import React, { useEffect, useState } from "react";
import { apiFetch } from "../api";
import { useAuth } from "../state";

const TEMPLATE_VARIABLES = [
  "target_name",
  "target_id",
  "alert_name",
  "severity",
  "category",
  "description",
  "message",
  "value",
  "warning_threshold",
  "alert_threshold",
  "checked_at",
  "alert_key",
];

export function AdminUsersPage() {
  const { tokens, refresh, me } = useAuth();
  const [users, setUsers] = useState([]);
  const [form, setForm] = useState({ email: "", password: "", role: "viewer" });
  const [emailSettings, setEmailSettings] = useState({
    enabled: false,
    smtp_host: "",
    smtp_port: 587,
    smtp_username: "",
    smtp_password: "",
    clear_smtp_password: false,
    from_name: "",
    from_email: "",
    use_starttls: true,
    use_ssl: false,
    warning_subject_template: "",
    alert_subject_template: "",
    warning_body_template: "",
    alert_body_template: "",
  });
  const [smtpState, setSmtpState] = useState({ has_password: false, updated_at: null });
  const [testRecipient, setTestRecipient] = useState("");
  const [smtpInfo, setSmtpInfo] = useState("");
  const [error, setError] = useState("");

  const load = async () => {
    const [userRows, smtp] = await Promise.all([
      apiFetch("/admin/users", {}, tokens, refresh),
      apiFetch("/admin/settings/email", {}, tokens, refresh),
    ]);
    setUsers(userRows);
    setEmailSettings((prev) => ({
      ...prev,
      enabled: !!smtp.enabled,
      smtp_host: smtp.smtp_host || "",
      smtp_port: smtp.smtp_port || 587,
      smtp_username: smtp.smtp_username || "",
      smtp_password: "",
      clear_smtp_password: false,
      from_name: smtp.from_name || "",
      from_email: smtp.from_email || "",
      use_starttls: !!smtp.use_starttls,
      use_ssl: !!smtp.use_ssl,
      warning_subject_template: smtp.warning_subject_template || "",
      alert_subject_template: smtp.alert_subject_template || "",
      warning_body_template: smtp.warning_body_template || "",
      alert_body_template: smtp.alert_body_template || "",
    }));
    setSmtpState({ has_password: !!smtp.has_password, updated_at: smtp.updated_at });
    setTestRecipient(smtp.from_email || "");
  };

  useEffect(() => {
    if (me?.role === "admin") load().catch((e) => setError(String(e.message || e)));
  }, [me]);

  if (me?.role !== "admin") return <div className="card">Admins only.</div>;

  const create = async (e) => {
    e.preventDefault();
    try {
      await apiFetch("/admin/users", { method: "POST", body: JSON.stringify(form) }, tokens, refresh);
      setForm({ email: "", password: "", role: "viewer" });
      await load();
    } catch (e) {
      setError(String(e.message || e));
    }
  };

  const remove = async (id) => {
    try {
      await apiFetch(`/admin/users/${id}`, { method: "DELETE" }, tokens, refresh);
      await load();
    } catch (e) {
      setError(String(e.message || e));
    }
  };

  const saveSmtp = async (e) => {
    e.preventDefault();
    setError("");
    setSmtpInfo("");
    try {
      const payload = {
        ...emailSettings,
        smtp_host: emailSettings.smtp_host.trim() || null,
        smtp_username: emailSettings.smtp_username.trim() || null,
        from_name: emailSettings.from_name.trim() || null,
        from_email: emailSettings.from_email.trim() || null,
        smtp_password: emailSettings.smtp_password || null,
        warning_subject_template: emailSettings.warning_subject_template.trim() || null,
        alert_subject_template: emailSettings.alert_subject_template.trim() || null,
        warning_body_template: emailSettings.warning_body_template.trim() || null,
        alert_body_template: emailSettings.alert_body_template.trim() || null,
      };
      await apiFetch("/admin/settings/email", { method: "PUT", body: JSON.stringify(payload) }, tokens, refresh);
      setSmtpInfo("SMTP settings saved.");
      await load();
    } catch (e) {
      setError(String(e.message || e));
    }
  };

  const sendTestMail = async () => {
    setError("");
    setSmtpInfo("");
    try {
      const recipient = testRecipient.trim();
      if (!recipient) {
        throw new Error("Please enter a test recipient email.");
      }
      await apiFetch(
        "/admin/settings/email/test",
        { method: "POST", body: JSON.stringify({ recipient }) },
        tokens,
        refresh
      );
      setSmtpInfo(`Test email sent to ${recipient}.`);
    } catch (e) {
      setError(String(e.message || e));
    }
  };

  const protocolMode = emailSettings.use_ssl ? "ssl" : emailSettings.use_starttls ? "starttls" : "plain";
  const setProtocolMode = (mode) => {
    if (mode === "ssl") {
      setEmailSettings({ ...emailSettings, use_ssl: true, use_starttls: false });
      return;
    }
    if (mode === "starttls") {
      setEmailSettings({ ...emailSettings, use_ssl: false, use_starttls: true });
      return;
    }
    setEmailSettings({ ...emailSettings, use_ssl: false, use_starttls: false });
  };

  return (
    <div className="admin-settings-page">
      <h2>Admin Settings</h2>
      <p className="muted admin-page-subtitle">Manage users and outgoing notifications for this NexaPG instance.</p>
      {error && <div className="card error">{error}</div>}

      <div className="card">
        <div className="admin-section-head">
          <h3>User Management</h3>
          <p className="muted">Create accounts and manage access roles.</p>
        </div>
        <form className="grid three admin-user-form" onSubmit={create}>
          <div className="admin-field">
            <label>Email</label>
            <input value={form.email} placeholder="user@example.com" onChange={(e) => setForm({ ...form, email: e.target.value })} />
          </div>
          <div className="admin-field">
            <label>Password</label>
            <input
              type="password"
              value={form.password}
              placeholder="Set initial password"
              onChange={(e) => setForm({ ...form, password: e.target.value })}
            />
          </div>
          <div className="admin-field">
            <label>Role</label>
            <select value={form.role} onChange={(e) => setForm({ ...form, role: e.target.value })}>
              <option value="viewer">viewer</option>
              <option value="operator">operator</option>
              <option value="admin">admin</option>
            </select>
          </div>
          <div className="form-actions field-full">
            <button className="primary-btn" type="submit">Create User</button>
          </div>
        </form>
      </div>

      <div className="card admin-users-table-wrap">
        <table>
          <thead>
            <tr>
              <th>ID</th>
              <th>Email</th>
              <th>Role</th>
              <th>Action</th>
            </tr>
          </thead>
          <tbody>
            {users.map((u) => (
              <tr key={u.id} className="admin-user-row">
                <td className="user-col-id">{u.id}</td>
                <td className="user-col-email">{u.email}</td>
                <td>
                  <span className={`pill role-pill role-${u.role}`}>{u.role}</span>
                </td>
                <td>
                  {u.id !== me.id && (
                    <button className="table-action-btn delete small-btn" onClick={() => remove(u.id)}>
                      <span aria-hidden="true">
                        <svg viewBox="0 0 24 24" width="12" height="12">
                          <path
                            d="M9 3h6l1 2h4v2H4V5h4l1-2zm1 6h2v8h-2V9zm4 0h2v8h-2V9zM7 9h2v8H7V9z"
                            fill="currentColor"
                          />
                        </svg>
                      </span>
                      <span>Delete</span>
                    </button>
                  )}
                </td>
              </tr>
            ))}
          </tbody>
        </table>
      </div>

      <div className="card">
        <div className="admin-section-head">
          <h3>Alert Email Notifications (SMTP)</h3>
          <p className="muted">Configure send-only SMTP for warning and alert notifications.</p>
        </div>
        {smtpInfo && <div className="test-connection-result ok">{smtpInfo}</div>}
        <form className="grid two admin-smtp-form" onSubmit={saveSmtp}>
          <div className="admin-subcard field-full">
            <h4>SMTP Settings</h4>
            <div className="grid two">
              <label className="toggle-check field-full">
                <input
                  type="checkbox"
                  checked={emailSettings.enabled}
                  onChange={(e) => setEmailSettings({ ...emailSettings, enabled: e.target.checked })}
                />
                <span className="toggle-ui" />
                <span>
                  <strong>Enable alert emails</strong>
                </span>
              </label>

              <div className="admin-field">
                <label>SMTP host</label>
                <input
                  value={emailSettings.smtp_host}
                  placeholder="smtp.example.com"
                  onChange={(e) => setEmailSettings({ ...emailSettings, smtp_host: e.target.value })}
                />
              </div>
              <div className="admin-field">
                <label>SMTP port</label>
                <input
                  type="number"
                  value={emailSettings.smtp_port}
                  onChange={(e) => setEmailSettings({ ...emailSettings, smtp_port: Number(e.target.value || 587) })}
                />
              </div>

              <div className="admin-field">
                <label>SMTP username</label>
                <input
                  value={emailSettings.smtp_username}
                  placeholder="alerts@example.com"
                  onChange={(e) => setEmailSettings({ ...emailSettings, smtp_username: e.target.value })}
                />
              </div>
              <div className="admin-field">
                <label>SMTP password</label>
                <input
                  type="password"
                  value={emailSettings.smtp_password}
                  placeholder={smtpState.has_password ? "Stored (enter to replace)" : "Set password"}
                  onChange={(e) => setEmailSettings({ ...emailSettings, smtp_password: e.target.value, clear_smtp_password: false })}
                />
              </div>

              <div className="admin-field">
                <label>From name</label>
                <input
                  value={emailSettings.from_name}
                  placeholder="NexaPG Alerts"
                  onChange={(e) => setEmailSettings({ ...emailSettings, from_name: e.target.value })}
                />
              </div>
              <div className="admin-field">
                <label>From email</label>
                <input
                  value={emailSettings.from_email}
                  placeholder="noreply@example.com"
                  onChange={(e) => setEmailSettings({ ...emailSettings, from_email: e.target.value })}
                />
              </div>

              <div className="admin-field field-full">
                <label>Transport mode</label>
                <div className="smtp-mode-picker" role="radiogroup" aria-label="SMTP transport mode">
                  <button
                    type="button"
                    className={`smtp-mode-btn ${protocolMode === "starttls" ? "active" : ""}`}
                    aria-pressed={protocolMode === "starttls"}
                    onClick={() => setProtocolMode("starttls")}
                  >
                    STARTTLS
                  </button>
                  <button
                    type="button"
                    className={`smtp-mode-btn ${protocolMode === "ssl" ? "active" : ""}`}
                    aria-pressed={protocolMode === "ssl"}
                    onClick={() => setProtocolMode("ssl")}
                  >
                    SSL/TLS (SMTPS)
                  </button>
                  <button
                    type="button"
                    className={`smtp-mode-btn ${protocolMode === "plain" ? "active" : ""}`}
                    aria-pressed={protocolMode === "plain"}
                    onClick={() => setProtocolMode("plain")}
                  >
                    No TLS
                  </button>
                </div>
                <small className="muted">Select exactly one mode to avoid STARTTLS/SSL conflicts.</small>
              </div>

              <label className="toggle-check field-full">
                <input
                  type="checkbox"
                  checked={emailSettings.clear_smtp_password}
                  onChange={(e) => setEmailSettings({ ...emailSettings, clear_smtp_password: e.target.checked, smtp_password: e.target.checked ? "" : emailSettings.smtp_password })}
                />
                <span className="toggle-ui" />
                <span>Clear stored SMTP password</span>
              </label>
            </div>
          </div>

          <div className="admin-subcard field-full">
            <h4>Template Settings</h4>
            <p className="muted template-help-text">
              If a template field is left empty, NexaPG automatically uses the built-in default template.
            </p>
            <div className="template-vars-grid">
              {TEMPLATE_VARIABLES.map((item) => (
                <code key={item} className="template-var-pill">
                  {"{" + item + "}"}
                </code>
              ))}
            </div>

            <div className="grid two">
              <div className="admin-field field-full">
                <label>Warning subject template</label>
                <input
                  value={emailSettings.warning_subject_template}
                  placeholder="[NexaPG][WARNING] {target_name} - {alert_name}"
                  onChange={(e) => setEmailSettings({ ...emailSettings, warning_subject_template: e.target.value })}
                />
              </div>
              <div className="admin-field field-full">
                <label>Alert subject template</label>
                <input
                  value={emailSettings.alert_subject_template}
                  placeholder="[NexaPG][ALERT] {target_name} - {alert_name}"
                  onChange={(e) => setEmailSettings({ ...emailSettings, alert_subject_template: e.target.value })}
                />
              </div>
              <div className="admin-field field-full">
                <label>Warning body template</label>
                <textarea
                  value={emailSettings.warning_body_template}
                  placeholder={"Severity: {severity}\nTarget: {target_name} (id={target_id})\nAlert: {alert_name}\nMessage: {message}\nChecked At: {checked_at}"}
                  onChange={(e) => setEmailSettings({ ...emailSettings, warning_body_template: e.target.value })}
                />
              </div>
              <div className="admin-field field-full">
                <label>Alert body template</label>
                <textarea
                  value={emailSettings.alert_body_template}
                  placeholder={"Severity: {severity}\nTarget: {target_name} (id={target_id})\nAlert: {alert_name}\nMessage: {message}\nCurrent Value: {value}\nWarning Threshold: {warning_threshold}\nAlert Threshold: {alert_threshold}\nChecked At: {checked_at}\nAlert Key: {alert_key}"}
                  onChange={(e) => setEmailSettings({ ...emailSettings, alert_body_template: e.target.value })}
                />
              </div>
            </div>
          </div>

          <div className="form-actions field-full">
            <input
              className="admin-test-recipient"
              value={testRecipient}
              placeholder="test recipient email"
              onChange={(e) => setTestRecipient(e.target.value)}
            />
            <button className="secondary-btn" type="button" onClick={sendTestMail}>Send Test Mail</button>
            <button className="primary-btn" type="submit">Save SMTP Settings</button>
          </div>
          <small className="muted field-full">
            Last updated: {smtpState.updated_at ? new Date(smtpState.updated_at).toLocaleString() : "not configured yet"}
          </small>
        </form>
      </div>
    </div>
  );
}