import { getLanguageService, TextDocument as HtmlTextDocument } from "vscode-html-languageservice";
import { isInsideHtml, virtualHtmlDocument } from "./html-regions.ts";
import { offsetAt, type Position, type TextDocument } from "./index.ts";

export interface HtmlCompletionItem {
  label: string;
  kind: number;
  detail?: string;
  documentation?: string;
  sortText?: string;
  insertText?: string;
}

const service = getLanguageService();

/** The virtual document as the HTML service's own document type. */
function htmlDocument(document: TextDocument) {
  const virtual = virtualHtmlDocument(document);
  return HtmlTextDocument.create(virtual.uri, "html", document.version ?? 1, virtual.text);
}

function markdown(value: unknown): string {
  if (typeof value === "string") return value;
  if (value && typeof value === "object" && "value" in value) {
    return String((value as { value: unknown }).value);
  }
  return "";
}

/**
 * HTML completions for a position inside a view block.
 *
 * Every item carries the `1` sortText prefix so the server can rank WRNexus
 * entries above these without filtering either list.
 */
export function htmlCompletions(document: TextDocument, position: Position): HtmlCompletionItem[] {
  if (!isInsideHtml(document, offsetAt(document.text, position))) return [];

  const virtual = htmlDocument(document);
  const parsed = service.parseHTMLDocument(virtual);
  const list = service.doComplete(virtual, position, parsed);

  return list.items.map((item) => ({
    label: item.label,
    kind: typeof item.kind === "number" ? item.kind : 1,
    detail: item.detail,
    documentation: markdown(item.documentation),
    sortText: `1${item.sortText ?? item.label}`,
    insertText: item.textEdit && "newText" in item.textEdit ? item.textEdit.newText : undefined,
  }));
}

export function htmlHover(document: TextDocument, position: Position): { contents: string } | null {
  if (!isInsideHtml(document, offsetAt(document.text, position))) return null;

  const virtual = htmlDocument(document);
  const result = service.doHover(virtual, position, service.parseHTMLDocument(virtual));
  if (!result) return null;

  const contents = markdown(result.contents);
  return contents ? { contents } : null;
}

export function htmlFoldingRanges(
  document: TextDocument,
): Array<{ startLine: number; endLine: number }> {
  return service
    .getFoldingRanges(htmlDocument(document))
    .map((range) => ({ startLine: range.startLine, endLine: range.endLine }));
}

/**
 * Detects `<Name attr="x" /` just before `position` and completes the `>`.
 *
 * `vscode-html-languageservice`'s own `doTagComplete` only reacts to a typed
 * `/` when it opens an end tag (`</`); it has no notion of a self-closing
 * start tag, since plain HTML has no such elements outside its fixed void-element
 * list. WRNexus components (`<Card />`) are exactly that case, so we complete
 * it ourselves rather than relying on the library.
 *
 * The scan tracks quote state from the tag's opening `<` up to `offset` (quotes
 * are only meaningful inside a tag) so a `/` inside an attribute value — e.g. the
 * first slash of `href="https://..."` — never misfires as a self-close: the
 * library already returns `null` there on purpose, because the cursor sits in an
 * attribute value, not a tag-close position.
 */
function selfClosingTagCompletion(text: string, offset: number): string | null {
  if (text.charAt(offset - 1) !== "/") return null;
  if (text.charAt(offset) === ">") return null;

  const tagStart = text.lastIndexOf("<", offset - 1);
  if (tagStart < 0) return null;
  if (!/^<[A-Za-z][\w-]*/.test(text.slice(tagStart))) return null;

  let quote: '"' | "'" | null = null;
  for (let i = tagStart + 1; i < offset - 1; i++) {
    const ch = text[i];
    if (quote) {
      if (ch === quote) quote = null;
      continue;
    }
    if (ch === '"' || ch === "'") {
      quote = ch;
      continue;
    }
    if (ch === "<" || ch === ">") return null;
  }
  if (quote) return null;

  return ">";
}

/**
 * The snippet that closes the tag being typed, or null.
 *
 * Void elements and already-closed tags return null, which is why this decision
 * belongs here rather than in the editor client.
 */
export function htmlTagComplete(document: TextDocument, position: Position): string | null {
  const offset = offsetAt(document.text, position);
  if (!isInsideHtml(document, offset)) return null;

  const virtual = htmlDocument(document);
  const result = service.doTagComplete(virtual, position, service.parseHTMLDocument(virtual));
  if (result) return result;

  return selfClosingTagCompletion(document.text, offset);
}