"use client";
import type { ExportFormat } from "@/lib/client/types";
import { toast } from "@/components/ui/toast";

/** Client-side export formats: the server formats plus `pdf` (= HTML opened in a new tab + `window.print()`). */
export type ClientExportFormat = ExportFormat | "pdf";

export interface ExportOption {
  format: ClientExportFormat;
  label: string;
  hint: string;
  description: string;
}

export const EXPORT_OPTIONS: ExportOption[] = [
  { format: "markdown", label: "Markdown", hint: ".md", description: "Readable transcript with headings and code blocks." },
  { format: "txt", label: "Plain text", hint: ".txt", description: "No markup, easy to paste anywhere." },
  { format: "json", label: "JSON", hint: ".json", description: "Full data: messages, parts, usage, settings." },
  { format: "html", label: "HTML", hint: ".html", description: "Self-contained page with print styles." },
  { format: "pdf", label: "PDF (print)", hint: "Print dialog", description: "Opens a print-optimized page — choose “Save as PDF”." },
];

export function exportUrl(conversationId: string, format: ClientExportFormat, opts: { download?: boolean; print?: boolean } = {}): string {
  const sp = new URLSearchParams();
  sp.set("format", format === "pdf" ? "html" : format);
  if (opts.download) sp.set("download", "1");
  if (opts.print) sp.set("print", "1");
  return `/api/conversations/${encodeURIComponent(conversationId)}/export?${sp.toString()}`;
}

function filenameFrom(res: Response, fallback: string): string {
  const cd = res.headers.get("content-disposition") ?? "";
  return /filename="?([^";]+)"?/.exec(cd)?.[1] ?? fallback;
}

async function download(url: string, fallbackName: string) {
  const res = await fetch(url, { credentials: "same-origin" });
  if (!res.ok) {
    let msg = `Export failed (${res.status})`;
    try {
      const body = (await res.json()) as { error?: { message?: string } };
      if (body.error?.message) msg = body.error.message;
    } catch {
      /* not json */
    }
    throw new Error(msg);
  }
  const blob = await res.blob();
  const a = document.createElement("a");
  a.href = URL.createObjectURL(blob);
  a.download = filenameFrom(res, fallbackName);
  document.body.appendChild(a);
  a.click();
  a.remove();
  setTimeout(() => URL.revokeObjectURL(a.href), 1000);
}

/**
 * Export a conversation from the browser.
 * - json / markdown / txt / html → file download
 * - pdf → opens the HTML export in a new tab which triggers `window.print()` ("Save as PDF"). Falls back to an
 *   HTML download when the pop-up is blocked.
 * Shows toasts; resolves when done. Throws only on network/API failure (already toasted).
 */
export async function exportConversation(conversationId: string, format: ClientExportFormat): Promise<void> {
  try {
    if (format === "pdf") {
      const w = window.open(exportUrl(conversationId, "pdf", { print: true }), "_blank", "noopener");
      if (!w) {
        await download(exportUrl(conversationId, "html", { download: true }), "conversation.html");
        toast.warning("Pop-up blocked", "The HTML version was downloaded instead — open it and use Print → Save as PDF.");
      }
      return;
    }
    const ext = format === "markdown" ? "md" : format;
    await download(exportUrl(conversationId, format, { download: true }), `conversation.${ext}`);
    toast.success("Export ready", "Your download should start now.");
  } catch (e) {
    toast.error("Export failed", e instanceof Error ? e.message : undefined);
    throw e;
  }
}