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							140 lines
						
					
					
						
							4.3 KiB
						
					
					
				
			
		
		
	
	
							140 lines
						
					
					
						
							4.3 KiB
						
					
					
				'use strict';
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// ::- Persistent data structure representing an ordered mapping from
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// strings to values, with some convenient update methods.
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function OrderedMap(content) {
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  this.content = content;
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}
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OrderedMap.prototype = {
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  constructor: OrderedMap,
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  find: function(key) {
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    for (var i = 0; i < this.content.length; i += 2)
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      if (this.content[i] === key) return i
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    return -1
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  },
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  // :: (string) → ?any
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  // Retrieve the value stored under `key`, or return undefined when
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  // no such key exists.
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  get: function(key) {
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    var found = this.find(key);
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    return found == -1 ? undefined : this.content[found + 1]
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  },
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  // :: (string, any, ?string) → OrderedMap
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  // Create a new map by replacing the value of `key` with a new
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  // value, or adding a binding to the end of the map. If `newKey` is
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  // given, the key of the binding will be replaced with that key.
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  update: function(key, value, newKey) {
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    var self = newKey && newKey != key ? this.remove(newKey) : this;
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    var found = self.find(key), content = self.content.slice();
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    if (found == -1) {
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      content.push(newKey || key, value);
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    } else {
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      content[found + 1] = value;
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      if (newKey) content[found] = newKey;
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    }
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    return new OrderedMap(content)
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  },
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  // :: (string) → OrderedMap
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  // Return a map with the given key removed, if it existed.
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  remove: function(key) {
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    var found = this.find(key);
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    if (found == -1) return this
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    var content = this.content.slice();
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    content.splice(found, 2);
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    return new OrderedMap(content)
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  },
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  // :: (string, any) → OrderedMap
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  // Add a new key to the start of the map.
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  addToStart: function(key, value) {
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    return new OrderedMap([key, value].concat(this.remove(key).content))
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  },
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  // :: (string, any) → OrderedMap
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  // Add a new key to the end of the map.
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  addToEnd: function(key, value) {
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    var content = this.remove(key).content.slice();
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    content.push(key, value);
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    return new OrderedMap(content)
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  },
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  // :: (string, string, any) → OrderedMap
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  // Add a key after the given key. If `place` is not found, the new
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  // key is added to the end.
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  addBefore: function(place, key, value) {
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    var without = this.remove(key), content = without.content.slice();
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    var found = without.find(place);
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    content.splice(found == -1 ? content.length : found, 0, key, value);
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    return new OrderedMap(content)
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  },
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  // :: ((key: string, value: any))
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  // Call the given function for each key/value pair in the map, in
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  // order.
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  forEach: function(f) {
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    for (var i = 0; i < this.content.length; i += 2)
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      f(this.content[i], this.content[i + 1]);
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  },
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  // :: (union<Object, OrderedMap>) → OrderedMap
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  // Create a new map by prepending the keys in this map that don't
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  // appear in `map` before the keys in `map`.
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  prepend: function(map) {
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    map = OrderedMap.from(map);
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    if (!map.size) return this
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    return new OrderedMap(map.content.concat(this.subtract(map).content))
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  },
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  // :: (union<Object, OrderedMap>) → OrderedMap
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  // Create a new map by appending the keys in this map that don't
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  // appear in `map` after the keys in `map`.
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  append: function(map) {
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    map = OrderedMap.from(map);
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    if (!map.size) return this
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    return new OrderedMap(this.subtract(map).content.concat(map.content))
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  },
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  // :: (union<Object, OrderedMap>) → OrderedMap
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  // Create a map containing all the keys in this map that don't
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  // appear in `map`.
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  subtract: function(map) {
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    var result = this;
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    map = OrderedMap.from(map);
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    for (var i = 0; i < map.content.length; i += 2)
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      result = result.remove(map.content[i]);
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    return result
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  },
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  // :: () → Object
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  // Turn ordered map into a plain object.
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  toObject: function() {
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    var result = {};
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    this.forEach(function(key, value) { result[key] = value; });
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    return result
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  },
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  // :: number
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  // The amount of keys in this map.
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  get size() {
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    return this.content.length >> 1
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  }
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};
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// :: (?union<Object, OrderedMap>) → OrderedMap
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// Return a map with the given content. If null, create an empty
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// map. If given an ordered map, return that map itself. If given an
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// object, create a map from the object's properties.
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OrderedMap.from = function(value) {
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  if (value instanceof OrderedMap) return value
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  var content = [];
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  if (value) for (var prop in value) content.push(prop, value[prop]);
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  return new OrderedMap(content)
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};
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module.exports = OrderedMap;
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