import { useEffect, useState } from "react";
import { Link, useNavigate } from "react-router-dom";
import {
  ArrowLeft,
  Eye,
  EyeOff,
  Loader2,
  Save,
  Plug,
  Trash2,
} from "lucide-react";
import { ThemeToggle } from "../components/ThemeToggle";
import { useToast } from "../lib/toast";
import {
  getConfigDisplay,
  setConfig,
  previewConfig,
  testConnectionWithConfig,
  saveConfig,
  loadConfig,
  DEFAULT_MODEL,
} from "../lib/llm";

const DEFAULTS = {
  api_endpoint: "",
  api_key: "",
  model_name: DEFAULT_MODEL,
};

export function SettingsPage() {
  const toast = useToast();
  const navigate = useNavigate();

  const [endpoint, setEndpoint] = useState(DEFAULTS.api_endpoint);
  const [model, setModel] = useState(DEFAULTS.model_name);
  const [apiKey, setApiKey] = useState(""); // never pre-populated from storage
  const [apiKeySet, setApiKeySet] = useState(false);
  const [showKey, setShowKey] = useState(false);

  const [loading, setLoading] = useState(true);
  const [saving, setSaving] = useState(false);
  const [testing, setTesting] = useState(false);

  // Load current (non-secret) values on mount.
  useEffect(() => {
    const cfg = getConfigDisplay();
    setEndpoint(cfg.api_endpoint);
    setModel(cfg.model_name);
    setApiKeySet(cfg.api_key_set);
    setLoading(false);
  }, []);

  const onSave = (e: React.FormEvent) => {
    e.preventDefault();
    setSaving(true);
    try {
      const result = setConfig({
        api_endpoint: endpoint.trim(),
        api_key: apiKey,
        model_name: model.trim(),
      });
      setApiKey("");
      setApiKeySet(result.api_key_set);
      toast.success("Configuration saved");
    } catch (err) {
      toast.error(
        err instanceof Error ? err.message : "Failed to save configuration",
      );
    } finally {
      setSaving(false);
    }
  };

  // Test using *in-memory* form values — don't persist until the user clicks
  // Save. An empty API key field still falls back to the previously saved key,
  // matching the behaviour of Save.
  const onTest = async () => {
    setTesting(true);
    const candidate = previewConfig({
      api_endpoint: endpoint.trim(),
      api_key: apiKey,
      model_name: model.trim(),
    });

    if (
      !candidate.api_endpoint ||
      !candidate.api_key ||
      !candidate.model_name
    ) {
      setTesting(false);
      toast.error("❌ Fill in endpoint, key, and model before testing");
      return;
    }

    const result = await testConnectionWithConfig(candidate);
    if (result.success) {
      toast.success(`✅ ${result.message}`);
    } else {
      toast.error(`❌ ${result.message}`);
    }
    setTesting(false);
  };

  const onClearKey = () => {
    if (!apiKeySet) return;
    if (!window.confirm("Clear the saved API key from this browser?")) return;
    const current = loadConfig();
    saveConfig({ ...current, api_key: "" });
    setApiKeySet(false);
    setApiKey("");
    toast.info("Saved API key cleared");
  };

  return (
    <div className="min-h-screen">
      <header className="sticky top-0 z-20 bg-bg/70 backdrop-blur border-b border-border">
        <div className="max-w-md mx-auto px-4 h-14 flex items-center justify-between">
          <button
            type="button"
            onClick={() => navigate("/")}
            className="btn-ghost p-2"
            aria-label="Back"
          >
            <ArrowLeft className="w-5 h-5" />
          </button>
          <h1 className="text-sm font-semibold text-fg">API Configuration</h1>
          <ThemeToggle />
        </div>
      </header>

      <main className="max-w-md mx-auto px-4 mt-16">
        <div className="card p-6">
          {loading ? (
            <div className="space-y-4 animate-pulse">
              <div className="h-4 w-1/3 bg-bg-hover rounded" />
              <div className="h-10 bg-bg-hover rounded" />
              <div className="h-4 w-1/3 bg-bg-hover rounded" />
              <div className="h-10 bg-bg-hover rounded" />
              <div className="h-4 w-1/3 bg-bg-hover rounded" />
              <div className="h-10 bg-bg-hover rounded" />
              <div className="h-12 bg-bg-hover rounded" />
              <div className="h-12 bg-bg-hover rounded" />
            </div>
          ) : (
            <form onSubmit={onSave} className="space-y-4">
              <div>
                <label
                  htmlFor="endpoint"
                  className="block text-xs uppercase tracking-wider text-fg-muted mb-1"
                >
                  API Endpoint URL
                </label>
                <input
                  id="endpoint"
                  type="text"
                  className="input"
                  placeholder="https://api.minimax.chat/v1"
                  value={endpoint}
                  onChange={(e) => setEndpoint(e.target.value)}
                  required
                />
              </div>

              <div>
                <label
                  htmlFor="apiKey"
                  className="block text-xs uppercase tracking-wider text-fg-muted mb-1"
                >
                  API Key
                </label>
                <div className="relative">
                  <input
                    id="apiKey"
                    type={showKey ? "text" : "password"}
                    className="input pr-10 font-mono"
                    placeholder={
                      apiKeySet
                        ? "API key saved — enter a new one to replace it"
                        : "sk-..."
                    }
                    value={apiKey}
                    onChange={(e) => setApiKey(e.target.value)}
                    autoComplete="off"
                    spellCheck={false}
                  />
                  <button
                    type="button"
                    onClick={() => setShowKey((s) => !s)}
                    className="absolute inset-y-0 right-0 flex items-center px-3 text-fg-muted hover:text-fg transition-colors"
                    aria-label={showKey ? "Hide API key" : "Show API key"}
                    tabIndex={-1}
                  >
                    {showKey ? (
                      <EyeOff className="w-4 h-4" />
                    ) : (
                      <Eye className="w-4 h-4" />
                    )}
                  </button>
                </div>
                {apiKeySet && !apiKey && (
                  <p className="mt-1 text-xs text-emerald-400">
                    A key is currently saved.
                  </p>
                )}
                {apiKeySet && (
                  <button
                    type="button"
                    onClick={onClearKey}
                    className="mt-2 inline-flex items-center gap-1 text-xs text-fg-muted hover:text-rose-300 transition-colors"
                  >
                    <Trash2 className="w-3.5 h-3.5" />
                    Clear saved key
                  </button>
                )}
              </div>

              <div>
                <label
                  htmlFor="model"
                  className="block text-xs uppercase tracking-wider text-fg-muted mb-1"
                >
                  Model Name
                </label>
                <input
                  id="model"
                  type="text"
                  className="input"
                  placeholder="MiniMax-M3"
                  value={model}
                  onChange={(e) => setModel(e.target.value)}
                  required
                />
              </div>

              <button
                type="submit"
                disabled={saving || testing}
                className="btn-primary w-full py-3"
              >
                {saving ? (
                  <Loader2 className="w-4 h-4 animate-spin" />
                ) : (
                  <Save className="w-4 h-4" />
                )}
                Save Configuration
              </button>

              <button
                type="button"
                onClick={onTest}
                disabled={saving || testing}
                className="btn-secondary w-full py-3"
              >
                {testing ? (
                  <Loader2 className="w-4 h-4 animate-spin" />
                ) : (
                  <Plug className="w-4 h-4" />
                )}
                Test Connection
              </button>
            </form>
          )}

          <p className="mt-6 text-center text-xs text-fg-muted">
            Your settings are stored in this browser's local storage. Do not use
            this app on a device that other people have access to.
          </p>

          <div className="mt-4 text-center">
            <Link
              to="/"
              className="text-xs text-fg-muted hover:text-fg transition-colors"
            >
              ← Back to generator
            </Link>
          </div>
        </div>
      </main>
    </div>
  );
}