export default function () {
	// Whether or not a node has a visible image fill on it.
	// Ignores "figma.mixed" fill values.
	function nodeHasImageFill(node) {
		return (
			'fills' in node &&
			Array.isArray(node.fills) &&
			Boolean(node.fills.find((paint) => paint.visible && paint.type === 'IMAGE'))
		)
	}

	// Returns all Figma nodes and descendants with image fills for an array of nodes
	function getImageNodes(nodes) {
		const imageNodes = []
		nodes.forEach((node) => {
			if (nodeHasImageFill(node)) {
				imageNodes.push(node)
			}

			// Checking node descendants
			if ('findAll' in node) {
				node.findAll((descendant) => {
					if (nodeHasImageFill(descendant)) {
						imageNodes.push(descendant)
					}
				})
			}
		})

		return imageNodes
	}

	// helper function for creating an annotation
	function createImageAnnotation(node, customLabel) {
		let DEFAULT_TEMPLATE = `🔵 **ALT TEXT**\n${node.name}`
		let markdown = customLabel || DEFAULT_TEMPLATE
		node.annotations = [
			{
				labelMarkdown: markdown,
				properties: [{ type: 'fills' }],
			},
		]
	}

	// helper function for notifying after annotations are created
	function showAnnotationNotification(count, skipped) {
		let msg = ''
		if (count > 0) {
			msg += `Created ${count} annotation${count > 1 ? 's' : ''}.`
		}
		if (skipped > 0) {
			msg += ` Skipped ${skipped} annotation${skipped > 1 ? 's' : ''}.`
		}
		figma.notify(msg)
	}

	// function to create annotations in selection
	// selection => selection can be figma.currentPage.selection or figma.currentPage
	// label (optional) => custom label to be annotated,
	//    if not provided will be labeled using image name
	function createAltTextAnnotations(selection, label) {
		let imageNodes = getImageNodes(selection)

		let count = 0 // number of annotations we'll create
		let skipped = 0 // number of annotations we'll skip

		imageNodes.forEach((node) => {
			// if an annotations already exists, we don't want to overwrite it
			if (node.annotations.length > 0) {
				skipped++
				return
			}

			createImageAnnotation(node, label)
			count++
		})

		showAnnotationNotification(count, skipped)
	}

	// runs plugin from menu commands
	figma.on('run', ({ command }) => {
		switch (command) {
			case 'all-images':
				createAltTextAnnotations([figma.currentPage])
				figma.closePlugin()
				break
			case 'selection':
				createAltTextAnnotations(figma.currentPage.selection)
				figma.closePlugin()
			default:
				// do nothing
				break
		}
	})
}