//
//  TravelAlbumPreviewModels.swift
//  suixinkan
//

import Foundation

/// 相册预览页横向滑动策略，由调用方通过配置注入。
enum TravelAlbumPreviewSwipeMode: Sendable, Equatable {
    /// 横滑只切换原图项目，关联图通过 Tab 切换。
    case projectsOnly
    /// 横滑依次切换当前项目的关联图，并在边界进入相邻项目原图。
    case includeVariants
}

/// 相册预览页配置。
struct TravelAlbumPreviewConfiguration: Sendable {
    let swipeMode: TravelAlbumPreviewSwipeMode

    /// 创建预览配置，默认只按原图项目分页。
    init(swipeMode: TravelAlbumPreviewSwipeMode = .projectsOnly) {
        self.swipeMode = swipeMode
    }
}

/// 预览图片类型，顺序同时决定 Tab 与关联图浏览顺序。
enum TravelAlbumPreviewAssetKind: Int, CaseIterable, Sendable, Hashable {
    case original
    case retouched
    case atmosphere
    case cover

    var title: String {
        switch self {
        case .original: "原图"
        case .retouched: "精修后"
        case .atmosphere: "氛围感"
        case .cover: "封面"
        }
    }
}

/// 预览页使用的单张图片信息，与后端关联图字段解耦。
struct TravelAlbumPreviewAsset: Identifiable, Sendable, Hashable {
    let id: String
    let kind: TravelAlbumPreviewAssetKind
    let fileURL: String
    let coverURL: String
    let fileName: String
    let fileSize: Int

    /// 实际用于展示的地址，优先使用原图地址。
    var displayURL: String {
        let trimmedFileURL = fileURL.trimmingCharacters(in: .whitespacesAndNewlines)
        return trimmedFileURL.isEmpty ? coverURL.trimmingCharacters(in: .whitespacesAndNewlines) : trimmedFileURL
    }

    /// 横滑预览地址，优先使用体积更小的封面图以降低解码开销。
    var previewURL: String {
        let trimmedCoverURL = coverURL.trimmingCharacters(in: .whitespacesAndNewlines)
        return trimmedCoverURL.isEmpty ? fileURL.trimmingCharacters(in: .whitespacesAndNewlines) : trimmedCoverURL
    }
}

/// 一张原图及其所有关联图片组成的预览项目。
struct TravelAlbumPreviewProject: Identifiable, Sendable, Hashable {
    let originalMaterialId: Int
    let assets: [TravelAlbumPreviewAsset]

    var id: Int { originalMaterialId }

    /// 按产品约定顺序返回实际存在的图片。
    var orderedAssets: [TravelAlbumPreviewAsset] {
        TravelAlbumPreviewAssetKind.allCases.compactMap(asset(for:))
    }

    /// 是否存在原图之外的关联图片。
    var hasVariants: Bool {
        orderedAssets.contains { $0.kind != .original }
    }

    /// 返回指定类型的图片。
    func asset(for kind: TravelAlbumPreviewAssetKind) -> TravelAlbumPreviewAsset? {
        assets.first { $0.kind == kind }
    }

    /// 将当前素材映射为仅含原图的预览项目；新接口接入后替换此适配层即可。
    init(material: TravelAlbumMaterial) {
        originalMaterialId = material.id
        assets = [
            TravelAlbumPreviewAsset(
                id: "original-\(material.id)",
                kind: .original,
                fileURL: material.fileUrl,
                coverURL: material.coverUrl,
                fileName: material.fileName,
                fileSize: material.fileSize
            ),
        ]
    }

    /// 创建包含关联图片的项目，主要供适配器和测试使用。
    init(originalMaterialId: Int, assets: [TravelAlbumPreviewAsset]) {
        self.originalMaterialId = originalMaterialId
        var seenKinds = Set<TravelAlbumPreviewAssetKind>()
        self.assets = assets.filter { seenKinds.insert($0.kind).inserted }
    }
}

/// 预览分页节点，记录当前图片所属项目及类型。
struct TravelAlbumPreviewNode: Sendable, Hashable {
    let projectIndex: Int
    let kind: TravelAlbumPreviewAssetKind
}

/// 预览页纯状态工具，负责构建节点和处理分组滑动边界。
enum TravelAlbumPreviewNavigator {
    /// 根据滑动模式生成页面节点。
    static func nodes(
        projects: [TravelAlbumPreviewProject],
        mode: TravelAlbumPreviewSwipeMode
    ) -> [TravelAlbumPreviewNode] {
        projects.enumerated().flatMap { index, project in
            switch mode {
            case .projectsOnly:
                [TravelAlbumPreviewNode(projectIndex: index, kind: .original)]
            case .includeVariants:
                project.orderedAssets.map { TravelAlbumPreviewNode(projectIndex: index, kind: $0.kind) }
            }
        }
    }

    /// 处理反向滑动边界：从项目原图向右滑时直接进入上一项目原图。
    static func backwardTargetIndex(
        nodes: [TravelAlbumPreviewNode],
        currentIndex: Int
    ) -> Int {
        guard nodes.indices.contains(currentIndex), currentIndex > 0 else { return max(0, currentIndex) }
        let current = nodes[currentIndex]
        guard current.kind == .original, current.projectIndex > 0 else { return currentIndex - 1 }
        return nodes.firstIndex {
            $0.projectIndex == current.projectIndex - 1 && $0.kind == .original
        } ?? currentIndex - 1
    }
}

/// 预览操作执行结果，便于后续替换真实业务接口。
enum TravelAlbumPreviewActionResult: Sendable, Equatable {
    case success(String?)
    case failure(String)
    case unavailable(String)
}

/// 预览页底部操作协议，所有操作均以原素材项目 ID 为目标。
protocol TravelAlbumPreviewActionHandling: AnyObject {
    func requestAIRetouch(originalMaterialId: Int) async -> TravelAlbumPreviewActionResult
    func deleteProject(originalMaterialId: Int) async -> TravelAlbumPreviewActionResult
    func refreshProject(originalMaterialId: Int) async -> TravelAlbumPreviewActionResult
}

/// 新接口接入前的占位操作实现，不修改任何业务数据。
final class PlaceholderTravelAlbumPreviewActionHandler: TravelAlbumPreviewActionHandling {
    func requestAIRetouch(originalMaterialId: Int) async -> TravelAlbumPreviewActionResult {
        .unavailable("AI修复功能待接口接入")
    }

    func deleteProject(originalMaterialId: Int) async -> TravelAlbumPreviewActionResult {
        .unavailable("项目删除接口待接入")
    }

    func refreshProject(originalMaterialId: Int) async -> TravelAlbumPreviewActionResult {
        .unavailable("关联图片刷新接口待接入")
    }
}