import DOMException from '../../exception/DOMException.js';
import DOMExceptionNameEnum from '../../exception/DOMExceptionNameEnum.js';
import File from '../../file/File.js';
import FormData from '../../form-data/FormData.js';

enum MultiparParserStateEnum {
	boundary = 0,
	headerStart = 2,
	header = 3,
	data = 5
}

const CHARACTER_CODE = {
	lf: 10,
	cr: 13
};

/**
 * Multipart reader.
 *
 * Based on:
 * https://github.com/node-fetch/node-fetch/blob/main/src/utils/multipart-parser.js (MIT)
 */
export default class MultipartReader {
	private formData = new FormData();
	private boundary: Uint8Array;
	private boundaryIndex = 0;
	private state = MultiparParserStateEnum.boundary;
	private data: {
		contentDisposition: { [key: string]: string } | null;
		value: number[];
		contentType: string | null;
		header: string;
	} = {
		contentDisposition: null,
		value: [],
		contentType: null,
		header: ''
	};

	/**
	 * Constructor.
	 *
	 * @param formData Form data.
	 * @param boundary Boundary.
	 */
	constructor(boundary: string) {
		const boundaryHeader = `--${boundary}`;
		this.boundary = new Uint8Array(boundaryHeader.length);

		for (let i = 0, max = boundaryHeader.length; i < max; i++) {
			this.boundary[i] = boundaryHeader.charCodeAt(i);
		}
	}

	/**
	 * Appends data.
	 *
	 * @param data Data.
	 */
	public write(data: Uint8Array): void {
		let char: number;
		let nextChar: number;

		for (let i = 0, max = data.length; i < max; i++) {
			char = data[i];
			nextChar = data[i + 1];

			switch (this.state) {
				case MultiparParserStateEnum.boundary:
					if (char === this.boundary[this.boundaryIndex]) {
						this.boundaryIndex++;
					} else {
						this.boundaryIndex = 0;
					}

					if (this.boundaryIndex === this.boundary.length) {
						this.state = MultiparParserStateEnum.headerStart;
						this.boundaryIndex = 0;
					}

					break;

				case MultiparParserStateEnum.headerStart:
					if (nextChar !== CHARACTER_CODE.cr && nextChar !== CHARACTER_CODE.lf) {
						this.data.header = '';
						this.state =
							data[i - 2] === CHARACTER_CODE.lf
								? MultiparParserStateEnum.data
								: MultiparParserStateEnum.header;
					}

					break;

				case MultiparParserStateEnum.header:
					if (char === CHARACTER_CODE.cr) {
						if (this.data.header) {
							const headerParts = this.data.header.split(':');
							const headerName = headerParts[0].toLowerCase();
							const headerValue = headerParts[1].trim();

							switch (headerName) {
								case 'content-disposition':
									this.data.contentDisposition = this.getContentDisposition(headerValue);
									break;
								case 'content-type':
									this.data.contentType = headerValue;
									break;
							}
						}

						this.state = MultiparParserStateEnum.headerStart;
					} else {
						this.data.header += String.fromCharCode(char);
					}

					break;

				case MultiparParserStateEnum.data:
					if (char === this.boundary[this.boundaryIndex]) {
						this.boundaryIndex++;
					} else {
						this.boundaryIndex = 0;
					}

					if (this.boundaryIndex === this.boundary.length) {
						this.state = MultiparParserStateEnum.headerStart;

						if (this.data.value.length) {
							this.appendFormData(
								this.data.contentDisposition.name,
								Buffer.from(this.data.value.slice(0, -(this.boundary.length + 1))),
								this.data.contentDisposition.filename,
								this.data.contentType
							);

							this.data.value = [];
							this.data.contentDisposition = null;
							this.data.contentType = null;
						}

						this.boundaryIndex = 0;
					} else {
						this.data.value.push(char);
					}

					break;
			}
		}
	}

	/**
	 * Ends the stream.
	 *
	 * @returns Form data.
	 */
	public end(): FormData {
		if (this.state !== MultiparParserStateEnum.data) {
			throw new DOMException(
				`Unexpected end of multipart stream. Expected state to be "${MultiparParserStateEnum.data}" but got "${this.state}".`,
				DOMExceptionNameEnum.invalidStateError
			);
		}

		this.appendFormData(
			this.data.contentDisposition.name,
			Buffer.from(this.data.value.slice(0, -2)),
			this.data.contentDisposition.filename,
			this.data.contentType
		);

		return this.formData;
	}

	/**
	 * Appends data.
	 *
	 * @param key Key.
	 * @param value value.
	 * @param filename Filename.
	 * @param type Type.
	 */
	private appendFormData(key: string, value: Buffer, filename?: string, type?: string): void {
		if (!value.length) {
			return;
		}

		if (filename) {
			this.formData.append(
				key,
				new File([value], filename, {
					type
				})
			);
		} else {
			this.formData.append(key, value.toString());
		}
	}

	/**
	 * Returns content disposition.
	 *
	 * @param headerValue Header value.
	 * @returns Content disposition.
	 */
	private getContentDisposition(headerValue: string): { [key: string]: string } {
		const regex = /([a-z]+) *= *"([^"]+)"/g;
		const contentDisposition: { [key: string]: string } = {};
		let match: RegExpExecArray;

		while ((match = regex.exec(headerValue))) {
			contentDisposition[match[1]] = match[2];
		}

		return contentDisposition;
	}
}