// SPDX-FileCopyrightText: 2026 FocusFlow contributors
// SPDX-License-Identifier: AGPL-3.0-only

/// Renders the Sidebar widget for the FocusFlow Flutter UI.
library;

import 'package:flutter/material.dart';

import '../theme/focus_flow_tokens.dart';

/// Primary screens the sidebar can switch the main content area to.
///
/// Only [today] and [backlog] are wired to real navigation. Projects and
/// Reports remain presentational-only nav items: they are outside the V1 MVP
/// boundary (AGENTS.md section 8 scopes V1 to Today + Backlog only).
enum SidebarScreen {
  /// The compact Today timeline screen.
  today,

  /// The backlog screen.
  backlog,
}

/// Sidebar for primary FocusFlow navigation.
class Sidebar extends StatelessWidget {
  /// Creates the FocusFlow sidebar with the given [activeScreen] highlighted.
  const Sidebar({
    required this.activeScreen,
    required this.onSelectToday,
    required this.onSelectBacklog,
    required this.onOpenSettings,
    super.key,
  });

  /// Screen currently shown in the main content area.
  final SidebarScreen activeScreen;

  /// Invoked when the Today nav item is activated.
  final VoidCallback onSelectToday;

  /// Invoked when the Backlog nav item is activated.
  final VoidCallback onSelectBacklog;

  /// Invoked when the Settings nav item is activated.
  final VoidCallback onOpenSettings;

  /// Builds the widget subtree for this component.
  /// The method translates the current widget configuration and state into Flutter UI without mutating scheduler domain data.
  @override
  Widget build(BuildContext context) {
    return DecoratedBox(
      decoration: const BoxDecoration(color: FocusFlowTokens.sidebarBackground),
      child: Padding(
        padding: const EdgeInsets.fromLTRB(18, 22, 18, 28),
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.start,
          children: [
            const _BrandRow(),
            const SizedBox(height: 34),
            _NavItem(
              label: 'Today',
              icon: Icons.calendar_today,
              active: activeScreen == SidebarScreen.today,
              onTap: onSelectToday,
            ),
            const SizedBox(height: 16),
            _NavItem(
              label: 'Backlog',
              icon: Icons.layers,
              active: activeScreen == SidebarScreen.backlog,
              onTap: onSelectBacklog,
            ),
            const SizedBox(height: 16),
            _NavItem(label: 'Projects', icon: Icons.work_outline, onTap: () {}),
            const SizedBox(height: 16),
            _NavItem(label: 'Reports', icon: Icons.bar_chart, onTap: () {}),
            const SizedBox(height: 30),
            const Divider(color: FocusFlowTokens.subtleBorder),
            const SizedBox(height: 18),
            _NavItem(
              label: 'Settings',
              icon: Icons.settings,
              onTap: onOpenSettings,
            ),
          ],
        ),
      ),
    );
  }
}

/// Private implementation type for `_BrandRow` in this library.
/// It keeps supporting state and behavior scoped to the owning file so the public API stays focused on the scheduler concepts that callers use directly.
class _BrandRow extends StatelessWidget {
  /// Creates a `_BrandRow` instance with the values required by its invariants.
  /// Callers should pass already-normalized scheduler data because validation and defaulting belong at the model or service boundary, not in arbitrary UI code.
  const _BrandRow();

  /// Builds the widget subtree for this component.
  /// The method translates the current widget configuration and state into Flutter UI without mutating scheduler domain data.
  @override
  Widget build(BuildContext context) {
    return Row(
      children: [
        Container(
          width: 42,
          height: 42,
          decoration: BoxDecoration(
            borderRadius: BorderRadius.circular(12),
            border: Border.all(color: FocusFlowTokens.accentMagenta),
            color: FocusFlowTokens.glassPanelStrong,
          ),
          child: const Icon(
            Icons.auto_awesome,
            color: FocusFlowTokens.accentMagenta,
          ),
        ),
        const SizedBox(width: 14),
        Expanded(
          child: Text(
            'FocusFlow',
            maxLines: 1,
            overflow: TextOverflow.ellipsis,
            style: Theme.of(context).textTheme.titleMedium,
          ),
        ),
      ],
    );
  }
}

/// Private implementation type for `_NavItem` in this library.
/// It keeps supporting state and behavior scoped to the owning file so the public API stays focused on the scheduler concepts that callers use directly.
class _NavItem extends StatelessWidget {
  /// Creates a `_NavItem` instance with the values required by its invariants.
  /// Callers should pass already-normalized scheduler data because validation and defaulting belong at the model or service boundary, not in arbitrary UI code.
  const _NavItem({
    required this.label,
    required this.icon,
    required this.onTap,
    this.active = false,
  });

  /// Stores the `label` value for this object.
  /// This field is part of the explicit state that downstream scheduling, persistence, or UI code reads when composing behavior.
  final String label;

  /// Stores the `icon` value for this object.
  /// This field is part of the explicit state that downstream scheduling, persistence, or UI code reads when composing behavior.
  final IconData icon;

  /// Stores the `onTap` value for this object.
  /// This field is part of the explicit state that downstream scheduling, persistence, or UI code reads when composing behavior.
  final VoidCallback onTap;

  /// Stores the `active` value for this object.
  /// This field is part of the explicit state that downstream scheduling, persistence, or UI code reads when composing behavior.
  final bool active;

  /// Builds the widget subtree for this component.
  /// The method translates the current widget configuration and state into Flutter UI without mutating scheduler domain data.
  @override
  Widget build(BuildContext context) {
    final color = active
        ? FocusFlowTokens.accentMagenta
        : FocusFlowTokens.textPrimary;
    return Material(
      color: Colors.transparent,
      child: InkWell(
        key: active
            ? ValueKey('nav-${label.toLowerCase()}-active')
            : ValueKey('nav-${label.toLowerCase()}'),
        borderRadius: BorderRadius.circular(FocusFlowTokens.navRadius),
        onTap: onTap,
        child: Container(
          height: 54,
          padding: const EdgeInsets.symmetric(horizontal: 16),
          decoration: BoxDecoration(
            borderRadius: BorderRadius.circular(FocusFlowTokens.navRadius),
            border: Border.all(
              color: active ? FocusFlowTokens.navBorder : Colors.transparent,
            ),
            color: active
                ? FocusFlowTokens.glassPanelStrong
                : Colors.transparent,
          ),
          child: Row(
            children: [
              Icon(icon, color: color, size: 24),
              const SizedBox(width: 16),
              Expanded(
                child: Text(
                  label,
                  maxLines: 1,
                  overflow: TextOverflow.ellipsis,
                  style: TextStyle(
                    color: color.withValues(alpha: active ? 1 : 0.88),
                    fontSize: FocusFlowTokens.sidebarNavSize,
                    fontWeight: FontWeight.w500,
                  ),
                ),
              ),
            ],
          ),
        ),
      ),
    );
  }
}