//
//  QuickLocationTabBar.swift
//  QuickLocation
//

import UIKit

protocol QuickLocationTabBarDelegate: AnyObject {
    func tabBar(_ tabBar: QuickLocationTabBar, didSelectTabAt index: Int)
}

final class QuickLocationTabBar: UIView {

    struct TabItem {
        let title: String
        let image: UIImage?
        let selectedImage: UIImage?

        init(title: String, image: UIImage?, selectedImage: UIImage? = nil) {
            self.title = title
            self.image = image
            self.selectedImage = selectedImage ?? image
        }
    }

    // MARK: - Design Constants (in iOS points, from Lanhu @2x 容器 2)
    private let barContentHeight: CGFloat = 56
    private let containerCornerRadius: CGFloat = 28
    private let horizontalInset: CGFloat = 18
    private let iconSize: CGFloat = 32
    private let iconLabelSpacing: CGFloat = 4
    private let labelHeight: CGFloat = 11

    private let selectedTextColor = UIColor(hexStr: "#1A1A1A")
    private let unselectedTextColor = UIColor(hexStr: "#AAAAAA")

    private let selectedFont = UIFont(name: "PingFangSC-Semibold", size: 11)
        ?? UIFont.systemFont(ofSize: 11, weight: .semibold)
    private let unselectedFont = UIFont.systemFont(ofSize: 11, weight: .regular)

    // MARK: - Properties
    weak var delegate: QuickLocationTabBarDelegate?

    private let items: [TabItem]
    private var tabViews: [UIView] = []
    private let containerView = UIView()

    private(set) var selectedIndex: Int = 0

    // MARK: - Init
    init(items: [TabItem]) {
        self.items = items
        super.init(frame: .zero)
        setupUI()
        updateSelection(animated: false)
    }

    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    // MARK: - Layout
    override var intrinsicContentSize: CGSize {
        CGSize(width: UIView.noIntrinsicMetric, height: barContentHeight + kSafeBottomMargin)
    }

    // MARK: - Setup
    private func setupUI() {
        backgroundColor = .clear

        containerView.backgroundColor = .white
        containerView.layer.cornerRadius = containerCornerRadius
        containerView.layer.shadowColor = UIColor(red: 0.059, green: 0.157, blue: 0.275, alpha: 0.1).cgColor
        containerView.layer.shadowOffset = .zero
        containerView.layer.shadowRadius = 8
        containerView.layer.shadowOpacity = 1
        addSubview(containerView)

        for (index, item) in items.enumerated() {
            let tabView = makeTabView(item: item, index: index)
            containerView.addSubview(tabView)
            tabViews.append(tabView)
        }

        containerView.translatesAutoresizingMaskIntoConstraints = false

        NSLayoutConstraint.activate([
            containerView.leadingAnchor.constraint(equalTo: leadingAnchor, constant: horizontalInset),
            containerView.trailingAnchor.constraint(equalTo: trailingAnchor, constant: -horizontalInset),
            containerView.bottomAnchor.constraint(equalTo: bottomAnchor, constant: -kSafeBottomMargin),
            containerView.heightAnchor.constraint(equalToConstant: barContentHeight)
        ])
    }

    private func makeTabView(item: TabItem, index: Int) -> UIView {
        let view = UIView()
        view.tag = index
        view.backgroundColor = .clear

        let imageView = UIImageView(image: item.image?.withRenderingMode(.alwaysOriginal))
        imageView.contentMode = .scaleAspectFit
        imageView.tag = 100
        view.addSubview(imageView)

        let label = UILabel()
        label.text = item.title
        label.font = unselectedFont
        label.textColor = unselectedTextColor
        label.textAlignment = .center
        label.tag = 200
        view.addSubview(label)

        let tap = UITapGestureRecognizer(target: self, action: #selector(tabTapped(_:)))
        view.addGestureRecognizer(tap)

        return view
    }

    // MARK: - Actions
    @objc private func tabTapped(_ gesture: UITapGestureRecognizer) {
        guard let view = gesture.view else { return }
        let index = view.tag
        guard index != selectedIndex else { return }
        selectedIndex = index
        updateSelection(animated: true)
        delegate?.tabBar(self, didSelectTabAt: index)
    }

    // MARK: - Selection
    func setSelectedIndex(_ index: Int, animated: Bool = true) {
        guard index != selectedIndex, index >= 0, index < items.count else { return }
        selectedIndex = index
        updateSelection(animated: animated)
    }

    private func updateSelection(animated: Bool) {
        for (i, view) in tabViews.enumerated() {
            let isSelected = i == selectedIndex
            if let imageView = view.viewWithTag(100) as? UIImageView {
                let img = isSelected ? items[i].selectedImage : items[i].image
                imageView.image = img?.withRenderingMode(.alwaysOriginal)
            }
            if let label = view.viewWithTag(200) as? UILabel {
                label.font = isSelected ? selectedFont : unselectedFont
                label.textColor = isSelected ? selectedTextColor : unselectedTextColor
            }
        }
    }

    override func layoutSubviews() {
        super.layoutSubviews()

        let containerWidth = containerView.bounds.width
        guard containerWidth > 0, !tabViews.isEmpty else { return }

        let tabWidth = containerWidth / CGFloat(tabViews.count)
        let tabHeight = containerView.bounds.height

        let totalHeight = iconSize + iconLabelSpacing + labelHeight
        let startY = (tabHeight - totalHeight) / 2

        for (i, view) in tabViews.enumerated() {
            view.frame = CGRect(
                x: CGFloat(i) * tabWidth,
                y: 0,
                width: tabWidth,
                height: tabHeight
            )

            if let imageView = view.viewWithTag(100) as? UIImageView {
                imageView.frame = CGRect(
                    x: (tabWidth - iconSize) / 2,
                    y: startY,
                    width: iconSize,
                    height: iconSize
                )
            }

            if let label = view.viewWithTag(200) as? UILabel {
                label.frame = CGRect(
                    x: 0,
                    y: startY + iconSize + iconLabelSpacing,
                    width: tabWidth,
                    height: labelHeight
                )
            }
        }
    }

    // MARK: - Hit Testing
    override func point(inside point: CGPoint, with event: UIEvent?) -> Bool {
        if containerView.frame.contains(point) {
            return true
        }
        let extendedBounds = bounds.insetBy(dx: 0, dy: -kSafeBottomMargin)
        return extendedBounds.contains(point)
    }
}