//
//  TravelAlbumAIRetouchTemplateViewModel.swift
//  suixinkan
//

import Foundation

/// AI 修图模板类别，决定页面分组、选择规则和提交字段。
enum TravelAlbumAIRetouchTemplateCategory: Int, Sendable, Hashable {
    case refined
    case atmosphere
    case cover

    var title: String {
        switch self {
        case .refined: "原图精修"
        case .atmosphere: "氛围感修图"
        case .cover: "封面风格模板"
        }
    }
}

/// AI 修图模板选择状态，负责实时加载、单选规则、校验和任务提交。
final class TravelAlbumAIRetouchTemplateViewModel {
    private(set) var refinedTemplates: [TravelAlbumAIRetouchTemplate] = []
    private(set) var atmosphereTemplates: [TravelAlbumAIRetouchTemplate] = []
    private(set) var coverTemplates: [TravelAlbumAIRetouchTemplate] = []
    private(set) var selectedRefinedTemplateId: Int?
    private(set) var selectedAtmosphereTemplateId: Int?
    private(set) var selectedCoverTemplateId: Int?
    private(set) var isLoading = false
    private(set) var isSubmitting = false
    private(set) var loadErrorMessage: String?

    let albumId: Int
    let scenicId: Int
    let materialIds: [Int]

    var onStateChange: (() -> Void)?
    var onShowMessage: ((String) -> Void)?
    var onSubmitted: (() -> Void)?

    /// 创建模板选择状态；素材 ID 会排序并去重，确保提交稳定。
    init(albumId: Int, scenicId: Int, materialIds: [Int]) {
        self.albumId = albumId
        self.scenicId = scenicId
        self.materialIds = Array(Set(materialIds)).sorted()
    }

    /// 选中不少于四张素材时才展示并要求选择封面模板。
    var showsCoverTemplates: Bool {
        materialIds.count >= 4
    }

    /// 当前必选模板缺失时用于底部提示的文案。
    var validationMessage: String? {
        guard !isLoading, loadErrorMessage == nil else { return nil }
        if refinedTemplates.isEmpty || selectedRefinedTemplateId == nil {
            return "暂无可用的原图精修模板"
        }
        if showsCoverTemplates, coverTemplates.isEmpty || selectedCoverTemplateId == nil {
            return "暂无可用的封面风格模板"
        }
        return nil
    }

    /// 是否满足提交条件。
    var canSubmit: Bool {
        !isLoading
            && !isSubmitting
            && loadErrorMessage == nil
            && !materialIds.isEmpty
            && selectedRefinedTemplateId != nil
            && (!showsCoverTemplates || selectedCoverTemplateId != nil)
    }

    /// 实时拉取当前景区模板并按规则设置默认选择。
    func loadTemplates(api: any TravelAlbumServing) async {
        guard scenicId > 0 else {
            loadErrorMessage = "请先选择景区"
            notifyStateChange()
            return
        }
        guard !isLoading else { return }
        isLoading = true
        loadErrorMessage = nil
        notifyStateChange()

        do {
            let response = try await api.aiRetouchTemplates(scenicId: scenicId)
            refinedTemplates = response.refinedTemplates
            atmosphereTemplates = response.atmosphereTemplates
            coverTemplates = response.coverTemplates
            selectedRefinedTemplateId = refinedTemplates.first?.id
            selectedAtmosphereTemplateId = nil
            selectedCoverTemplateId = showsCoverTemplates ? coverTemplates.first?.id : nil
            isLoading = false
            notifyStateChange()
        } catch is CancellationError {
            isLoading = false
            notifyStateChange()
        } catch {
            refinedTemplates = []
            atmosphereTemplates = []
            coverTemplates = []
            selectedRefinedTemplateId = nil
            selectedAtmosphereTemplateId = nil
            selectedCoverTemplateId = nil
            isLoading = false
            loadErrorMessage = error.localizedDescription.isEmpty ? "模板加载失败" : error.localizedDescription
            notifyStateChange()
        }
    }

    /// 返回指定分组的模板。
    func templates(for category: TravelAlbumAIRetouchTemplateCategory) -> [TravelAlbumAIRetouchTemplate] {
        switch category {
        case .refined: refinedTemplates
        case .atmosphere: atmosphereTemplates
        case .cover: coverTemplates
        }
    }

    /// 返回指定分组当前选中的模板 ID。
    func selectedTemplateId(for category: TravelAlbumAIRetouchTemplateCategory) -> Int? {
        switch category {
        case .refined: selectedRefinedTemplateId
        case .atmosphere: selectedAtmosphereTemplateId
        case .cover: selectedCoverTemplateId
        }
    }

    /// 选择模板；氛围感模板再次点击时取消，必选分组保持单选。
    func toggleTemplate(id: Int, category: TravelAlbumAIRetouchTemplateCategory) {
        guard templates(for: category).contains(where: { $0.id == id }) else { return }
        switch category {
        case .refined:
            selectedRefinedTemplateId = id
        case .atmosphere:
            selectedAtmosphereTemplateId = selectedAtmosphereTemplateId == id ? nil : id
        case .cover:
            guard showsCoverTemplates else { return }
            selectedCoverTemplateId = id
        }
        notifyStateChange()
    }

    /// 提交 AI 修图任务，成功后通知页面退出选择态。
    func submit(api: any TravelAlbumServing) async {
        guard !isSubmitting else { return }
        guard let refinedTemplateId = selectedRefinedTemplateId else {
            onShowMessage?("请选择原图精修模板")
            return
        }
        guard !showsCoverTemplates || selectedCoverTemplateId != nil else {
            onShowMessage?("请选择封面风格模板")
            return
        }
        guard !materialIds.isEmpty else {
            onShowMessage?("请选择要修图的照片")
            return
        }

        isSubmitting = true
        notifyStateChange()
        defer {
            isSubmitting = false
            notifyStateChange()
        }

        do {
            try await api.submitAIRetouch(
                TravelAlbumAIRetouchRequest(
                    userEquityTravelId: albumId,
                    materialIds: materialIds,
                    refinedTemplateId: refinedTemplateId,
                    atmosphereTemplateId: selectedAtmosphereTemplateId,
                    aiPreviewTabs: showsCoverTemplates ? selectedCoverTemplateId : nil
                )
            )
            onSubmitted?()
        } catch is CancellationError {
            return
        } catch {
            onShowMessage?(error.localizedDescription.isEmpty ? "AI修图任务提交失败" : error.localizedDescription)
        }
    }

    private func notifyStateChange() {
        onStateChange?()
    }
}