// RDEPUBJavaScriptBridge.swift
// 原生与 WebView 之间的 JavaScript 桥接层
// 定义所有 JS 消息类型（progression/selection/link/error 等），
// 生成注入到 WebView 的用户脚本，以及分页渲染、搜索高亮等执行脚本。

import Foundation

/// JS 桥接消息类型枚举，每种消息对应 WebView 向原生发送的一种事件
enum RDEPUBJavaScriptBridgeMessage: String, CaseIterable {
    /// 阅读进度变化事件
    case progressionChanged = "ssReaderProgressionChanged"
    /// 文本选择变化事件
    case selectionChanged = "ssReaderSelectionChanged"
    /// 内部链接点击事件（ss-reader:// 协议）
    case internalLink = "ssReaderInternalLink"
    /// 外部链接点击事件（http/https/mailto/tel）
    case externalLink = "ssReaderExternalLink"
    /// JavaScript 运行时错误事件
    case javaScriptError = "ssReaderJSError"
    /// 固定版式渲染就绪事件
    case fixedLayoutReady = "ssReaderFixedLayoutReady"
}

/// JavaScript 桥接工具集，负责生成注入脚本和执行脚本
enum RDEPUBJavaScriptBridge {
    /// 所有需要注册的 JS 消息名称列表，用于 WKUserContentController 注册
    static var messageNames: [String] {
        RDEPUBJavaScriptBridgeMessage.allCases.map(\.rawValue)
    }

    /// 获取注入到 WebView 的桥接用户脚本（在 document end 注入）
    /// 将消息类型占位符替换为实际值，使 JS 端能通过 window.webkit.messageHandlers 发送消息
    static var userScript: String {
        [
            RDEPUBAssetRepository.string(for: .rangyCoreScript),
            RDEPUBAssetRepository.string(for: .rangySerializerScript),
            RDEPUBAssetRepository.string(for: .cssInjectorScript),
            RDEPUBAssetRepository.string(for: .weReadAPIScript),
            RDEPUBAssetRepository.string(
                for: .bridgeScript,
                replacements: [
                    "PROGRESSION_CHANGED_MESSAGE": RDEPUBJavaScriptBridgeMessage.progressionChanged.rawValue,
                    "SELECTION_CHANGED_MESSAGE": RDEPUBJavaScriptBridgeMessage.selectionChanged.rawValue,
                    "INTERNAL_LINK_MESSAGE": RDEPUBJavaScriptBridgeMessage.internalLink.rawValue,
                    "EXTERNAL_LINK_MESSAGE": RDEPUBJavaScriptBridgeMessage.externalLink.rawValue,
                    "JAVASCRIPT_ERROR_MESSAGE": RDEPUBJavaScriptBridgeMessage.javaScriptError.rawValue,
                    "FIXED_LAYOUT_READY_MESSAGE": RDEPUBJavaScriptBridgeMessage.fixedLayoutReady.rawValue
                ]
            )
        ].joined(separator: "\n\n")
    }

    /// 生成重排模式下的分页渲染脚本
    /// 注入 CSS 分页样式、设置页码参数、高亮和目标位置，最后触发进度汇报
    /// - Parameter request: 重排渲染请求，包含展示样式、高亮、目标位置等信息
    /// - Returns: 可直接通过 evaluateJavaScript 执行的脚本字符串
    static func applyPresentationScript(for request: RDEPUBReflowableRenderRequest) -> String {
        let style = escapedJavaScriptTemplateLiteral(RDEPUBStyleSheetBuilder.renderCSS(for: request.presentation))
        let pageStride = max(1, request.presentation.viewportSize.width)
        let searchScript = applySearchScript(for: request.searchPresentation)

        return """
        (function() {
            if (!window.WeReadApi) { return false; }
            window.WeReadApi.applySharedTheme({
                backgroundColor: \(javaScriptStringLiteral(request.presentation.themeBackgroundColor)),
                textColor: \(javaScriptStringLiteral(request.presentation.themeTextColor)),
                includeFrames: false
            });
            window.WeReadApi.applyPagination(`\(style)`);
            window.WeReadApi.setPageMetrics(\(request.totalPagesInChapter), \(pageStride));
            window.WeReadApi.clearHighlights();
            window.WeReadApi.setHighlights(\(jsonString(from: highlightsPayload(request.highlights), fallback: "[]")));
            if (\(jsonString(from: targetLocationPayload(request.targetLocation), fallback: "null")) !== null) {
                window.WeReadApi.scrollToLocation(\(jsonString(from: targetLocationPayload(request.targetLocation), fallback: "null")), \(request.pageIndex));
            } else {
                window.WeReadApi.scrollToPage(\(request.pageIndex));
            }
            window.WeReadApi.reportProgression();
            return true;
        })();
        \(searchScript)
        """
    }

    /// 生成固定版式模式下的主题应用脚本
    /// 仅应用共享主题（背景色），不涉及分页逻辑（固定版式由 HTML 自身布局决定）
    /// - Parameter request: 固定版式渲染请求，包含背景色等信息
    /// - Returns: 可直接通过 evaluateJavaScript 执行的脚本字符串
    static func applyFixedPresentationScript(for request: RDEPUBFixedRenderRequest) -> String {
        """
        (function() {
            if (!window.WeReadApi) { return false; }
            window.WeReadApi.applySharedTheme({
                backgroundColor: \(javaScriptStringLiteral(request.backgroundColorCSS)),
                textColor: null,
                includeFrames: true
            });
            return true;
        })();
        """
    }

    /// 生成搜索高亮脚本
    /// 在当前文档和所有 iframe 中查找关键词并用 span 标记高亮，
    /// 活跃匹配项使用特殊样式并自动滚动到视图中央
    /// - Parameter presentation: 搜索展示信息（关键词、各资源的匹配数量等）
    /// - Returns: 搜索高亮脚本字符串
    static func applySearchScript(for presentation: RDEPUBSearchPresentation?) -> String {
        let payload = jsonString(from: searchPayload(presentation), fallback: "null")
        return """
        (function() {
            if (!window.WeReadApi) { return false; }
            window.WeReadApi.setSearchPresentation(\(payload));
            return true;
        })();
        """
    }

    /// 生成获取当前装饰数据的脚本
    /// 从 WebView 中读取高亮和搜索高亮的 DOM 装饰信息，用于同步原生标注状态
    /// - Returns: 可直接通过 evaluateJavaScript 执行的脚本字符串，返回包含 highlights 和 search 的对象
    static func resolveDecorationsScript() -> String {
        """
        (function() {
            if (!window.WeReadApi) { return { highlights: [], search: [] }; }
            return window.WeReadApi.resolveDecorations();
        })();
        """
    }

    /// 转义字符串中的反斜杠和反引号，避免 JS 模板字面量语法错误
    private static func escapedJavaScriptTemplateLiteral(_ string: String) -> String {
        string
            .replacingOccurrences(of: "\\", with: "\\\\")
            .replacingOccurrences(of: "`", with: "\\`")
    }

    /// 将高亮数组转换为 JS 可用的字典数组
    private static func highlightsPayload(_ highlights: [RDEPUBHighlight]) -> [[String: String]] {
        highlights.compactMap { highlight in
            guard let rangeInfo = highlight.rangeInfo, !rangeInfo.isEmpty else { return nil }
            return [
                "id": highlight.id,
                "rangeInfo": rangeInfo,
                "color": highlight.color,
                "style": highlight.style.rawValue
            ]
        }
    }

    /// 将目标位置转换为 JS 可用的字典（含 progression、fragment）
    private static func targetLocationPayload(_ location: RDEPUBLocation?) -> [String: Any]? {
        guard let location else { return nil }
        return [
            "progression": location.progression,
            "lastProgression": location.lastProgression ?? location.progression,
            "fragment": location.fragment as Any
        ]
    }

    /// 将搜索展示信息转换为 JS 可用的字典
    private static func searchPayload(_ presentation: RDEPUBSearchPresentation?) -> [String: Any]? {
        guard let presentation else { return nil }
        return [
            "keyword": presentation.keyword,
            "resources": presentation.resources.map { resource in
                [
                    "href": resource.href,
                    "matchCount": resource.matchCount,
                    "activeLocalMatchIndex": resource.activeLocalMatchIndex as Any
                ]
            }
        ]
    }

    /// 将任意对象序列化为 JSON 字符串，失败时返回 fallback
    private static func jsonString(from object: Any?, fallback: String) -> String {
        guard let object else { return fallback }
        guard JSONSerialization.isValidJSONObject(object),
              let data = try? JSONSerialization.data(withJSONObject: object, options: []),
              let string = String(data: data, encoding: .utf8) else {
            return fallback
        }
        return string
    }

    /// 将 Swift 字符串转换为 JavaScript 字符串字面量
    /// nil 值转为 "null"，非空值序列化为 JSON 字符串后去除外层方括号
    private static func javaScriptStringLiteral(_ value: String?) -> String {
        guard let value else { return "null" }
        return jsonString(from: [value], fallback: "[null]")
            .replacingOccurrences(of: "[", with: "")
            .replacingOccurrences(of: "]", with: "")
    }
}