import 'dart:convert';

import 'package:flutter/foundation.dart';
import 'package:shared_preferences/shared_preferences.dart';

import '../config/app_config.dart';
import 'chart_config.dart';
import 'grid_config.dart';

/// Owns the dashboard's display configuration.
///
/// - Grid shape and channel-to-cell assignment (GridConfig).
/// - Per-channel display config (ChartConfig × 16).
/// - Status indicator display names (List<String> × 8).
///
/// Persistence: shared_preferences under the `layout.` prefix.
class LayoutController extends ChangeNotifier {
  LayoutController._({
    required this.grid,
    required this.charts,
    required this.statusNames,
  });

  GridConfig grid;
  /// Indexed 0..15 corresponding to channels 1..16.
  List<ChartConfig> charts;
  /// Indexed 0..7 corresponding to status1..status8.
  List<String> statusNames;

  static Future<LayoutController> load() async {
    final p = await SharedPreferences.getInstance();
    final gridJson = p.getString('layout.grid');
    final chartsJson = p.getString('layout.charts');
    final statusJson = p.getString('layout.statusNames');

    final grid = gridJson != null
        ? GridConfig.fromJson(jsonDecode(gridJson) as Map<String, dynamic>)
        : GridConfig(
            rows: AppConfig.defaultGridRows,
            cols: AppConfig.defaultGridCols,
          );

    final charts = chartsJson != null
        ? (jsonDecode(chartsJson) as List)
            .map((e) => ChartConfig.fromJson(e as Map<String, dynamic>))
            .toList()
        : List<ChartConfig>.generate(
            AppConfig.channelCount,
            (i) => ChartConfig(
              channel: i + 1,
              name: AppConfig.defaultChannelNames[i],
              enabled: i < AppConfig.defaultGridRows * AppConfig.defaultGridCols,
            ),
          );

    final statusNames = statusJson != null
        ? (jsonDecode(statusJson) as List).cast<String>()
        : List<String>.from(AppConfig.defaultStatusNames);

    final ctrl = LayoutController._(
      grid: grid,
      charts: charts,
      statusNames: statusNames,
    );

    // First-run convenience: auto-assign enabled channels to grid cells if
    // the saved grid is empty.
    if (gridJson == null) {
      ctrl.grid.autoAssign(
        ctrl.charts.where((c) => c.enabled).map((c) => c.channel).toList(),
      );
    }
    return ctrl;
  }

  Future<void> save() async {
    final p = await SharedPreferences.getInstance();
    await p.setString('layout.grid', jsonEncode(grid.toJson()));
    await p.setString(
      'layout.charts',
      jsonEncode(charts.map((c) => c.toJson()).toList()),
    );
    await p.setString('layout.statusNames', jsonEncode(statusNames));
    notifyListeners();
  }

  /// Channel 1..16 → ChartConfig.
  ChartConfig configFor(int channel) => charts[channel - 1];

  /// Replace state from another LayoutController (used by the Layout dialog
  /// when applying edits from a working copy).
  void copyFrom(LayoutController other) {
    grid = GridConfig(
      rows: other.grid.rows,
      cols: other.grid.cols,
      cellChannels: List<int?>.from(other.grid.cellChannels),
    );
    charts = other.charts
        .map((c) => ChartConfig(
              channel: c.channel,
              name: c.name,
              enabled: c.enabled,
              yMode: c.yMode,
              yMin: c.yMin,
              yMax: c.yMax,
            ))
        .toList();
    statusNames = List<String>.from(other.statusNames);
    notifyListeners();
  }

  LayoutController clone() {
    return LayoutController._(
      grid: GridConfig(
        rows: grid.rows,
        cols: grid.cols,
        cellChannels: List<int?>.from(grid.cellChannels),
      ),
      charts: charts
          .map((c) => ChartConfig(
                channel: c.channel,
                name: c.name,
                enabled: c.enabled,
                yMode: c.yMode,
                yMin: c.yMin,
                yMax: c.yMax,
              ))
          .toList(),
      statusNames: List<String>.from(statusNames),
    );
  }

  /// Mutators that notify on change.

  void setChannelEnabled(int channel, bool enabled) {
    final c = configFor(channel);
    if (c.enabled == enabled) return;
    c.enabled = enabled;
    if (!enabled) {
      // Also clear from any grid cell.
      for (var i = 0; i < grid.cellChannels.length; i++) {
        if (grid.cellChannels[i] == channel) grid.cellChannels[i] = null;
      }
    }
    notifyListeners();
  }

  void setChannelName(int channel, String name) {
    final c = configFor(channel);
    if (c.name == name) return;
    c.name = name;
    notifyListeners();
  }

  void setYMode(int channel, YMode mode) {
    final c = configFor(channel);
    if (c.yMode == mode) return;
    c.yMode = mode;
    notifyListeners();
  }

  void setYRange(int channel, double yMin, double yMax) {
    final c = configFor(channel);
    if (c.yMin == yMin && c.yMax == yMax) return;
    c.yMin = yMin;
    c.yMax = yMax;
    notifyListeners();
  }

  /// Mouse-wheel Y zoom on a chart. Switches mode to userZoomed and updates
  /// the range, keeping the pivot screen-Y fixed.
  void zoomY({
    required int channel,
    required double pivotValue,
    required double factor,
  }) {
    final c = configFor(channel);
    final span = c.yMax - c.yMin;
    final newSpan = span * factor;
    final fraction = (pivotValue - c.yMin) / span;
    c.yMin = pivotValue - newSpan * fraction;
    c.yMax = c.yMin + newSpan;
    c.yMode = YMode.userZoomed;
    notifyListeners();
  }

  void setStatusName(int statusIdx, String name) {
    if (statusNames[statusIdx] == name) return;
    statusNames[statusIdx] = name;
    notifyListeners();
  }

  void setGridSize(int rows, int cols) {
    grid.resize(rows, cols);
    notifyListeners();
  }

  void assignCellToChannel(int cellNumber, int? channel) {
    grid.assign(cellNumber, channel);
    notifyListeners();
  }
}