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solvent.go
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solvent.go
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package solvent
import (
"fmt"
"slices"
"sort"
"strings"
"time"
"github.com/eldelto/core/internal/crdt"
"github.com/google/uuid"
)
// OrderValue represents an ordering value with its correspondent update timestamp
type OrderValue struct {
Value float64
UpdatedAt int64
}
// Title represents a title value with its correspondent update timestamp
type Title struct {
Value string
UpdatedAt int64
}
// ToDoItem representa a single task that needs to be done
type ToDoItem struct {
ID uuid.UUID
Title string
Checked bool
OrderValue OrderValue
}
// Identifier returns the ID of the ToDoItem
func (t *ToDoItem) Identifier() string {
return t.ID.String()
}
// Merge combines the current ToDoItem with the one passed in as
// parameter or returns a CannotBeMerged error if the ToDoItems
// cannot be merged (e.g. they have different IDs)
func (t *ToDoItem) Merge(other crdt.Mergeable) (crdt.Mergeable, error) {
if t.Identifier() != other.Identifier() {
err := crdt.NewCannotBeMergedError(t, other)
return nil, err
}
otherToDoItem, ok := other.(*ToDoItem)
if !ok {
err := crdt.NewTypeMismatchError(t, other)
return nil, err
}
mergedToDoItem := ToDoItem{
ID: t.ID,
Title: t.Title,
Checked: t.Checked,
OrderValue: t.OrderValue,
}
if otherToDoItem.Checked {
mergedToDoItem.Checked = true
}
if otherToDoItem.OrderValue.UpdatedAt > t.OrderValue.UpdatedAt {
mergedToDoItem.OrderValue = otherToDoItem.OrderValue
}
return &mergedToDoItem, nil
}
func (t *ToDoItem) String() string {
b := strings.Builder{}
b.WriteString("- [")
if t.Checked {
b.WriteRune('X')
} else {
b.WriteRune(' ')
}
b.WriteString("] ")
b.WriteString(t.Title)
return b.String()
}
// ToDoList represents a whole list of ToDoItems
type ToDoList struct {
ID uuid.UUID
Title Title
ToDoItems crdt.PSet[*ToDoItem]
CreatedAt int64
}
// NewToDoList create a new ToDoList object with the given title
// or returns an UnknownError when the ID generation fails
func newToDoList(title string) (*ToDoList, error) {
id, err := randomUUID()
if err != nil {
return nil, err
}
titleStruct := Title{
Value: title,
UpdatedAt: time.Now().UTC().UnixNano(),
}
toDoList := ToDoList{
ID: id,
Title: titleStruct,
ToDoItems: crdt.NewPSet[*ToDoItem]("ToDoListPSet"),
CreatedAt: time.Now().UTC().UnixNano(),
}
return &toDoList, nil
}
// Rename sets the title of the ToDoList to the given one and updates
// the UpdatedAt field
// TODO: Use types for ToDoListID and ToDoItemID
func (tdl *ToDoList) Rename(title string) {
newTitle := Title{
Value: title,
UpdatedAt: time.Now().UTC().UnixNano(),
}
tdl.Title = newTitle
}
// AddItem creates a new ToDoItem object and adds it to the ToDoList
// it is called on
func (tdl *ToDoList) AddItem(title string) (uuid.UUID, error) {
id, err := randomUUID()
if err != nil {
return uuid.Nil, err
}
orderValue := OrderValue{
Value: tdl.nextOrderValue(),
UpdatedAt: time.Now().UTC().UnixNano(),
}
item := ToDoItem{
ID: id,
Title: title,
Checked: false,
OrderValue: orderValue,
}
err = tdl.ToDoItems.Add(&item)
return id, err
}
// GetItem returns the ToDoItem matching the given id or returns a
// NotFoundError if no match could be found
func (tdl *ToDoList) GetItem(id uuid.UUID) (ToDoItem, error) {
item, ok := tdl.ToDoItems.LiveView()[id.String()]
if !ok {
return ToDoItem{}, newNotFoundError(id)
}
return *item, nil
}
// RemoveItem removes the ToDoItem with the given id from the ToDoList
// but won't return an error if no match could be found as it is the
// desired state
func (tdl *ToDoList) RemoveItem(id uuid.UUID) {
item, err := tdl.GetItem(id)
if err == nil {
tdl.ToDoItems.Remove(&item)
}
}
// CheckItem checks the ToDoItem with the given id or returns a
// NotFoundError if no match could be found
func (tdl *ToDoList) CheckItem(id uuid.UUID) (uuid.UUID, error) {
item, err := tdl.GetItem(id)
if err != nil {
return uuid.Nil, fmt.Errorf("failed to check item: %w", err)
}
item.Checked = true
tdl.ToDoItems.Add(&item)
return item.ID, nil
}
// UncheckItem unchecks the ToDoItem with the given id by creating a new
// ToDoItem object with the same attributes or returns a NotfoundError
// if no match could be found
func (tdl *ToDoList) UncheckItem(id uuid.UUID) (uuid.UUID, error) {
item, err := tdl.GetItem(id)
if err != nil {
return uuid.Nil, fmt.Errorf("failed to uncheck item: %w", err)
}
tdl.RemoveItem(item.ID)
newID, err := randomUUID()
if err != nil {
return newID, fmt.Errorf("failed to uncheck item: %w", err)
}
newItem := ToDoItem{
ID: newID,
Title: item.Title,
Checked: false,
OrderValue: item.OrderValue,
}
if err := tdl.ToDoItems.Add(&newItem); err != nil {
return uuid.Nil, fmt.Errorf("failed to uncheck item: %w", err)
}
return newID, nil
}
// TODO: Implement RenameItem(id uuid.UUID, title string)
// GetItems returns a slice with all ToDoItems that are in the liveSet
// but not in the tombstoneSet and are therefore considered active
func (tdl *ToDoList) GetItems() []ToDoItem {
return tdl.GetOrderedItems(false)
}
func (tdl *ToDoList) GetOrderedItems(doneToBottom bool) []ToDoItem {
// TODO: Benchmark pre-allocation
liveView := tdl.ToDoItems.LiveView()
items := make([]ToDoItem, 0, len(liveView))
for _, item := range liveView {
if doneToBottom && item.Checked {
item.OrderValue.Value = item.OrderValue.Value + 1000
}
items = append(items, *item)
}
slices.SortFunc(items, func(a, b ToDoItem) int {
return int((a.OrderValue.Value - b.OrderValue.Value) * 1000)
})
return items
}
// MoveItem moves the ToDoItem with the given id to the targeted index
// or returns a NotFoundError if no match could be found
func (tdl *ToDoList) MoveItem(id uuid.UUID, targetIndex int) error {
item, err := tdl.GetItem(id)
if err != nil {
return fmt.Errorf("failed to move item: %w", err)
}
items := tdl.GetItems()
index := clampIndex(targetIndex, items)
sort.Slice(items, func(i, j int) bool { return items[i].OrderValue.Value < items[j].OrderValue.Value })
orderValueMid := items[index].OrderValue.Value
var orderValueAdjacent float64
if orderValueMid < item.OrderValue.Value {
// Moving item up
if (index - 1) >= 0 {
orderValueAdjacent = items[index-1].OrderValue.Value
} else {
orderValueAdjacent = 0.0
}
} else if orderValueMid > item.OrderValue.Value {
// Moving item down
if (index + 1) < len(items) {
orderValueAdjacent = items[index+1].OrderValue.Value
} else {
orderValueAdjacent = tdl.nextOrderValue()
}
} else {
// Already on correct position
return nil
}
newOrderValue := OrderValue{
Value: (orderValueMid + orderValueAdjacent) / 2,
UpdatedAt: time.Now().UTC().UnixNano(),
}
item.OrderValue = newOrderValue
if err := tdl.ToDoItems.Add(&item); err != nil {
return fmt.Errorf("failed to move item: %w", err)
}
return nil
}
// Identifier returns the ID of the ToDoList
func (tdl *ToDoList) Identifier() string {
return tdl.ID.String()
}
// Merge combines the current ToDoList with the one passed in as
// parameter or returns a CannotBeMerged error if the ToDoLists or
// their ToDoListItems cannot be merged (e.g. they have different IDs)
func (tdl *ToDoList) Merge(other crdt.Mergeable) (crdt.Mergeable, error) {
if tdl.Identifier() != other.Identifier() {
return nil, crdt.NewCannotBeMergedError(tdl, other)
}
otherToDoList, ok := other.(*ToDoList)
if !ok {
err := crdt.NewTypeMismatchError(tdl, other)
return nil, err
}
var title Title
if otherToDoList.Title.UpdatedAt > tdl.Title.UpdatedAt {
title = otherToDoList.Title
} else {
title = tdl.Title
}
mergedToDoItems, err := tdl.ToDoItems.Merge(&otherToDoList.ToDoItems)
if err != nil {
return nil, err
}
mergedToDoList := ToDoList{
ID: tdl.ID,
Title: title,
ToDoItems: *mergedToDoItems.(*crdt.PSet[*ToDoItem]),
CreatedAt: tdl.CreatedAt,
}
return &mergedToDoList, nil
}
func (tdl *ToDoList) IsCompleted() bool {
liveView := tdl.ToDoItems.LiveView()
for _, item := range liveView {
if !item.Checked {
return false
}
}
return true
}
func (tdl *ToDoList) String() string {
b := strings.Builder{}
b.WriteString(tdl.Title.Value)
b.WriteByte('\n')
b.WriteByte('\n')
for _, item := range tdl.GetItems() {
b.WriteString(item.String())
b.WriteByte('\n')
}
return b.String()
}
type Notebook struct {
ID uuid.UUID
ToDoLists crdt.PSet[*ToDoList]
CreatedAt int64
}
func NewNotebook() (*Notebook, error) {
id, err := randomUUID()
if err != nil {
return nil, err
}
notebook := Notebook{
ID: id,
ToDoLists: crdt.NewPSet[*ToDoList]("ToDoListPSet"),
CreatedAt: time.Now().UTC().UnixNano(),
}
return ¬ebook, nil
}
func (n *Notebook) AddList(title string) (*ToDoList, error) {
list, err := newToDoList(title)
if err != nil {
return nil, err
}
err = n.ToDoLists.Add(list)
if err != nil {
return nil, err
}
return list, nil
}
func (n *Notebook) RemoveList(id uuid.UUID) {
list, err := n.GetList(id)
if err == nil {
n.ToDoLists.Remove(list)
}
}
func (n *Notebook) GetList(id uuid.UUID) (*ToDoList, error) {
// TODO: Move Get method to PSet?
list, ok := n.ToDoLists.LiveView()[id.String()]
if !ok {
return nil, newNotFoundError(id)
}
return list, nil
}
func (n *Notebook) GetLists() []*ToDoList {
liveView := n.ToDoLists.LiveView()
lists := make([]*ToDoList, 0, len(liveView))
for _, list := range liveView {
lists = append(lists, list)
}
return lists
}
func (n *Notebook) GetOpenLists() []*ToDoList {
liveView := n.ToDoLists.LiveView()
lists := make([]*ToDoList, 0, len(liveView))
for _, list := range liveView {
if !list.IsCompleted() {
lists = append(lists, list)
}
}
slices.SortFunc(lists, func(a, b *ToDoList) int {
return int(b.CreatedAt - a.CreatedAt)
})
return lists
}
func (n *Notebook) GetCompletedLists() []*ToDoList {
liveView := n.ToDoLists.LiveView()
lists := make([]*ToDoList, 0, len(liveView))
for _, list := range liveView {
if list.IsCompleted() {
lists = append(lists, list)
}
}
slices.SortFunc(lists, func(a, b *ToDoList) int {
return int(b.CreatedAt - a.CreatedAt)
})
return lists
}
func (n *Notebook) Identifier() string {
return n.ID.String()
}
func (n *Notebook) Merge(other crdt.Mergeable) (crdt.Mergeable, error) {
if n.Identifier() != other.Identifier() {
err := crdt.NewCannotBeMergedError(n, other)
return nil, err
}
otherNotebook, ok := other.(*Notebook)
if !ok {
err := crdt.NewTypeMismatchError(n, other)
return nil, err
}
mergedToDoLists, err := n.ToDoLists.Merge(&otherNotebook.ToDoLists)
if err != nil {
return nil, err
}
mergedNotebook := Notebook{
ID: n.ID,
ToDoLists: *mergedToDoLists.(*crdt.PSet[*ToDoList]),
CreatedAt: n.CreatedAt,
}
return &mergedNotebook, nil
}
func randomUUID() (uuid.UUID, error) {
id, err := uuid.NewRandom()
if err != nil {
err = &UnknownError{
message: "item creation failed with nested error",
err: err,
}
}
return id, err
}
func (tdl *ToDoList) nextOrderValue() float64 {
orderValue := 0.0
for _, item := range tdl.ToDoItems.LiveView() {
if item.OrderValue.Value > orderValue {
orderValue = item.OrderValue.Value
}
}
return orderValue + 10
}
func clampIndex(index int, list []ToDoItem) int {
max := len(list) - 1
if index < 0 {
return 0
} else if index > max {
return max
} else {
return index
}
}
// NotFoundError indicates that a ToDoListItem with the given ID
// does not exist
type NotFoundError struct {
ID uuid.UUID
message string
}
func newNotFoundError(id uuid.UUID) *NotFoundError {
return &NotFoundError{
ID: id,
message: fmt.Sprintf("item with ID '%v' could not be found", id),
}
}
func (e *NotFoundError) Error() string {
return e.message
}
// UnknownError indicates an unhandled error from another library that
// gets wrapped
type UnknownError struct {
err error
message string
}
func (e *UnknownError) Error() string {
return e.message
}
func (e *UnknownError) Unwrap() error {
return e.err
}