// 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: .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
            ]
        )
    }

    /// 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.RDReaderBridge) { return false; }
            window.RDReaderBridge.applyPagination(`\(style)`);
            window.RDReaderBridge.setPageMetrics(\(request.totalPagesInChapter), \(pageStride));
            window.RDReaderBridge.clearHighlights();
            window.RDReaderBridge.setHighlights(\(jsonString(from: highlightsPayload(request.highlights), fallback: "[]")));
            if (\(jsonString(from: targetLocationPayload(request.targetLocation), fallback: "null")) !== null) {
                window.RDReaderBridge.scrollToLocation(\(jsonString(from: targetLocationPayload(request.targetLocation), fallback: "null")), \(request.pageIndex));
            } else {
                window.RDReaderBridge.scrollToPage(\(request.pageIndex));
            }
            window.RDReaderBridge.reportProgression();
            return true;
        })();
        \(searchScript)
        """
    }

    /// 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() {
            var payload = \(payload);
            function normalizeHref(rawHref) {
                if (!rawHref) { return ''; }
                var value = String(rawHref);
                value = value.replace(/^.*?:\\/\\/[^/]+\\//, '');
                value = value.split('#')[0];
                value = value.replace(/^\\/+/, '');
                try {
                    value = decodeURIComponent(value);
                } catch (error) {
                }
                return value;
            }

            function ensureStyle(doc) {
                if (!doc || !doc.head || doc.getElementById('ss-reader-search-style')) { return; }
                var style = doc.createElement('style');
                style.id = 'ss-reader-search-style';
                style.textContent = '.ss-reader-search-mark{background:rgba(248,225,108,0.55);color:inherit;border-radius:2px;padding:0;}.ss-reader-search-mark-active{background:rgba(255,159,67,0.75);color:inherit;border-radius:2px;padding:0;}';
                doc.head.appendChild(style);
            }

            function clearMarks(doc) {
                if (!doc || !doc.body) { return; }
                var marks = doc.querySelectorAll('span.ss-reader-search-mark, span.ss-reader-search-mark-active');
                marks.forEach(function(mark) {
                    var textNode = doc.createTextNode(mark.textContent || '');
                    if (mark.parentNode) {
                        mark.parentNode.replaceChild(textNode, mark);
                    }
                });
                doc.body.normalize();
            }

            function searchableDocuments(rootDoc) {
                var items = [];
                if (!rootDoc) { return items; }
                items.push({ doc: rootDoc, href: normalizeHref(rootDoc.location && rootDoc.location.href) });
                var frames = rootDoc.querySelectorAll ? rootDoc.querySelectorAll('iframe') : [];
                frames.forEach(function(frame) {
                    try {
                        if (frame.contentDocument) {
                            items.push({
                                doc: frame.contentDocument,
                                href: normalizeHref(frame.contentWindow && frame.contentWindow.location && frame.contentWindow.location.href)
                            });
                        }
                    } catch (error) {
                    }
                });
                return items;
            }

            function textNodes(doc) {
                if (!doc || !doc.body) { return []; }
                var walker = doc.createTreeWalker(doc.body, NodeFilter.SHOW_TEXT, {
                    acceptNode: function(node) {
                        if (!node || !node.nodeValue || !node.nodeValue.trim()) {
                            return NodeFilter.FILTER_REJECT;
                        }
                        var parent = node.parentNode;
                        if (!parent || !parent.nodeName) {
                            return NodeFilter.FILTER_REJECT;
                        }
                        var name = parent.nodeName.toLowerCase();
                        if (['script', 'style', 'noscript'].indexOf(name) >= 0) {
                            return NodeFilter.FILTER_REJECT;
                        }
                        if (parent.classList && (parent.classList.contains('ss-reader-search-mark') || parent.classList.contains('ss-reader-search-mark-active'))) {
                            return NodeFilter.FILTER_REJECT;
                        }
                        return NodeFilter.FILTER_ACCEPT;
                    }
                });

                var nodes = [];
                while (walker.nextNode()) {
                    nodes.push(walker.currentNode);
                }
                return nodes;
            }

            function applyToDocument(doc, resourceState, keyword) {
                clearMarks(doc);
                ensureStyle(doc);
                if (!doc || !doc.body || !resourceState || !keyword || resourceState.matchCount <= 0) {
                    return;
                }

                var lowerKeyword = String(keyword).toLowerCase();
                var activeIndex = typeof resourceState.activeLocalMatchIndex === 'number' ? resourceState.activeLocalMatchIndex : null;
                var currentLocalIndex = 0;
                var activeElement = null;

                textNodes(doc).forEach(function(node) {
                    var source = node.nodeValue || '';
                    var lowerSource = source.toLowerCase();
                    var cursor = 0;
                    var replaced = false;
                    var fragment = doc.createDocumentFragment();

                    while (cursor < source.length) {
                        var foundIndex = lowerSource.indexOf(lowerKeyword, cursor);
                        if (foundIndex < 0) {
                            break;
                        }

                        replaced = true;
                        if (foundIndex > cursor) {
                            fragment.appendChild(doc.createTextNode(source.slice(cursor, foundIndex)));
                        }

                        var mark = doc.createElement('span');
                        mark.className = currentLocalIndex === activeIndex ? 'ss-reader-search-mark-active' : 'ss-reader-search-mark';
                        mark.textContent = source.slice(foundIndex, foundIndex + keyword.length);
                        fragment.appendChild(mark);
                        if (currentLocalIndex === activeIndex) {
                            activeElement = mark;
                        }

                        currentLocalIndex += 1;
                        cursor = foundIndex + keyword.length;
                    }

                    if (!replaced) {
                        return;
                    }

                    if (cursor < source.length) {
                        fragment.appendChild(doc.createTextNode(source.slice(cursor)));
                    }
                    if (node.parentNode) {
                        node.parentNode.replaceChild(fragment, node);
                    }
                });

                if (activeElement && activeElement.scrollIntoView) {
                    activeElement.scrollIntoView({ block: 'center', inline: 'center', behavior: 'auto' });
                }
            }

            var docs = searchableDocuments(document);
            var states = new Map();
            if (payload && Array.isArray(payload.resources)) {
                payload.resources.forEach(function(resource) {
                    states.set(normalizeHref(resource.href), resource);
                });
            }

            docs.forEach(function(item) {
                applyToDocument(item.doc, states.get(item.href), payload && payload.keyword ? payload.keyword : '');
            });
            return true;
        })();
        """
    }

    /// 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
    }
}