/**
 * Smart Keys › Enter › Insert documentation comment stub: Enter right after a `/**` that opens a
 * new comment closes it, the caret on the summary line. In PHP the stub of a function lists its
 * parameters (`@param`) and return type (`@return`), as PhpStorm does.
 */
import { EditorSelection } from "@codemirror/state";
import type { Command } from "@codemirror/view";

/** `@param` / `@return` lines for the PHP function declared in `text` (the code below the `/**`). */
export function phpDocTags(text: string): string[] {
  const m =
    /^\s*(?:#\[[^\]]*\]\s*)*(?:(?:abstract|final|public|protected|private|static)\s+)*function\s+&?\s*(\w+)\s*\(/.exec(
      text,
    );
  if (!m) return [];
  let depth = 1;
  let i = m[0].length;
  for (; i < text.length && depth > 0; i++) {
    const c = text[i];
    if (c === "(" || c === "[") depth++;
    else if (c === ")" || c === "]") depth--;
  }
  if (depth > 0) return [];
  const tags = splitTopLevel(text.slice(m[0].length, i - 1)).flatMap((param) => {
    const p = /^(?:#\[[^\]]*\]\s*)*(?:(?:public|protected|private|readonly)\s+)*([^$=.]*?)\s*(\.\.\.)?\s*(\$\w+)/.exec(
      param.trim(),
    );
    if (!p) return [];
    // `&$x` passes by reference: the `&` belongs to no type (`Foo&Bar` is an intersection).
    const type = p[1]!.replace(/&\s*$/, "").trim().replace(/\s+/g, " ");
    const name = (p[2] ?? "") + p[3];
    return [type ? `@param ${type} ${name}` : `@param ${name}`];
  });
  const ret = /^\s*:\s*([?\w\\|&() ]+?)\s*(?:\{|;|$)/.exec(text.slice(i));
  const type = ret?.[1]?.trim();
  if (type && type !== "void" && m[1] !== "__construct") tags.push(`@return ${type}`);
  return tags;
}

function splitTopLevel(params: string): string[] {
  const out: string[] = [];
  let depth = 0;
  let start = 0;
  for (let i = 0; i < params.length; i++) {
    const c = params[i];
    if (c === "(" || c === "[") depth++;
    else if (c === ")" || c === "]") depth--;
    else if (c === "," && depth === 0) {
      out.push(params.slice(start, i));
      start = i + 1;
    }
  }
  out.push(params.slice(start));
  return out.filter((p) => p.trim());
}

/** The Enter command for documents of `language` (stub tags in PHP). */
export function enterInDocComment(language: string | undefined): Command {
  return (view) => {
    const { state } = view;
    if (state.readOnly || state.selection.ranges.length !== 1) return false;
    const r = state.selection.main;
    if (!r.empty) return false;
    const block = state.languageDataAt<{ block?: { open: string; close: string } }>("commentTokens", r.head)[0]?.block;
    if (block?.open !== "/*" || block.close !== "*/") return false;
    const line = state.doc.lineAt(r.head);
    const before = line.text.slice(0, r.head - line.from);
    if (before.trim() !== "/**" || line.text.slice(r.head - line.from).trim()) return false;
    // A `/**` that already starts a doc block (the next line continues it) only breaks the line.
    const next = line.number < state.doc.lines ? state.doc.line(line.number + 1).text.trimStart() : "";
    if (next.startsWith("*")) return false;
    const indent = /^[ \t]*/.exec(before)![0];
    const br = state.lineBreak;
    const below = line.number < state.doc.lines ? state.sliceDoc(state.doc.line(line.number + 1).from) : "";
    const tags = language === "php" ? phpDocTags(below.slice(0, 4000)) : [];
    const summary = `${br}${indent} * `;
    const insert = summary + tags.map((t) => `${br}${indent} * ${t}`).join("") + `${br}${indent} */`;
    view.dispatch(
      state.update({
        changes: { from: r.head, insert },
        selection: EditorSelection.cursor(r.head + summary.length),
        scrollIntoView: true,
        userEvent: "input",
      }),
    );
    return true;
  };
}