a-star-for-async-data
Version:
A* search algorithm for asynchronous data sources
239 lines (238 loc) • 9.85 kB
JavaScript
;
var __generator = (this && this.__generator) || function (thisArg, body) {
var _ = { label: 0, sent: function() { if (t[0] & 1) throw t[1]; return t[1]; }, trys: [], ops: [] }, f, y, t, g;
return g = { next: verb(0), "throw": verb(1), "return": verb(2) }, typeof Symbol === "function" && (g[Symbol.iterator] = function() { return this; }), g;
function verb(n) { return function (v) { return step([n, v]); }; }
function step(op) {
if (f) throw new TypeError("Generator is already executing.");
while (_) try {
if (f = 1, y && (t = y[op[0] & 2 ? "return" : op[0] ? "throw" : "next"]) && !(t = t.call(y, op[1])).done) return t;
if (y = 0, t) op = [0, t.value];
switch (op[0]) {
case 0: case 1: t = op; break;
case 4: _.label++; return { value: op[1], done: false };
case 5: _.label++; y = op[1]; op = [0]; continue;
case 7: op = _.ops.pop(); _.trys.pop(); continue;
default:
if (!(t = _.trys, t = t.length > 0 && t[t.length - 1]) && (op[0] === 6 || op[0] === 2)) { _ = 0; continue; }
if (op[0] === 3 && (!t || (op[1] > t[0] && op[1] < t[3]))) { _.label = op[1]; break; }
if (op[0] === 6 && _.label < t[1]) { _.label = t[1]; t = op; break; }
if (t && _.label < t[2]) { _.label = t[2]; _.ops.push(op); break; }
if (t[2]) _.ops.pop();
_.trys.pop(); continue;
}
op = body.call(thisArg, _);
} catch (e) { op = [6, e]; y = 0; } finally { f = t = 0; }
if (op[0] & 5) throw op[1]; return { value: op[0] ? op[1] : void 0, done: true };
}
};
Object.defineProperty(exports, "__esModule", { value: true });
var logLevels = {
'none': 0,
'info': 1,
'debug': 2
};
var log_level = 0;
function log(msg) {
if (log_level >= logLevels.info) {
console.log(msg);
}
}
// fn runGenerator : based on code by Kyle Simpson (https://davidwalsh.name/async-generators on Dec 7, 2016)
function runGenerator(it) {
var ret;
var value = undefined;
var promise = new Promise(function (resolve, reject) {
// asynchronously iterate over generator
(function iterate(val) {
try {
ret = it.next(val);
if (!ret.done) {
value = ret.value;
// poor man's "is it a promise?" test
if (ret.value && typeof ret.value === "object" && "then" in ret.value) {
// wait on the promise
ret.value.then(iterate);
}
else {
// avoid synchronous recursion
setTimeout(function () {
iterate(ret.value);
}, 0);
}
}
else {
resolve(value);
}
}
catch (err) {
reject(err);
}
})();
});
return promise;
}
var Astar = /** @class */ (function () {
function Astar(customCallbackFuncs) {
if (customCallbackFuncs === void 0) { customCallbackFuncs = {}; }
this.exitArcsForNodeId = customCallbackFuncs.exitArcsForNodeId || this.exitArcsForNodeId;
this.h = customCallbackFuncs.h || this.h;
}
// Calculate the heuristic cost to traverse from one node to another.
Astar.prototype.h = function (from, to) {
return 0;
};
// Promisify h
Astar.prototype.lookupH = function (from, to) {
return Promise.resolve(this.h(from, to));
};
// This function is used to test the goal state if the user provides a non function
// for the search goal.
Astar.prototype.exactMatchGoalFunc = function (goalNodeId) {
return function (testNodeId) {
return Promise.resolve(goalNodeId === testNodeId);
};
};
/*
* Clean-up a passed in goal function to ensure that it is usable.
*
* Functions are assumed to test a given node to see if it is a goal
* node. It should return a boolean or a Promise thereof.
* Boolean functions are Promisified.
*
* Simple non-func values are assumed to be goal node IDs.
*
* TODO: Perhaps we can have a built in function to handle arrays?
* (Or is that best left to the caller?)
*/
Astar.prototype.cleanGoalFunc = function (goalOrGoalFunc) {
if (goalOrGoalFunc && {}.toString.call(goalOrGoalFunc) !== '[object Function]') {
return this.exactMatchGoalFunc(String(goalOrGoalFunc));
}
else {
var goalFunc_1 = goalOrGoalFunc;
// A goal function was provided. Le'ts be sure it's promisified.
return function (a) {
return Promise.resolve(goalFunc_1(a));
};
}
};
/*
* This is a function that should return an array of edge data in the following
* form (or a Promise that resolves to this data):
*
* [
* { from: <originNodeId>, to: <targetNodeId>}, cost: <edgeCost> },
* .
* .
* .
* ]
*
*/
Astar.prototype.exitArcsForNodeId = function (nodeId) {
return [];
};
// Promisify exitArcsForNodeId
Astar.prototype.lookupExitArcsForNodeId = function (nodeId) {
return Promise.resolve(this.exitArcsForNodeId(nodeId));
};
// By "extracting" the find path into a generator we can use synchronous-y constructs
// while still providing async functionalities.
Astar.prototype.findPathGenerator = function (startNodeId, goalOrGoalFunc) {
var goalFunc, cameFrom, fCosts, gCosts, open, closed, iteration, bestId, nodeId, edges, _i, edges_1, edge_1, toNodeId, bestGCost, newGCost, gCostExists, _a, _b, _c, path, edge;
return __generator(this, function (_d) {
switch (_d.label) {
case 0:
goalFunc = this.cleanGoalFunc(goalOrGoalFunc);
startNodeId = String(startNodeId);
log("Finding path between " + startNodeId + " and " + goalOrGoalFunc);
cameFrom = {};
fCosts = {};
gCosts = {};
open = {};
closed = {};
iteration = 1;
open[startNodeId] = startNodeId;
cameFrom[startNodeId] = false;
gCosts[startNodeId] = 0;
fCosts[startNodeId] = 0; // Is this correct?
_d.label = 1;
case 1:
if (!true) return [3 /*break*/, 9];
bestId = null;
// Select the best candidate from the open nodes.
for (nodeId in open) {
if (bestId === null || fCosts[nodeId] < fCosts[bestId]) {
bestId = nodeId;
}
}
if (bestId === null) {
throw "No path to goal";
}
return [4 /*yield*/, goalFunc(bestId)];
case 2:
if (_d.sent()) {
// We have a solution!
return [3 /*break*/, 9];
}
return [4 /*yield*/, this.lookupExitArcsForNodeId(bestId)];
case 3:
edges = _d.sent();
_i = 0, edges_1 = edges;
_d.label = 4;
case 4:
if (!(_i < edges_1.length)) return [3 /*break*/, 8];
edge_1 = edges_1[_i];
toNodeId = String(edge_1.to);
if (!!closed[toNodeId]) return [3 /*break*/, 7];
bestGCost = gCosts[bestId];
newGCost = bestGCost + edge_1.cost;
gCostExists = gCosts.hasOwnProperty(toNodeId);
if (!(!gCostExists || gCosts[toNodeId] > newGCost)) return [3 /*break*/, 6];
gCosts[toNodeId] = newGCost;
_a = fCosts;
_b = toNodeId;
_c = newGCost;
return [4 /*yield*/, this.lookupH(startNodeId, toNodeId)];
case 5:
_a[_b] = _c + (_d.sent());
cameFrom[toNodeId] = edge_1;
_d.label = 6;
case 6:
open[toNodeId] = toNodeId;
_d.label = 7;
case 7:
_i++;
return [3 /*break*/, 4];
case 8:
;
closed[bestId] = true;
delete open[bestId];
iteration++;
return [3 /*break*/, 1];
case 9:
path = [];
for (edge = cameFrom[bestId]; edge !== false; edge = cameFrom[String(edge.from)]) {
path.unshift(edge);
}
return [4 /*yield*/, {
cost: gCosts[bestId],
path: path
}];
case 10:
_d.sent();
return [2 /*return*/];
}
});
};
Astar.prototype.findPath = function (startNodeId, goalFunc) {
var pathGenerator = this.findPathGenerator(startNodeId, goalFunc);
return runGenerator(pathGenerator);
};
return Astar;
}());
exports.Astar = Astar;
Astar.Debug = function () {
log_level = 1;
return Astar;
};