Implement data models for Checkvist API entities

Add models.go with all data structures:
- Checklist struct with fields for ID, Name, Public, Archived, etc.
- Task struct with full task data including status, priority, due dates
- TaskStatus enum (StatusOpen, StatusClosed, StatusInvalidated)
- Note struct for task comments
- User struct for user information
- Tags type as map[string]bool for efficient lookup
- DueDate struct with smart syntax support and constructors
  (DueAt, DueString, DueInDays) and constants (DueToday, DueTomorrow,
  DueNextWeek, DueNextMonth)

Closes checkvist-api-e9p

.beads/issues.jsonl

@@ -16,7 +16,7 @@
 {"id":"checkvist-api-br3","title":"Core API Operations","description":"Phase 2: Implement CRUD operations for Checklists, Tasks, and Notes. All P0 (must-have) features for the library.","status":"open","priority":0,"issue_type":"epic","owner":"mail@oliverjakoubek.de","created_at":"2026-01-14T12:30:53.20627925+01:00","created_by":"Oliver Jakoubek","updated_at":"2026-01-14T12:30:53.20627925+01:00"}
 {"id":"checkvist-api-c2k","title":"Implement Checklist operations","description":"Create checklists.go with ChecklistService:\n- client.Checklists() returns ChecklistService\n- List(ctx) ([]Checklist, error) - GET /checklists.json\n- Get(ctx, id) (*Checklist, error) - GET /checklists/{id}.json\n- Create(ctx, name) (*Checklist, error) - POST /checklists.json\n- Update(ctx, id, name) (*Checklist, error) - PUT /checklists/{id}.json\n- Delete(ctx, id) error - DELETE /checklists/{id}.json\n- Support archived filter in List\nContext support for all methods.","status":"open","priority":0,"issue_type":"feature","owner":"mail@oliverjakoubek.de","created_at":"2026-01-14T12:30:53.566197933+01:00","created_by":"Oliver Jakoubek","updated_at":"2026-01-14T12:30:53.566197933+01:00","dependencies":[{"issue_id":"checkvist-api-c2k","depends_on_id":"checkvist-api-8u6","type":"blocks","created_at":"2026-01-14T12:32:54.533462004+01:00","created_by":"Oliver Jakoubek"},{"issue_id":"checkvist-api-c2k","depends_on_id":"checkvist-api-lpn","type":"blocks","created_at":"2026-01-14T12:32:54.859645166+01:00","created_by":"Oliver Jakoubek"}]}
 {"id":"checkvist-api-cb8","title":"Extended Features","description":"Phase 3: Implement P1 (should-have) features including client-side filtering and builder patterns for fluent interfaces.","status":"open","priority":1,"issue_type":"epic","owner":"mail@oliverjakoubek.de","created_at":"2026-01-14T12:30:55.624242123+01:00","created_by":"Oliver Jakoubek","updated_at":"2026-01-14T12:30:55.624242123+01:00"}
-{"id":"checkvist-api-e9p","title":"Implement data models","description":"Create models.go with all data structures:\n- Checklist struct (ID, Name, Public, Archived, ReadOnly, TaskCount, TaskCompleted, Tags, TagsAsText, UpdatedAt)\n- Task struct (ID, ChecklistID, ParentID, Content, Status, Position, Priority, Tags, TagsAsText, DueDateRaw, DueDate, AssigneeIDs, CommentsCount, UpdateLine, UpdatedAt, CreatedAt, Children, Notes)\n- TaskStatus enum (StatusOpen=0, StatusClosed=1, StatusInvalidated=2)\n- Note struct (ID, TaskID, Comment, UpdatedAt, CreatedAt)\n- Tags type (map[string]bool)\n- User struct (ID, Username, Email)\n- DueDate struct with constructors (DueAt, DueString, DueInDays) and constants (DueToday, DueTomorrow, DueNextWeek, DueNextMonth)","status":"open","priority":0,"issue_type":"task","owner":"mail@oliverjakoubek.de","created_at":"2026-01-14T12:31:06.900391036+01:00","created_by":"Oliver Jakoubek","updated_at":"2026-01-14T12:31:06.900391036+01:00","dependencies":[{"issue_id":"checkvist-api-e9p","depends_on_id":"checkvist-api-5wr","type":"blocks","created_at":"2026-01-14T12:32:46.433908937+01:00","created_by":"Oliver Jakoubek"}]}
+{"id":"checkvist-api-e9p","title":"Implement data models","description":"Create models.go with all data structures:\n- Checklist struct (ID, Name, Public, Archived, ReadOnly, TaskCount, TaskCompleted, Tags, TagsAsText, UpdatedAt)\n- Task struct (ID, ChecklistID, ParentID, Content, Status, Position, Priority, Tags, TagsAsText, DueDateRaw, DueDate, AssigneeIDs, CommentsCount, UpdateLine, UpdatedAt, CreatedAt, Children, Notes)\n- TaskStatus enum (StatusOpen=0, StatusClosed=1, StatusInvalidated=2)\n- Note struct (ID, TaskID, Comment, UpdatedAt, CreatedAt)\n- Tags type (map[string]bool)\n- User struct (ID, Username, Email)\n- DueDate struct with constructors (DueAt, DueString, DueInDays) and constants (DueToday, DueTomorrow, DueNextWeek, DueNextMonth)","status":"closed","priority":0,"issue_type":"task","owner":"mail@oliverjakoubek.de","created_at":"2026-01-14T12:31:06.900391036+01:00","created_by":"Oliver Jakoubek","updated_at":"2026-01-14T13:22:22.273934664+01:00","closed_at":"2026-01-14T13:22:22.273934664+01:00","close_reason":"Closed","dependencies":[{"issue_id":"checkvist-api-e9p","depends_on_id":"checkvist-api-5wr","type":"blocks","created_at":"2026-01-14T12:32:46.433908937+01:00","created_by":"Oliver Jakoubek"}]}
 {"id":"checkvist-api-lpn","title":"Implement authentication with auto token renewal","description":"Add to client.go:\n- Authenticate(ctx context.Context) error - explicit login\n- refreshToken(ctx context.Context) error - token renewal\n- ensureAuthenticated(ctx context.Context) error - auto-auth before requests\n- CurrentUser(ctx context.Context) (*User, error) - get logged in user\n- Token management: store token and expiry, auto-refresh before expiry\n- Thread-safe token access using mutex\n- Support for optional 2FA token\nAPI endpoints:\n- POST /auth/login.json?version=2 (login)\n- POST /auth/refresh_token.json?version=2 (refresh)\n- GET /auth/curr_user.json (current user)\nToken sent via X-Client-Token header","status":"open","priority":0,"issue_type":"task","owner":"mail@oliverjakoubek.de","created_at":"2026-01-14T12:31:08.358878117+01:00","created_by":"Oliver Jakoubek","updated_at":"2026-01-14T12:31:08.358878117+01:00","dependencies":[{"issue_id":"checkvist-api-lpn","depends_on_id":"checkvist-api-ymg","type":"blocks","created_at":"2026-01-14T12:32:47.656124681+01:00","created_by":"Oliver Jakoubek"}]}
 {"id":"checkvist-api-mnh","title":"Implement error types and sentinel errors","description":"Create errors.go with:\n- APIError struct (StatusCode, Message, RequestID, Err) with Error() and Unwrap() methods\n- Sentinel errors: ErrUnauthorized, ErrNotFound, ErrRateLimited, ErrBadRequest, ErrServerError\n- Helper function to create APIError from HTTP response","status":"open","priority":0,"issue_type":"task","owner":"mail@oliverjakoubek.de","created_at":"2026-01-14T12:31:07.619359293+01:00","created_by":"Oliver Jakoubek","updated_at":"2026-01-14T12:31:07.619359293+01:00","dependencies":[{"issue_id":"checkvist-api-mnh","depends_on_id":"checkvist-api-5wr","type":"blocks","created_at":"2026-01-14T12:32:46.754134799+01:00","created_by":"Oliver Jakoubek"}]}
 {"id":"checkvist-api-nrk","title":"Create README with quickstart","description":"Create README.md (in English) with:\n- Project description\n- Installation: go get code.beautifulmachines.dev/jakoubek/checkvist-api\n- Quick start example (init client, list checklists, create task)\n- API overview (Checklists, Tasks, Notes, Filters)\n- Builder pattern examples\n- Error handling examples\n- Configuration options\n- Link to GoDoc\n- License (MIT)","status":"open","priority":0,"issue_type":"task","owner":"mail@oliverjakoubek.de","created_at":"2026-01-14T12:31:38.724338606+01:00","created_by":"Oliver Jakoubek","updated_at":"2026-01-14T12:31:38.724338606+01:00","dependencies":[{"issue_id":"checkvist-api-nrk","depends_on_id":"checkvist-api-c2k","type":"blocks","created_at":"2026-01-14T12:33:15.785698203+01:00","created_by":"Oliver Jakoubek"},{"issue_id":"checkvist-api-nrk","depends_on_id":"checkvist-api-rl9","type":"blocks","created_at":"2026-01-14T12:33:16.125115134+01:00","created_by":"Oliver Jakoubek"}]}

models.go

@@ -1,4 +1,165 @@
 package checkvist
 
+import (
+	"fmt"
+	"time"
+)
+
 // models.go contains data structures for Checkvist entities:
 // Checklist, Task, Note, User, Tags, TaskStatus, and DueDate.
+
+// TaskStatus represents the status of a task.
+type TaskStatus int
+
+const (
+	// StatusOpen indicates the task is open/incomplete.
+	StatusOpen TaskStatus = 0
+	// StatusClosed indicates the task is completed.
+	StatusClosed TaskStatus = 1
+	// StatusInvalidated indicates the task has been invalidated.
+	StatusInvalidated TaskStatus = 2
+)
+
+// String returns the string representation of the TaskStatus.
+func (s TaskStatus) String() string {
+	switch s {
+	case StatusOpen:
+		return "open"
+	case StatusClosed:
+		return "closed"
+	case StatusInvalidated:
+		return "invalidated"
+	default:
+		return fmt.Sprintf("unknown(%d)", s)
+	}
+}
+
+// Tags represents a set of tags as a map for efficient lookup.
+type Tags map[string]bool
+
+// Checklist represents a Checkvist checklist.
+type Checklist struct {
+	// ID is the unique identifier of the checklist.
+	ID int `json:"id"`
+	// Name is the title of the checklist.
+	Name string `json:"name"`
+	// Public indicates whether the checklist is publicly accessible.
+	Public bool `json:"public"`
+	// Archived indicates whether the checklist is archived.
+	Archived bool `json:"archived"`
+	// ReadOnly indicates whether the checklist is read-only for the current user.
+	ReadOnly bool `json:"read_only"`
+	// TaskCount is the total number of tasks in the checklist.
+	TaskCount int `json:"task_count"`
+	// TaskCompleted is the number of completed tasks in the checklist.
+	TaskCompleted int `json:"task_completed"`
+	// Tags contains the parsed tags from TagsAsText.
+	Tags Tags `json:"-"`
+	// TagsAsText is the raw tags string from the API.
+	TagsAsText string `json:"tags_as_text"`
+	// UpdatedAt is the timestamp of the last update.
+	UpdatedAt time.Time `json:"updated_at"`
+}
+
+// Task represents a task within a Checkvist checklist.
+type Task struct {
+	// ID is the unique identifier of the task.
+	ID int `json:"id"`
+	// ChecklistID is the ID of the checklist this task belongs to.
+	ChecklistID int `json:"checklist_id"`
+	// ParentID is the ID of the parent task, or 0 if this is a root task.
+	ParentID int `json:"parent_id"`
+	// Content is the text content of the task.
+	Content string `json:"content"`
+	// Status is the current status of the task (open, closed, invalidated).
+	Status TaskStatus `json:"status"`
+	// Position is the position of the task within its siblings.
+	Position int `json:"position"`
+	// Priority is the priority level (1 = highest, 2 = high, 0 = normal).
+	Priority int `json:"priority"`
+	// Tags contains the parsed tags from TagsAsText.
+	Tags Tags `json:"-"`
+	// TagsAsText is the raw tags string from the API.
+	TagsAsText string `json:"tags_as_text"`
+	// DueDateRaw is the raw due date string from the API.
+	DueDateRaw string `json:"due"`
+	// DueDate is the parsed due date, if available in ISO format.
+	DueDate *time.Time `json:"-"`
+	// AssigneeIDs contains the IDs of users assigned to this task.
+	AssigneeIDs []int `json:"assignee_ids"`
+	// CommentsCount is the number of notes/comments on this task.
+	CommentsCount int `json:"comments_count"`
+	// UpdateLine contains brief update information.
+	UpdateLine string `json:"update_line"`
+	// UpdatedAt is the timestamp of the last update.
+	UpdatedAt time.Time `json:"updated_at"`
+	// CreatedAt is the timestamp when the task was created.
+	CreatedAt time.Time `json:"created_at"`
+	// Children contains nested child tasks (when fetched with tree structure).
+	Children []*Task `json:"tasks,omitempty"`
+	// Notes contains the comments/notes attached to this task.
+	Notes []Note `json:"notes,omitempty"`
+}
+
+// Note represents a comment/note on a task.
+type Note struct {
+	// ID is the unique identifier of the note.
+	ID int `json:"id"`
+	// TaskID is the ID of the task this note belongs to.
+	TaskID int `json:"task_id"`
+	// Comment is the text content of the note.
+	Comment string `json:"comment"`
+	// UpdatedAt is the timestamp of the last update.
+	UpdatedAt time.Time `json:"updated_at"`
+	// CreatedAt is the timestamp when the note was created.
+	CreatedAt time.Time `json:"created_at"`
+}
+
+// User represents a Checkvist user.
+type User struct {
+	// ID is the unique identifier of the user.
+	ID int `json:"id"`
+	// Username is the user's display name.
+	Username string `json:"username"`
+	// Email is the user's email address.
+	Email string `json:"email"`
+}
+
+// DueDate represents a due date for task creation using Checkvist's smart syntax.
+type DueDate struct {
+	value string
+}
+
+// Common due date constants using Checkvist's smart syntax.
+var (
+	// DueToday sets the due date to today.
+	DueToday = DueDate{value: "^today"}
+	// DueTomorrow sets the due date to tomorrow.
+	DueTomorrow = DueDate{value: "^tomorrow"}
+	// DueNextWeek sets the due date to next week.
+	DueNextWeek = DueDate{value: "^next week"}
+	// DueNextMonth sets the due date to next month.
+	DueNextMonth = DueDate{value: "^next month"}
+)
+
+// DueAt creates a DueDate from a Go time.Time value.
+func DueAt(t time.Time) DueDate {
+	return DueDate{value: "^" + t.Format("2006-01-02")}
+}
+
+// DueString creates a DueDate from a raw smart syntax string.
+// The string should use Checkvist's smart syntax (e.g., "^2026-02-01", "^friday").
+func DueString(s string) DueDate {
+	return DueDate{value: s}
+}
+
+// DueInDays creates a DueDate for n days from now.
+func DueInDays(n int) DueDate {
+	t := time.Now().AddDate(0, 0, n)
+	return DueDate{value: "^" + t.Format("2006-01-02")}
+}
+
+// String returns the smart syntax string for the due date.
+func (d DueDate) String() string {
+	return d.value
+}