            headers.put("session", session);
        }
        return new WebResourceResponsePacket(outHeader(ctx), 302, "text/plain; charset=utf-8", headers, new byte[0], null);
    }

    private static String renderForm(String errOrOk) {
        String line = "";
        if (errOrOk != null && !errOrOk.isBlank()) {
            boolean ok = errOrOk.startsWith("OK:");
            line = "<p class='" + (ok ? "ok" : "err") + "'>" + errOrOk + "</p>";
        }

        String body = """
                <div class="card">
                  <h2>Register</h2>
                  %s
                  <form method="post" action="register.html" class="form">
                    <label><span class="muted">Username</span><input type="text" name="username" autocomplete="username" required></label>
                    <label><span class="muted">Password</span><input type="password" name="password" autocomplete="new-password" required></label>
                    <button type="submit">Create account</button>
                  </form>
                  <div class="row" style="margin-top: 12px;">
                    <div class="col"><a href="login.html">Login</a></div>
                    <div class="col"><a href="index.html">Home</a></div>
                  </div>
                </div>
                """.formatted(line);

        return Html.page("Register", body);
    }

    private static String resolveIp(WebPageContext ctx) {
        if (ctx.client == null || ctx.client.getConnection() == null) return "";
        if (ctx.client.getConnection().getTcpSocket() == null) return "";
        if (ctx.client.getConnection().getTcpSocket().getInetAddress() == null) return "";
        return ctx.client.getConnection().getTcpSocket().getInetAddress().getHostAddress();
    }

    private static String headerIgnoreCase(Map<String, String> headers, String key) {
        if (headers == null || headers.isEmpty() || key == null) return null;
        for (Map.Entry<String, String> e : headers.entrySet()) {
            if (e.getKey() != null && e.getKey().equalsIgnoreCase(key)) return e.getValue();
        }
        return null;
    }

    private static Map<String, List<String>> parseFormUrlEncoded(byte[] body) {
        if (body == null || body.length == 0) return Map.of();

        String raw = new String(body, StandardCharsets.UTF_8);
        Map<String, List<String>> out = new LinkedHashMap<>();

        int start = 0;
        while (start <= raw.length()) {
            int amp = raw.indexOf('&', start);
            if (amp < 0) amp = raw.length();

            String pair = raw.substring(start, amp);
            if (!pair.isEmpty()) {
                int eq = pair.indexOf('=');
                String k = (eq < 0) ? pair : pair.substring(0, eq);
                String v = (eq < 0) ? "" : pair.substring(eq + 1);

                String key = decodeFormToken(k);
                String val = decodeFormToken(v);

                if (!key.isEmpty()) out.computeIfAbsent(key, __ -> new ArrayList<>(1)).add(val);
            }

            start = amp + 1;
            if (amp == raw.length()) break;
        }

        Map<String, List<String>> frozen = new LinkedHashMap<>();
        for (Map.Entry<String, List<String>> e : out.entrySet()) frozen.put(e.getKey(), List.copyOf(e.getValue()));
        return Map.copyOf(frozen);
    }

    private static String first(Map<String, List<String>> params, String key) {
        if (params == null || key == null) return null;
        List<String> v = params.get(key);
        if (v == null || v.isEmpty()) return null;
        String t = v.getFirst();
        if (t == null) return null;
        String s = t.trim();
        return s.isEmpty() ? null : s;
    }

    private static String decodeFormToken(String s) {
        if (s == null || s.isEmpty()) return "";
        byte[] tmp = new byte[s.length()];
        int n = 0;

        for (int i = 0; i < s.length(); i++) {
            char c = s.charAt(i);

            if (c == '+') {
                tmp[n++] = (byte) ' ';
                continue;
            }
            if (c == '%' && i + 2 < s.length()) {
                int hi = hex(c = s.charAt(i + 1));
                int lo = hex(s.charAt(i + 2));
                if (hi >= 0 && lo >= 0) {
                    tmp[n++] = (byte) ((hi << 4) | lo);
                    i += 2;
                    continue;
                }
            }

            byte[] b = String.valueOf(s.charAt(i)).getBytes(StandardCharsets.UTF_8);
            for (byte bb : b) tmp[n++] = bb;
        }

        return new String(tmp, 0, n, StandardCharsets.UTF_8);
    }

    private static int hex(char c) {
        if (c >= '0' && c <= '9') return c - '0';
        if (c >= 'a' && c <= 'f') return 10 + (c - 'a');
        if (c >= 'A' && c <= 'F') return 10 + (c - 'A');
        return -1;
    }

    private static WebPacketHeader outHeader(WebPageContext ctx) {
        WebPacketHeader in = (ctx != null && ctx.request != null) ? ctx.request.getHeader() : null;
        if (in == null) {
            return new WebPacketHeader(0, 0, 0, 0, WebPacketFlags.RESOURCE, System.currentTimeMillis());
        }
        return new WebPacketHeader(
                in.getRequestId(),
                in.getTabId(),
                in.getPageId(),
                in.getFrameId(),
                in.getFlags() | WebPacketFlags.RESOURCE,
                System.currentTimeMillis()
        );
    }
}