/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at <http://mozilla.org/MPL/2.0/>. */

import { buildScopeList, parseSourceScopes } from "./visitor";

const parsedScopesCache = new Map();

export default function getScopes(location) {
  const sourceId = location.source.id;
  let parsedScopes = parsedScopesCache.get(sourceId);
  if (!parsedScopes) {
    parsedScopes = parseSourceScopes(sourceId);
    parsedScopesCache.set(sourceId, parsedScopes);
  }
  return parsedScopes ? findScopes(parsedScopes, location) : [];
}

export function clearScopes(sourceIds) {
  for (const sourceId of sourceIds) {
    parsedScopesCache.delete(sourceId);
  }
}

export { buildScopeList };

/**
 * Searches all scopes and their bindings at the specific location.
 */
function findScopes(scopes, location) {
  // Find inner most in the tree structure.
  let searchInScopes = scopes;
  const found = [];
  while (searchInScopes) {
    const foundOne = searchInScopes.some(s => {
      if (
        compareLocations(s.start, location) <= 0 &&
        compareLocations(location, s.end) < 0
      ) {
        // Found the next scope, trying to search recusevly in its children.
        found.unshift(s);
        searchInScopes = s.children;
        return true;
      }
      return false;
    });
    if (!foundOne) {
      break;
    }
  }
  return found.map(i => ({
    type: i.type,
    scopeKind: i.scopeKind,
    displayName: i.displayName,
    start: i.start,
    end: i.end,
    bindings: i.bindings,
  }));
}

function compareLocations(a, b) {
  // According to type of Location.column can be undefined, if will not be the
  // case here, ignoring flow error.
  return a.line == b.line ? a.column - b.column : a.line - b.line;
}