From ff44b8c6548504c62f220aebac469f7b5f9794ed Mon Sep 17 00:00:00 2001
From: Snider <snider@host.uk.com>
Date: Fri, 13 Mar 2026 12:08:17 +0000
Subject: [PATCH] feat(window): add LayoutManager with JSON persistence

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 pkg/window/layout.go      | 132 ++++++++++++++++++++++++++++++++++++--
 pkg/window/window_test.go |  47 ++++++++++++++
 2 files changed, 175 insertions(+), 4 deletions(-)

diff --git a/pkg/window/layout.go b/pkg/window/layout.go
index db411b0..578af63 100644
--- a/pkg/window/layout.go
+++ b/pkg/window/layout.go
@@ -1,8 +1,132 @@
 // pkg/window/layout.go
 package window
 
-// LayoutManager persists named window arrangements.
-// Full implementation in Task 4.
-type LayoutManager struct{}
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+	"path/filepath"
+	"sync"
+	"time"
+)
 
-func NewLayoutManager() *LayoutManager { return &LayoutManager{} }
+// Layout is a named window arrangement.
+type Layout struct {
+	Name      string                 `json:"name"`
+	Windows   map[string]WindowState `json:"windows"`
+	CreatedAt int64                  `json:"createdAt"`
+	UpdatedAt int64                  `json:"updatedAt"`
+}
+
+// LayoutInfo is a summary of a layout.
+type LayoutInfo struct {
+	Name        string `json:"name"`
+	WindowCount int    `json:"windowCount"`
+	CreatedAt   int64  `json:"createdAt"`
+	UpdatedAt   int64  `json:"updatedAt"`
+}
+
+// LayoutManager persists named window arrangements to ~/.config/Core/layouts.json.
+type LayoutManager struct {
+	configDir string
+	layouts   map[string]Layout
+	mu        sync.RWMutex
+}
+
+// NewLayoutManager creates a LayoutManager loading from the default config directory.
+func NewLayoutManager() *LayoutManager {
+	lm := &LayoutManager{
+		layouts: make(map[string]Layout),
+	}
+	configDir, err := os.UserConfigDir()
+	if err == nil {
+		lm.configDir = filepath.Join(configDir, "Core")
+	}
+	lm.load()
+	return lm
+}
+
+func (lm *LayoutManager) filePath() string {
+	return filepath.Join(lm.configDir, "layouts.json")
+}
+
+func (lm *LayoutManager) load() {
+	if lm.configDir == "" {
+		return
+	}
+	data, err := os.ReadFile(lm.filePath())
+	if err != nil {
+		return
+	}
+	lm.mu.Lock()
+	defer lm.mu.Unlock()
+	_ = json.Unmarshal(data, &lm.layouts)
+}
+
+func (lm *LayoutManager) save() {
+	if lm.configDir == "" {
+		return
+	}
+	lm.mu.RLock()
+	data, err := json.MarshalIndent(lm.layouts, "", "  ")
+	lm.mu.RUnlock()
+	if err != nil {
+		return
+	}
+	_ = os.MkdirAll(lm.configDir, 0o755)
+	_ = os.WriteFile(lm.filePath(), data, 0o644)
+}
+
+// SaveLayout creates or updates a named layout.
+func (lm *LayoutManager) SaveLayout(name string, windowStates map[string]WindowState) error {
+	if name == "" {
+		return fmt.Errorf("layout name cannot be empty")
+	}
+	now := time.Now().UnixMilli()
+	lm.mu.Lock()
+	existing, exists := lm.layouts[name]
+	layout := Layout{
+		Name:      name,
+		Windows:   windowStates,
+		UpdatedAt: now,
+	}
+	if exists {
+		layout.CreatedAt = existing.CreatedAt
+	} else {
+		layout.CreatedAt = now
+	}
+	lm.layouts[name] = layout
+	lm.mu.Unlock()
+	lm.save()
+	return nil
+}
+
+// GetLayout returns a layout by name.
+func (lm *LayoutManager) GetLayout(name string) (Layout, bool) {
+	lm.mu.RLock()
+	defer lm.mu.RUnlock()
+	l, ok := lm.layouts[name]
+	return l, ok
+}
+
+// ListLayouts returns info summaries for all layouts.
+func (lm *LayoutManager) ListLayouts() []LayoutInfo {
+	lm.mu.RLock()
+	defer lm.mu.RUnlock()
+	infos := make([]LayoutInfo, 0, len(lm.layouts))
+	for _, l := range lm.layouts {
+		infos = append(infos, LayoutInfo{
+			Name: l.Name, WindowCount: len(l.Windows),
+			CreatedAt: l.CreatedAt, UpdatedAt: l.UpdatedAt,
+		})
+	}
+	return infos
+}
+
+// DeleteLayout removes a layout by name.
+func (lm *LayoutManager) DeleteLayout(name string) {
+	lm.mu.Lock()
+	delete(lm.layouts, name)
+	lm.mu.Unlock()
+	lm.save()
+}
diff --git a/pkg/window/window_test.go b/pkg/window/window_test.go
index 00d300c..7e0bc50 100644
--- a/pkg/window/window_test.go
+++ b/pkg/window/window_test.go
@@ -219,3 +219,50 @@ func TestStateManager_Persistence_Good(t *testing.T) {
 	assert.Equal(t, 42, got.X)
 	assert.Equal(t, 500, got.Width)
 }
+
+// --- LayoutManager Tests ---
+
+// newTestLayoutManager creates a clean LayoutManager with a temp dir for testing.
+func newTestLayoutManager(t *testing.T) *LayoutManager {
+	return &LayoutManager{
+		configDir: t.TempDir(),
+		layouts:   make(map[string]Layout),
+	}
+}
+
+func TestLayoutManager_SaveGet_Good(t *testing.T) {
+	lm := newTestLayoutManager(t)
+	states := map[string]WindowState{
+		"editor":   {X: 0, Y: 0, Width: 960, Height: 1080},
+		"terminal": {X: 960, Y: 0, Width: 960, Height: 1080},
+	}
+	err := lm.SaveLayout("coding", states)
+	require.NoError(t, err)
+
+	layout, ok := lm.GetLayout("coding")
+	assert.True(t, ok)
+	assert.Equal(t, "coding", layout.Name)
+	assert.Len(t, layout.Windows, 2)
+}
+
+func TestLayoutManager_GetLayout_Bad(t *testing.T) {
+	lm := newTestLayoutManager(t)
+	_, ok := lm.GetLayout("nonexistent")
+	assert.False(t, ok)
+}
+
+func TestLayoutManager_ListLayouts_Good(t *testing.T) {
+	lm := newTestLayoutManager(t)
+	_ = lm.SaveLayout("a", map[string]WindowState{})
+	_ = lm.SaveLayout("b", map[string]WindowState{})
+	layouts := lm.ListLayouts()
+	assert.Len(t, layouts, 2)
+}
+
+func TestLayoutManager_DeleteLayout_Good(t *testing.T) {
+	lm := newTestLayoutManager(t)
+	_ = lm.SaveLayout("temp", map[string]WindowState{})
+	lm.DeleteLayout("temp")
+	_, ok := lm.GetLayout("temp")
+	assert.False(t, ok)
+}