import { useMemo, useState } from 'react';
import { Alert, Button, Toggle } from '@cameleer/design-system';
import { useRenderPreview } from '../../../api/queries/alertRules';
import { describeApiError } from '../../../api/errors';
import { toRequest, type FormState } from './form-state';

/**
 * Pure helper: returns a human-readable reason why saving should be blocked,
 * or null when the rule is safe to save (from the wizard's perspective).
 *
 * Currently covers: a rule with no webhooks AND no targets would be rejected
 * at the server edge (Task 3.3 validator) and would never notify anyone, so
 * the wizard blocks it earlier with a clear reason. The helper is exported
 * so `RuleEditorWizard` can also drive the Save button's `disabled` state
 * off the same single source of truth.
 */
export function computeSaveBlockReason(form: FormState): string | null {
  const noWebhooks = (form.webhooks ?? []).length === 0;
  const noTargets = (form.targets ?? []).length === 0;
  if (noWebhooks && noTargets) {
    return 'Add at least one webhook or target \u2014 a rule with no recipients never notifies anyone.';
  }
  return null;
}

export function ReviewStep({
  form,
  setForm,
  ruleId,
}: {
  form: FormState;
  setForm?: (f: FormState) => void;
  /**
   * Present only in edit mode. When absent the notification-preview button is
   * hidden, because the backend `/render-preview` endpoint is id-bound and
   * has no stateless variant — rendering against an unsaved draft would
   * require a new endpoint and is explicitly out of scope here.
   */
  ruleId?: string;
}) {
  const req = toRequest(form);
  const saveBlockReason = useMemo(() => computeSaveBlockReason(form), [form]);

  const previewMutation = useRenderPreview();
  const [preview, setPreview] = useState<{ title: string; message: string } | null>(null);
  const [previewError, setPreviewError] = useState<string | null>(null);

  const onPreview = async () => {
    setPreviewError(null);
    try {
      const res = await previewMutation.mutateAsync({ id: ruleId!, req: {} });
      setPreview({ title: res.title ?? '', message: res.message ?? '' });
    } catch (e) {
      setPreview(null);
      setPreviewError(describeApiError(e));
    }
  };

  return (
    <div style={{ display: 'grid', gap: 12, maxWidth: 720 }}>
      {saveBlockReason && (
        <Alert variant="error" title="Rule cannot be saved yet">
          {saveBlockReason}
        </Alert>
      )}
      <div>
        <strong>Name:</strong> {form.name}
      </div>
      <div>
        <strong>Severity:</strong> {form.severity}
      </div>
      <div>
        <strong>Scope:</strong> {form.scopeKind}
        {form.scopeKind !== 'env' &&
          ` (app=${form.appSlug}${form.routeId ? `, route=${form.routeId}` : ''}${form.agentId ? `, agent=${form.agentId}` : ''})`}
      </div>
      <div>
        <strong>Condition kind:</strong> {form.conditionKind}
      </div>
      <div>
        <strong>Intervals:</strong> eval {form.evaluationIntervalSeconds}s &middot; for {form.forDurationSeconds}s &middot; re-notify {form.reNotifyMinutes}m
      </div>
      <div>
        <strong>Targets:</strong> {form.targets.length}
      </div>
      <div>
        <strong>Webhooks:</strong> {form.webhooks.length}
      </div>
      {setForm && (
        <div style={{ display: 'flex', alignItems: 'center', gap: 8 }}>
          <Toggle
            checked={form.enabled}
            onChange={(e) => setForm({ ...form, enabled: e.target.checked })}
            label="Enabled on save"
          />
        </div>
      )}

      {ruleId && (
        <div style={{ display: 'grid', gap: 8 }}>
          <div>
            <Button
              variant="secondary"
              onClick={onPreview}
              disabled={previewMutation.isPending}
            >
              {previewMutation.isPending ? 'Rendering\u2026' : 'Preview notification'}
            </Button>
          </div>
          {previewError && (
            <Alert variant="error" title="Preview failed">
              {previewError}
            </Alert>
          )}
          {preview && (
            <div
              aria-label="Rendered notification preview"
              style={{
                border: '1px solid var(--border)',
                borderRadius: 8,
                padding: 12,
                background: 'var(--surface-raised, var(--surface))',
                display: 'grid',
                gap: 6,
              }}
            >
              <div style={{ fontSize: 11, color: 'var(--text-muted)' }}>
                Rendered notification preview
              </div>
              <div style={{ fontWeight: 600, fontSize: 14 }}>
                {preview.title || <em style={{ color: 'var(--text-muted)' }}>(empty title)</em>}
              </div>
              <pre
                style={{
                  margin: 0,
                  fontSize: 12,
                  fontFamily: 'inherit',
                  whiteSpace: 'pre-wrap',
                  color: 'var(--text)',
                }}
              >
                {preview.message || '(empty message)'}
              </pre>
            </div>
          )}
        </div>
      )}

      <details>
        <summary>Raw request JSON</summary>
        <pre
          style={{
            fontSize: 11,
            background: 'var(--code-bg)',
            padding: 8,
            borderRadius: 6,
            overflow: 'auto',
          }}
        >
          {JSON.stringify(req, null, 2)}
        </pre>
      </details>
    </div>
  );
}