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// SPDX-FileCopyrightText: 2024 Shota FUJI <pockawoooh@gmail.com>
//
// SPDX-License-Identifier: Apache-2.0

import type * as Mdast from "../../deps/npm/mdast/types.ts";
import type { Extension } from "../../deps/npm/mdast-util-from-markdown/mod.ts";
import { SKIP, visit } from "../../deps/npm/unist-util-visit/mod.ts";

import type { OfmWikilinkEmbed } from "../mdast_util_ofm_wikilink/mod.ts";

const SEPARATOR = "|";
const SIZE_ATTR_REGEXP_PATTERN = /^([1-9][0-9]*)(x([1-9][0-9]*))?$/;

function parseSegment(
	segment: string,
): { width: number; height: number | null } | null {
	const match = segment.match(SIZE_ATTR_REGEXP_PATTERN);
	if (!match) {
		return null;
	}

	const wStr = match[1];
	const hStr = match[3];

	const width = parseInt(wStr, 10);
	const height = typeof hStr === "string" ? parseInt(hStr, 10) : null;

	// Reject invalid values
	if (
		!Number.isFinite(width) || width <= 0 ||
		(typeof height === "number" && (!Number.isFinite(height) || height <= 0))
	) {
		return null;
	}

	return { width, height };
}

function setSizeToNode(node: Mdast.Node, width: number, height: number | null) {
	node.data ??= {};

	// @ts-expect-error: unist-related libraries heavily relies on ambient module declarations,
	//                   which Deno does not support. APIs also don't accept type parameters.
	node.data.width = width;

	if (typeof height === "number") {
		// @ts-expect-error: unist-related libraries heavily relies on ambient module declarations,
		//                   which Deno does not support. APIs also don't accept type parameters.
		node.data.height = height;
	}

	node.data.hProperties = {
		...node.data.hProperties ?? {},
		width,
		height: typeof height === "number" ? height : undefined,
	};
}

/**
 * This function parses Obsidian's image size attribute extension, and modifies
 * image label and data in-place.
 *
 * @param tree - Tree to change. This function mutates this argument.
 */
export function ofmImageSize(): Extension {
	return {
		transforms: [
			(root: Mdast.Root | OfmWikilinkEmbed) => {
				visit(root, (node) => {
					return node.type === "image" || node.type === "imageReference" ||
						node.type === "ofmWikilinkEmbed";
				}, (node) => {
					switch (node.type) {
						case "image":
						case "imageReference": {
							if (!node.alt) {
								return SKIP;
							}

							const segments = node.alt.split(SEPARATOR);

							switch (segments.length) {
								case 1: {
									const result = parseSegment(segments[0]);
									if (!result) {
										return SKIP;
									}

									setSizeToNode(node, result.width, result.height);
									return;
								}
								case 2: {
									const [alt, segment] = segments;
									const result = parseSegment(segment);
									if (!result) {
										return SKIP;
									}

									setSizeToNode(node, result.width, result.height);

									node.alt = alt;

									return;
								}
								default: {
									return SKIP;
								}
							}
						}
						case "ofmWikilinkEmbed": {
							if (!node.label) {
								return SKIP;
							}

							const result = parseSegment(node.label);
							if (!result) {
								return SKIP;
							}

							setSizeToNode(node, result.width, result.height);
							return SKIP;
						}
					}
				});
			},
		],
	};
}