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

/// Renders the Backlog Pane widget for the FocusFlow Flutter UI.
library;

import 'package:flutter/material.dart';
import 'package:scheduler_core/scheduler_core.dart';

import '../controllers/scheduler_command_controller.dart';
import '../controllers/scheduler_read_controller.dart';
import 'read_state_view.dart';
import 'schedule_components.dart';

/// Read-driven pane that renders backlog content and command controls.
class BacklogPane extends StatelessWidget {
  /// Creates a backlog pane from a read [controller].
  const BacklogPane({
    required this.controller,
    this.commandController,
    super.key,
  });

  /// Controller that loads backlog data.
  final UiReadController<BacklogQueryResult> controller;

  /// Optional command controller for mutating backlog items.
  final SchedulerCommandController? commandController;

  /// 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 ReadStateView<BacklogQueryResult>(
      controller: controller,
      title: 'Backlog',
      emptyTitle: 'Backlog is clear',
      emptyMessage: 'Captured tasks will appear here when they need planning.',
      dataBuilder: (context, result) =>
          BacklogContent(result: result, commandController: commandController),
    );
  }
}

/// Populated backlog view for a loaded backlog query result.
class BacklogContent extends StatelessWidget {
  /// Creates backlog content for [result].
  const BacklogContent({
    required this.result,
    this.commandController,
    super.key,
  });

  /// Loaded backlog result to display.
  final BacklogQueryResult result;

  /// Optional command controller for capture and scheduling actions.
  final SchedulerCommandController? commandController;

  /// 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 ListView(
      padding: const EdgeInsets.all(16),
      children: [
        Text('Backlog', style: Theme.of(context).textTheme.headlineMedium),
        const SizedBox(height: 12),
        if (commandController != null) ...[
          QuickCaptureForm(commandController: commandController!),
          const SizedBox(height: 12),
          CommandStatusBanner(controller: commandController!),
          const SizedBox(height: 12),
        ],
        for (final item in result.items)
          BacklogRow(
            item: item,
            onSchedule: commandController == null
                ? null
                : (durationMinutes) {
                    return commandController!.scheduleBacklogItem(
                      taskId: item.task.id,
                      durationMinutes: durationMinutes,
                      expectedUpdatedAt: item.task.updatedAt,
                    );
                  },
          ),
      ],
    );
  }
}

/// Small form for quickly capturing a task into the backlog.
class QuickCaptureForm extends StatefulWidget {
  /// Creates a quick capture form.
  const QuickCaptureForm({required this.commandController, super.key});

  /// Command controller used to submit captured task titles.
  final SchedulerCommandController commandController;

  /// Creates the mutable state object used by this stateful widget.
  /// Flutter calls this once for each mounted widget instance before lifecycle callbacks and builds begin.
  @override
  State<QuickCaptureForm> createState() => _QuickCaptureFormState();
}

/// Private implementation type for `_QuickCaptureFormState` 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 _QuickCaptureFormState extends State<QuickCaptureForm> {
  /// Stores the `titleController` value for this object.
  /// This field is part of the explicit state that downstream scheduling, persistence, or UI code reads when composing behavior.
  final titleController = TextEditingController();

  /// Releases resources owned by this object before it leaves the tree.
  /// Controllers, listeners, and other disposable collaborators should be cleaned up here to avoid stale callbacks.
  @override
  void dispose() {
    titleController.dispose();
    super.dispose();
  }

  /// 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: [
        Expanded(
          child: TextField(
            key: const ValueKey('quick-capture-title'),
            controller: titleController,
            decoration: const InputDecoration(labelText: 'Quick capture'),
            textInputAction: TextInputAction.done,
          ),
        ),
        const SizedBox(width: 8),
        FilledButton.icon(
          onPressed: () async {
            final title = titleController.text.trim();
            if (title.isEmpty) {
              return;
            }
            await widget.commandController.quickCaptureToBacklog(title);
            titleController.clear();
          },
          icon: const Icon(Icons.add),
          label: const Text('Capture'),
        ),
      ],
    );
  }
}

/// Displays the latest command state for backlog interactions.
class CommandStatusBanner extends StatelessWidget {
  /// Creates a command status banner.
  const CommandStatusBanner({required this.controller, super.key});

  /// Command controller whose state should be rendered.
  final SchedulerCommandController controller;

  /// 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 AnimatedBuilder(
      animation: controller,
      builder: (context, _) {
        return switch (controller.state) {
          SchedulerCommandIdle() => const SizedBox.shrink(),
          SchedulerCommandRunning(label: final label) => Text(label),
          SchedulerCommandSuccess(message: final message) => Text(message),
          SchedulerCommandFailure(failure: final failure, error: final error) =>
            Text(
              'Command issue: '
              '${failure?.detailCode ?? failure?.code.name ?? error ?? 'unexpected'}',
            ),
        };
      },
    );
  }
}