/**
 * S3 Backup Browser
 *
 * Lists backup files in the Litestream S3 bucket as a scrollable TUI.
 *
 * Credentials are read from the same environment variables used by
 * scripts/prod/litestream-backup:
 *   LITESTREAM_ACCESS_KEY_ID
 *   LITESTREAM_SECRET_ACCESS_KEY
 *
 * Usage:
 *   /backups
 */

import { ListObjectsV2Command, S3Client } from "@aws-sdk/client-s3";
import type { ExtensionAPI } from "@mariozechner/pi-coding-agent";
import { BorderedLoader, DynamicBorder } from "@mariozechner/pi-coding-agent";
import {
  Container,
  type SelectItem,
  SelectList,
  Text,
} from "@mariozechner/pi-tui";

// ── S3 configuration (mirrors scripts/prod/litestream-backup) ────────────────
const S3_ENDPOINT = "https://nbg1.your-objectstorage.com";
const S3_BUCKET = "ffmusiclibrary";
const S3_PREFIX = "prod/";
const S3_REGION = "nbg1";

// ── Helpers ─────────────────────────────────────────────────────────────────

function humanSize(bytes: number): string {
  if (bytes === 0) return "0 B";
  const units = ["B", "KB", "MB", "GB", "TB"];
  const i = Math.min(Math.floor(Math.log(bytes) / Math.log(1024)), units.length - 1);
  return `${(bytes / 1024 ** i).toFixed(1)} ${units[i]}`;
}

function formatDate(d: Date): string {
  // YYYY-MM-DD HH:MM
  const pad = (n: number) => String(n).padStart(2, "0");
  return `${d.getFullYear()}-${pad(d.getMonth() + 1)}-${pad(d.getDate())} ${pad(d.getHours())}:${pad(d.getMinutes())}`;
}

/**
 * Strip the known prefix from an S3 key for cleaner display.
 */
function displayKey(key: string): string {
  if (key.startsWith(S3_PREFIX)) return key.slice(S3_PREFIX.length);
  return key;
}

export interface S3Object {
  key: string;
  size: number;
  lastModified: Date;
}

/**
 * Fetch all objects (handles pagination via ContinuationToken).
 */
async function listAllObjects(
  client: S3Client,
  signal?: AbortSignal,
): Promise<S3Object[]> {
  const results: S3Object[] = [];
  let continuationToken: string | undefined;

  do {
    const command = new ListObjectsV2Command({
      Bucket: S3_BUCKET,
      Prefix: S3_PREFIX,
      ...(continuationToken ? { ContinuationToken: continuationToken } : {}),
    });

    const response = await client.send(command, { abortSignal: signal });

    if (response.Contents) {
      for (const obj of response.Contents) {
        results.push({
          key: obj.Key ?? "",
          size: obj.Size ?? 0,
          lastModified: obj.LastModified ?? new Date(0),
        });
      }
    }

    continuationToken = response.IsTruncated
      ? response.NextContinuationToken
      : undefined;
  } while (continuationToken);

  // Sort by size descending, then alphabetically descending
  results.sort((a, b) => {
    const sizeDiff = b.size - a.size;
    if (sizeDiff !== 0) return sizeDiff;
    return b.key.localeCompare(a.key);
  });
  return results;
}

// ── Extension ───────────────────────────────────────────────────────────────

export default function s3BrowserExtension(pi: ExtensionAPI) {
  pi.registerCommand("backups", {
    description: "List backup files in the S3 bucket",
    handler: async (_args, ctx) => {
      // ── Validate credentials ────────────────────────────────────────────

      const accessKeyId = process.env.LITESTREAM_ACCESS_KEY_ID;
      const secretAccessKey = process.env.LITESTREAM_SECRET_ACCESS_KEY;

      if (!accessKeyId || !secretAccessKey) {
        ctx.ui.notify(
          "Missing LITESTREAM_ACCESS_KEY_ID or LITESTREAM_SECRET_ACCESS_KEY env vars",
          "error",
        );
        return;
      }

      // ── Fetch objects with loader UI ────────────────────────────────────

      const objects = await ctx.ui.custom<S3Object[] | null>(
        (tui, theme, _kb, done) => {
          const loader = new BorderedLoader(
            tui,
            theme,
            "Fetching backup list from S3...",
          );
          loader.onAbort = () => done(null);

          const doFetch = async (): Promise<S3Object[]> => {
            const client = new S3Client({
              region: S3_REGION,
              endpoint: S3_ENDPOINT,
              credentials: { accessKeyId, secretAccessKey },
              forcePathStyle: true,
            });
            return listAllObjects(client, loader.signal);
          };

          doFetch()
            .then(done)
            .catch((err) => {
              console.error("[s3-browser] Fetch failed:", err);
              done(null);
            });

          return loader;
        },
      );

      if (objects === null) {
        ctx.ui.notify("Cancelled or fetch failed — check logs for details", "info");
        return;
      }

      if (objects.length === 0) {
        ctx.ui.notify("No backup files found in bucket", "info");
        return;
      }

      // ── Build the file list UI ──────────────────────────────────────────

      const totalSize = objects.reduce((sum, o) => sum + o.size, 0);

      const items: SelectItem[] = objects.map((obj) => ({
        value: obj.key,
        label: displayKey(obj.key),
        description: `${humanSize(obj.size)}  │  ${formatDate(obj.lastModified)}`,
      }));

      // Summary header line
      const summary = `${objects.length} files  ·  ${humanSize(totalSize)} total`;

      const selectedKey = await ctx.ui.custom<string | null>((tui, theme, _kb, done) => {
        const container = new Container();

        // Top border
        container.addChild(
          new DynamicBorder((s: string) => theme.fg("accent", s)),
        );

        // Header
        container.addChild(
          new Text(theme.fg("accent", theme.bold("S3 Backups — ffmusiclibrary/prod/")), 1, 0),
        );
        container.addChild(
          new Text(theme.fg("muted", summary), 1, 0),
        );

        // Spacer before list
        container.addChild(
          new Text(theme.fg("dim", "─".repeat(40)), 1, 0),
        );

        // SelectList
        const selectList = new SelectList(items, Math.min(items.length, 20), {
          selectedPrefix: (t: string) => theme.fg("accent", t),
          selectedText: (t: string) => theme.fg("accent", t),
          description: (t: string) => theme.fg("muted", t),
          scrollInfo: (t: string) => theme.fg("dim", t),
          noMatch: (t: string) => theme.fg("warning", t),
        });
        selectList.onSelect = (item) => done(item.value);
        selectList.onCancel = () => done(null);
        container.addChild(selectList);

        // Footer hint
        container.addChild(
          new Text(
            theme.fg("dim", "↑↓ navigate  ·  enter select  ·  esc close"),
            1,
            0,
          ),
        );

        // Bottom border
        container.addChild(
          new DynamicBorder((s: string) => theme.fg("accent", s)),
        );

        return {
          render(width: number) {
            return container.render(width);
          },
          invalidate() {
            container.invalidate();
          },
          handleInput(data: string) {
            selectList.handleInput(data);
            tui.requestRender();
          },
        };
      });

      if (selectedKey) {
        const obj = objects.find((o) => o.key === selectedKey);
        if (obj) {
          ctx.ui.notify(
            `${displayKey(obj.key)}  —  ${humanSize(obj.size)}  —  ${formatDate(obj.lastModified)}`,
            "info",
          );
        }
      }
    },
  });
}