import type { EditorView } from "@codemirror/view";

export type PlainleafEditorAction =
  | "undo"
  | "redo"
  | "heading-1"
  | "heading-2"
  | "bold"
  | "italic"
  | "bullet-list"
  | "numbered-list"
  | "task-list"
  | "quote"
  | "code"
  | "link"
  | "image";

const blockPrefix =
  /^\s*(?:#{1,6}\s+|[-*+]\s+(?:\[[ xX]\]\s+)?|\d+[.)]\s+|>\s+)?/;

function replaceSelectedLines(
  view: EditorView,
  makePrefix: (index: number) => string,
  activePrefix: RegExp,
): void {
  const selection = view.state.selection.main;
  const firstLine = view.state.doc.lineAt(selection.from);
  const lastPosition = Math.max(selection.from, selection.to - 1);
  const lastLine = view.state.doc.lineAt(lastPosition);
  const source = view.state.doc.sliceString(firstLine.from, lastLine.to);
  const lines = source.split("\n");
  const remove = lines.every((line) => !line.trim() || activePrefix.test(line));
  const replacement = lines
    .map((line, index) => {
      if (!line.trim()) return line;
      const content = line.replace(blockPrefix, "");
      return remove ? content : `${makePrefix(index)}${content}`;
    })
    .join("\n");

  view.dispatch({
    changes: { from: firstLine.from, to: lastLine.to, insert: replacement },
    selection: {
      anchor: firstLine.from,
      head: firstLine.from + replacement.length,
    },
  });
}

function wrapSelection(
  view: EditorView,
  before: string,
  after = before,
  placeholder = "文字",
): void {
  const selection = view.state.selection.main;
  const selected = view.state.doc.sliceString(selection.from, selection.to);
  const text = selected || placeholder;
  const insert = `${before}${text}${after}`;
  view.dispatch({
    changes: { from: selection.from, to: selection.to, insert },
    selection: selected
      ? {
          anchor: selection.from + before.length,
          head: selection.to + before.length,
        }
      : {
          anchor: selection.from + before.length,
          head: selection.from + before.length + placeholder.length,
        },
  });
}

export function applyPlainleafEditorAction(
  view: EditorView,
  action: PlainleafEditorAction,
): boolean {
  switch (action) {
    case "heading-1":
      replaceSelectedLines(view, () => "# ", /^\s*#\s+/);
      break;
    case "heading-2":
      replaceSelectedLines(view, () => "## ", /^\s*##\s+/);
      break;
    case "bullet-list":
      replaceSelectedLines(view, () => "- ", /^\s*[-*+]\s+/);
      break;
    case "numbered-list":
      replaceSelectedLines(view, (index) => `${index + 1}. `, /^\s*\d+[.)]\s+/);
      break;
    case "task-list":
      replaceSelectedLines(view, () => "- [ ] ", /^\s*[-*+]\s+\[[ xX]\]\s+/);
      break;
    case "quote":
      replaceSelectedLines(view, () => "> ", /^\s*>\s+/);
      break;
    case "bold":
      wrapSelection(view, "**");
      break;
    case "italic":
      wrapSelection(view, "_");
      break;
    case "code": {
      const selection = view.state.selection.main;
      const selected = view.state.doc.sliceString(selection.from, selection.to);
      if (selected.includes("\n"))
        wrapSelection(view, "```\n", "\n```", "代码");
      else wrapSelection(view, "`", "`", "代码");
      break;
    }
    case "link": {
      const selection = view.state.selection.main;
      const selected = view.state.doc.sliceString(selection.from, selection.to);
      const label = selected || "链接文字";
      const insert = `[${label}](https://)`;
      const urlFrom = selection.from + label.length + 3;
      view.dispatch({
        changes: { from: selection.from, to: selection.to, insert },
        selection: { anchor: urlFrom, head: urlFrom + 8 },
      });
      break;
    }
    case "undo":
    case "redo":
    case "image":
      return false;
  }
  view.focus();
  return true;
}