import UIKit

/// 负责管理文本选区、UITextView 代理和菜单定位。
/// 对齐 WXRead 的选择模型：UITextView 处理原生选择，高亮通过 attributed string 属性绘制。
final class RDEPUBTextSelectionController: NSObject, UITextViewDelegate {

    private var isSelectionFromInteraction = false
    private var selectionMenuAnchorRect: CGRect?

    /// 选区变化回调，通知视图层更新 UI
    var onSelectionChanged: ((RDEPUBSelection?) -> Void)?
    /// 获取当前页面数据
    var pageProvider: (() -> RDEPUBTextPage?)?

    // MARK: - UITextViewDelegate

    func textViewDidChangeSelection(_ textView: UITextView) {
        textViewDidChangeSelection(textView, page: pageProvider?())
    }

    func textViewDidChangeSelection(_ textView: UITextView, page: RDEPUBTextPage?) {
        guard !isSelectionFromInteraction else { return }
        guard let page else {
            onSelectionChanged?(nil)
            return
        }

        let selectedRange = textView.selectedRange
        guard selectedRange.location != NSNotFound,
              selectedRange.length > 0,
              let attributedText = textView.attributedText else {
            onSelectionChanged?(nil)
            return
        }

        let source = attributedText.string as NSString
        let selectedText = source.substring(with: selectedRange).trimmingCharacters(in: .whitespacesAndNewlines)
        guard !selectedText.isEmpty else {
            onSelectionChanged?(nil)
            return
        }

        let globalStart = page.pageStartOffset + selectedRange.location
        let globalEnd = globalStart + selectedRange.length
        let totalLength = max(page.chapterContent.length - 1, 1)
        let selection = RDEPUBSelection(
            location: RDEPUBLocation(
                href: page.href,
                progression: Double(globalStart) / Double(totalLength),
                lastProgression: Double(max(globalEnd - 1, globalStart)) / Double(totalLength),
                fragment: nil
            ),
            text: selectedText,
            rangeInfo: RDEPUBTextOffsetRangeInfo(href: page.href, start: globalStart, end: globalEnd).jsonString()
        )
        onSelectionChanged?(selection)
    }

    // MARK: - 选区清除

    func clearSelection() {
        isSelectionFromInteraction = false
        selectionMenuAnchorRect = nil
        UIMenuController.shared.setMenuVisible(false, animated: true)
        onSelectionChanged?(nil)
    }

    func clearSelection(textView: UITextView) {
        textView.selectedRange = NSRange(location: 0, length: 0)
        clearSelection()
    }

    // MARK: - 菜单显示

    func showSelectionMenuIfNeeded(
        in hostView: UIView,
        textView: UITextView,
        interactionController: RDEPUBPageInteractionController
    ) {
        guard textView.selectedRange.length > 0,
              let textRange = textView.selectedTextRange else { return }

        let rect = textView.firstRect(for: textRange)
        guard !rect.isNull, !rect.isEmpty else { return }

        let menuRect = hostView.convert(rect, from: textView)
        hostView.becomeFirstResponder()
        let menuController = UIMenuController.shared
        menuController.menuItems = [
            UIMenuItem(title: "拷贝", action: #selector(RDEPUBTextContentView.rd_copy(_:))),
            UIMenuItem(title: "高亮", action: #selector(RDEPUBTextContentView.rd_highlight(_:))),
            UIMenuItem(title: "批注", action: #selector(RDEPUBTextContentView.rd_annotate(_:)))
        ]
        menuController.setTargetRect(menuRect, in: hostView)
        menuController.setMenuVisible(true, animated: true)
    }
}