"use strict";

const syncpipe = require("syncpipe");
const defaultValue = require("default-value"); // FIXME: Move to config validation

const invertMapping = require("./util/invert-mapping");

module.exports = function generateTaskGraph({ tags, tasks }) {
	let tagsMapping = invertMapping(tags);

	let tasksMap = syncpipe(tasks, [
		_ => Object.entries(_),
		_ => _.map(([ name, taskDefinition ]) => {
			return [ name, {
				... taskDefinition,
				name: name,
				tags: tagsMapping[name],
				dependencies: [],
				dependents: []
			}];
		}),
		_ => new Map(_)
	]);

	function getTask(name) {
		if (tasksMap.has(name)) {
			return tasksMap.get(name);
		} else {
			throw new Error(`Encountered dependency reference to non-existent task '${name}'`);
		}
	}

	for (let task of tasksMap.values()) {
		for (let dependencyName of defaultValue(task.dependsOn, [])) {
			task.dependencies.push(getTask(dependencyName));
			getTask(dependencyName).dependents.push(task);
		}

		// NOTE: We are mutating a local copy of the task definition here, that we created further up
		delete task.dependsOn;
	}

	return tasksMap;
};