//
//  XSSearchViewController.swift
//  XSeri
//
//  Created by 长沙鸿瑶 on 2026/2/2.
//

import UIKit
import SnapKit
import LYEmptyView

final class XSSearchViewController: XSViewController {

    private enum Mode {
        case idle
        case suggest
        case result
    }

    private let headerView = XSSearchHeaderView()
    private let historyHotView = XSSearchHistoryHotView()

    private lazy var suggestionCollectionView: XSCollectionView = {
        let layout = UICollectionViewFlowLayout()
        layout.minimumLineSpacing = 12
        layout.minimumInteritemSpacing = 0
        layout.sectionInset = .init(top: 0, left: 16, bottom: 0, right: 16)
        let collectionView = XSCollectionView(frame: .zero, collectionViewLayout: layout)
        collectionView.isScrollEnabled = true
        collectionView.keyboardDismissMode = .onDrag
        collectionView.delegate = self
        collectionView.dataSource = self
        collectionView.register(XSSearchSuggestionCell.self, forCellWithReuseIdentifier: "XSSearchSuggestionCell")
        return collectionView
    }()

    private lazy var resultCollectionView: XSCollectionView = {
        let layout = UICollectionViewFlowLayout()
        layout.minimumLineSpacing = 16
        layout.minimumInteritemSpacing = 8
        layout.sectionInset = .init(top: 0, left: 16, bottom: 0, right: 16)
        let collectionView = XSCollectionView(frame: .zero, collectionViewLayout: layout)
        collectionView.isScrollEnabled = true
        collectionView.keyboardDismissMode = .onDrag
        collectionView.delegate = self
        collectionView.dataSource = self
        collectionView.register(XSSearchResultCell.self, forCellWithReuseIdentifier: "XSSearchResultCell")
        return collectionView
    }()

    private var history: [String] = []
    private var suggestionItems: [XSShortModel] = []
    private var resultItems: [XSShortModel] = []
    private var currentSuggestKeyword = ""
    private var currentResultKeyword = ""

    private var mode: Mode = .idle {
        didSet {
            xs_updateVisibility()
        }
    }

    private var suggestionTask: Task<Void, Never>?
    private var resultTask: Task<Void, Never>?
    private var hotTask: Task<Void, Never>?

    deinit {
        suggestionTask?.cancel()
        resultTask?.cancel()
        hotTask?.cancel()
    }

    override func viewDidLoad() {
        super.viewDidLoad()

        xs_setupUI()
        xs_bindData()
        xs_loadHistory()
        xs_loadHotSearches()
    }
    
    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        self.navigationController?.setNavigationBarHidden(true, animated: true)
    }
    
    
    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        let _ = self.headerView.becomeFirstResponder()
    }

}

extension XSSearchViewController {

    private func xs_setupUI() {
        view.addSubview(headerView)
        view.addSubview(historyHotView)
        view.addSubview(suggestionCollectionView)
        view.addSubview(resultCollectionView)

        headerView.snp.makeConstraints { make in
            make.top.equalToSuperview().offset(XSScreen.safeTop + 12)
            make.left.equalToSuperview().offset(16)
            make.right.equalToSuperview().offset(-16)
            make.height.equalTo(38)
        }

        historyHotView.snp.makeConstraints { make in
            make.top.equalTo(headerView.snp.bottom).offset(22)
            make.left.right.equalToSuperview()
        }

        suggestionCollectionView.snp.makeConstraints { make in
            make.top.equalTo(headerView.snp.bottom).offset(22)
            make.left.right.equalToSuperview()
            make.bottom.equalTo(view.safeAreaLayoutGuide)
        }

        resultCollectionView.snp.makeConstraints { make in
            make.top.equalTo(headerView.snp.bottom).offset(22)
            make.left.right.equalToSuperview()
            make.bottom.equalTo(view.safeAreaLayoutGuide)
        }

        // 搜索结果为空时显示空白样式
        resultCollectionView.ly_emptyView = XSEmpty.xs_emptyView()
        // 联想为空时显示空白样式
        suggestionCollectionView.ly_emptyView = XSEmpty.xs_emptyView()
    }

    private func xs_bindData() {
        headerView.placeholder = XSSearchData.searchPlaceholder
        headerView.didTapBack = { [weak self] in
            self?.navigationController?.popViewController(animated: true)
        }
        headerView.didBeginEditing = { [weak self] text in
            guard let self = self else { return }
            // 已经显示搜索结果时，不在进入编辑时立刻切换联想
            if self.mode == .result { return }
            self.xs_handleSuggest(text)
        }
        headerView.didChangeText = { [weak self] text in
            self?.xs_handleSuggest(text)
        }
        headerView.didTapSearch = { [weak self] text in
            self?.xs_submitSearch(text)
        }

        historyHotView.historyTitle = XSSearchData.recentTitle
        historyHotView.didTapClear = { [weak self] in
            self?.xs_clearHistory()
        }
        historyHotView.didSelectHistory = { [weak self] text in
            self?.headerView.text = text
            self?.xs_submitSearch(text)
        }
        historyHotView.didSelectHot = { [weak self] model in
            self?.xs_pushDetail(model: model)
        }
        historyHotView.hotTitle = XSSearchData.hotSearchesTitle
        xs_updateVisibility()
    }
}

// MARK: - Data
extension XSSearchViewController {

    private func xs_loadHotSearches() {
        hotTask?.cancel()
        hotTask = Task { [weak self] in
            // 热门榜单数据来源接口
            let hotList = await XSHomeAPI.requestHotSearchList() ?? []
            let topList = await XSHomeAPI.requestTopSearchList() ?? []
            
            guard !Task.isCancelled else { return } 
            await MainActor.run {
                self?.xs_updateHotSection(hotList: Array(hotList.prefix(5)), topList: Array(topList.prefix(5)))
            }
        }
    }

    private func xs_updateHotSection(hotList: [XSShortModel], topList: [XSShortModel]) {
        
        var arr: [XSSearchHotSection] = []
        
        if !hotList.isEmpty {
            arr.append(XSSearchHotSection(icon: UIImage(named: "hot_icon_03"), title: XSSearchData.hotSectionTitles[0], style: .gold, items: hotList))
        }
        if !topList.isEmpty {
            arr.append(XSSearchHotSection(icon: UIImage(named: "hot_icon_04"), title: XSSearchData.hotSectionTitles[1], style: .purple, items: topList))
        }
        historyHotView.hotSections = arr
        
        xs_updateVisibility()
    }

    private func xs_fetchSuggestions(_ keyword: String) {
        suggestionTask?.cancel()
        let expectedKeyword = keyword
        suggestionTask = Task { [weak self] in
            // 联想词同样走搜索接口
            let list = await XSHomeAPI.requestSearch(text: keyword) ?? []
            guard !Task.isCancelled else { return }
            await MainActor.run {
                guard let self = self,
                      self.mode == .suggest,
                      self.currentSuggestKeyword == expectedKeyword else {
                    return
                }
                self.suggestionItems = list
                self.suggestionCollectionView.reloadData()
            }
        }
    }

    private func xs_fetchResults(_ keyword: String) {
        resultTask?.cancel()
        let expectedKeyword = keyword
        resultTask = Task { [weak self] in
            // 搜索结果走搜索接口
            let list = await XSHomeAPI.requestSearch(text: keyword) ?? []
            guard !Task.isCancelled else { return }
            await MainActor.run {
                guard let self = self,
                      self.mode == .result,
                      self.currentResultKeyword == expectedKeyword else {
                    return
                }
                self.resultItems = list
                self.resultCollectionView.reloadData()
            }
        }
    }
}

// MARK: - Actions
extension XSSearchViewController {

    private func xs_handleSuggest(_ text: String?) {
        let keyword = (text ?? "").trimmingCharacters(in: .whitespacesAndNewlines)
        if keyword.isEmpty {
            suggestionTask?.cancel()
            resultTask?.cancel()
            currentSuggestKeyword = ""
            mode = .idle
            suggestionItems = []
            suggestionCollectionView.reloadData()
            return
        }

        resultTask?.cancel()
        resultItems = []
        resultCollectionView.reloadData()
        resultCollectionView.isHidden = true
        currentSuggestKeyword = keyword
        mode = .suggest
        suggestionCollectionView.isHidden = false
        xs_fetchSuggestions(keyword)
    }

    private func xs_submitSearch(_ text: String?) {
        let keyword = (text ?? "").trimmingCharacters(in: .whitespacesAndNewlines)
        guard !keyword.isEmpty else {
            mode = .idle
            return
        }

        suggestionTask?.cancel()
        suggestionItems = []
        suggestionCollectionView.reloadData()
        suggestionCollectionView.isHidden = true
        currentResultKeyword = keyword
        view.endEditing(true)
        mode = .result
        xs_addHistory(keyword)
        xs_fetchResults(keyword)
    }
}

// MARK: - History
extension XSSearchViewController {

    private func xs_loadHistory() {
        history = UserDefaults.standard.stringArray(forKey: XSSearchData.historyKey) ?? []
        historyHotView.historyTags = history
        xs_updateVisibility()
    }

    private func xs_addHistory(_ keyword: String) {
        // 搜索历史本地缓存，最多保留 10 条
        history.removeAll { $0.caseInsensitiveCompare(keyword) == .orderedSame }
        history.insert(keyword, at: 0)
        if history.count > 10 {
            history = Array(history.prefix(10))
        }
        UserDefaults.standard.set(history, forKey: XSSearchData.historyKey)
        historyHotView.historyTags = history
        xs_updateVisibility()
    }

    private func xs_clearHistory() {
        history = []
        UserDefaults.standard.removeObject(forKey: XSSearchData.historyKey)
        historyHotView.historyTags = []
        xs_updateVisibility()
    }
}

// MARK: - Layout
extension XSSearchViewController {

    private func xs_updateVisibility() {
        switch mode {
        case .idle:
            historyHotView.isHidden = !historyHotView.hasContent
            suggestionCollectionView.isHidden = true
            resultCollectionView.isHidden = true
            headerView.style = .home
        case .suggest:
            historyHotView.isHidden = true
            suggestionCollectionView.isHidden = false
            resultCollectionView.isHidden = true
            headerView.style = .input
        case .result:
            historyHotView.isHidden = true
            suggestionCollectionView.isHidden = true
            resultCollectionView.isHidden = false
            headerView.style = .input
        }
    }
}

// MARK: - UICollectionViewDelegate UICollectionViewDataSource
extension XSSearchViewController: UICollectionViewDelegate, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout {

    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        if collectionView == suggestionCollectionView {
            return suggestionItems.count
        }
        return resultItems.count
    }

    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        if collectionView == suggestionCollectionView {
            let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "XSSearchSuggestionCell", for: indexPath) as! XSSearchSuggestionCell
            let item = suggestionItems[indexPath.row]
            let keyword = headerView.text ?? ""
            cell.configure(model: item, keyword: keyword)
            return cell
        } else {
            let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "XSSearchResultCell", for: indexPath) as! XSSearchResultCell
            cell.configure(model: resultItems[indexPath.row])
            return cell
        }
    }

    func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
        if collectionView == suggestionCollectionView {
            let item = suggestionItems[indexPath.row]
            xs_pushDetail(model: item)
        } else if collectionView == resultCollectionView {
            let item = resultItems[indexPath.row]
            xs_pushDetail(model: item)
        }
    }

    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
        if collectionView == suggestionCollectionView {
            let width = XSScreen.width - 32
            return CGSize(width: floor(width), height: 104)
        } else {
            let width = (XSScreen.width - 32 - 16) / 3
            return CGSize(width: floor(width), height: 186)
        }
    }
}

// MARK: - Detail
extension XSSearchViewController {

    private func xs_pushDetail(model: XSShortModel) {
        let shortId = model.short_play_id ?? model.short_play_video_id ?? model.id
        guard let shortId = shortId, !shortId.isEmpty else { return }
        let controller = XSShortDetailViewController()
        controller.shortId = shortId
        navigationController?.pushViewController(controller, animated: true)
    }
}