export const MAX_IMAGE_BYTES = 10 * 1024 * 1024

export const ALLOWED_IMAGE_MIME_TYPES = ['image/png', 'image/jpeg', 'image/webp', 'image/svg+xml']

export const ALLOWED_IMAGE_EXTENSIONS = ['.png', '.jpg', '.jpeg', '.webp', '.svg']

export const IMAGE_TYPE_REJECTION_TEXT = 'Use a PNG, JPEG, WEBP or SVG image, up to 10 MB.'

export type ImageRejectionKind = 'type' | 'size'

export type ImageValidationResult = { ok: true } | { ok: false; kind: ImageRejectionKind }

export function fileExtension(filename: string) {
	const index = filename.lastIndexOf('.')
	return index === -1 ? '' : filename.slice(index).toLowerCase()
}

export function validateImageFile(file: File): ImageValidationResult {
	if (file.size > MAX_IMAGE_BYTES) {
		return { ok: false, kind: 'size' }
	}
	const typeAllowed = ALLOWED_IMAGE_MIME_TYPES.includes(file.type)
	const extensionAllowed = ALLOWED_IMAGE_EXTENSIONS.includes(fileExtension(file.name))
	if (!typeAllowed || !extensionAllowed) {
		return { ok: false, kind: 'type' }
	}
	return { ok: true }
}

export function formatMegabytes(bytes: number) {
	return (bytes / (1024 * 1024)).toFixed(1)
}

export function isSizeRejectionBody(body: string) {
	return body.toLowerCase().includes('exceed')
}

export function rejectionTitle(filename: string) {
	return `"${filename}" can't be used`
}

export function sizeRejectionText(filename: string, bytes: number) {
	return `${filename} is ${formatMegabytes(bytes)} MB. Images can be up to 10 MB.`
}

export function formatWholeKB(bytes: number): string {
	const kb = bytes / 1024
	const rounded = Math.round(kb * 10) / 10
	if (rounded === 0) {
		return '0.0'
	}
	return Number.isInteger(rounded) ? String(rounded) : rounded.toFixed(1)
}

export function formatUploadProgress(loadedBytes: number, totalBytes: number): string {
	if (totalBytes < 1024 * 1024) {
		return `Uploading ${formatWholeKB(loadedBytes)} of ${formatWholeKB(totalBytes)} KB`
	}
	return `Uploading ${formatMegabytes(loadedBytes)} of ${formatMegabytes(totalBytes)} MB`
}