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

import '../../data/models.dart';
import '../format.dart';
import '../tokens.dart';
import 'buttons.dart';

/// The customer's journey: seven milestones, not nine backend states.
///
/// Operational detail — "Miler on the way", "Order created" — is shown as
/// context beneath the milestone that is currently happening, so a transition
/// informs without becoming another permanent row.
///
/// ── Newest first, and only as many as matter ──
///
/// The list used to run oldest-to-newest, full height, every time: seven rows
/// of which four were grey placeholders for things that have not happened. On
/// a screen whose job is "where is my parcel right now", the answer was at the
/// bottom, below the scroll. It now leads with what just happened and, when
/// [maxRows] is set, keeps the rest behind one line — the same compression the
/// design applies to the live tracking card.
class DmMilestones extends StatelessWidget {
  const DmMilestones({
    super.key,
    required this.booking,
    this.stage,
    this.title = 'Recent updates',
    this.maxRows,
    this.onExpand,
    this.showStep = false,
  });

  final Booking booking;

  /// Journey to show. Defaults to the pickup's own stage; a destination order
  /// passes its own.
  final JourneyStage? stage;

  final String title;

  /// Show at most this many rows, newest first. Null shows the whole journey.
  final int? maxRows;

  /// Tapped from the "Full timeline" action. Null hides the action.
  final VoidCallback? onExpand;

  /// Puts "Step N of 5" opposite the title. Only where the whole rail is on
  /// screen — a counter over a compressed list counts rows nobody can see.
  final bool showStep;

  @override
  Widget build(BuildContext context) {
    final current = stage ?? booking.stage;
    final currentMilestone = CustomerMilestone.of(current);
    final milestones = CustomerMilestone.values;
    final currentIndex = currentMilestone.index;

    // ── Chronological, because the line is the progress ──
    //
    // This ran newest-first, on the argument that "where is my parcel right
    // now" should not be at the bottom of the list. That was right when the
    // rail was a list of rows and wrong now that it is a rail: the travelled
    // part of the spine is drawn crimson and the rest grey, and a reversed
    // order makes a filling line read backwards. The answer is also no longer
    // down here — the crimson card at the top of tracking says it outright,
    // so this is free to answer the other question, which is *how far along*.
    //
    // Compressed, it shows the current milestone and the two before it: recent
    // activity stays on screen without the rail claiming the whole page.
    final ordered = [for (var i = 0; i < milestones.length; i++) i];
    final shown = maxRows == null
        ? ordered
        : ordered
              .sublist(
                (currentIndex - maxRows! + 1).clamp(0, milestones.length),
                (currentIndex + 1).clamp(1, milestones.length),
              )
              .toList();

    return Padding(
      padding: const EdgeInsets.symmetric(horizontal: 2),
      child: Column(
        crossAxisAlignment: CrossAxisAlignment.start,
        children: [
          Row(
            children: [
              Expanded(
                child: Text(
                  title.toUpperCase(),
                  // Neutral. It heads a rail that is deliberately receding,
                  // beside a crimson action — two accents on a group nobody
                  // is meant to study.
                  style: DmText.eyebrow,
                ),
              ),
              // ── "Step 2 of 5" ──
              //
              // The rail shows where the parcel is; the counter says how much
              // of the journey that is. A customer looking at five rows with
              // one of them lit has to count to know, and counting is the one
              // thing a progress indicator exists to save them.
              if (showStep)
                Text(
                  'Step ${currentIndex + 1} of ${milestones.length}',
                  style: DmText.label.copyWith(
                    fontSize: 12.5,
                    color: DmColors.brand,
                  ),
                ),
              if (onExpand != null && shown.length < ordered.length)
                DmTextAction(
                  // Was "All 7 stages". The number counts something the
                  // customer has no model for — they do not know a parcel has
                  // seven of anything — and it changes with the backend's own
                  // vocabulary.
                  label: 'Full timeline',
                  onPressed: onExpand,
                  minHeight: 24,
                ),
            ],
          ),
          const SizedBox(height: 16),
          for (var n = 0; n < shown.length; n++)
            _MilestoneRow(
              milestone: milestones[shown[n]],
              done: shown[n] < currentIndex,
              isCurrent: shown[n] == currentIndex,
              first: n == 0,
              last: n == shown.length - 1,
              time: shown[n] <= currentIndex
                  ? relativeTime(booking.timeOf(milestones[shown[n]].firstStage))
                  : '',
              detail: shown[n] == currentIndex ? _detailFor(current) : null,
            ),
        ],
      ),
    );
  }

  /// One line of operational context for the stage actually in progress.
  String? _detailFor(JourneyStage current) => switch (current) {
    JourneyStage.booked => 'Matching the nearest available Miler',
    JourneyStage.assigned =>
      booking.miler == null
          ? null
          : '${booking.miler!.name} accepted this pickup',
    JourneyStage.onTheWay =>
      booking.milerDistanceKm == null
          ? 'Miler on the way'
          : 'Miler on the way · ${booking.milerDistanceKm} km away, '
                'about ${booking.milerEtaMinutes} min',
    JourneyStage.arrived => 'Miler arrived at your door · verification OTP ready',
    JourneyStage.pickedUp => 'Weighing and sealing your packages',
    JourneyStage.orderCreated =>
      booking.isMultiDestination
          ? 'Order created for each destination · tracking issued'
          : 'Order created · tracking number issued',
    JourneyStage.inTransit => 'Moving through our network',
    JourneyStage.outForDelivery => 'Out with the delivery Miler',
    JourneyStage.delivered => null,
  };
}

/// One milestone on the spine.
///
/// ── The line is the progress bar ──
///
/// Every connector used to be the same grey hairline, which made the rail a
/// list of dots that happened to be joined up: to work out how far along a
/// parcel was you had to find the filled dots and count them. The segment
/// *above* a node is now crimson when that node has been reached and grey when
/// it has not, so the line fills from the top as the parcel moves and "how far
/// along" is answered before a single word is read.
///
/// ── Identity left, time right ──
///
/// The same split the Miler app's route rail uses: what happened on the left,
/// when it happened on the right, on one baseline. Four stacked left-aligned
/// lines make the eye walk down the block to find the time; two columns answer
/// both in one fixation, and down a rail the times stack into a scan column.
class _MilestoneRow extends StatelessWidget {
  const _MilestoneRow({
    required this.milestone,
    required this.done,
    required this.isCurrent,
    required this.first,
    required this.last,
    required this.time,
    this.detail,
  });

  final CustomerMilestone milestone;
  final bool done;
  final bool isCurrent;
  final bool first;
  final bool last;
  final String time;
  final String? detail;

  @override
  Widget build(BuildContext context) {
    final upcoming = !done && !isCurrent;
    final reached = done || isCurrent;

    return IntrinsicHeight(
      child: Row(
        crossAxisAlignment: CrossAxisAlignment.start,
        children: [
          SizedBox(
            width: 14,
            child: Column(
              children: [
                // The segment above this node, which is what says whether the
                // parcel has got here. Absent on the first row: a line running
                // up out of the top of the rail has nowhere to come from.
                SizedBox(
                  height: 6,
                  child: first
                      ? null
                      : Center(
                          child: Container(
                            width: 2,
                            color: reached
                                ? DmColors.brand
                                : DmColors.border,
                          ),
                        ),
                ),
                _Marker(done: done, isCurrent: isCurrent),
                if (!last)
                  Expanded(
                    child: Center(
                      child: Container(
                        width: 2,
                        // Crimson only as far as the parcel has come. The
                        // segment below the current node is the road ahead.
                        color: done ? DmColors.brand : DmColors.border,
                      ),
                    ),
                  ),
              ],
            ),
          ),
          const SizedBox(width: 14),
          Expanded(
            child: Padding(
              padding: EdgeInsets.only(top: 2, bottom: last ? 0 : 18),
              child: Column(
                crossAxisAlignment: CrossAxisAlignment.start,
                mainAxisSize: MainAxisSize.min,
                children: [
                  Row(
                    crossAxisAlignment: CrossAxisAlignment.baseline,
                    textBaseline: TextBaseline.alphabetic,
                    children: [
                      Expanded(
                        child: Text(
                          milestone.label,
                          // The one happening now is the only thing on the
                          // rail set in the brand colour, and the only one at
                          // full weight. Everything behind it is history and
                          // everything ahead of it has not happened.
                          style: switch ((isCurrent, upcoming)) {
                            (true, _) => DmText.cardTitle.copyWith(
                              fontSize: 15.5,
                              color: DmColors.brand,
                            ),
                            (_, true) => DmText.small.copyWith(
                              color: DmColors.ink4,
                            ),
                            _ => DmText.cardTitle.copyWith(fontSize: 14.5),
                          },
                        ),
                      ),
                      if (time.isNotEmpty) ...[
                        const SizedBox(width: 10),
                        Text(
                          time,
                          // Always quiet. The crimson on the current row is
                          // the "you are here" marker and it belongs to the
                          // milestone; a timestamp set in it made the accent
                          // mean "recent" on one row and "now" on the next.
                          style: DmText.monoSm.copyWith(color: DmColors.ink3),
                        ),
                      ],
                    ],
                  ),
                  if (detail != null) ...[
                    const SizedBox(height: 3),
                    Text(detail!, style: DmText.small),
                  ],
                ],
              ),
            ),
          ),
        ],
      ),
    );
  }
}

/// The node itself.
///
/// Three states and three shapes, so the rail is readable without colour: a
/// filled disc behind you, a ring with a lit centre where you are, a hollow
/// outline ahead.
class _Marker extends StatelessWidget {
  const _Marker({required this.done, required this.isCurrent});

  final bool done;
  final bool isCurrent;

  @override
  Widget build(BuildContext context) {
    if (isCurrent) {
      return Container(
        width: 14,
        height: 14,
        alignment: Alignment.center,
        decoration: BoxDecoration(
          color: DmColors.surface,
          shape: BoxShape.circle,
          border: Border.all(color: DmColors.brand, width: 2),
          boxShadow: const [
            BoxShadow(color: DmColors.brandSoft, spreadRadius: 3.5),
          ],
        ),
        child: Container(
          width: 5,
          height: 5,
          decoration: const BoxDecoration(
            color: DmColors.brand,
            shape: BoxShape.circle,
          ),
        ),
      );
    }
    if (done) {
      return Container(
        width: 14,
        height: 14,
        alignment: Alignment.center,
        decoration: const BoxDecoration(
          color: DmColors.brand,
          shape: BoxShape.circle,
        ),
        child: const Icon(
          LucideIcons.check,
          size: 9,
          color: Colors.white,
        ),
      );
    }
    return Container(
      width: 14,
      height: 14,
      decoration: BoxDecoration(
        color: DmColors.canvas,
        shape: BoxShape.circle,
        border: Border.all(color: DmColors.border, width: 2),
      ),
    );
  }
}