// Document content storage
let documentContent = '';

// Process uploaded document
async function processDocument(file) {
    return new Promise((resolve) => {
        const reader = new FileReader();
        reader.onload = (e) => {
            documentContent = e.target.result;
            resolve({ success: true });
        };
        reader.readAsText(file);
    });
}
// Enhanced document search with better matching and context
function searchDocument(question) {
    if (!documentContent) return "Please upload a document first.";

    const questionLower = question.toLowerCase();
    const docLower = documentContent.toLowerCase();
    
    // Split into meaningful units (paragraphs or sections)
    const sections = documentContent.split(/\n\s*\n+/);
    
    // First try exact matches or very close matches
    for (const section of sections) {
        const sectionLower = section.toLowerCase();
        
        // Check for direct question matches
        if (sectionLower.includes(questionLower)) {
            return extractBestAnswer(section, questionLower);
        }
        
        // Check for "what is" questions
        if (questionLower.startsWith('what is') || questionLower.startsWith('what are')) {
            const targetTerm = questionLower.split(' ').slice(2).join(' ');
            if (sectionLower.includes(targetTerm)) {
                return extractDefinition(section, targetTerm);
            }
        }
        
        // Check for "how to" questions
        if (questionLower.startsWith('how to') || questionLower.startsWith('how do')) {
            const action = questionLower.split(' ').slice(2).join(' ');
            if (sectionLower.includes(action)) {
                return extractInstructions(section, action);
            }
        }
    }

    // Try semantic matching with weighted keywords
    const keywords = extractKeywords(questionLower);
    let bestMatch = { text: '', score: 0 };
    
    for (const section of sections) {
        const sectionLower = section.toLowerCase();
        let score = 0;
        
        for (const keyword of keywords) {
            if (sectionLower.includes(keyword)) {
                score += keyword.weight;
                
                // Bonus for proximity to other keywords
                const keywordPos = sectionLower.indexOf(keyword);
                for (const otherKeyword of keywords) {
                    if (otherKeyword !== keyword) {
                        const otherPos = sectionLower.indexOf(otherKeyword);
                        if (otherPos !== -1 && Math.abs(keywordPos - otherPos) < 100) {
                            score += 5;
                        }
                    }
                }
            }
        }
        
        if (score > bestMatch.score) {
            bestMatch = { text: section, score };
        }
    }
    
    if (bestMatch.score > 0) {
        return extractRelevantPart(bestMatch.text, keywords);
    }
    
    // As last resort, try to find any relevant information
    const relevant = findAnyRelevant(questionLower, sections);
    if (relevant) return relevant;
    
    return "I found some information that might be relevant, but couldn't find a direct answer to your question. Try asking differently or check these sections:\n" + 
           findPossibleSections(questionLower, sections);
}

// Helper functions
function extractKeywords(question) {
    const words = question.split(' ').filter(w => w.length > 3);
    const weights = {
        'what': 1, 'how': 2, 'why': 2, 'when': 2, 'where': 2,
        'is': 1, 'are': 1, 'does': 2, 'do': 1, 'can': 2,
        'explain': 3, 'describe': 3, 'define': 3, 'list': 2
    };
    
    return words.map(word => ({
        word: word,
        weight: weights[word] || 1
    }));
}

function extractBestAnswer(text, question) {
    // Split into sentences
    const sentences = text.split(/[.!?]+/).map(s => s.trim()).filter(s => s);
    
    // Find the most relevant sentence
    for (const sentence of sentences) {
        if (sentence.toLowerCase().includes(question)) {
            return sentence + '.';
        }
    }
    
    // If no exact match, return first few sentences
    return sentences.slice(0, 3).join(' ') + '...';
}

function extractDefinition(text, term) {
    const sentences = text.split(/[.!?]+/);
    for (let i = 0; i < sentences.length; i++) {
        if (sentences[i].toLowerCase().includes(term)) {
            // Try to get the definition sentence
            if (sentences[i].toLowerCase().includes('is') || sentences[i].toLowerCase().includes('are')) {
                return sentences[i].trim() + '.';
            }
            // Or combine with next sentence
            if (i < sentences.length - 1) {
                return (sentences[i] + ' ' + sentences[i+1]).trim() + '.';
            }
        }
    }
    return text.split('\n')[0]; // Fallback to first line
}

function findAnyRelevant(question, sections) {
    const keywords = extractKeywords(question).map(k => k.word);
    
    for (const section of sections) {
        const sectionLower = section.toLowerCase();
        let matches = 0;
        
        for (const keyword of keywords) {
            if (sectionLower.includes(keyword)) matches++;
        }
        
        if (matches >= keywords.length / 2) {
            return "This might help:\n" + section.split('\n').slice(0, 3).join('\n') + '...';
        }
    }
    
    return null;
}

function findPossibleSections(question, sections) {
    const keywords = extractKeywords(question).map(k => k.word);
    const relevantSections = [];
    
    for (const section of sections) {
        const sectionLower = section.toLowerCase();
        let matches = 0;
        
        for (const keyword of keywords) {
            if (sectionLower.includes(keyword)) matches++;
        }
        
        if (matches > 0) {
            const firstLine = section.split('\n')[0];
            if (firstLine && !relevantSections.includes(firstLine)) {
                relevantSections.push(firstLine);
            }
        }
    }
    
    return relevantSections.slice(0, 3).map(s => "• " + s).join('\n');
}
async function askQuestion(question) {
    if (!documentContent) {
        return { answer: "Please upload a document first." };
    }
    
    const answer = searchDocument(question);
    
    // Enhance simple answers with more context
    let enhancedAnswer = answer;
    if (answer.includes('is') && !answer.includes('.')) {
        // Try to find the next sentence for more context
        const sentences = documentContent.split(/[.!?]+/);
        const idx = sentences.findIndex(s => s.trim() + '.' === answer);
        if (idx !== -1 && idx < sentences.length - 1) {
            enhancedAnswer += ' ' + sentences[idx+1].trim() + '.';
        }
    }
    
    return { answer: enhancedAnswer };
}