feat(todos): refactor to demonstrate controller/state separation with lvt:state

[adnaan]

Summary

• Refactor monolithic TodoState (16 fields) into three focused structs demonstrating the controller/state separation pattern
• Add lvt:"state" tag usage to show selective Redis persistence
• Update templates to use nested access patterns

Changes

New Struct Organization

Struct	Purpose	Fields	Persisted?
TodoPrefs	User preferences	SearchQuery, SortBy, CurrentPage, PageSize	Yes (lvt:"state")
TodoView	Computed display data	FilteredTodos, PaginatedTodos, counts, pagination flags	No
TodoController	Main controller	Title, Prefs, View, DB	Prefs only

Template Updates

All field access now uses nested paths:

• {{ .TotalCount }} → {{ .View.TotalCount }}
• {{ .SearchQuery }} → {{ .Prefs.SearchQuery }}
• {{ range .PaginatedTodos }} → {{ range .View.PaginatedTodos }}

Benefits Demonstrated

1. Clear separation: Dependencies (DB) vs persisted state (Prefs) vs computed (View)
2. Minimal serialization: Only 4 fields persist to Redis instead of 16
3. Self-documenting: lvt:"state" tag shows what survives session restores
4. Fresh data: View is always recalculated from database on Init()

Test plan

• All E2E tests pass
• WebSocket tests pass
• Build succeeds

🤖 Generated with Claude Code

[Copilot]

Pull request overview

This PR refactors the monolithic TodoState struct into three focused structs (TodoPrefs, TodoView, and TodoController) to demonstrate the controller/state separation pattern using the lvt:"state" tag for selective Redis persistence.

Key changes:

• Split 16 fields into three structs: TodoPrefs (4 persisted user preferences), TodoView (10 computed display fields), and TodoController (main controller with both)
• Added lvt:"state" tag to Prefs field to enable selective persistence of only user preferences
• Updated all template field accesses to use nested paths (e.g., .View.TotalCount, .Prefs.SearchQuery)

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
todos/main.go	Refactored struct definitions, added TodoPrefs and TodoView structs, renamed TodoState to TodoController, updated all method receivers and field accesses to use nested structure, enhanced Init() with nil checks
todos/todos.tmpl	Updated all template variable accesses from flat structure to nested structure using .View.* and .Prefs.* paths for proper field resolution

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[Copilot]

Potential division by zero: If c.Prefs.PageSize is 0 (which could happen if persisted state from Redis has an invalid value), this will cause a panic. Consider adding validation in Init() to ensure PageSize is always positive, or add a guard here.

[Copilot]

Missing validation for restored state: When Prefs is restored from Redis (not nil), there's no validation to ensure PageSize is positive. This can lead to division by zero in applyPagination() at line 344. Consider adding validation: if c.Prefs.PageSize <= 0 { c.Prefs.PageSize = 3 }

Suggested change

	}
	}
	// Validate PageSize is always positive
	if c.Prefs.PageSize <= 0 {
	c.Prefs.PageSize = 3
	}