代码编辑器拖拽完全指南

/* 拖拽状态定义 */
interface DragState {
    isDragging: boolean;
    startPosition: Position | null;
    currentPosition: Position | null;
    dragType: 'move' | 'copy';
    selectedText: string;
}

class DragDropManager {
    constructor(editor) {
        this.editor = editor;
        this.state: DragState = {
            isDragging: false,
            startPosition: null,
            currentPosition: null,
            dragType: 'move',
            selectedText: ''
        };
    }
}

/* 处理拖拽开始 */
onDragStart(event: MouseEvent) {
    const selection = this.editor.getSelection();

    /* 只有选中文本时才启动拖拽 */
    if (selection && !selection.isEmpty()) {
        this.state.isDragging = true;
        this.state.startPosition = getPositionFromMouseEvent(event);
        this.state.selectedText = this.editor.getTextInRange(selection);

        /* 按住 Ctrl 键时是复制操作 */
        this.state.dragType = event.ctrlKey ? 'copy' : 'move';

        /* 设置拖拽数据 */
        event.dataTransfer?.setData('text/plain', this.state.selectedText);
        event.dataTransfer!.effectAllowed = this.state.dragType === 'copy'
            ? 'copy' : 'move';
    }
}

/* 处理拖拽过程 */
onDragOver(event: DragEvent) {
    if (!this.state.isDragging) return;

    event.preventDefault();
    this.state.currentPosition = getPositionFromMouseEvent(event);

    /* 显示插入标记 */
    this.showInsertionMarker(this.state.currentPosition);

    /* 更新拖拽光标 */
    event.dataTransfer!.dropEffect = this.state.dragType === 'copy'
        ? 'copy' : 'move';
}

/* 处理拖拽结束 */
onDragEnd(event: DragEvent) {
    this.hideInsertionMarker();

    if (this.state.currentPosition) {
        const startPos = this.state.startPosition!;
        const endPos = this.state.currentPosition;

        /* 移动或复制文本 */
        if (this.state.dragType === 'move') {
            this.moveText(startPos, endPos, this.state.selectedText);
        } else {
            this.copyText(endPos, this.state.selectedText);
        }
    }

    this.reset();
}

/* 移动文本到新位置 */
moveText(fromStart: Position, fromEnd: Position, toPos: Position) {
    /* 计算目标位置（可能需要调整因为原文本被删除） */
    let adjustedToPos = toPos;

    /* 如果目标在源文本之后，需要调整位置 */
    if (isPositionAfter(toPos, fromEnd)) {
        const sourceLength = getTextRangeLength(fromStart, fromEnd);
        adjustedToPos = adjustPosition(toPos, -sourceLength);
    }

    /* 先获取文本，然后删除源文本，最后插入到目标位置 */
    const text = this.editor.getTextInRange(fromStart, fromEnd);

    this.editor.executeOperation({
        type: 'composite',
        operations: [
            { type: 'delete', start: fromStart, end: fromEnd },
            { type: 'insert', position: adjustedToPos, text: text }
        ]
    });
}

/* 复制文本到新位置 */
copyText(position: Position, text: string) {
    this.editor.insertText(position, text);
}

/* 显示插入标记 */
showInsertionMarker(position: Position) {
    const coords = this.editor.positionToCoordinates(position);

    const marker = this.editor.getInsertionMarkerElement();
    marker.style.left = `${coords.left}px`;
    marker.style.top = `${coords.top}px`;
    marker.style.height = `${coords.height}px`;
    marker.style.display = 'block';

    /* 标记当前位置 */
    this.currentMarkerPosition = position;
}

/* 隐藏插入标记 */
hideInsertionMarker() {
    const marker = this.editor.getInsertionMarkerElement();
    marker.style.display = 'none';
}

/* 处理从外部拖入的文本 */
onDrop(event: DragEvent) {
    event.preventDefault();

    /* 获取拖入的文本 */
    const text = event.dataTransfer?.getData('text/plain');
    if (!text) return;

    /* 获取放置位置 */
    const position = getPositionFromMouseEvent(event);

    /* 插入文本 */
    this.editor.insertText(position, text);

    /* 聚焦编辑器 */
    this.editor.focus();
}