ReadViewSDK/Sources/RDReaderView/EPUBCore/RDEPUBWebView+Reflowable.swift

// RDEPUBWebView+Reflowable.swift
// RDEPUBWebView 的重排模式渲染扩展
// 处理重排（Reflowable）模式的加载流程：构建渲染请求、
// 生成加载签名（去重）、通过 JS 桥接应用分页样式和高亮、
// 处理重复请求跳过和已有文档复用等优化逻辑。

import UIKit
import WebKit

extension RDEPUBWebView {
    /// 便捷方法：加载重排模式的指定页面
    public func loadPage(
        parser: RDEPUBParser,
        spineIndex: Int,
        pageIndex: Int,
        totalPagesInChapter: Int,
        viewportSize: CGSize,
        padding: UIEdgeInsets,
        fontSize: CGFloat,
        lineHeightMultiple: CGFloat,
        themeBackgroundColor: String?,
        themeTextColor: String?,
        targetLocation: RDEPUBLocation?,
        highlights: [RDEPUBHighlight]
    ) {
        let href = parser.spine.indices.contains(spineIndex) ? parser.spine[spineIndex].href : ""
        let request = RDEPUBRenderRequest.reflowable(
            RDEPUBReflowableRenderRequest(
                spineIndex: spineIndex,
                href: href,
                pageIndex: pageIndex,
                totalPagesInChapter: totalPagesInChapter,
                presentation: RDEPUBPresentationStyle(
                    viewportSize: viewportSize,
                    contentInsets: padding,
                    fontSize: fontSize,
                    lineHeightMultiple: lineHeightMultiple,
                    themeBackgroundColor: themeBackgroundColor,
                    themeTextColor: themeTextColor
                ),
                targetLocation: targetLocation,
                highlights: highlights,
                searchPresentation: nil
            )
        )
        load(publication: parser.makePublication(), request: request)
    }

    /// 处理重排模式加载：设置状态、去重检查、加载资源或直接应用样式
    func handleReflowableLoad(
        publication: RDEPUBPublication,
        request: RDEPUBReflowableRenderRequest,
        loadSignature: String,
        in webView: WKWebView
    ) {
        guard publication.spine.indices.contains(request.spineIndex),
              let requestURL = publication.resourceResolver.resourceURL(forRelativePath: request.href) else {
            return
        }

        currentPageIndex = request.pageIndex
        currentTotalPagesInChapter = max(1, request.totalPagesInChapter)
        viewportSize = request.presentation.viewportSize
        currentPadding = request.presentation.contentInsets
        currentFontSize = request.presentation.fontSize
        currentLineHeightMultiple = request.presentation.lineHeightMultiple
        currentThemeBackgroundColor = request.presentation.themeBackgroundColor
        currentThemeTextColor = request.presentation.themeTextColor
        targetLocation = request.targetLocation
        pendingHighlights = request.highlights
        fixedSpread = nil
        isFixedLayout = false
        pendingProgressionRequest = true

        if currentLoadSignature == loadSignature {
            if didRenderCurrentRequest || webView.isLoading {
                let reason = didRenderCurrentRequest ? "already-rendered" : "still-loading"
                RDEPUBWebViewDebug.log(debugScope, message: "skip duplicate request href=\(request.href) page=\(request.pageIndex) reason=\(reason)")
                return
            }

            if webView.url == requestURL {
                RDEPUBWebViewDebug.log(debugScope, message: "reuse existing document href=\(request.href) page=\(request.pageIndex)")
                applyPresentation()
                return
            }
        }

        currentLoadSignature = loadSignature
        RDEPUBWebViewDebug.logNavigationEvent(debugScope, webView: webView, event: "load-request", url: requestURL)
        webView.load(URLRequest(url: requestURL))
    }

    /// 生成重排模式加载签名（包含所有渲染参数的哈希，用于去重）
    func reflowableLoadSignature(publicationKey: String, request: RDEPUBReflowableRenderRequest) -> String {
        let targetSignature = [
            request.targetLocation?.href ?? "",
            String(request.targetLocation?.progression ?? 0),
            String(request.targetLocation?.lastProgression ?? 0),
            request.targetLocation?.fragment ?? ""
        ].joined(separator: "|")
        let highlightSignature = request.highlights
            .map { [$0.id, $0.rangeInfo ?? "", $0.color, $0.style.rawValue].joined(separator: "|") }
            .joined(separator: ",")
        let presentation = request.presentation
        return [
            publicationKey,
            "reflowable",
            String(request.spineIndex),
            request.href,
            String(request.pageIndex),
            String(request.totalPagesInChapter),
            String(format: "%.2f", presentation.viewportSize.width),
            String(format: "%.2f", presentation.viewportSize.height),
            String(format: "%.2f", presentation.contentInsets.top),
            String(format: "%.2f", presentation.contentInsets.left),
            String(format: "%.2f", presentation.contentInsets.bottom),
            String(format: "%.2f", presentation.contentInsets.right),
            String(format: "%.2f", presentation.fontSize),
            String(format: "%.2f", presentation.lineHeightMultiple),
            presentation.themeBackgroundColor ?? "",
            presentation.themeTextColor ?? "",
            targetSignature,
            highlightSignature
        ].joined(separator: "#")
    }

    /// 应用分页展示样式：通过 JS 桥接注入 CSS、设置分页参数和高亮，然后触发渲染完成
    func applyPresentation() {
        guard let webView, let currentRenderRequest else { return }
        guard case .reflowable(let request) = currentRenderRequest else {
            return
        }

        let script = RDEPUBJavaScriptBridge.applyPresentationScript(for: request)
        RDEPUBWebViewDebug.logJavaScript(
            debugScope,
            webView: webView,
            action: "applyPresentation",
            details: "spine=\(request.spineIndex) page=\(request.pageIndex) total=\(request.totalPagesInChapter)"
        )

        webView.evaluateJavaScript(script) { [weak self] _, error in
            guard let self else { return }
            if let error {
                RDEPUBWebViewDebug.logJavaScript(self.debugScope, webView: webView, action: "applyPresentationFailed", details: error.localizedDescription)
                self.delegate?.epubWebView(self, didLogJavaScriptError: error.localizedDescription)
                return
            }
            self.applySearchDecorationsIfNeeded {
                self.rendered()
            }
        }
    }
}