/**
 * File Upload Component with Drag & Drop and Preview
 * For image/file upload interfaces
 */

const { useState, useRef, useCallback, useEffect } = window.PreactLib || {};

export function FileUpload({ 
    accept = 'image/*',
    multiple = true,
    maxFiles = null,
    onFilesSelected,
    className = ''
}) {
    const html = window.html;
    const [isDragOver, setIsDragOver] = useState(false);
    const inputRef = useRef(null);

    const handleFiles = useCallback((files) => {
        const fileArray = Array.from(files);
        if (onFilesSelected) {
            onFilesSelected(fileArray);
        }
    }, [onFilesSelected]);

    const onDragOver = useCallback((e) => {
        e.preventDefault();
        setIsDragOver(true);
    }, []);

    const onDragLeave = useCallback((e) => {
        e.preventDefault();
        setIsDragOver(false);
    }, []);

    const onDrop = useCallback((e) => {
        e.preventDefault();
        setIsDragOver(false);
        handleFiles(e.dataTransfer.files);
    }, [handleFiles]);

    const onClick = () => {
        inputRef.current?.click();
    };

    const onInputChange = (e) => {
        handleFiles(e.target.files);
        // Reset input so same file can be selected again
        e.target.value = '';
    };

    return html`
        <div 
            class="border-2 border-dashed rounded-3 p-5 text-center ${isDragOver ? 'border-primary bg-primary bg-opacity-10' : 'border-secondary'} ${className}"
            onDragOver=${onDragOver}
            onDragLeave=${onDragLeave}
            onDrop=${onDrop}
            onClick=${onClick}
            style="cursor: pointer; transition: all 0.2s ease;"
        >
            <input 
                ref=${inputRef}
                type="file" 
                accept=${accept}
                multiple=${multiple}
                onChange=${onInputChange}
                style="display: none;"
            />
            <i class="bi bi-cloud-upload display-4 text-primary mb-3"></i>
            <h5 class="mb-2">Drag & Drop files here</h5>
            <p class="text-muted mb-0">or click to browse</p>
            ${accept ? html`<p class="text-muted small mt-2">Accepted: ${accept}</p>` : ''}
            ${multiple && maxFiles ? html`<p class="text-muted small">Max ${maxFiles} files</p>` : ''}
        </div>
    `;
}

// === File Preview Card ===
export function FilePreviewCard({ 
    file, 
    index, 
    onRemove, 
    onDragStart, 
    onDrop,
    onDragOver,
    isDragging = false
}) {
    const html = window.html;
    const [previewUrl, setPreviewUrl] = useState(null);

    useEffect(() => {
        if (file && file.type?.startsWith('image/')) {
            const url = URL.createObjectURL(file);
            setPreviewUrl(url);
            return () => URL.revokeObjectURL(url);
        }
    }, [file]);

    const cardClass = isDragging 
        ? 'preview-card dragging' 
        : 'preview-card';

    return html`
        <div 
            class="${cardClass}"
            draggable="true"
            data-index=${index}
            onDragStart=${(e) => onDragStart?.(e, index)}
            onDragOver=${(e) => onDragOver?.(e, index)}
            onDrop=${(e) => onDrop?.(e, index)}
        >
            ${previewUrl ? html`
                <img src=${previewUrl} class="preview-img" alt=${file.name} />
            ` : html`
                <div class="preview-img d-flex align-items-center justify-content-center bg-secondary">
                    <i class="bi bi-file-earmark display-4"></i>
                </div>
            `}
            <div class="preview-overlay">
                ${file.name}
            </div>
            <button 
                class="remove-btn"
                onClick=${(e) => {
                    e.stopPropagation();
                    onRemove?.(index);
                }}
            >
                &times;
            </button>
        </div>
    `;
}

// === File Preview Grid ===
export function FilePreviewGrid({ 
    files = [], 
    onFilesChange,
    sortable = true,
    className = ''
}) {
    const html = window.html;
    const [draggedIndex, setDraggedIndex] = useState(null);

    if (files.length === 0) return null;

    const removeFile = (index) => {
        const newFiles = files.filter((_, i) => i !== index);
        onFilesChange?.(newFiles);
    };

    const handleDragStart = (e, index) => {
        if (!sortable) return;
        setDraggedIndex(index);
        e.target.classList.add('dragging');
    };

    const handleDragOver = (e, index) => {
        if (!sortable || draggedIndex === null) return;
        e.preventDefault();
        if (draggedIndex !== index) {
            e.currentTarget.classList.add('drag-over');
        }
    };

    const handleDragLeave = (e) => {
        e.currentTarget.classList.remove('drag-over');
    };

    const handleDrop = (e, dropIndex) => {
        if (!sortable || draggedIndex === null) return;
        e.preventDefault();
        e.currentTarget.classList.remove('drag-over');

        if (draggedIndex !== dropIndex) {
            const newFiles = [...files];
            const [draggedFile] = newFiles.splice(draggedIndex, 1);
            newFiles.splice(dropIndex, 0, draggedFile);
            onFilesChange?.(newFiles);
        }
        setDraggedIndex(null);
    };

    const handleDragEnd = (e) => {
        e.target.classList.remove('dragging');
        setDraggedIndex(null);
        document.querySelectorAll('.drag-over').forEach(el => {
            el.classList.remove('drag-over');
        });
    };

    return html`
        <div class="row g-3 ${className}">
            ${files.map((file, index) => html`
                <div class="col-6 col-md-4 col-lg-3">
                    <${FilePreviewCard} 
                        file=${file}
                        index=${index}
                        onRemove=${removeFile}
                        onDragStart=${handleDragStart}
                        onDragOver=${handleDragOver}
                        onDrop=${handleDrop}
                        isDragging=${draggedIndex === index}
                    />
                </div>
            `)}
        </div>
    `;
}

// === Complete Upload Interface ===
export function UploadInterface({ 
    accept = 'image/*',
    multiple = true,
    maxFiles = null,
    onUpload,
    className = ''
}) {
    const html = window.html;
    const [files, setFiles] = useState([]);
    const [isUploading, setIsUploading] = useState(false);
    const [status, setStatus] = useState(null);

    const handleFilesSelected = (newFiles) => {
        if (maxFiles && files.length + newFiles.length > maxFiles) {
            setStatus({
                type: 'danger',
                message: `Maximum ${maxFiles} files allowed`
            });
            return;
        }
        setFiles([...files, ...newFiles]);
        setStatus(null);
    };

    const handleUpload = async () => {
        if (files.length === 0) return;

        setIsUploading(true);
        setStatus({ type: 'info', message: `Uploading ${files.length} files...` });

        try {
            if (onUpload) {
                await onUpload(files);
            }
            setStatus({ type: 'success', message: 'Upload successful!' });
            setFiles([]);
        } catch (error) {
            setStatus({ type: 'danger', message: `Upload failed: ${error.message}` });
        } finally {
            setIsUploading(false);
        }
    };

    return html`
        <div class="${className}">
            <${FileUpload} 
                accept=${accept}
                multiple=${multiple}
                onFilesSelected=${handleFilesSelected}
                className="mb-4"
            />

            ${files.length > 0 ? html`
                <>
                    <h6 class="text-white-50 border-bottom border-secondary pb-2 mb-3">
                        Preview ${sortable ? html`<span class="small">(Drag to reorder)</span>` : ''}
                    </h6>
                    <${FilePreviewGrid} 
                        files=${files}
                        onFilesChange=${setFiles}
                        sortable=${sortable}
                        className="mb-4"
                    />
                </>
            ` : ''}

            ${status ? html`
                <div class="alert alert-${status.type} alert-dismissible fade show" role="alert">
                    ${status.message}
                    <button type="button" class="btn-close" data-bs-dismiss="alert"></button>
                </div>
            ` : ''}

            ${files.length > 0 ? html`
                <${Button} 
                    variant="success" 
                    size="lg"
                    className="w-100 py-3"
                    onClick=${handleUpload}
                    loading=${isUploading}
                >
                    ${isUploading ? 'Uploading...' : `Upload ${files.length} File${files.length > 1 ? 's' : ''}`}
                </${Button}>
            ` : ''}
        </div>
    `;
}

export default FileUpload;