import React, { useCallback, useEffect, useMemo, useState } from "react";
import { createPortal } from "react-dom";
import type { ReactNode } from "react";
import ReactMarkdown from "react-markdown";
import remarkGfm from "remark-gfm";
import { Download, FileText, Loader2, X } from "lucide-react";

import { apiFetch } from "@/core/api/fetch-client";
import {
  downloadMermaidSvgFile,
  isMermaidFile,
  renderMermaidToSvg,
} from "@/core/utils/mermaid";
import {
  createMarkdownAnchorResolver,
  isInPageAnchor,
  scrollToInPageAnchor,
} from "@/core/utils/markdown";
import { buildArtifactDownloadUrl } from "@/roundtable-planning/api/multi-agent";

interface ArtifactPreviewModalProps {
  /** The thread that owns the artifact. Both fetch and download URLs use it. */
  threadId: string;
  /** Virtual path under the sandbox (e.g. `mnt/user-data/outputs/foo.md`). */
  path: string;
  /** Bare filename — shown in the modal header. */
  name: string;
  /** Mime type from the listing; drives the renderer choice. */
  mimeType: string | null;
  onClose: () => void;
}

function extractTextFromChildren(children: ReactNode): string {
  if (typeof children === "string" || typeof children === "number") return String(children);
  if (Array.isArray(children)) return children.map(extractTextFromChildren).join("");
  return "";
}

function createMarkdownComponents(content: string) {
  const anchorResolver = createMarkdownAnchorResolver(content);
  const heading = (level: 1 | 2 | 3 | 4 | 5 | 6, className: string) => {
    const Tag = `h${level}` as const;
    return ({ children, id }: any) => (
      <Tag id={id ?? anchorResolver.getHeadingId(level, extractTextFromChildren(children))} className={className}>
        {children}
      </Tag>
    );
  };

  return {
  p: ({ children }: any) => <p className="my-1.5 whitespace-pre-wrap leading-relaxed">{children}</p>,
  ul: ({ children }: any) => <ul className="list-disc pl-5 my-1.5 space-y-1">{children}</ul>,
  ol: ({ children }: any) => <ol className="list-decimal pl-5 my-1.5 space-y-1">{children}</ol>,
  li: ({ children }: any) => <li className="leading-snug">{children}</li>,
  h1: heading(1, "text-base font-bold mt-3 mb-2 scroll-mt-4"),
  h2: heading(2, "text-sm font-bold mt-3 mb-1.5 scroll-mt-4"),
  h3: heading(3, "text-xs font-bold mt-2 mb-1 scroll-mt-4"),
  h4: heading(4, "text-xs font-bold mt-1.5 mb-1 scroll-mt-4"),
  strong: ({ children }: any) => <strong className="font-bold text-slate-900">{children}</strong>,
  em: ({ children }: any) => <em className="italic">{children}</em>,
  code: ({ children, className }: any) => {
    const isBlock = /language-/.test(className ?? "");
    if (isBlock) {
      return (
        <pre className="bg-slate-100 text-slate-800 rounded-md p-3 my-2 overflow-x-auto text-[12px] font-mono">
          <code>{children}</code>
        </pre>
      );
    }
    return <code className="bg-slate-100 text-slate-800 rounded px-1 py-0.5 text-[12px] font-mono">{children}</code>;
  },
  blockquote: ({ children }: any) => (
    <blockquote className="border-l-2 border-slate-300 pl-3 my-2 text-slate-600 italic">{children}</blockquote>
  ),
  a: ({ children, href }: any) => {
    const resolvedHref = anchorResolver.resolveHref(href, extractTextFromChildren(children));
    if (resolvedHref === null) {
      return (
        <span
          className="text-primary/80 underline decoration-dotted underline-offset-2 cursor-not-allowed"
          title="未在当前 Markdown 中找到对应章节"
        >
          {children}
        </span>
      );
    }
    const finalHref = resolvedHref ?? href;
    const isExternal = typeof href === "string" && /^https?:\/\//i.test(href);
    return (
      <a
        href={finalHref}
        target={isExternal ? "_blank" : undefined}
        rel={isExternal ? "noopener noreferrer" : undefined}
        className="text-primary underline hover:opacity-80"
        onClick={(event) => {
          if (isInPageAnchor(finalHref)) {
            event.preventDefault();
            scrollToInPageAnchor(event.currentTarget, finalHref);
          }
        }}
      >
        {children}
      </a>
    );
  },
  table: ({ children }: any) => <table className="my-2 border-collapse text-[12px] w-full">{children}</table>,
  th: ({ children }: any) => (
    <th className="border border-slate-300 px-2 py-1 bg-slate-50 font-bold text-left">{children}</th>
  ),
  td: ({ children }: any) => <td className="border border-slate-200 px-2 py-1">{children}</td>,
  hr: () => <hr className="my-3 border-slate-200" />,
  };
}

function isMarkdown(mimeType: string | null, name: string): boolean {
  if (mimeType === "text/markdown") return true;
  return /\.(md|markdown)$/i.test(name);
}

function isMermaid(mimeType: string | null, name: string): boolean {
  if (mimeType === "text/vnd.mermaid") return true;
  return isMermaidFile(name);
}

export const ArtifactPreviewModal: React.FC<ArtifactPreviewModalProps> = ({
  threadId,
  path,
  name,
  mimeType,
  onClose,
}) => {
  const [content, setContent] = useState<string | null>(null);
  const [loading, setLoading] = useState<boolean>(true);
  const [error, setError] = useState<string | null>(null);
  const [mermaidSvg, setMermaidSvg] = useState<string | null>(null);

  // Esc closes the modal. Attached once per mount.
  useEffect(() => {
    const onKey = (e: KeyboardEvent) => {
      if (e.key === "Escape") onClose();
    };
    document.addEventListener("keydown", onKey);
    return () => document.removeEventListener("keydown", onKey);
  }, [onClose]);

  // Fetch the artifact body via the same URL the original download link used.
  // The GET endpoint already returns text/* as decoded UTF-8, so res.text()
  // gives us a renderable string directly.
  useEffect(() => {
    let cancelled = false;
    const ctrl = new AbortController();
    setLoading(true);
    setError(null);
    setContent(null);

    (async () => {
      try {
        const url = buildArtifactDownloadUrl(threadId, path);
        const res = await apiFetch(url, { method: "GET", signal: ctrl.signal });
        if (!res.ok) {
          throw new Error(`HTTP ${res.status}`);
        }
        const text = await res.text();
        if (!cancelled) setContent(text);
      } catch (err) {
        if (cancelled || (err as Error).name === "AbortError") return;
        setError((err as Error).message);
      } finally {
        if (!cancelled) setLoading(false);
      }
    })();

    return () => {
      cancelled = true;
      ctrl.abort();
    };
  }, [threadId, path]);

  const handleDownload = useCallback(() => {
    if (typeof window === "undefined") return;
    if (isMermaid(mimeType, name) && content) {
      void downloadMermaidSvgFile(content, name).catch((err) => {
        setError((err as Error).message);
      });
      return;
    }
    const url = buildArtifactDownloadUrl(threadId, path, { download: true });
    window.open(url, "_blank", "noopener,noreferrer");
  }, [content, mimeType, name, path, threadId]);

  const renderAsMarkdown = isMarkdown(mimeType, name);
  const renderAsMermaid = isMermaid(mimeType, name);

  useEffect(() => {
    if (!renderAsMermaid || !content) {
      setMermaidSvg(null);
      return;
    }

    let cancelled = false;
    void renderMermaidToSvg(content)
      .then((svg) => {
        if (!cancelled) setMermaidSvg(svg);
      })
      .catch((err) => {
        if (!cancelled) setError((err as Error).message);
      });

    return () => {
      cancelled = true;
    };
  }, [content, renderAsMermaid]);
  const markdownComponents = useMemo(
    () => createMarkdownComponents(content ?? ""),
    [content],
  );

  // 经 portal 挂到 body：脱离会商页 <main>(`relative z-0`) 的层叠上下文，
  // 否则 fixed 弹窗会被会商页头(z-40)/全局顶栏(z-45)盖住顶部。
  return createPortal(
    <div
      className="fixed inset-0 z-[100] flex items-center justify-center bg-slate-900/40 backdrop-blur-sm p-6"
      onMouseDown={(e) => {
        // Only close on outer-overlay click — clicks inside the modal panel
        // bubble up here too, so check the target.
        if (e.target === e.currentTarget) onClose();
      }}
    >
      <div className="bg-white rounded-2xl shadow-2xl w-full max-w-3xl max-h-[80vh] flex flex-col overflow-hidden">
        {/* Header */}
        <div className="shrink-0 px-5 py-3.5 border-b border-slate-150 flex items-center justify-between gap-3 bg-gradient-to-r from-slate-50 to-white">
          <div className="flex items-center gap-2 min-w-0">
            <FileText className="w-4 h-4 text-primary shrink-0" />
            <span className="text-sm font-bold text-slate-800 truncate" title={name}>{name}</span>
          </div>
          <div className="flex items-center gap-1.5 shrink-0">
            <button
              type="button"
              onClick={handleDownload}
              className="bg-white border border-slate-200 text-slate-600 hover:bg-slate-50 text-[11px] font-bold px-2.5 py-1.5 rounded-lg flex items-center gap-1 transition"
              title="下载原文件"
            >
              <Download className="w-3 h-3" />
              下载
            </button>
            <button
              type="button"
              onClick={onClose}
              className="p-1.5 text-slate-500 hover:text-slate-800 hover:bg-slate-100 rounded-lg transition"
              aria-label="关闭"
            >
              <X className="w-4 h-4" />
            </button>
          </div>
        </div>

        {/* Body */}
        <div
          data-markdown-anchor-root
          className="flex-1 min-h-0 overflow-y-auto px-5 py-4 text-sm text-slate-700"
        >
          {loading ? (
            <div className="flex items-center justify-center gap-2 py-12 text-slate-400">
              <Loader2 className="w-4 h-4 animate-spin text-primary" />
              <span className="text-xs">正在加载文件内容…</span>
            </div>
          ) : error ? (
            <div className="text-rose-600 text-xs py-6 text-center">
              加载失败:{error}
            </div>
          ) : content === null ? null : renderAsMermaid ? (
            mermaidSvg ? (
              <div
                className="rounded-2xl border border-slate-200 bg-white p-4 shadow-sm"
                dangerouslySetInnerHTML={{ __html: mermaidSvg }}
              />
            ) : (
              <div className="flex items-center justify-center gap-2 py-12 text-slate-400">
                <Loader2 className="w-4 h-4 animate-spin text-primary" />
                <span className="text-xs">正在生成图表预览</span>
              </div>
            )
          ) : renderAsMarkdown ? (
            <ReactMarkdown remarkPlugins={[remarkGfm]} components={markdownComponents}>

              {content}
            </ReactMarkdown>
          ) : (
            <pre className="whitespace-pre-wrap break-words text-xs text-slate-700 font-mono">{content}</pre>
          )}
        </div>
      </div>
    </div>,
    document.body,
  );
};