'use client';

import { useState } from 'react';
import { useMutation, useQuery, useQueryClient } from '@tanstack/react-query';
import { CheckCircle2, HardDrive, Loader2, RefreshCw, ServerCog, XCircle } from 'lucide-react';

import { PageHeader } from '@/components/shared/page-header';
import { Button } from '@/components/ui/button';
import { Card, CardContent, CardDescription, CardHeader, CardTitle } from '@/components/ui/card';
import {
  Dialog,
  DialogContent,
  DialogDescription,
  DialogFooter,
  DialogHeader,
  DialogTitle,
} from '@/components/ui/dialog';
import { apiFetch } from '@/lib/api/client';

type BackendName = 's3' | 'filesystem';

interface StorageStatus {
  backend: BackendName;
  fileCount: number;
  totalBytes: number;
  tablesTracked: string[];
}

interface MigrationResult {
  rowsConsidered: number;
  rowsMigrated: number;
  rowsSkippedAlreadyDone: number;
  totalBytes: number;
  flipped: boolean;
  dryRun: boolean;
}

export function StorageAdminPanel() {
  const queryClient = useQueryClient();
  const [confirmOpen, setConfirmOpen] = useState(false);
  const [dryRun, setDryRun] = useState<MigrationResult | null>(null);
  const [testResult, setTestResult] = useState<{ ok: boolean; error?: string } | null>(null);

  const status = useQuery({
    queryKey: ['admin', 'storage', 'status'],
    queryFn: () => apiFetch<{ data: StorageStatus }>('/api/v1/admin/storage'),
  });

  const dryRunMutation = useMutation({
    mutationFn: async (opts: { from: BackendName; to: BackendName }) =>
      apiFetch<{ data: MigrationResult }>('/api/v1/admin/storage/migrate', {
        method: 'POST',
        body: JSON.stringify({ ...opts, dryRun: true }),
      }),
    onSuccess: (result) => {
      setDryRun(result.data);
      setConfirmOpen(true);
    },
  });

  const migrateMutation = useMutation({
    mutationFn: async (opts: { from: BackendName; to: BackendName }) =>
      apiFetch<{ data: MigrationResult }>('/api/v1/admin/storage/migrate', {
        method: 'POST',
        body: JSON.stringify({ ...opts, dryRun: false }),
      }),
    onSuccess: () => {
      setConfirmOpen(false);
      setDryRun(null);
      queryClient.invalidateQueries({ queryKey: ['admin', 'storage', 'status'] });
    },
  });

  const testMutation = useMutation({
    mutationFn: async () =>
      apiFetch<{ ok: boolean; error?: string }>('/api/v1/admin/storage', {
        method: 'POST',
      }),
    onSuccess: (r) => setTestResult(r),
    onError: (e: Error) => setTestResult({ ok: false, error: e.message }),
  });

  if (status.isLoading) {
    return (
      <div className="flex items-center gap-2 text-sm text-muted-foreground">
        <Loader2 className="h-4 w-4 animate-spin" /> Loading storage status…
      </div>
    );
  }
  if (status.isError || !status.data?.data) {
    return <div className="text-sm text-destructive">Failed to load storage status.</div>;
  }
  const s = status.data.data;
  const otherBackend: BackendName = s.backend === 's3' ? 'filesystem' : 's3';

  return (
    <div className="space-y-6">
      <PageHeader
        title="Storage Backend"
        description="Where the CRM stores per-berth PDFs, brochures, GDPR exports, and other binary files."
      />

      <div className="grid gap-4 lg:grid-cols-3">
        <Card className="lg:col-span-2">
          <CardHeader className="flex flex-row items-start gap-3 space-y-0 pb-2">
            {s.backend === 's3' ? (
              <ServerCog className="mt-0.5 h-5 w-5 text-muted-foreground" />
            ) : (
              <HardDrive className="mt-0.5 h-5 w-5 text-muted-foreground" />
            )}
            <div>
              <CardTitle className="text-base">Active backend: {s.backend}</CardTitle>
              <CardDescription>
                {s.backend === 's3'
                  ? 'Files stored in an S3-compatible object store (MinIO, AWS S3, Backblaze B2, Cloudflare R2, Wasabi, Tigris).'
                  : 'Files stored on the local filesystem under storage_filesystem_root. Single-node deployments only.'}
              </CardDescription>
            </div>
          </CardHeader>
          <CardContent className="space-y-4">
            <dl className="grid grid-cols-2 gap-3 text-sm">
              <div>
                <dt className="text-muted-foreground">Tracked tables</dt>
                <dd>
                  {s.tablesTracked.length === 0
                    ? '(none yet — Phase 6b)'
                    : s.tablesTracked.join(', ')}
                </dd>
              </div>
              <div>
                <dt className="text-muted-foreground">File count</dt>
                <dd>{s.fileCount}</dd>
              </div>
            </dl>

            <div className="flex flex-wrap gap-3">
              <Button
                variant="outline"
                disabled={dryRunMutation.isPending}
                onClick={() => dryRunMutation.mutate({ from: s.backend, to: otherBackend })}
              >
                {dryRunMutation.isPending && <Loader2 className="mr-2 h-4 w-4 animate-spin" />}
                Switch to {otherBackend}
              </Button>
              {s.backend === 's3' && (
                <Button
                  variant="outline"
                  onClick={() => testMutation.mutate()}
                  disabled={testMutation.isPending}
                >
                  {testMutation.isPending && <Loader2 className="mr-2 h-4 w-4 animate-spin" />}
                  Test connection
                </Button>
              )}
              <Button variant="ghost" onClick={() => status.refetch()} disabled={status.isFetching}>
                <RefreshCw className="mr-2 h-4 w-4" /> Refresh
              </Button>
            </div>

            {testResult && (
              <div className="rounded-md border p-3 text-sm">
                {testResult.ok ? (
                  <div className="flex items-center gap-2 text-emerald-600">
                    <CheckCircle2 className="h-4 w-4" /> Connection OK — round-trip succeeded.
                  </div>
                ) : (
                  <div className="flex items-center gap-2 text-destructive">
                    <XCircle className="h-4 w-4" /> {testResult.error ?? 'Connection failed'}
                  </div>
                )}
              </div>
            )}
          </CardContent>
        </Card>

        <Card>
          <CardHeader>
            <CardTitle className="text-base">Backup notes</CardTitle>
          </CardHeader>
          <CardContent className="space-y-2 text-sm text-muted-foreground">
            {s.backend === 's3' ? (
              <p>
                S3 mode: configure your provider&apos;s lifecycle / replication / versioning
                policies as your primary backup. The CRM does not duplicate object storage in its
                own backups.
              </p>
            ) : (
              <p>
                Filesystem mode: include the storage root directory in your backup tool (restic,
                borg, snapshots). It sits next to the database; the two should be backed up
                together.
              </p>
            )}
            <p className="pt-2 text-xs">
              Filesystem mode refuses to start when MULTI_NODE_DEPLOYMENT=true. For multi-node
              deployments, switch to an S3-compatible backend.
            </p>
          </CardContent>
        </Card>
      </div>

      <Dialog open={confirmOpen} onOpenChange={setConfirmOpen}>
        <DialogContent>
          <DialogHeader>
            <DialogTitle>Switch storage backend</DialogTitle>
            <DialogDescription>
              Move all tracked files from the current backend to the new backend, verify each file
              via sha256, then atomically flip the active backend.
            </DialogDescription>
          </DialogHeader>
          {dryRun && (
            <div className="rounded-md border p-3 text-sm">
              <dl className="grid grid-cols-2 gap-2">
                <dt className="text-muted-foreground">Rows considered</dt>
                <dd>{dryRun.rowsConsidered}</dd>
                <dt className="text-muted-foreground">Already migrated (resumable)</dt>
                <dd>{dryRun.rowsSkippedAlreadyDone}</dd>
                <dt className="text-muted-foreground">Total bytes</dt>
                <dd>{Math.round(dryRun.totalBytes / 1024)} KB</dd>
              </dl>
            </div>
          )}
          <DialogFooter>
            <Button variant="outline" onClick={() => setConfirmOpen(false)}>
              Cancel
            </Button>
            <Button
              disabled={migrateMutation.isPending}
              onClick={() => migrateMutation.mutate({ from: s.backend, to: otherBackend })}
            >
              {migrateMutation.isPending && <Loader2 className="mr-2 h-4 w-4 animate-spin" />}
              Migrate now
            </Button>
          </DialogFooter>
        </DialogContent>
      </Dialog>
    </div>
  );
}