Implement unified Atom model for multi-source abstraction

- Create internal/models/atom.go with Atom struct and enums
- Add mapper functions for Task, Card, Note, and Meal types
- Normalize priority scales (1-4) and assign brand colors
- Update Phase 2 plan with Atom architecture as Step 1
- Document architectural decision in SESSION_STATE.md

This abstraction enables consistent handling, sorting, and rendering
of items from Trello, Todoist, Obsidian, and PlanToEat sources.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

1 files changed, 135 insertions, 0 deletions

diff --git a/internal/models/atom.go b/internal/models/atom.go
new file mode 100644
index 0000000..47695d9
--- /dev/null
+++ b/internal/models/atom.go
@@ -0,0 +1,135 @@
+package models
+
+import "time"
+
+type AtomSource string
+
+const (
+	SourceTrello   AtomSource = "trello"
+	SourceTodoist  AtomSource = "todoist"
+	SourceObsidian AtomSource = "obsidian"
+	SourceMeal     AtomSource = "plantoeat"
+)
+
+type AtomType string
+
+const (
+	TypeTask AtomType = "task"
+	TypeNote AtomType = "note"
+	TypeMeal AtomType = "meal"
+)
+
+// Atom represents a unified unit of work or information
+type Atom struct {
+	ID          string
+	Title       string
+	Description string
+	Source      AtomSource
+	Type        AtomType
+
+	// Metadata
+	URL       string
+	DueDate   *time.Time
+	CreatedAt time.Time
+
+	Priority int // Normalized: 1 (Low) to 4 (Urgent)
+
+	// UI Helpers (to be populated by mappers)
+	SourceIcon string // e.g., "trello-icon.svg" or emoji
+	ColorClass string // e.g., "border-blue-500"
+
+	// Original Data (for write operations)
+	Raw interface{}
+}
+
+// TaskToAtom converts a Todoist Task to an Atom
+func TaskToAtom(t Task) Atom {
+	// Todoist priority: 1 (normal) to 4 (urgent)
+	// Keep as-is since it already matches our 1-4 scale
+	priority := t.Priority
+	if priority < 1 {
+		priority = 1
+	}
+	if priority > 4 {
+		priority = 4
+	}
+
+	return Atom{
+		ID:          t.ID,
+		Title:       t.Content,
+		Description: t.Description,
+		Source:      SourceTodoist,
+		Type:        TypeTask,
+		URL:         t.URL,
+		DueDate:     t.DueDate,
+		CreatedAt:   t.CreatedAt,
+		Priority:    priority,
+		SourceIcon:  "✓", // Checkmark emoji for tasks
+		ColorClass:  "border-red-500",
+		Raw:         t,
+	}
+}
+
+// CardToAtom converts a Trello Card to an Atom
+func CardToAtom(c Card) Atom {
+	// Trello doesn't have explicit priority, default to medium (2)
+	// Can be enhanced later with label-based priority detection
+	priority := 2
+
+	return Atom{
+		ID:          c.ID,
+		Title:       c.Name,
+		Description: c.ListName, // Use list name as description
+		Source:      SourceTrello,
+		Type:        TypeTask,
+		URL:         c.URL,
+		DueDate:     c.DueDate,
+		CreatedAt:   time.Time{}, // Trello ID contains timestamp, can be parsed later
+		Priority:    priority,
+		SourceIcon:  "📋", // Clipboard emoji for boards
+		ColorClass:  "border-blue-500",
+		Raw:         c,
+	}
+}
+
+// NoteToAtom converts an Obsidian Note to an Atom
+func NoteToAtom(n Note) Atom {
+	// Notes don't have priority, default to low (1)
+	priority := 1
+
+	return Atom{
+		ID:          n.Path, // Use path as unique ID
+		Title:       n.Title,
+		Description: n.Content,
+		Source:      SourceObsidian,
+		Type:        TypeNote,
+		URL:         "",     // Obsidian notes don't have URLs
+		DueDate:     nil,    // Notes typically don't have due dates
+		CreatedAt:   n.Modified, // Use modified time as created time
+		Priority:    priority,
+		SourceIcon:  "📝", // Memo emoji for notes
+		ColorClass:  "border-purple-500",
+		Raw:         n,
+	}
+}
+
+// MealToAtom converts a PlanToEat Meal to an Atom
+func MealToAtom(m Meal) Atom {
+	// Meals don't have priority, default to low (1)
+	priority := 1
+
+	return Atom{
+		ID:          m.ID,
+		Title:       m.RecipeName,
+		Description: m.MealType, // breakfast, lunch, dinner
+		Source:      SourceMeal,
+		Type:        TypeMeal,
+		URL:         m.RecipeURL,
+		DueDate:     &m.Date, // Meal date is effectively the "due date"
+		CreatedAt:   time.Time{},
+		Priority:    priority,
+		SourceIcon:  "🍽️", // Fork and knife emoji for meals
+		ColorClass:  "border-green-500",
+		Raw:         m,
+	}
+}