prejs_file_api.js

/**
 * Web Worker API for libzim JavaScript bindings
 * 
 * This file provides the pre-JS portion of the web worker that handles ZIM file operations.
 * It is concatenated with postjs_file_api.js during the Emscripten build process (see Makefile)
 * to create a complete web worker script that can be used with WebAssembly or asm.js builds.
 * 
 * Supported actions: getEntryByPath, search, searchWithSnippets, suggest, getArticleCount, init
 */

self.addEventListener('message', function(e) {
    var action = e.data.action;
    var path = e.data.path;
    var outgoingMessagePort = e.ports[0];
    console.debug('WebWorker called with action=' + action);
    
    // Retrieve content from ZIM archive by path
    if (action === 'getEntryByPath') {
        var follow = e.data.follow;
        var entry = Module[action](path);
        if (entry) {
            var item = {};
            if (follow || !entry.isRedirect()) {
                item = entry.getItem(follow);
                // It's necessary to keep an instance of the blob till the end of this block,
                // to ensure that the corresponding content is not deleted on the C side.
                var blob = item.getData();
                var content = blob.getContent();
                // TODO : is there a more efficient way to make the Array detachable? So that it can be transfered back from the WebWorker without a copy?
                var contentArray = new Uint8Array(content);
                outgoingMessagePort.postMessage({ content: contentArray, mimetype: item.getMimetype(), isRedirect: entry.isRedirect()});
            }
            else {
                outgoingMessagePort.postMessage({ content: new Uint8Array(), isRedirect: true, redirectPath: entry.getRedirectEntry().getPath()});
            }
        }
        else {
            outgoingMessagePort.postMessage({ content: new Uint8Array(), mimetype: 'unknown', isRedirect: false});
        }
    } 
    // Full-text search across ZIM archive content (basic version - paths only)
    else if (action === 'search') {
        var text = e.data.text;
        var numResults = e.data.numResults || 50;
        var entries = Module[action](text, numResults);
        console.debug('Found nb results = ' + entries.size(), entries);
        var serializedResults = [];
        for (var i=0; i<entries.size(); i++) {
            var entry = entries.get(i);
            serializedResults.push({
                path: entry.getPath(),
                title: entry.getTitle(),
                snippet: null,
                score: null,
                wordCount: null
            });
        }
        outgoingMessagePort.postMessage({ results: serializedResults });
    } 
    // NEW: Enhanced full-text search with content snippets
    else if (action === 'searchWithSnippets') {
        var text = e.data.text;
        var numResults = e.data.numResults || 50;
        try {
            var searchResults = Module['searchWithSnippets'](text, numResults);
            console.debug('Found nb search results with snippets = ' + searchResults.size(), searchResults);
            var serializedResults = [];
            for (var i=0; i<searchResults.size(); i++) {
                var result = searchResults.get(i);
                try {
                    serializedResults.push({
                        path: result.getPath(),
                        title: result.getTitle(),
                        snippet: result.getSnippet(),
                        score: result.getScore(),
                        wordCount: result.getWordCount()
                    });
                } catch (error) {
                    console.warn('Error processing search result ' + i + ':', error);
                    // Include basic info even if snippet extraction fails
                    serializedResults.push({
                        path: result.getPath() || '',
                        title: result.getTitle() || '',
                        snippet: '',
                        score: 0,
                        wordCount: 0
                    });
                }
            }
            outgoingMessagePort.postMessage({ results: serializedResults });
        } catch (error) {
            console.error('searchWithSnippets error:', error);
            outgoingMessagePort.postMessage({ results: [], error: error.message });
        }
    } 
    // Title-based suggestions for autocomplete (faster than full-text search)
    else if (action === 'suggest') {
        var text = e.data.text;
        var numResults = e.data.numResults || 10;
        var suggestions = Module[action](text, numResults);
        console.debug('Found nb suggestions = ' + suggestions.size(), suggestions);
        var serializedSuggestions = [];
        for (var i=0; i<suggestions.size(); i++) {
            var entry = suggestions.get(i);
            serializedSuggestions.push({path: entry.getPath(), title: entry.getTitle()});
        }
        outgoingMessagePort.postMessage({ suggestions: serializedSuggestions });
    } 
    // Get total number of articles in the ZIM archive
    else if (action === 'getArticleCount') {
        var articleCount = Module[action]();
        outgoingMessagePort.postMessage(articleCount);
    } 
    // Initialize the ZIM archive with file system mounting
    else if (action === 'init') {
        var files = e.data.files;
        var assemblerType = e.data.assemblerType || 'runtime';
        // When using split ZIM files, we need to remove the last two letters of the suffix (like .zimaa -> .zim)
        var baseZimFileName = files[0].name.replace(/\.zim..$/, '.zim');
        Module = {};
        Module['onRuntimeInitialized'] = function() {
            Module.loadArchive('/work/' + baseZimFileName);
            console.debug(assemblerType + ' initialized');
            outgoingMessagePort.postMessage('runtime initialized');
        };
        Module['arguments'] = [];
        for (let i = 0; i < files.length; i++) {
              Module['arguments'].push('/work/' + files[i].name);
        }
        // Mount file system for ZIM file access (Electron vs browser environments)
        Module['preRun'] = function() {
            FS.mkdir('/work');
            if (files[0].readMode === 'electron') {
                var path = files[0].path.replace(/[^\\/]+$/, '');
                FS.mount(NODEFS, {
                    root: path
                }, '/work');    
            } else {
                FS.mount(WORKERFS, {
                    files: files
                }, '/work');
            }
        };
        console.debug('baseZimFileName = ' + baseZimFileName);
        console.debug("Module['arguments'] = " + Module['arguments']);

        // File continues in postjs_file_api.js - handles invalid actions and closes the event listener
        // Between prejs and postjs: Emscripten injects the compiled WebAssembly/asm.js Module code and bindings