gems/opal-task/internal/engine/modifier.go

package engine

import (
	"fmt"
	"strings"
)

type Modifier struct {
	SetAttributes map[string]*string // key -> value (nil = clear)
	AddTags       []string
	RemoveTags    []string
}

func NewModifier() *Modifier {
	return &Modifier{
		SetAttributes: make(map[string]*string),
		AddTags:       []string{},
		RemoveTags:    []string{},
	}
}

// ParseModifier parses command-line args into Modifier
func ParseModifier(args []string) (*Modifier, error) {
	m := NewModifier()

	for _, arg := range args {
		if strings.HasPrefix(arg, "+") {
			// Add tag
			m.AddTags = append(m.AddTags, strings.TrimPrefix(arg, "+"))
		} else if strings.HasPrefix(arg, "-") && !strings.Contains(arg, ":") {
			// Remove tag
			m.RemoveTags = append(m.RemoveTags, strings.TrimPrefix(arg, "-"))
		} else if strings.Contains(arg, ":") {
			// Attribute modification
			parts := strings.SplitN(arg, ":", 2)
			key := parts[0]
			value := parts[1]

			if value == "" {
				// Clear attribute (priority: with no value)
				m.SetAttributes[key] = nil
			} else {
				m.SetAttributes[key] = &value
			}
		}
	}

	return m, nil
}

// Apply applies modifier to task
func (m *Modifier) Apply(task *Task) error {
	// Apply attribute changes
	for key, valuePtr := range m.SetAttributes {
		switch key {
		case "priority":
			if valuePtr == nil {
				task.Priority = PriorityDefault
			} else {
				task.Priority = Priority(priorityStringToInt(*valuePtr))
			}
		case "project":
			task.Project = valuePtr
		case "due":
			if valuePtr == nil {
				task.Due = nil
			} else {
				parsed, err := ParseDate(*valuePtr)
				if err != nil {
					return fmt.Errorf("invalid due date: %w", err)
				}
				task.Due = &parsed
			}
		case "scheduled":
			if valuePtr == nil {
				task.Scheduled = nil
			} else {
				parsed, err := ParseDate(*valuePtr)
				if err != nil {
					return fmt.Errorf("invalid scheduled date: %w", err)
				}
				task.Scheduled = &parsed
			}
		case "wait":
			if valuePtr == nil {
				task.Wait = nil
			} else {
				parsed, err := ParseDate(*valuePtr)
				if err != nil {
					return fmt.Errorf("invalid wait date: %w", err)
				}
				task.Wait = &parsed
			}
		case "until":
			if valuePtr == nil {
				task.Until = nil
			} else {
				parsed, err := ParseDate(*valuePtr)
				if err != nil {
					return fmt.Errorf("invalid until date: %w", err)
				}
				task.Until = &parsed
			}
		case "recur":
			if valuePtr == nil {
				task.RecurrenceDuration = nil
			} else {
				duration, err := ParseRecurrencePattern(*valuePtr)
				if err != nil {
					return fmt.Errorf("invalid recurrence: %w", err)
				}
				task.RecurrenceDuration = &duration
			}
		}
	}

	// Apply tag changes
	for _, tag := range m.AddTags {
		if err := task.AddTag(tag); err != nil {
			return err
		}
	}

	for _, tag := range m.RemoveTags {
		if err := task.RemoveTag(tag); err != nil {
			return err
		}
	}

	task.Modified = timeNow()

	return task.Save()
}

// ApplyToNew applies modifier to a new task (before it's saved)
// This is used when creating tasks with modifiers
func (m *Modifier) ApplyToNew(task *Task) error {
	// Apply attribute changes (same as Apply but without Save)
	for key, valuePtr := range m.SetAttributes {
		switch key {
		case "priority":
			if valuePtr == nil {
				task.Priority = PriorityDefault
			} else {
				task.Priority = Priority(priorityStringToInt(*valuePtr))
			}
		case "project":
			task.Project = valuePtr
		case "due":
			if valuePtr == nil {
				task.Due = nil
			} else {
				parsed, err := ParseDate(*valuePtr)
				if err != nil {
					return fmt.Errorf("invalid due date: %w", err)
				}
				task.Due = &parsed
			}
		case "scheduled":
			if valuePtr == nil {
				task.Scheduled = nil
			} else {
				parsed, err := ParseDate(*valuePtr)
				if err != nil {
					return fmt.Errorf("invalid scheduled date: %w", err)
				}
				task.Scheduled = &parsed
			}
		case "wait":
			if valuePtr == nil {
				task.Wait = nil
			} else {
				parsed, err := ParseDate(*valuePtr)
				if err != nil {
					return fmt.Errorf("invalid wait date: %w", err)
				}
				task.Wait = &parsed
			}
		case "until":
			if valuePtr == nil {
				task.Until = nil
			} else {
				parsed, err := ParseDate(*valuePtr)
				if err != nil {
					return fmt.Errorf("invalid until date: %w", err)
				}
				task.Until = &parsed
			}
		case "recur":
			if valuePtr == nil {
				task.RecurrenceDuration = nil
			} else {
				duration, err := ParseRecurrencePattern(*valuePtr)
				if err != nil {
					return fmt.Errorf("invalid recurrence: %w", err)
				}
				task.RecurrenceDuration = &duration
			}
		}
	}

	// Note: Tags are added after task is saved (in CreateTask function)
	return nil
}