import 'package:flutter/material.dart';

import '../tokens.dart';

/// One stop on a rail: where it goes, plus anything worth saying about it.
class DmRailStop {
  const DmRailStop({required this.label, this.note, this.trailing});

  final String label;

  /// Second line under the label.
  final String? note;

  /// Right-aligned text, e.g. "2 packages".
  final String? trailing;
}

/// What a node on the thread stands for.
enum DmNodeKind {
  /// Where the parcel starts. A hollow circle: a door, not a decision.
  origin,

  /// A sorting hub in between. An outlined diamond — the parcel passes
  /// through, it does not stop here.
  hub,

  /// The destination. A filled crimson diamond, the only solid node on the
  /// thread, so the eye lands on where the parcel is going.
  drop,

  /// A leg that has not been arranged yet — dashed outline.
  pending,
}

/// Pickup → drop, drawn as a vertical thread.
///
/// One component for a journey wherever it appears: an order card, the review
/// summary, tracking. It takes a single [drop] or, when a pickup serves several
/// places, a list of [drops] hanging off the same origin.
class DmRouteRail extends StatelessWidget {
  const DmRouteRail({
    super.key,
    required this.pickup,
    this.pickupNote,
    this.pickupEyebrow,
    this.pickupTrailing,
    this.drop,
    this.dropNote,
    this.dropsEyebrow,
    this.drops,
    this.compact = false,
    this.hub,
    this.hubNote,
    this.hubTrailing,
  }) : assert(drop != null || drops != null, 'give the rail somewhere to go');

  final String pickup;
  final String? pickupNote;

  /// Uppercase micro-label above the origin, e.g. "PICKUP".
  final String? pickupEyebrow;

  /// Action rendered at the right of the origin row.
  final Widget? pickupTrailing;

  /// The single-destination case.
  final String? drop;
  final String? dropNote;

  /// Uppercase micro-label above the first destination.
  final String? dropsEyebrow;

  /// Several destinations hanging off one pickup.
  final List<DmRailStop>? drops;

  final bool compact;

  /// The sorting hub between pickup and drop, when the customer has been told
  /// about it. Omitted on a hyperlocal run, which never sees a hub.
  final String? hub;
  final String? hubNote;
  final Widget? hubTrailing;

  @override
  Widget build(BuildContext context) {
    final stops = drops ?? [DmRailStop(label: drop!, note: dropNote)];

    return Column(
      crossAxisAlignment: CrossAxisAlignment.start,
      children: [
        _Leg(
          eyebrow: pickupEyebrow,
          label: pickup,
          note: compact ? null : pickupNote,
          trailing: pickupTrailing,
          kind: DmNodeKind.origin,
          connector: true,
          dashedConnector: hub != null,
          compact: compact,
        ),
        if (hub != null)
          _Leg(
            label: hub!,
            note: compact ? null : hubNote,
            trailing: hubTrailing,
            kind: DmNodeKind.hub,
            labelColor: DmColors.brand,
            connector: true,
            dashedConnector: true,
            compact: compact,
          ),
        for (var i = 0; i < stops.length; i++)
          _Leg(
            eyebrow: i == 0 ? dropsEyebrow : null,
            label: stops[i].label,
            note: compact ? null : stops[i].note,
            trailingText: stops[i].trailing,
            kind: DmNodeKind.drop,
            connector: i != stops.length - 1,
            compact: compact,
          ),
      ],
    );
  }
}

class _Leg extends StatelessWidget {
  const _Leg({
    required this.label,
    required this.note,
    required this.kind,
    required this.connector,
    required this.compact,
    this.dashedConnector = false,
    this.eyebrow,
    this.trailing,
    this.trailingText,
    this.labelColor,
  });

  final String label;
  final String? note;
  final DmNodeKind kind;
  final bool connector;
  final bool dashedConnector;
  final bool compact;
  final String? eyebrow;
  final Widget? trailing;
  final String? trailingText;
  final Color? labelColor;

  @override
  Widget build(BuildContext context) {
    return IntrinsicHeight(
      child: Row(
        crossAxisAlignment: CrossAxisAlignment.start,
        children: [
          SizedBox(
            width: 15,
            child: Column(
              children: [
                SizedBox(height: eyebrow == null ? 3 : 19),
                _Node(kind: kind),
                if (connector)
                  Expanded(
                    child: Padding(
                      padding: const EdgeInsets.symmetric(vertical: 4),
                      child: CustomPaint(
                        painter: _Thread(dashed: dashedConnector),
                        size: const Size(1.5, double.infinity),
                      ),
                    ),
                  ),
              ],
            ),
          ),
          const SizedBox(width: 12),
          Expanded(
            child: Padding(
              padding: EdgeInsets.only(bottom: connector ? (compact ? 13 : 16) : 0),
              child: Column(
                crossAxisAlignment: CrossAxisAlignment.start,
                mainAxisSize: MainAxisSize.min,
                children: [
                  if (eyebrow != null) ...[
                    Text(eyebrow!.toUpperCase(), style: DmText.eyebrow),
                    const SizedBox(height: 4),
                  ],
                  Row(
                    crossAxisAlignment: CrossAxisAlignment.start,
                    children: [
                      Expanded(
                        child: Text(
                          label,
                          style: DmText.cardTitle.copyWith(color: labelColor),
                        ),
                      ),
                      if (trailingText != null) ...[
                        const SizedBox(width: 10),
                        ConstrainedBox(
                          constraints: const BoxConstraints(maxWidth: 120),
                          child: Text(
                            trailingText!,
                            textAlign: TextAlign.right,
                            style: DmText.small,
                          ),
                        ),
                      ],
                      ?trailing,
                    ],
                  ),
                  if (note != null) ...[
                    const SizedBox(height: 3),
                    Text(note!, style: DmText.small),
                  ],
                ],
              ),
            ),
          ),
        ],
      ),
    );
  }
}

class _Node extends StatelessWidget {
  const _Node({required this.kind});

  final DmNodeKind kind;

  @override
  Widget build(BuildContext context) {
    return SizedBox(
      width: 15,
      height: 15,
      child: Center(
        child: switch (kind) {
          DmNodeKind.origin => Container(
              width: 11,
              height: 11,
              decoration: BoxDecoration(
                shape: BoxShape.circle,
                border: Border.all(color: DmColors.ink4, width: 2),
              ),
            ),
          // Rotated squares rather than a second circle: on a thread of three
          // identical dots nothing tells you which end matters, and at 11pt a
          // diamond is distinguishable from a circle at a glance where two
          // shades of the same dot are not.
          DmNodeKind.hub => Transform.rotate(
              angle: 0.785398,
              child: Container(
                width: 10,
                height: 10,
                decoration: BoxDecoration(
                  color: DmColors.surface,
                  borderRadius: BorderRadius.circular(2),
                  border: Border.all(color: DmColors.brand, width: 2),
                ),
              ),
            ),
          DmNodeKind.drop => Transform.rotate(
              angle: 0.785398,
              child: Container(
                width: 10,
                height: 10,
                decoration: BoxDecoration(
                  color: DmColors.brand,
                  borderRadius: BorderRadius.circular(2),
                ),
              ),
            ),
          DmNodeKind.pending => Transform.rotate(
              angle: 0.785398,
              child: Container(
                width: 10,
                height: 10,
                decoration: BoxDecoration(
                  color: DmColors.surface,
                  borderRadius: BorderRadius.circular(2),
                  border: Border.all(color: DmColors.ink4, width: 1.5),
                ),
              ),
            ),
        },
      ),
    );
  }
}

/// The line between two nodes. Solid where the parcel is handled, dashed
/// across a leg it merely travels — the distinction the design draws between
/// a doorstep and a trunk route.
class _Thread extends CustomPainter {
  const _Thread({required this.dashed});

  final bool dashed;

  @override
  void paint(Canvas canvas, Size size) {
    final paint = Paint()
      ..color = DmColors.border
      ..strokeWidth = 1.5
      ..strokeCap = StrokeCap.round;

    final x = size.width / 2;
    if (!dashed) {
      canvas.drawLine(Offset(x, 0), Offset(x, size.height), paint);
      return;
    }

    const dash = 2.0;
    const gap = 4.0;
    var y = 0.0;
    while (y < size.height) {
      canvas.drawLine(
        Offset(x, y),
        Offset(x, (y + dash).clamp(0, size.height)),
        paint,
      );
      y += dash + gap;
    }
  }

  @override
  bool shouldRepaint(covariant _Thread oldDelegate) =>
      oldDelegate.dashed != dashed;
}