const error = msg => {
	console.error(`[${japaste.name}] ${msg}`)
	alert(`${msg}`)
}

const toDoubleWidth = str => str.split('').map(char => {
	const code = char.charCodeAt(0)
	if (code >= 33 && code <= 126) {
		return String.fromCharCode(code + 0xFEE0)
	}
	return char
}).join('')

const toSingleWidth = str => str.split('').map(char => {
	const code = char.charCodeAt(0)
	if (code >= 0xFF01 && code <= 0xFF5E) {
		return String.fromCharCode(code - 0xFEE0)
	}
	return char
}).join('')

const splitAt = (str, ...indices) => indices.reduce((acc, idx) => {
	acc[1].push(str.slice(acc[0], idx))
	acc[0] = idx
	return acc
}, [0, []])[1]

const isDoubleWidth = char => {
	const code = char.charCodeAt(0)
	return code >= 0xFF01 && code <= 0xFF5E
}

const splitJpNumber = number => {
	const digits = toSingleWidth(number.replace(/[^0-9０-９]/g, ''))

	if (digits.length === 7) {
		return splitAt(digits, 3, 7)
	}

	if (digits.startsWith('03') || digits.startsWith('06')) {
		return splitAt(digits, 2, 6, 10)
	}

	return splitAt(digits, 3, 7, 11)
}

const setClipboard = async text => {
	try {
		await navigator.clipboard.writeText(text)
		return text
	} catch (err) {
		console.error(err)
		return ''
	}
}

const readClipboard = async () => {
	try {
		return navigator.clipboard.readText()
	} catch (err) {
		console.error(err)
		return ''
	}
}

const getNextInputField = currentInput => {
	const { form } = currentInput
	const inputs = Array.from(form.elements)
	const currentIndex = inputs.indexOf(currentInput)

	if (currentIndex > -1 && currentIndex < inputs.length - 1) {
		const nextInput = inputs[currentIndex + 1]
		if (nextInput.tagName === 'INPUT') return nextInput
	}

	return null
}

const copySubmit = async event => {
	event.stopPropagation()
	event.preventDefault()

	await setClipboard(event.currentTarget.elements[0].value)
}

const pasteSubmit = async event => {
	event.stopPropagation()
	event.preventDefault()

	const num = await readClipboard()

	if (!num) {
		error('Failed to read clipboard.')
		return
	}

	const parts = splitJpNumber(num)

	const form = event.currentTarget
	let field = form.elements[0]

	if (!field) {
		error('Cannot get active element.')
		return
	}

	if (field.tagName !== 'INPUT') {
		error('Please click on an input field before running this bookmarklet.')
		return
	}

	const firstFieldValue = field.value.trim()

	if (toSingleWidth(firstFieldValue) === parts[0]) {
		if (!isDoubleWidth(firstFieldValue)) {
			parts.forEach((part, i) => {
				parts[i] = toDoubleWidth(part)
			})
		}
	}

	while (field && parts.length && parts[0].length) {
		let nextField
		field.value = parts.shift()
		if (parts.length) nextField = getNextInputField(field)
		if (!nextField) break
		field = nextField
	}
}


const main = () => {
	document.getElementById('pn1f').addEventListener('submit', copySubmit)
	document.getElementById('pc1f').addEventListener('submit', copySubmit)
	document.getElementById('pn3f').addEventListener('submit', pasteSubmit)
	document.getElementById('pc2f').addEventListener('submit', pasteSubmit)
}

main()