//! {"category": "libraries"}

class DatabaseList {
	constructor(name) {
		this._name = name;
	}

	_getList() {
		let self = this;
		return database.get(this._name).then(function(node) {
			return JSON.parse(node);
		}).catch(function(error) {
			return self._emptyNode();
		});
	}

	_randomKey() {
		let kAlphabet = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
		let kBytes = 32;
		let result = "";
		for (let i = 0; i < kBytes; i++) {
			result += kAlphabet.charAt(Math.floor(Math.random() * kAlphabet.length));
		}
		return this._name + "_" + result;
	}

	_emptyNode() {
		return {next: null, previous: null};
	}

	_getNode() {
		var self = this;
		var key = self._randomKey();
		return database.get(key).then(function(found) {
			if (!found) {
				return key;
			} else {
				return self._getNode();
			}
		});
	}

	_getRelative(node, next, count) {
	}

	_insertEnd(item, after) {
		let self = this;
		return this._getList().then(function(listNode) {
			let readPromises = [self._getNode()];
			readPromises.push(listNode.previous ? database.get(listNode.previous).then(JSON.parse) : null);
			readPromises.push(listNode.next ? database.get(listNode.next).then(JSON.parse) : null);
			return Promise.all(readPromises).then(function(results) {
				let newNodeName = results[0];
				let previousNode = results[1];
				let nextNode = results[2];
				let newNode = self._emptyNode();
				let oldPrevious = listNode.previous;
				let oldNext = listNode.next;
				newNode.value = item;
				newNode.previous = listNode.previous || newNodeName;
				newNode.next = listNode.next || newNodeName;
				if (after) {
					listNode.previous = newNodeName;
					listNode.next = listNode.next || newNodeName;
				} else {
					listNode.next = newNodeName;
					listNode.previous = listNode.previous || newNodeName;
				}
				let writePromises = [
					database.set(self._name, JSON.stringify(listNode)),
					database.set(newNodeName, JSON.stringify(newNode)),
				];
				if (oldPrevious && oldPrevious == oldNext) {
					previousNode.next = newNodeName;
					previousNode.previous = newNodeName;
					writePromises.push(database.set(oldPrevious, JSON.stringify(previousNode)));
				} else {
					if (previousNode) {
						previousNode.next = newNodeName;
						writePromises.push(database.set(oldPrevious, JSON.stringify(previousNode)));
					}
					if (nextNode) {
						nextNode.previous = newNodeName;
						writePromises.push(database.set(oldNext, JSON.stringify(nextNode)));
					}
				}
				return Promise.all(writePromises);
			});
		});
	}

	_removeEnd(after) {
		let self = this;
		return this._getList().then(function(listNode) {
			if (listNode.next) {
				if (listNode.next == listNode.previous) {
					return database.get(listNode.next).then(JSON.parse).then(function(removedNode) {
						let removedName = listNode.next;
						listNode.next = null;
						listNode.previous = null;
						return Promise.all([
							database.remove(removedName),
							database.set(self._name, JSON.stringify(listNode)),
						]).then(function() {
							return removedNode.value;
						});
					});
				} else {
					let name1 = listNode.previous;
					let name2 = listNode.next;
					return Promise.all([
						database.get(listNode.previous),
						database.get(listNode.next),
					]).then(function(nodes) {
						var node1 = JSON.parse(nodes[0]);
						var node2 = JSON.parse(nodes[1]);
						if (after) {
							let name0 = node1.previous;
							return database.get(name0).then(JSON.parse).then(function(node0) {
								node0.next = name2;
								node2.previous = name0;
								listNode.previous = name0;
								return Promise.all([
									database.set(name0, JSON.stringify(node0)),
									database.remove(name1),
									database.set(name2, JSON.stringify(node2)),
									database.set(self._name, JSON.stringify(listNode)),
								])
							}).then(function() {
								return node1.value;
							});
						} else {
							let name3 = node2.next;
							return database.get(name3).then(JSON.parse).then(function(node3) {
								node1.next = name3;
								node3.previous = name1;
								listNode.next = name3;
								terminal.print(name1, " ", name2, " ", name3, " ", self._name);
								terminal.print(JSON.stringify(listNode));
								return Promise.all([
									database.set(name1, JSON.stringify(node1)),
									database.remove(name2),
									database.set(name3, JSON.stringify(node3)),
									database.set(self._name, JSON.stringify(listNode)),
								])
							}).then(function() {
								return node2.value;
							});
						}
					});
				}
			}
		});
	}

	push(item) {
		return this._insertEnd(item, true);
	}

	pop() {
		return this._removeEnd(true);
	}

	shift() {
		return this._removeEnd(false);
	}

	unshift(item) {
		return this._insertEnd(item, false);
	}

	_sliceInternal(head, count, next, end, result) {
		let self = this;
		if (head[next] == end && count > 0) {
			result.push(head.value);
			return new Promise(function(resolve, reject) { resolve(result); });
		} else {
			if (count > 0) {
				return database.get(head[next]).then(JSON.parse).then(function(retrieved) {
					return self._sliceInternal(retrieved, count - 1, next, end, result).then(function(result) {
						result.push(head.value);
						return result;
					});
				});
			} else {
				return new Promise(function(resolve, reject) { resolve(result); });
			}
		}
	}

	get(count) {
		let self = this;
		return self._getList().then(function(listNode) {
			if (listNode.next) {
				return database.get(count > 0 ? listNode.next : listNode.previous).then(JSON.parse).then(function(head) {
					if (head) {
						return self._sliceInternal(
							head,
							Math.abs(count),
							count > 0 ? "next" : "previous",
							count > 0 ? listNode.next : listNode.previous,
							[]).then(function(result) {
							result.reverse();
							return result;
						});
					} else {
						return null;
					}
				});
			}
		});
	}
}

function wipeDatabase() {
	let promises = [];
	return database.getAll().then(function(list) {
		for (let i = 0; i < list.length; i++) {
			promises.push(database.remove(list[i]));
		}
	});
	return Promise.all(promises);
}

function dumpDatabase() {
	return database.getAll().then(function(list) {
		let promises = [];
		for (let i = 0; i < list.length; i++) {
			promises.push(database.get(list[i]));
		}
		return Promise.all(promises).then(function(values) {
			for (let i = 0; i < list.length; i++) {
				terminal.print(list[i], " ", values[i]);
			}
		});
	}).catch(function(error) {
		terminal.print(error);
	});
}

if (imports.terminal) {
	x = new DatabaseList("list");
	core.register("onInput", function(input) {
		if (input == "clear") {
			wipeDatabase().then(function() {
				terminal.print("Database is now empty.");
			});
		} else if (input.substring(0, "push ".length) == "push ") {
			x.push(input.substring("push ".length)).then(dumpDatabase).catch(terminal.print);
		} else if (input.substring(0, "unshift ".length) == "unshift ") {
			x.unshift(input.substring("unshift ".length)).then(dumpDatabase).catch(terminal.print);
		} else if (input == "pop") {
			x.pop().then(function(out) {
				terminal.print("POPPED: ", out);
			}).then(dumpDatabase).catch(terminal.print);
		} else if (input == "shift") {
			x.shift().then(function(out) {
				terminal.print("SHIFTED: ", out);
			}).then(dumpDatabase).catch(terminal.print);
		} else if (input.substring(0, "get ".length) == "get ") {
			let parts = input.split(" ");
			x.get(parseInt(parts[1])).then(function(result) {
				terminal.print(JSON.stringify(result))
			}).catch(terminal.print);
		} else {
			dumpDatabase();
		}
	});
}