# Design: UI Foundation

## Icon Library: Lucide Svelte

### Installation
```bash
npm install lucide-svelte
```

### Usage Pattern
```svelte
<script>
  import { Menu, X, Sun, Moon, Home, Users } from 'lucide-svelte';
</script>

<Menu size={20} />
<Home size={18} class="text-base-content" />
```

### Icon Mapping for Navigation
| Nav Item        | Lucide Icon      |
|-----------------|------------------|
| Dashboard       | `LayoutDashboard`|
| Team Members    | `Users`          |
| Projects        | `Folder`         |
| Allocations     | `Calendar`       |
| Actuals         | `CheckCircle`    |
| Forecast        | `TrendingUp`     |
| Utilization     | `BarChart3`      |
| Costs           | `DollarSign`     |
| Variance        | `AlertTriangle`  |
| Settings        | `Settings`       |
| Master Data     | `Database`       |

---

## Types

### `src/lib/types/layout.ts`
```typescript
export type SidebarState = 'expanded' | 'collapsed' | 'hidden';

export interface NavItem {
  label: string;
  href: string;
  icon: string; // Lucide icon name
  badge?: string | number; // Optional notification badge
}

export interface NavSection {
  title: string;
  items: NavItem[];
  roles?: string[]; // If set, only visible to these roles
}

export type Theme = 'light' | 'dark';
```

---

## Stores

### `src/lib/stores/layout.ts`
```typescript
import { writable } from 'svelte/store';
import { browser } from '$app/environment';
import type { SidebarState, Theme } from '$lib/types/layout';

const DEFAULT_SIDEBAR_STATE: SidebarState = 'expanded';
const DEFAULT_THEME: Theme = 'light';

function createLayoutStore() {
  // Initialize from localStorage or defaults
  const getInitialState = (): SidebarState => {
    if (!browser) return DEFAULT_SIDEBAR_STATE;
    const stored = localStorage.getItem('headroom_sidebar_state');
    return (stored as SidebarState) || DEFAULT_SIDEBAR_STATE;
  };

  const getInitialTheme = (): Theme => {
    if (!browser) return DEFAULT_THEME;
    const stored = localStorage.getItem('headroom_theme');
    if (stored) return stored as Theme;
    // Respect system preference on first visit
    if (window.matchMedia('(prefers-color-scheme: dark)').matches) {
      return 'dark';
    }
    return DEFAULT_THEME;
  };

  const sidebarState = writable<SidebarState>(getInitialState());
  const theme = writable<Theme>(getInitialTheme());

  // Apply theme to document
  if (browser) {
    theme.subscribe((value) => {
      document.documentElement.setAttribute('data-theme', value);
      localStorage.setItem('headroom_theme', value);
    });

    sidebarState.subscribe((value) => {
      localStorage.setItem('headroom_sidebar_state', value);
    });
  }

  return {
    sidebarState: { subscribe: sidebarState.subscribe },
    theme: { subscribe: theme.subscribe },
    toggleSidebar: () => {
      sidebarState.update((current) => {
        if (current === 'expanded') return 'collapsed';
        if (current === 'collapsed') return 'hidden';
        return 'expanded';
      });
    },
    setSidebarState: (state: SidebarState) => sidebarState.set(state),
    toggleTheme: () => {
      theme.update((current) => (current === 'light' ? 'dark' : 'light'));
    },
    setTheme: (newTheme: Theme) => theme.set(newTheme),
  };
}

export const layoutStore = createLayoutStore();
```

### `src/lib/stores/period.ts`
```typescript
import { writable, derived } from 'svelte/store';
import { browser } from '$app/environment';

function createPeriodStore() {
  const getCurrentMonth = (): string => {
    const now = new Date();
    return `${now.getFullYear()}-${String(now.getMonth() + 1).padStart(2, '0')}`;
  };

  const getInitialPeriod = (): string => {
    if (!browser) return getCurrentMonth();
    const stored = localStorage.getItem('headroom_selected_period');
    return stored || getCurrentMonth();
  };

  const selectedPeriod = writable<string>(getInitialPeriod());

  if (browser) {
    selectedPeriod.subscribe((value) => {
      localStorage.setItem('headroom_selected_period', value);
    });
  }

  // Derived values for convenience
  const selectedMonth = derived(selectedPeriod, ($period) => {
    const [year, month] = $period.split('-').map(Number);
    return { year, month };
  });

  const selectedDate = derived(selectedPeriod, ($period) => {
    const [year, month] = $period.split('-').map(Number);
    return new Date(year, month - 1, 1);
  });

  return {
    selectedPeriod: { subscribe: selectedPeriod.subscribe },
    selectedMonth,
    selectedDate,
    setPeriod: (period: string) => selectedPeriod.set(period),
    previousMonth: () => {
      selectedPeriod.update((current) => {
        const [year, month] = current.split('-').map(Number);
        const date = new Date(year, month - 2, 1);
        return `${date.getFullYear()}-${String(date.getMonth() + 1).padStart(2, '0')}`;
      });
    },
    nextMonth: () => {
      selectedPeriod.update((current) => {
        const [year, month] = current.split('-').map(Number);
        const date = new Date(year, month, 1);
        return `${date.getFullYear()}-${String(date.getMonth() + 1).padStart(2, '0')}`;
      });
    },
    currentMonth: () => selectedPeriod.set(getCurrentMonth()),
  };
}

export const periodStore = createPeriodStore();
```

---

## Navigation Configuration

### `src/lib/config/navigation.ts`
```typescript
import type { NavSection } from '$lib/types/layout';

export const navigationSections: NavSection[] = [
  {
    title: 'PLANNING',
    items: [
      { label: 'Dashboard', href: '/dashboard', icon: 'LayoutDashboard' },
      { label: 'Team Members', href: '/team-members', icon: 'Users' },
      { label: 'Projects', href: '/projects', icon: 'Folder' },
      { label: 'Allocations', href: '/allocations', icon: 'Calendar' },
      { label: 'Actuals', href: '/actuals', icon: 'CheckCircle' },
    ],
  },
  {
    title: 'REPORTS',
    items: [
      { label: 'Forecast', href: '/reports/forecast', icon: 'TrendingUp' },
      { label: 'Utilization', href: '/reports/utilization', icon: 'BarChart3' },
      { label: 'Costs', href: '/reports/costs', icon: 'DollarSign' },
      { label: 'Variance', href: '/reports/variance', icon: 'AlertTriangle' },
      { label: 'Allocation Matrix', href: '/reports/allocation', icon: 'Grid3X3' },
    ],
  },
  {
    title: 'ADMIN',
    roles: ['superuser'],
    items: [
      { label: 'Settings', href: '/settings', icon: 'Settings' },
      { label: 'Master Data', href: '/master-data', icon: 'Database' },
    ],
  },
];
```

---

## Theme CSS

### Update `src/app.css`
```css
@import 'tailwindcss';
@import 'daisyui';

/* Theme variables - optional customization */
:root {
  --sidebar-width-expanded: 240px;
  --sidebar-width-collapsed: 64px;
  --topbar-height: 56px;
}

/* Ensure theme attribute works */
[data-theme='light'] {
  color-scheme: light;
}

[data-theme='dark'] {
  color-scheme: dark;
}
```

---

## File Structure
```
src/lib/
├── types/
│   └── layout.ts          # NEW
├── stores/
│   ├── layout.ts          # NEW
│   ├── period.ts          # NEW
│   └── auth.ts            # EXISTS
├── config/
│   └── navigation.ts      # NEW
└── ...
```