import 'package:flutter/widgets.dart';

import 'package:miler/views/helpers/constants/Colorconstants.dart';
import 'package:miler/views/helpers/constants/design_constants.dart';

/// ─────────────────────────────────────────────────────────────────────────
/// FOUR LAYERS, AND WHAT EACH ONE MEANS
///
/// The app had **five** near-identical light surfaces — `pureSurface`,
/// `surface`, `neutralLight`, `cardSurface`, `daylightSurface` — and measured
/// against the page ground, three of them were invisible:
///
/// ```
///   neutralLight   #F2F4F8   1.021 : 1   ← indistinguishable
///   cardSurface    #EDEFF4   1.023 : 1   ← indistinguishable
///   surface        #FCF9F8   1.073 : 1   ← and warm, unlike everything else
///   pureSurface    #FFFFFF   1.124 : 1   ← the one that mattered, and too close
/// ```
///
/// Five tokens doing the work of two is why the app looked flat *and* why
/// individual screens grew their own borders and shadows: a surface that will
/// not separate on its own has to be outlined, and once one screen outlines
/// something every screen does, in its own way.
///
/// The fix was not more containers. It was giving the ground somewhere to be:
/// the canvas moved down to #DEE3EA, white now separates at 1.290:1, and the
/// layers below are named for **what a surface means** rather than for what
/// colour it happens to be.
///
/// ── The ladder ──
///
/// ```
///   0  canvas     the page itself. Never white.
///   1  working    a region the rider reads or works in. White, no border.
///   2  raised     something that acts: a command bar, a live card. Shadow.
///   3  floating   over everything, with a scrim: sheets, dialogs.
/// ```
///
/// A container is justified when it is one of these layers. It is not
/// justified because the content inside it is a group — grouping is done by
/// whitespace, type and the timeline, which is why a route reads as a route
/// without a box around each stop.
/// ─────────────────────────────────────────────────────────────────────────
abstract final class MilerSurface {
  /// **Layer 0.** The page. Every scaffold in the app sits on this.
  ///
  /// Deliberately not white: a canvas that is white leaves nothing for a white
  /// surface to be distinguishable *from*, which is the state this app was in.
  static const Color canvas = ColorConstants.daylightSurface;

  /// **Layer 1.** A region the rider reads or works in — a sheet's body, a
  /// details page, a grouped operational block.
  ///
  /// No border. At 1.290:1 against [canvas] it separates on its own, and an
  /// outline on top of a step that already works is a line to read past.
  static const Color working = ColorConstants.pureSurface;

  /// **Layer 2.** Something that *acts*: the floating command bar, the live
  /// card, a control that owns the bottom of the screen.
  ///
  /// Same fill as [working] — the difference is [raisedShadow], because what
  /// separates an action surface from a reading surface is that it appears to
  /// sit above the page rather than in it.
  static const Color raised = ColorConstants.pureSurface;

  /// **Layer 3.** Over everything, with a scrim beneath: modal sheets and
  /// dialogs. Painted by `milerGlassSheet`; this names the layer.
  static const Color floating = ColorConstants.glassCard;

  /// A quiet tonal block *inside* layer 1 — a fact grid, a folded group.
  ///
  /// The only nesting the system allows, and only when the block is a
  /// different **kind** of thing from what surrounds it. Never for grouping.
  static const Color inset = ColorConstants.neutralLight;

  /// Layer 2's lift. One shadow, used everywhere something is raised, so
  /// "floating" looks the same on every screen.
  static const List<BoxShadow> raisedShadow = DesignConstants.shadowSm;

  /// Layer 3's lift.
  static const List<BoxShadow> floatingShadow = DesignConstants.shadowFloat;

  /// The dim behind a layer-3 surface. Separation comes from the scrim first
  /// and the shadow second — a sheet that needs a heavy shadow to be legible
  /// is a sheet whose scrim is too weak.
  static const Color scrim = Color(0x66000000);

  /// The gutter a layer-1 panel leaves around itself, so the canvas reads as
  /// ground rather than as a hairline. One number, because two panels a few
  /// points apart is how a page stops looking composed.
  static const double panelGutter = 12;

  /// The breathing room *inside* a layer-1 panel.
  static const double panelPad = 14;
}

/// ── Layer 1, as a widget ──
///
/// The ladder above says a working region is *white, standing on the canvas,
/// with no border*. Home was the screen that proved why that has to be a
/// widget rather than a paragraph: its sheet was painted with the canvas and
/// its content placed straight onto it, so the whole page came out one flat
/// grey with nothing white anywhere on it. Every rule was followed except the
/// one that does the work — something has to actually stand on the ground.
///
/// No border and no shadow, deliberately. White separates from the canvas at
/// 1.290 : 1, which is above the ~1.25 : 1 where two tones start reading as
/// two surfaces, so an outline here would be a line to read past rather than
/// a line that says anything.
class MilerPanel extends StatelessWidget {
  final Widget child;

  /// Space below this panel before the next one. The canvas showing through
  /// the gap is what makes them read as separate regions.
  final double gap;

  /// Set false where the child already owns its own horizontal padding — a
  /// list whose rows need to bleed to the panel edge, for instance.
  final bool padded;

  const MilerPanel({
    super.key,
    required this.child,
    this.gap = 10,
    this.padded = true,
  });

  @override
  Widget build(BuildContext context) {
    return Container(
      margin: EdgeInsets.fromLTRB(
        MilerSurface.panelGutter,
        0,
        MilerSurface.panelGutter,
        gap,
      ),
      padding: padded
          ? EdgeInsets.symmetric(
              horizontal: MilerSurface.panelPad,
              vertical: MilerSurface.panelPad,
            )
          : EdgeInsets.zero,
      decoration: BoxDecoration(
        color: MilerSurface.working,
        borderRadius: BorderRadius.circular(DesignConstants.radiusXl),
      ),
      child: child,
    );
  }
}