import type { Plugin } from "unified"
import { visit } from "unist-util-visit"

type AlertKind = "note" | "tip" | "important" | "warning" | "caution"

const ALERT_KINDS = new Set<AlertKind>(["note", "tip", "important", "warning", "caution"])

/**
 * Remark plugin that recognizes GitHub-style alert blockquotes.
 *
 * It annotates the blockquote with `data-mwc-alert` and injects a marker span
 * as the first child of the first paragraph. Inline markdown inside the
 * blockquote remains intact.
 *
 * Supports both:
 * - Marker only:
 *   `> [!NOTE]`
 *   `> Body`
 * - Marker with title on same line:
 *   `> [!TIP] Title`
 *   `> Body`
 *
 * If the marker and body are in the same paragraph, the plugin splits the
 * paragraph at the first newline so the title stays on its own line.
 *
 * @example
 * > [!NOTE]
 * > This is `code`
 */
export const remarkGithubAlerts: Plugin<[], any> = () => (tree: any) => {
	visit(tree, "blockquote", (node: any) => {
		const children = Array.isArray(node.children) ? node.children : []
		if (children.length === 0) return

		const firstParagraph = children.find((child: any) => child?.type === "paragraph")
		if (!firstParagraph) return

		const paragraphChildren = Array.isArray(firstParagraph.children) ? firstParagraph.children : []
		const firstTextNodeIndex = paragraphChildren.findIndex(
			(child: any) =>
				child?.type === "text" && typeof child.value === "string" && child.value.trim().length > 0
		)
		if (firstTextNodeIndex === -1) return
		const firstTextNode = paragraphChildren[firstTextNodeIndex]

		const raw = String(firstTextNode.value)
		const markerMatch = raw.match(/^\s*\[!(NOTE|TIP|IMPORTANT|WARNING|CAUTION)\]\s*([\s\S]*)$/i)
		if (!markerMatch) return

		const alertType = markerMatch[1]
		if (!alertType) return
		const kind = alertType.toLowerCase() as AlertKind
		if (!ALERT_KINDS.has(kind)) return

		const afterMarker = markerMatch[2] ?? ""
		const splitIndex = afterMarker.indexOf("\n")
		const titleLine = splitIndex === -1 ? afterMarker : afterMarker.slice(0, splitIndex)
		const restLine = splitIndex === -1 ? "" : afterMarker.slice(splitIndex + 1)

		// Update the marker text node to remove marker and keep title line.
		firstTextNode.value = titleLine

		// Inject marker span at start of first paragraph via raw HTML.
		firstParagraph.children = [
			{
				type: "html",
				value: `<span data-mwc-alert-marker>[!${alertType.toUpperCase()}]</span>`,
			},
			...(titleLine.trim() ? [{ type: "text", value: " " }] : []),
			...paragraphChildren,
		]

		// If there is remaining content on the same paragraph line (after newline),
		// split it into a new paragraph inserted right after the first paragraph.
		if (restLine.trim()) {
			const newParagraph = {
				type: "paragraph",
				children: [{ type: "text", value: restLine.trimStart() }],
			}
			const firstIndex = children.indexOf(firstParagraph)
			if (firstIndex !== -1) {
				children.splice(firstIndex + 1, 0, newParagraph)
				node.children = children
			}
		}

		const data = (node.data ||= {})
		const hProperties = (data.hProperties ||= {}) as Record<string, any>
		hProperties["data-mwc-alert"] = kind
	})
}