import type MarkdownIt from "markdown-it";
import type StateInline from "markdown-it/lib/rules_inline/state_inline.mjs";
import { escapeHtml } from "../html.ts";
import { slugify } from "../slug.ts";
import { noteUrl, wikiUrl } from "../urls.ts";

export interface WikilinkEnv {
	wikiSlug?: string;
	ownerHandle?: string;
}

export interface WikilinkTarget {
	ownerHandle?: string;
	wikiSlug?: string;
	noteSlug: string;
	label: string;
	section?: string;
}

export function parseWikilinkTarget(
	content: string,
	currentWikiSlug?: string,
	currentOwnerHandle?: string,
): WikilinkTarget | null {
	const trimmed = content.trim();
	if (!trimmed) return null;

	const pipeIdx = trimmed.indexOf("|");
	const beforePipe = (
		pipeIdx >= 0 ? trimmed.slice(0, pipeIdx) : trimmed
	).trim();
	const rawLabel = (pipeIdx >= 0 ? trimmed.slice(pipeIdx + 1) : "").trim();

	const hashIdx = beforePipe.indexOf("#");
	const rawTarget = (
		hashIdx >= 0 ? beforePipe.slice(0, hashIdx) : beforePipe
	).trim();
	const section =
		hashIdx >= 0 ? beforePipe.slice(hashIdx + 1).trim() : undefined;

	// [[#section]] — anchor-only link in the same note
	if (!rawTarget && section) {
		return { noteSlug: "", label: rawLabel || section, section };
	}

	if (!rawTarget) return null;

	const sectionSuffix = section ? `#${section}` : "";

	// [[@handle/wiki/note]] or [[@handle/wiki/]] — explicit cross-user link
	if (rawTarget.startsWith("@")) {
		const withoutAt = rawTarget.slice(1);
		const firstSlash = withoutAt.indexOf("/");
		if (firstSlash > 0) {
			const handle = withoutAt.slice(0, firstSlash);
			const rest = withoutAt.slice(firstSlash + 1);
			const secondSlash = rest.indexOf("/");
			if (secondSlash > 0) {
				const wikiSlug = rest.slice(0, secondSlash);
				const noteSlug = rest.slice(secondSlash + 1).trim();
				const defaultLabel = noteSlug
					? `@${handle}/${wikiSlug}/${noteSlug}${sectionSuffix}`
					: `@${handle}/${wikiSlug}`;
				return {
					ownerHandle: handle,
					wikiSlug,
					noteSlug,
					label: rawLabel || defaultLabel,
					...(section ? { section } : {}),
				};
			}
			// [[@handle/wiki]] — wiki home
			const wikiSlug = rest.trim();
			return {
				ownerHandle: handle,
				wikiSlug,
				noteSlug: "",
				label: rawLabel || `@${handle}/${wikiSlug}`,
				...(section ? { section } : {}),
			};
		}
		return null;
	}

	// [[note]] or [[note#section]] — note in the same wiki
	// Slugs never contain "/"; reject anything with a slash (use [[@handle/wiki/note]] instead)
	if (rawTarget.includes("/")) return null;

	return {
		...(currentOwnerHandle ? { ownerHandle: currentOwnerHandle } : {}),
		...(currentWikiSlug ? { wikiSlug: currentWikiSlug } : {}),
		noteSlug: rawTarget,
		label: rawLabel || `${rawTarget}${sectionSuffix}`,
		...(section ? { section } : {}),
	};
}

export function wikilinkPlugin(mdi: MarkdownIt): void {
	mdi.inline.ruler.push("wikilink", (state: StateInline, silent: boolean) => {
		const src = state.src;
		const pos = state.pos;

		if (src[pos] !== "[" || src[pos + 1] !== "[") return false;

		const closeIdx = src.indexOf("]]", pos + 2);
		if (closeIdx === -1) return false;

		if (!silent) {
			const env = state.env as WikilinkEnv;
			const target = parseWikilinkTarget(
				src.slice(pos + 2, closeIdx),
				env.wikiSlug,
				env.ownerHandle,
			);
			if (!target) return false;

			const anchor = target.section ? `#${slugify(target.section)}` : "";
			const noteSlug = target.noteSlug ? slugify(target.noteSlug) : "";
			const wikiSlug = target.wikiSlug ? slugify(target.wikiSlug) : "";
			let href: string;
			if (!wikiSlug && !noteSlug && target.section) {
				// [[#section]] — anchor only
				href = anchor;
			} else if (!noteSlug && wikiSlug && target.ownerHandle) {
				// [[@handle/wiki/]] — wiki home page
				href = wikiUrl(target.ownerHandle, wikiSlug) + anchor;
			} else if (wikiSlug && target.ownerHandle) {
				// [[@handle/wiki/note]]
				href = noteUrl(target.ownerHandle, wikiSlug, noteSlug) + anchor;
			} else {
				// [[note]] or [[note#section]] — bare slug in same wiki
				href = noteSlug + anchor;
			}

			const token = state.push("html_inline", "", 0);
			token.content = `<a href="${escapeHtml(href)}" class="wikilink">${escapeHtml(target.label)}</a>`;
		}

		state.pos = closeIdx + 2;
		return true;
	});
}