"use client";

import { useRef, useState, useCallback, useEffect, type ReactNode } from "react";
import {
  Bold,
  Italic,
  Code,
  Quote,
  List,
  Heading2,
  Link as LinkIcon,
  Image as ImageIcon,
  Eye,
  Pencil,
  Maximize2,
  Minimize2,
} from "lucide-react";
import { apiUploadPostImage } from "@/lib/api";
import { toast } from "@/lib/toast";
import MarkdownBodyClient from "@/components/MarkdownBodyClient";

type MarkdownEditorProps = {
  value: string;
  onChange: (value: string) => void;
  placeholder?: string;
  rows?: number;
  disabled?: boolean;
  onSubmitShortcut?: () => void;
  id?: string;
};

type WrapOpts = {
  before: string;
  after?: string;
  placeholder?: string;
  linePrefix?: string;
};

function applyWrap(
  el: HTMLTextAreaElement,
  value: string,
  opts: WrapOpts
): { next: string; selStart: number; selEnd: number } {
  const start = el.selectionStart;
  const end = el.selectionEnd;
  const selected = value.slice(start, end);
  const after = opts.after ?? "";

  if (opts.linePrefix) {
    const block = selected || opts.placeholder || "列表项";
    const lines = block.split("\n").map((l) =>
      l.startsWith(opts.linePrefix!) ? l : `${opts.linePrefix}${l}`
    );
    const inserted = lines.join("\n");
    const next = value.slice(0, start) + inserted + value.slice(end);
    return {
      next,
      selStart: start,
      selEnd: start + inserted.length,
    };
  }

  const inner = selected || opts.placeholder || "";
  const inserted = opts.before + inner + after;
  const next = value.slice(0, start) + inserted + value.slice(end);
  const selStart = start + opts.before.length;
  const selEnd = selStart + inner.length;
  return { next, selStart, selEnd };
}

export default function MarkdownEditor({
  value,
  onChange,
  placeholder,
  rows = 16,
  disabled,
  onSubmitShortcut,
  id,
}: MarkdownEditorProps) {
  const taRef = useRef<HTMLTextAreaElement>(null);
  const fileRef = useRef<HTMLInputElement>(null);
  const [mode, setMode] = useState<"write" | "preview">("write");
  const [uploading, setUploading] = useState(false);
  const [fullscreen, setFullscreen] = useState(false);

  useEffect(() => {
    if (!fullscreen) return;
    const onKey = (e: KeyboardEvent) => {
      if (e.key === "Escape") {
        e.preventDefault();
        setFullscreen(false);
      }
    };
    const prev = document.body.style.overflow;
    document.body.style.overflow = "hidden";
    window.addEventListener("keydown", onKey);
    return () => {
      document.body.style.overflow = prev;
      window.removeEventListener("keydown", onKey);
    };
  }, [fullscreen]);

  const runWrap = useCallback(
    (opts: WrapOpts) => {
      const el = taRef.current;
      if (!el || disabled) return;
      const { next, selStart, selEnd } = applyWrap(el, value, opts);
      onChange(next);
      requestAnimationFrame(() => {
        el.focus();
        el.setSelectionRange(selStart, selEnd);
      });
    },
    [value, onChange, disabled]
  );

  const insertAtCursor = useCallback(
    (text: string) => {
      const el = taRef.current;
      if (!el) {
        onChange(value + (value.endsWith("\n") || !value ? "" : "\n") + text);
        return;
      }
      const start = el.selectionStart;
      const end = el.selectionEnd;
      const padBefore = start > 0 && value[start - 1] !== "\n" ? "\n" : "";
      const padAfter = end < value.length && value[end] !== "\n" ? "\n" : "";
      const inserted = padBefore + text + padAfter;
      const next = value.slice(0, start) + inserted + value.slice(end);
      onChange(next);
      const caret = start + inserted.length;
      requestAnimationFrame(() => {
        el.focus();
        el.setSelectionRange(caret, caret);
      });
    },
    [value, onChange]
  );

  const handleImagePick = async (file: File | null) => {
    if (!file || disabled) return;
    if (!/^image\/(jpeg|png|webp)$/i.test(file.type)) {
      toast("仅支持 JPEG / PNG / WebP", "error");
      return;
    }
    if (file.size > 5 * 1024 * 1024) {
      toast("图片不能超过 5MB", "error");
      return;
    }
    setUploading(true);
    try {
      const res = await apiUploadPostImage(file);
      if (!res.url) {
        toast(res.error || "上传失败", "error");
        return;
      }
      const alt = file.name.replace(/\.[^.]+$/, "") || "图片";
      insertAtCursor(`![${alt}](${res.url})`);
      setMode("write");
      toast("图片已插入", "ok");
    } catch {
      toast("上传失败", "error");
    } finally {
      setUploading(false);
      if (fileRef.current) fileRef.current.value = "";
    }
  };

  const tools: {
    key: string;
    label: string;
    icon: ReactNode;
    onClick: () => void;
  }[] = [
    {
      key: "bold",
      label: "粗体",
      icon: <Bold size={15} />,
      onClick: () => runWrap({ before: "**", after: "**", placeholder: "粗体" }),
    },
    {
      key: "italic",
      label: "斜体",
      icon: <Italic size={15} />,
      onClick: () => runWrap({ before: "*", after: "*", placeholder: "斜体" }),
    },
    {
      key: "code",
      label: "行内代码",
      icon: <Code size={15} />,
      onClick: () => runWrap({ before: "`", after: "`", placeholder: "code" }),
    },
    {
      key: "quote",
      label: "引用",
      icon: <Quote size={15} />,
      onClick: () =>
        runWrap({ before: "", linePrefix: "> ", placeholder: "引用内容" }),
    },
    {
      key: "list",
      label: "列表",
      icon: <List size={15} />,
      onClick: () =>
        runWrap({ before: "", linePrefix: "- ", placeholder: "列表项" }),
    },
    {
      key: "h2",
      label: "二级标题",
      icon: <Heading2 size={15} />,
      onClick: () => runWrap({ before: "## ", after: "", placeholder: "标题" }),
    },
    {
      key: "link",
      label: "链接",
      icon: <LinkIcon size={15} />,
      onClick: () =>
        runWrap({ before: "[", after: "](https://)", placeholder: "链接文字" }),
    },
    {
      key: "image",
      label: uploading ? "上传中…" : "插入图片",
      icon: <ImageIcon size={15} />,
      onClick: () => fileRef.current?.click(),
    },
  ];

  return (
    <div className={`j13-md-editor${fullscreen ? " is-fullscreen" : ""}`}>
      <div className="j13-md-toolbar">
        <div className="flex items-center gap-0.5 flex-1 flex-wrap min-w-0">
          {tools.map((t) => (
            <button
              key={t.key}
              type="button"
              className="j13-md-tool"
              data-tip={t.label}
              aria-label={t.label}
              disabled={disabled || (t.key === "image" && uploading)}
              onClick={t.onClick}
            >
              {t.icon}
            </button>
          ))}
        </div>
        <div className="flex items-center gap-2 shrink-0">
          <div className="j13-md-mode" role="tablist" aria-label="编辑模式">
            <button
              type="button"
              role="tab"
              aria-selected={mode === "write"}
              className={mode === "write" ? "is-on" : ""}
              onClick={() => setMode("write")}
            >
              <Pencil size={12} /> 编写
            </button>
            <button
              type="button"
              role="tab"
              aria-selected={mode === "preview"}
              className={mode === "preview" ? "is-on" : ""}
              onClick={() => setMode("preview")}
            >
              <Eye size={12} /> 预览
            </button>
          </div>
          <button
            type="button"
            className="j13-md-tool"
            data-tip={fullscreen ? "退出全屏 (Esc)" : "全屏写作"}
            aria-label={fullscreen ? "退出全屏" : "全屏写作"}
            onClick={() => setFullscreen((v) => !v)}
          >
            {fullscreen ? <Minimize2 size={15} /> : <Maximize2 size={15} />}
          </button>
        </div>
      </div>

      <input
        ref={fileRef}
        type="file"
        accept="image/jpeg,image/png,image/webp"
        className="hidden"
        onChange={(e) => handleImagePick(e.target.files?.[0] ?? null)}
      />

      {mode === "write" ? (
        <textarea
          ref={taRef}
          id={id}
          value={value}
          disabled={disabled}
          rows={rows}
          placeholder={placeholder}
          className="j13-md-textarea"
          onChange={(e) => onChange(e.target.value)}
          onKeyDown={(e) => {
            if ((e.ctrlKey || e.metaKey) && e.key === "Enter") {
              e.preventDefault();
              onSubmitShortcut?.();
            }
          }}
        />
      ) : (
        <div className="j13-md-preview">
          {value.trim() ? (
            <MarkdownBodyClient content={value} />
          ) : (
            <p className="meta text-center py-16">暂无内容可预览</p>
          )}
        </div>
      )}

      <div className="j13-md-foot">
        <span>Markdown · Ctrl/⌘ + Enter 提交</span>
        <span className="tabular-nums">{value.length} 字</span>
      </div>
    </div>
  );
}