import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:lucide_icons_flutter/lucide_icons.dart';

import '../tokens.dart';

/// Top bar for pushed screens: a square back affordance, a quiet title, an
/// optional trailing slot (usually the booking reference in mono), and the
/// booking step indicator.
///
/// ── It knows whether anything is under it ──
///
/// The bar used to be a flat slab of canvas, the same colour as the page, with
/// no line under it. Content scrolled beneath it and simply disappeared — an
/// address row would slide up and vanish behind a back arrow with nothing to
/// say it had gone anywhere. A bar that never changes is not a layer; it is
/// paint.
///
/// It listens to the [ScrollNotificationObserver] that [Scaffold] installs
/// around its body — the same mechanism Material's own `AppBar` uses for
/// `scrolledUnderElevation` — and the moment a list has scrolled under it, the
/// canvas turns to surface and a hairline fades in along the bottom. At the top
/// of a page it is invisible again. Nothing is announced, nothing moves; the
/// screen just stops looking like one plane.
class DmTopBar extends StatefulWidget implements PreferredSizeWidget {
  const DmTopBar({
    super.key,
    this.title,
    this.trailing,
    this.progress,
    this.steps,
    this.stepLabel,
    this.onBack,
    this.background = DmColors.canvas,
  });

  final String? title;
  final Widget? trailing;

  /// 0..1 — omit to hide the step indicator.
  final double? progress;

  /// When given, the indicator is drawn as [steps] separate segments rather
  /// than one continuous rail. Discrete steps are countable; a filled bar is
  /// only a proportion, and "how many screens until I am done" is the question
  /// a customer is actually asking.
  final int? steps;

  /// The line above the segments — "Step 2 of 4 · Destination".
  final String? stepLabel;

  final VoidCallback? onBack;
  final Color background;

  /// The +1 is the hairline. A transparent [BorderSide] still measures 1pt, so
  /// the bar is the same height scrolled or not — but it is a point taller than
  /// the row inside it, and without this the Column overflows by exactly that
  /// on every screen with a top bar.
  @override
  Size get preferredSize => Size.fromHeight(57 + (progress == null ? 0 : 42));

  @override
  State<DmTopBar> createState() => _DmTopBarState();
}

class _DmTopBarState extends State<DmTopBar> {
  ScrollNotificationObserverState? _observer;
  bool _under = false;

  @override
  void didChangeDependencies() {
    super.didChangeDependencies();
    _observer?.removeListener(_onScroll);
    _observer = ScrollNotificationObserver.maybeOf(context);
    _observer?.addListener(_onScroll);
  }

  @override
  void dispose() {
    _observer?.removeListener(_onScroll);
    _observer = null;
    super.dispose();
  }

  void _onScroll(ScrollNotification notification) {
    // The predicate is what keeps a horizontal strip inside the page — or a
    // list inside a sheet over it — from driving the bar behind them.
    if (!defaultScrollNotificationPredicate(notification)) return;
    if (notification is! ScrollUpdateNotification &&
        notification is! ScrollMetricsNotification) {
      return;
    }
    // A few points of slack: a list that rests one pixel off the top, or a
    // bounce at the end of an overscroll, should not flicker the line on.
    final under = notification.metrics.extentBefore > 4;
    if (under != _under && mounted) setState(() => _under = under);
  }

  @override
  Widget build(BuildContext context) {
    final current = widget.progress == null || widget.steps == null
        ? 0
        : (widget.progress! * widget.steps!).round().clamp(0, widget.steps!);

    return AnimatedContainer(
      duration: DmMotion.base,
      curve: DmMotion.ease,
      decoration: BoxDecoration(
        color: _under ? DmColors.surface : widget.background,
        border: Border(
          bottom: BorderSide(
            color: _under ? DmColors.border : Colors.transparent,
          ),
        ),
      ),
      child: SafeArea(
        bottom: false,
        child: Column(
          mainAxisSize: MainAxisSize.min,
          children: [
            SizedBox(
              height: 56,
              child: Row(
                children: [
                  const SizedBox(width: DmSpace.pad - 14),
                  DmBackButton(onPressed: widget.onBack),
                  const SizedBox(width: 4),
                  Expanded(
                    child: widget.title == null
                        ? const SizedBox.shrink()
                        : Text(
                            widget.title!,
                            style: DmText.heading.copyWith(fontSize: 17),
                            maxLines: 1,
                            overflow: TextOverflow.ellipsis,
                          ),
                  ),
                  ?widget.trailing,
                  const SizedBox(width: DmSpace.pad),
                ],
              ),
            ),
            if (widget.progress != null)
              Padding(
                padding: const EdgeInsets.fromLTRB(
                  DmSpace.pad,
                  0,
                  DmSpace.pad,
                  16,
                ),
                child: DmStepBar(
                  progress: widget.progress!,
                  steps: widget.steps,
                  current: current,
                  label: widget.stepLabel,
                ),
              ),
          ],
        ),
      ),
    );
  }
}

/// Back.
///
/// ── Why it lost its box ──
///
/// It was a 40pt white square with a hairline border and a 12pt corner, which
/// on a canvas of white bordered cards read as *a card containing an arrow*
/// rather than as a way out of the screen. On the send screen, where the title
/// is now the route underneath it, that left a small empty card alone in the
/// top-left corner of an otherwise open page.
///
/// A back affordance is the one control in an app that needs no explaining and
/// no container. It is the glyph, a 48pt target around it, and a circular
/// ripple in the brand wash when it is pressed.
class DmBackButton extends StatelessWidget {
  const DmBackButton({super.key, this.onPressed});

  final VoidCallback? onPressed;

  @override
  Widget build(BuildContext context) {
    return Semantics(
      button: true,
      label: 'Back',
      child: SizedBox(
        width: DmSpace.tap,
        height: DmSpace.tap,
        child: InkResponse(
          onTap: onPressed ?? () => Navigator.of(context).maybePop(),
          radius: 24,
          highlightShape: BoxShape.circle,
          splashColor: DmColors.brandSoft,
          highlightColor: DmColors.brandSoft,
          child: const Icon(
            LucideIcons.arrowLeft,
            size: 22,
            color: DmColors.ink,
          ),
        ),
      ),
    );
  }
}

/// Booking progress.
///
/// With [steps] it draws that many segments, captioned "Step n of m" in mono;
/// without, it falls back to a single filled rail for callers that only know a
/// fraction.
class DmStepBar extends StatelessWidget {
  const DmStepBar({
    super.key,
    required this.progress,
    this.steps,
    this.current = 0,
    this.label,
    this.onFill = false,
    this.caption = true,
  });

  final double progress;
  final int? steps;
  final int current;
  final String? label;

  /// Drawn on a crimson field (the live-tracking card), where the track is a
  /// lightened white and the fill is solid white.
  final bool onFill;

  /// Whether to print "Step n of m" above the segments.
  ///
  /// True inside the booking flow, where the customer is answering questions
  /// and "how many left" is the thing they want. False on tracking, where the
  /// same segments describe a journey nobody is working through — there,
  /// counting the stages turns a parcel into a progress bar with homework.
  final bool caption;

  @override
  Widget build(BuildContext context) {
    final track = onFill ? const Color(0x52FFFFFF) : DmColors.border;
    final fill = onFill ? Colors.white : DmColors.brand;

    final bar = steps == null
        ? ClipRRect(
            borderRadius: DmRadius.all(DmRadius.pill),
            child: SizedBox(
              height: 3,
              child: Stack(
                children: [
                  Positioned.fill(child: ColoredBox(color: track)),
                  FractionallySizedBox(
                    widthFactor: progress.clamp(0, 1),
                    child: AnimatedContainer(
                      duration: DmMotion.slow,
                      curve: DmMotion.ease,
                      decoration: BoxDecoration(
                        color: fill,
                        borderRadius: DmRadius.all(DmRadius.pill),
                      ),
                    ),
                  ),
                ],
              ),
            ),
          )
        : Row(
            children: [
              for (var i = 0; i < steps!; i++) ...[
                if (i > 0) const SizedBox(width: 4),
                Expanded(
                  child: AnimatedContainer(
                    duration: DmMotion.base,
                    curve: DmMotion.ease,
                    height: 3,
                    decoration: BoxDecoration(
                      color: i < current ? fill : track,
                      borderRadius: DmRadius.all(DmRadius.pill),
                    ),
                  ),
                ),
              ],
            ],
          );

    if (!caption || (label == null && steps == null)) return bar;

    return Column(
      crossAxisAlignment: CrossAxisAlignment.start,
      children: [
        if (label != null || steps != null) ...[
          Row(
            crossAxisAlignment: CrossAxisAlignment.end,
            children: [
              if (steps != null)
                Text.rich(
                  TextSpan(
                    style: DmText.monoSm.copyWith(
                      color: onFill ? DmColors.onBrand3 : DmColors.ink3,
                    ),
                    children: [
                      const TextSpan(text: 'Step '),
                      TextSpan(
                        text: '$current',
                        style: TextStyle(color: onFill ? Colors.white : DmColors.brand),
                      ),
                      TextSpan(text: ' of ${steps!}'),
                    ],
                  ),
                ),
              const Spacer(),
              if (label != null)
                Flexible(
                  child: Text(
                    label!,
                    textAlign: TextAlign.right,
                    maxLines: 1,
                    overflow: TextOverflow.ellipsis,
                    style: DmText.label.copyWith(
                      fontSize: 12.5,
                      color: onFill ? DmColors.onBrand3 : DmColors.ink,
                    ),
                  ),
                ),
            ],
          ),
          const SizedBox(height: 9),
        ],
        bar,
      ],
    );
  }
}

/// Sticky bottom action area.
///
/// `edge: true` lifts it onto white with a hairline above — used when the
/// content behind it scrolls, so the action never looks like the end of the
/// list. On a short screen the canvas variant keeps the page quiet.
class DmFooter extends StatelessWidget {
  const DmFooter({
    super.key,
    required this.children,
    this.edge = false,
    this.background,
    this.divider = false,
  });

  final List<Widget> children;

  /// White bed, hairline above.
  final bool edge;

  final Color? background;

  /// Retained for call-site compatibility; superseded by [edge].
  final bool divider;

  @override
  Widget build(BuildContext context) {
    final lifted = edge || divider;
    return DecoratedBox(
      decoration: BoxDecoration(
        color: background ?? (lifted ? DmColors.surface : DmColors.canvas),
        border: lifted
            ? const Border(top: BorderSide(color: DmColors.border))
            : null,
      ),
      child: SafeArea(
        top: false,
        child: Padding(
          padding: const EdgeInsets.fromLTRB(DmSpace.pad, 14, DmSpace.pad, 12),
          child: Column(
            mainAxisSize: MainAxisSize.min,
            children: [
              for (var i = 0; i < children.length; i++) ...[
                if (i > 0) const SizedBox(height: 4),
                children[i],
              ],
            ],
          ),
        ),
      ),
    );
  }
}

/// The crimson field at the top of a tab root.
///
/// Home, Orders and Account all open with one. It does three jobs at once —
/// it states where you are (eyebrow + title), it holds that destination's one
/// control (a segmented filter, an address switcher, a phone number), and it
/// gives the app a recognisable brand surface that the white canvas below can
/// then stay completely quiet.
///
/// The arcs are drawn, not an asset: they are struck from the same geometry as
/// the mark, they scale to any header height, and they cost no bytes.
class DmBrandHeader extends StatelessWidget {
  const DmBrandHeader({
    super.key,
    required this.title,
    this.eyebrow,
    this.leading,
    this.action,
    this.child,
  });

  final String title;
  final String? eyebrow;

  /// Sits at the top-left of the header — the avatar on Account.
  final Widget? leading;

  /// Top-right — refresh, help.
  final Widget? action;

  /// The control that belongs to this destination, under the title.
  final Widget? child;

  @override
  Widget build(BuildContext context) {
    return ClipRRect(
      borderRadius: const BorderRadius.vertical(
        bottom: Radius.circular(DmRadius.header),
      ),
      child: DecoratedBox(
        // Lit from the top-left like every other brand object in the app, so
        // the crimson field has a direction instead of sitting flat. The spread
        // is deliberately narrow — a header that reads as a gradient rather
        // than as a colour has stopped being the brand.
        decoration: const BoxDecoration(
          gradient: LinearGradient(
            begin: Alignment.topLeft,
            end: Alignment.bottomRight,
            colors: [Color(0xFFA0150A), DmColors.brand, Color(0xFF7A0C04)],
            stops: [0.0, 0.52, 1.0],
          ),
        ),
        child: CustomPaint(
          painter: const DmArcField(),
          child: SafeArea(
            bottom: false,
            child: Padding(
              padding: const EdgeInsets.fromLTRB(
                DmSpace.headerPad,
                2,
                DmSpace.headerPad,
                18,
              ),
              child: Column(
                crossAxisAlignment: CrossAxisAlignment.start,
                mainAxisSize: MainAxisSize.min,
                children: [
                  SizedBox(
                    height: 48,
                    child: Row(
                      children: [
                        ?leading,
                        const Spacer(),
                        ?action,
                      ],
                    ),
                  ),
                  const SizedBox(height: 10),
                  if (eyebrow != null) ...[
                    Text(eyebrow!.toUpperCase(), style: DmText.headerEyebrow),
                    const SizedBox(height: 8),
                  ],
                  Text(title, style: DmText.headerTitle),
                  if (child != null) ...[const SizedBox(height: 18), child!],
                ],
              ),
            ),
          ),
        ),
      ),
    );
  }
}

/// Thin arc strokes struck from the mark's geometry, at the opacity the design
/// uses. Decorative only — it never carries meaning, so it is not announced.
class DmArcField extends CustomPainter {
  const DmArcField({this.opacity = 0.15});

  final double opacity;

  @override
  void paint(Canvas canvas, Size size) {
    // The arcs are authored on a 340-square field anchored to the top-right,
    // then scaled — so the same geometry reads identically on a 210pt Orders
    // header and a 260pt Account one.
    const field = 340.0;
    final scale = size.width / 390 * 1.0;
    canvas.save();
    canvas.translate(size.width - field * scale + 62 * scale, -72 * scale);
    canvas.scale(scale);

    final paint = Paint()
      ..style = PaintingStyle.stroke
      ..strokeWidth = 1.5 / scale
      ..color = Colors.white.withValues(alpha: opacity);

    canvas.drawCircle(const Offset(250, 90), 120, paint);
    canvas.drawCircle(const Offset(250, 90), 170, paint);

    for (final (y1, y2, cx, cy) in const [
      (300.0, 40.0, 60.0, 300.0),
      (330.0, 60.0, 70.0, 330.0),
    ]) {
      final path = Path()
        ..moveTo(-20, y1)
        ..cubicTo(cx, cy, field - 40, y2 + 140, field, y2);
      canvas.drawPath(path, paint);
    }

    canvas.restore();
  }

  @override
  bool shouldRepaint(covariant DmArcField oldDelegate) =>
      oldDelegate.opacity != opacity;
}

/// The segmented filter recessed into the brand header — Orders' Active /
/// Completed / Cancelled, with each tab's count.
///
/// The selected tab lifts out as a white pill and keeps its figure; the others
/// stay in the recess. One control, three states, no separate count row.
class DmSegmented extends StatelessWidget {
  const DmSegmented({
    super.key,
    required this.labels,
    required this.counts,
    required this.index,
    required this.onChanged,
  });

  final List<String> labels;

  /// Null where a tab has no meaningful figure yet (still loading).
  final List<int?> counts;
  final int index;
  final ValueChanged<int> onChanged;

  @override
  Widget build(BuildContext context) {
    return Container(
      padding: const EdgeInsets.all(5),
      decoration: BoxDecoration(
        color: DmColors.onBrandSunken,
        borderRadius: DmRadius.all(DmRadius.lg),
      ),
      child: Row(
        children: [
          for (var i = 0; i < labels.length; i++) ...[
            if (i > 0) const SizedBox(width: 4),
            Expanded(
              child: _Segment(
                label: labels[i],
                count: i < counts.length ? counts[i] : null,
                selected: i == index,
                onTap: () => onChanged(i),
              ),
            ),
          ],
        ],
      ),
    );
  }
}

class _Segment extends StatelessWidget {
  const _Segment({
    required this.label,
    required this.count,
    required this.selected,
    required this.onTap,
  });

  final String label;
  final int? count;
  final bool selected;
  final VoidCallback onTap;

  @override
  Widget build(BuildContext context) {
    return Semantics(
      button: true,
      selected: selected,
      child: GestureDetector(
        behavior: HitTestBehavior.opaque,
        onTap: () {
          HapticFeedback.selectionClick();
          onTap();
        },
        child: AnimatedContainer(
          duration: DmMotion.base,
          curve: DmMotion.ease,
          padding: const EdgeInsets.symmetric(horizontal: 4, vertical: 11),
          decoration: BoxDecoration(
            color: selected ? Colors.white : Colors.transparent,
            borderRadius: DmRadius.all(DmRadius.sm),
          ),
          child: Row(
            mainAxisAlignment: MainAxisAlignment.center,
            children: [
              Flexible(
                child: Text(
                  label,
                  maxLines: 1,
                  overflow: TextOverflow.ellipsis,
                  style: DmText.label.copyWith(
                    fontSize: 13,
                    color: selected ? DmColors.brand : DmColors.onBrand3,
                  ),
                ),
              ),
              if (count != null) ...[
                const SizedBox(width: 6),
                Container(
                  padding: const EdgeInsets.symmetric(horizontal: 6, vertical: 2),
                  decoration: BoxDecoration(
                    color: selected ? DmColors.brandSoft : DmColors.onBrandRaise,
                    borderRadius: DmRadius.all(DmRadius.pill),
                  ),
                  child: Text(
                    '$count',
                    style: DmText.monoSm.copyWith(
                      fontSize: 11,
                      color: selected ? DmColors.brand : Colors.white,
                    ),
                  ),
                ),
              ],
            ],
          ),
        ),
      ),
    );
  }
}

/// The recessed strip under a header title that carries one live fact — the
/// address a pickup is coming from, or the customer's phone number.
class DmHeaderTrack extends StatelessWidget {
  const DmHeaderTrack({
    super.key,
    required this.child,
    this.leading,
    this.trailing,
    this.onTap,
  });

  final Widget child;
  final Widget? leading;
  final Widget? trailing;
  final VoidCallback? onTap;

  @override
  Widget build(BuildContext context) {
    return Semantics(
      button: onTap != null,
      child: GestureDetector(
        behavior: HitTestBehavior.opaque,
        onTap: onTap,
        child: Container(
          padding: const EdgeInsets.fromLTRB(14, 13, 14, 13),
          decoration: BoxDecoration(
            color: DmColors.onBrandSunken,
            borderRadius: DmRadius.all(DmRadius.lg),
          ),
          child: Row(
            children: [
              if (leading != null) ...[leading!, const SizedBox(width: 10)],
              Expanded(child: child),
              if (trailing != null) ...[const SizedBox(width: 10), trailing!],
            ],
          ),
        ),
      ),
    );
  }
}

/// Large title for a screen that has no brand header.
class DmPageTitle extends StatelessWidget {
  const DmPageTitle(this.text, {super.key, this.subtitle});

  final String text;
  final String? subtitle;

  @override
  Widget build(BuildContext context) {
    return Padding(
      padding: const EdgeInsets.fromLTRB(DmSpace.pad, 24, DmSpace.pad, 16),
      child: Column(
        crossAxisAlignment: CrossAxisAlignment.start,
        children: [
          Text(text, style: DmText.pageTitle),
          if (subtitle != null) ...[
            const SizedBox(height: 6),
            Text(subtitle!, style: DmText.lede),
          ],
        ],
      ),
    );
  }
}

/// Sentence-case heading above a group of fields or rows.
class DmGroupHead extends StatelessWidget {
  const DmGroupHead(this.text, {super.key, this.top = 24});

  final String text;
  final double top;

  @override
  Widget build(BuildContext context) {
    return Padding(
      padding: EdgeInsets.only(top: top, bottom: 10),
      child: Text(text, style: DmText.sectionHead),
    );
  }
}

/// Screen heading and its supporting line — shared by every booking step.
class DmScreenHeader extends StatelessWidget {
  const DmScreenHeader({super.key, required this.title, this.lede, this.leding});

  final String title;
  final String? lede;

  /// Rich alternative to [lede].
  final Widget? leding;

  @override
  Widget build(BuildContext context) {
    return Column(
      crossAxisAlignment: CrossAxisAlignment.start,
      children: [
        const SizedBox(height: 4),
        Text(title, style: DmText.title),
        if (lede != null) ...[
          const SizedBox(height: 8),
          Text(lede!, style: DmText.lede),
        ],
        if (leding != null) ...[const SizedBox(height: 10), leding!],
        const SizedBox(height: 22),
      ],
    );
  }
}