import Foundation

/// 自动修图设置状态，负责加载真实精修模板、单选和配置校验，不直接创建修图任务。
final class TravelAlbumAutoRetouchSettingViewModel {
    /// 设置页当前层级。
    enum Stage: Sendable, Equatable {
        case mode
        case templates
    }

    let scenicId: Int
    let startsWithModeSelection: Bool
    private(set) var stage: Stage
    private(set) var templates: [TravelAlbumAIRetouchTemplate] = []
    private(set) var selectedTemplateId: Int?
    private(set) var isEnabled: Bool
    private(set) var isLoading = false
    private(set) var errorMessage: String?

    var onStateChange: (() -> Void)?

    /// 创建自动修图配置状态。
    init(
        scenicId: Int,
        configuration: TravelAlbumAutoRetouchConfiguration,
        startsWithModeSelection: Bool
    ) {
        self.scenicId = scenicId
        self.startsWithModeSelection = startsWithModeSelection
        self.stage = startsWithModeSelection ? .mode : .templates
        self.isEnabled = configuration.enabled
        self.selectedTemplateId = configuration.refinedTemplateId
    }

    /// 当前可提交配置；启用状态必须已经选择服务端模板。
    var pendingConfiguration: TravelAlbumAutoRetouchConfiguration? {
        if !isEnabled { return .disabled }
        guard let selectedTemplateId,
              templates.contains(where: { $0.id == selectedTemplateId }) else {
            return nil
        }
        return TravelAlbumAutoRetouchConfiguration(
            enabled: true,
            refinedTemplateId: selectedTemplateId
        )
    }

    /// 拉取当前景区的真实精修模板。
    func loadTemplates(api: any TravelAlbumServing) async {
        guard scenicId > 0 else {
            errorMessage = "请先选择景区"
            notify()
            return
        }
        guard !isLoading else { return }
        isLoading = true
        errorMessage = nil
        notify()
        defer {
            isLoading = false
            notify()
        }
        do {
            let response = try await api.aiRetouchTemplates(scenicId: scenicId)
            templates = response.refinedTemplates
            if !templates.contains(where: { $0.id == selectedTemplateId }) {
                selectedTemplateId = nil
            }
            if templates.isEmpty { errorMessage = "暂无可用的原图精修模板" }
        } catch is CancellationError {
            return
        } catch {
            templates = []
            errorMessage = error.localizedDescription.isEmpty ? "模板加载失败" : error.localizedDescription
        }
    }

    /// 选择一级修图方式。
    func selectMode(enabled: Bool) {
        isEnabled = enabled
        if enabled {
            stage = .templates
        } else {
            selectedTemplateId = nil
        }
        notify()
    }

    /// 选择一个真实精修模板。
    func selectTemplate(id: Int) {
        guard templates.contains(where: { $0.id == id }) else { return }
        isEnabled = true
        selectedTemplateId = id
        notify()
    }

    /// 从模板列表返回修图方式层级。
    func returnToModeSelection() {
        guard startsWithModeSelection else { return }
        stage = .mode
        notify()
    }

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