// app/static/script.js
document.addEventListener('DOMContentLoaded', () => {
    // --- State ---
    let currentFile = null;
    let currentXHR = null;

    // --- DOM Elements ---
    const states = {
        initial: document.getElementById('state-initial'),
        uploading: document.getElementById('state-uploading'),
        complete: document.getElementById('state-complete'),
        error: document.getElementById('state-error'),
    };
    const dropZone = document.getElementById('drop-zone');
    const browseBtn = document.getElementById('browse-btn');
    const fileInput = document.getElementById('file-input');
    const fileNameEl = document.getElementById('file-name');
    const fileSizeEl = document.getElementById('file-size');
    const progressBar = document.getElementById('progress-bar');
    const statusText = document.getElementById('status-text');
    const downloadLink = document.getElementById('download-link');
    const uploadAnotherBtn = document.getElementById('upload-another-btn');
    const errorMessage = document.getElementById('error-message');
    const retryBtn = document.getElementById('retry-btn');
    
    // New elements for copy functionality
    const downloadUrlInput = document.getElementById('download-url-input');
    const copyLinkBtn = document.getElementById('copy-link-btn');

    // --- UI State Management ---
    function switchState(state) {
        Object.values(states).forEach(el => el.classList.remove('active'));
        if (states[state]) {
            states[state].classList.add('active');
        }
    }

    // --- Event Listeners ---
    browseBtn.addEventListener('click', () => fileInput.click());
    fileInput.addEventListener('change', handleFileSelect);
    
    dropZone.addEventListener('dragover', (e) => {
        e.preventDefault();
        dropZone.classList.add('drag-over');
    });
    dropZone.addEventListener('dragleave', () => dropZone.classList.remove('drag-over'));
    dropZone.addEventListener('drop', (e) => {
        e.preventDefault();
        dropZone.classList.remove('drag-over');
        if (e.dataTransfer.files.length > 0) {
            handleFileSelect({ target: { files: e.dataTransfer.files } });
        }
    });

    uploadAnotherBtn.addEventListener('click', resetUploader);
    retryBtn.addEventListener('click', resetUploader);
    copyLinkBtn.addEventListener('click', handleCopyLink);

    // --- Core Functions ---
    function handleFileSelect(event) {
        const file = event.target.files[0];
        if (!file) return;
        
        currentFile = file;
        fileNameEl.textContent = file.name;
        fileSizeEl.textContent = formatBytes(file.size);
        
        startUpload(file);
    }

    function startUpload(file) {
        switchState('uploading');
        statusText.textContent = 'Uploading...';
        progressBar.style.width = '0%';

        const formData = new FormData();
        formData.append('file', file);

        const xhr = new XMLHttpRequest();
        currentXHR = xhr;

        xhr.upload.addEventListener('progress', (event) => {
            if (event.lengthComputable) {
                const percentage = (event.loaded / event.total) * 100;
                progressBar.style.width = `${percentage}%`;
                statusText.textContent = `${formatBytes(event.loaded)} / ${formatBytes(event.total)}`;
            }
        });

        xhr.addEventListener('load', () => {
            if (xhr.status >= 200 && xhr.status < 300) {
                const response = JSON.parse(xhr.responseText);
                
                // Construct the full, absolute URL for sharing
                const fullUrl = `${window.location.origin}${response.download_url}`;
                
                downloadLink.href = response.download_url;
                downloadLink.download = response.filename;
                downloadUrlInput.value = fullUrl;

                switchState('complete');
            } else {
                handleUploadError(xhr);
            }
        });

        xhr.addEventListener('error', () => handleUploadError(xhr));
        xhr.addEventListener('abort', () => console.log('Upload aborted.'));

        xhr.open('POST', '/upload', true);
        xhr.send(formData);
    }
    
    // NEW: Function to handle copying the link
    function handleCopyLink() {
        // Use the modern Navigator Clipboard API
        navigator.clipboard.writeText(downloadUrlInput.value).then(() => {
            // Provide visual feedback
            copyLinkBtn.textContent = 'Copied!';
            copyLinkBtn.classList.add('copied');
            
            // Revert back after a couple of seconds
            setTimeout(() => {
                copyLinkBtn.textContent = 'Copy';
                copyLinkBtn.classList.remove('copied');
            }, 2000);
        }).catch(err => {
            console.error('Failed to copy text: ', err);
            // You could add an error state to the button here if needed
        });
    }

    function handleUploadError(xhr) {
        let message = 'An unknown network error occurred.';
        try {
            const errorData = JSON.parse(xhr.responseText);
            message = errorData.detail || 'Upload failed.';
        } catch (e) {
            if (xhr.statusText) {
                message = xhr.statusText;
            }
        }
        errorMessage.textContent = message;
        switchState('error');
    }

    function resetUploader() {
        if (currentXHR) {
            currentXHR.abort();
            currentXHR = null;
        }
        currentFile = null;
        fileInput.value = '';
        downloadUrlInput.value = ''; // Clear the URL input
        switchState('initial');
    }

    function formatBytes(bytes, decimals = 2) {
        if (bytes === 0) return '0 Bytes';
        const k = 1024;
        const dm = decimals < 0 ? 0 : decimals;
        const sizes = ['Bytes', 'KB', 'MB', 'GB', 'TB'];
        const i = Math.floor(Math.log(bytes) / Math.log(k));
        return parseFloat((bytes / Math.pow(k, i)).toFixed(dm)) + ' ' + sizes[i];
    }

    switchState('initial');
});