'use strict'

var visit = require('unist-util-visit')

module.exports = getDefinitionFactory

var own = {}.hasOwnProperty

// Get a definition in `node` by `identifier`.
function getDefinitionFactory(node, options) {
  return getterFactory(gather(node, options))
}

// Gather all definitions in `node`
function gather(node) {
  var cache = {}

  if (!node || !node.type) {
    throw new Error('mdast-util-definitions expected node')
  }

  visit(node, 'definition', ondefinition)

  return cache

  function ondefinition(definition) {
    var id = normalise(definition.identifier)
    if (!own.call(cache, id)) {
      cache[id] = definition
    }
  }
}

// Factory to get a node from the given definition-cache.
function getterFactory(cache) {
  return getter

  // Get a node from the bound definition-cache.
  function getter(identifier) {
    var id = identifier && normalise(identifier)
    return id && own.call(cache, id) ? cache[id] : null
  }
}

function normalise(identifier) {
  return identifier.toUpperCase()
}