import 'package:flutter/foundation.dart';

import 'package:miler/data/miler_api.dart';

/// ─────────────────────────────────────────────────────────────────────────
/// THE CONSIGNMENT'S OWN VOCABULARY
///
/// A booking and a consignment are two different objects with two different
/// state machines, and the app has been paying for treating them as one.
///
///   booking     Pending_Pickup → Miler_Assigned → Pickup_Scheduled
///               → Picked_Up → **Converted_To_Consignment** | Cancelled
///
///   consignment Created → Inwarded_at_Hub → Tripsheet_Loaded → In_Transit
///               → **Out_for_Delivery** → **Delivered** | RTO | …
///
/// `Converted_To_Consignment` is where the booking's story ENDS. There is no
/// booking `Delivered`, and `GET /miler/bookings` therefore reports the same
/// terminal word for a parcel sitting in a hub, a parcel on a rider's bike and
/// a parcel handed over an hour ago. Any code that decides "is this stop still
/// mine to deliver?" from a booking status is asking the wrong object — which
/// is exactly the defect this file exists to close.
///
/// ── What this is not ──
///
/// Not a local mirror and not a cache to write into. The consignment's state
/// belongs to the server; the only honest way to know it is to ask. Nothing
/// here ever *sets* a state — see [ConsignmentGate].
/// ─────────────────────────────────────────────────────────────────────────
enum ConsignmentState {
  created,
  inwardedAtHub,
  tripsheetLoaded,
  inTransit,

  /// **In the rider's hands, not yet on the road.**
  ///
  /// Added by the backend on 21 Aug 2026 and it closes the gap this app had
  /// been modelling locally: `pickup-complete` used to push hyperlocal work
  /// straight to [outForDelivery], so the hub saw "actively delivering" for
  /// food still on the kitchen counter and there was no server state meaning
  /// *collected, holding*. Now the pivot lands here and
  /// `POST /consignments/:id/start-delivery` makes the release.
  collectedByMiler,

  /// Released to a rider. **The only state `deliver` accepts.**
  outForDelivery,

  /// Handed over. Terminal.
  delivered,

  rtoInitiated,
  returnedToSender,
  missing,
  damaged,
  cancelled,

  /// The server said something this build does not know. Deliberately not
  /// deliverable and deliberately not "finished" — an unrecognised state is a
  /// reason to ask, never a reason to act.
  unknown,
}

/// Normalises the backend's `eventstatus` / `status` spelling.
ConsignmentState consignmentStateFromRaw(dynamic raw) {
  final s = (raw?.toString() ?? '').trim().toLowerCase().replaceAll(' ', '_');
  switch (s) {
    case 'created':
      return ConsignmentState.created;
    case 'inwarded_at_hub':
      return ConsignmentState.inwardedAtHub;
    case 'tripsheet_loaded':
      return ConsignmentState.tripsheetLoaded;
    case 'in_transit':
      return ConsignmentState.inTransit;
    case 'collected_by_miler':
    case 'collectedbymiler':
      return ConsignmentState.collectedByMiler;
    case 'out_for_delivery':
    case 'outfordelivery':
      return ConsignmentState.outForDelivery;
    case 'delivered':
      return ConsignmentState.delivered;
    case 'rto_initiated':
      return ConsignmentState.rtoInitiated;
    case 'returned_to_sender':
      return ConsignmentState.returnedToSender;
    case 'missing':
      return ConsignmentState.missing;
    case 'damaged':
      return ConsignmentState.damaged;
    case 'cancelled':
    case 'canceled':
      return ConsignmentState.cancelled;
    default:
      return ConsignmentState.unknown;
  }
}

extension ConsignmentStateX on ConsignmentState {
  /// `POST /miler/consignments/:id/deliver` is refused unless the consignment
  /// is `Out_for_Delivery`. One state, no inference, no other spelling.
  bool get isDeliverable => this == ConsignmentState.outForDelivery;

  /// Already handed over. The work is done server-side; the rider's device is
  /// the thing that is behind.
  bool get isDelivered => this == ConsignmentState.delivered;

  /// Closed for good, one way or another — nothing left for a rider to do.
  bool get isClosed =>
      this == ConsignmentState.delivered ||
      this == ConsignmentState.cancelled ||
      this == ConsignmentState.returnedToSender;

  /// Collected and waiting on the rider's own **Start round**, not on anyone
  /// else. Deliberately *not* [awaitsHub]: telling a rider the hub has his
  /// parcel while it is in his own box is the error this state exists to
  /// prevent.
  bool get needsRelease => this == ConsignmentState.collectedByMiler;

  /// Still inside the hub's half of the network. **This is the case the
  /// "not released yet" guard is for** — a logistics consignment sitting at a
  /// hub genuinely cannot be delivered by this rider, and must stay blocked.
  ///
  /// ── `Created` is not one of these, and treating it as one stranded riders ──
  ///
  /// It was listed here, and it is the wrong half of the network. The backend's
  /// own contract for the pivot is:
  ///
  /// ```
  ///   hyperlocal   pickup-complete → Out_for_Delivery   (compatibility mode)
  ///                                → Collected_By_Miler (flag on)
  ///   hub-routed   pickup-complete → Created + next_action: inward_at_hub
  /// ```
  ///
  /// So `Created` means *the consignment exists and nothing has happened to it
  /// yet* — the parcel is *in the rider's own hands*, waiting either on his
  /// release or on him carrying it to the hub. The hub has never seen it. The
  /// rider slid **Start ride**, and the app answered "This parcel is with the
  /// hub — it will be delivered from there, not by you" about a bag on his own
  /// back, with no way forward from that screen.
  ///
  /// Genuine hub custody starts at [ConsignmentState.inwardedAtHub] — the state
  /// whose name says the hub took it in. See [awaitsHubInward] for `Created`.
  bool get awaitsHub =>
      this == ConsignmentState.inwardedAtHub ||
      this == ConsignmentState.tripsheetLoaded ||
      this == ConsignmentState.inTransit;

  /// Converted, and not yet moved anywhere by anyone.
  ///
  /// The parcel is with **this rider**. On a hyperlocal run this is a state the
  /// release moves out of; on a hub-routed one his next act is to inward it at
  /// the hub, which is not something this app does yet. Either way it is not a
  /// reason to tell him the parcel is somebody else's — see [awaitsHub].
  bool get awaitsHubInward => this == ConsignmentState.created;

  /// After a successful `skip`, whether the stop is **still the rider's
  /// problem**.
  ///
  /// A skip is a failed attempt, not a closed consignment, and what the server
  /// does with one is the server's business: it may move the consignment to a
  /// failure state, or leave it `Out_for_Delivery` for a second attempt or an
  /// RTO decision taken elsewhere. The app cannot tell from the skip's own
  /// 200, so it reads the consignment afterwards and asks this.
  ///
  /// **Unknown counts as open.** A read that failed is not permission to
  /// declare a stop finished — writing a terminal local record over a
  /// consignment the hub still calls open leaves two systems disagreeing about
  /// whether a parcel is anyone's problem, with the rider's screen the only
  /// one saying it is not.
  bool get isOpenAfterSkip =>
      isDeliverable || needsRelease || this == ConsignmentState.unknown;

  /// `skip` is accepted from both halves of the rider's custody — the backend
  /// widened it on 21 Aug 2026 so a failed attempt is reportable the moment
  /// the parcel is collected, not only once the round has started.
  bool get canSkip => needsRelease || isDeliverable;

  /// Why **Start ride** could not set off, in words a rider can act on — or
  /// null when this state is not a reason to refuse one.
  ///
  /// ── The screen was reading the state machine out loud ──
  ///
  /// When `start-delivery` refuses, the backend answers with an assertion
  /// about its own model: *"consignment is Inwarded_At_Hub, not
  /// Collected_By_Miler"*. That sentence was passed through to the rider
  /// verbatim, on the reasoning that the server's own words beat a guess — and
  /// that reasoning is right about *whose* answer it is and wrong about *what
  /// kind of sentence* it is. `Inwarded_At_Hub` is a database enum. It is not
  /// something a man holding a phone at a kitchen counter can do anything
  /// with, and he had no way to tell it from a bug.
  ///
  /// So the state is translated here, in the file that owns the vocabulary,
  /// exactly once. Every sentence answers the only two questions he has: is
  /// this mine, and is sliding again going to help.
  ///
  /// Null for [outForDelivery], [collectedByMiler] and [unknown] — the first
  /// two are not refusals at all and the third is not an answer, so the caller
  /// falls back rather than inventing a cause.
  String? get startRefusalSentence => switch (this) {
    // Converted and not yet routed. The one refusal here that a second slide
    // in a minute genuinely can clear.
    ConsignmentState.created =>
      'Your office is still setting this one up. Give it a moment and slide '
          'again.',
    // The logistics network has it. Said without naming a building the rider
    // has never been to — what matters is that it is not his round.
    ConsignmentState.inwardedAtHub ||
    ConsignmentState.tripsheetLoaded ||
    ConsignmentState.inTransit =>
      "This one has already been handed on — it's not yours to deliver.",
    ConsignmentState.delivered =>
      'This one has already been delivered. Nothing left to start.',
    ConsignmentState.rtoInitiated || ConsignmentState.returnedToSender =>
      'This one is going back to the sender, so there is no delivery to '
          'start.',
    ConsignmentState.missing || ConsignmentState.damaged =>
      'Your office has flagged a problem with this parcel. They have to clear '
          'it before it can go out.',
    ConsignmentState.cancelled =>
      'This one has been cancelled. There is nothing to deliver.',
    ConsignmentState.outForDelivery ||
    ConsignmentState.collectedByMiler ||
    ConsignmentState.unknown => null,
  };
}

/// The consignment state a **start-delivery** refusal names, or
/// [ConsignmentState.unknown] when it names none this build knows.
///
/// ── Reading a state out of a sentence, safely ──
///
/// Parsing prose is normally a bad idea, and this is the case where it is not,
/// because it does not depend on the prose. `POST
/// /miler/consignments/:id/start-delivery` accepts **exactly one** state —
/// `Collected_By_Miler`. So of the state names a refusal from that endpoint
/// mentions, the only one that cannot be describing where the consignment
/// actually *is* is the one that would have been accepted. Drop that, and
/// whatever is left is the answer — whichever order the words come in, and
/// however the sentence is later reworded.
///
/// This exists because the state read can fail twice: the row need not carry
/// `consignmentstatus`, and `GET /miler/consignments/:id` can 404 on an older
/// deployment. In that case the refusal itself is the only thing that knows
/// what happened, and throwing it away costs the rider a real answer.
///
/// Matches only the wire's own shape — capitalised words joined by
/// underscores — so an ordinary sentence yields nothing.
ConsignmentState consignmentStateNamedInRefusal(String message) {
  if (message.isEmpty) return ConsignmentState.unknown;
  for (final m in RegExp(
    r'[A-Za-z]+(?:_[A-Za-z]+)+',
  ).allMatches(message)) {
    final state = consignmentStateFromRaw(m.group(0));
    if (state == ConsignmentState.unknown) continue;
    // The state the endpoint requires, not the state it found.
    if (state == ConsignmentState.collectedByMiler) continue;
    return state;
  }
  return ConsignmentState.unknown;
}

/// True when [message] is the backend talking to itself.
///
/// A refusal carrying a wire enum — `Inwarded_At_Hub`, `Out_for_Delivery` — is
/// a state-machine assertion, not a sentence for a rider, and it must never
/// reach a screen. Anything else the server says is prose written for a person
/// and is worth more than a generic apology, so it is still passed through.
bool namesWireState(String message) =>
    RegExp(r'[A-Za-z]+(?:_[A-Za-z]+)+').hasMatch(message);

/// What the app is allowed to do with a consignment, decided from the
/// authoritative server state rather than from a booking row or a local flag.
enum DeliverGate {
  /// `Out_for_Delivery` — post the delivery.
  deliverable,

  /// `Delivered` — the server already has it. Reconcile locally; do not post
  /// again and do not show the rider an error for work he completed.
  alreadyDelivered,

  /// Collected but the round has not been started. The rider unblocks this
  /// himself — **Start round** on the Deliveries tab.
  needsRelease,

  /// A real hub-side hold. Block, and say so.
  awaitingHub,

  /// `Created` — converted, never released, never inwarded. The parcel is in
  /// this rider's hands, so the hub-hold wording is a lie; but it is not
  /// `Out_for_Delivery` either, so `deliver` will refuse it. Blocked, with the
  /// one sentence that is actually true about it. See
  /// [ConsignmentStateX.awaitsHubInward].
  awaitingInward,

  /// Closed some other way (cancelled, returned). Not deliverable, not an
  /// error the rider caused.
  closed,

  /// The state could not be read — no id, no network, an unparseable answer.
  /// **Not a block.** A read failure is not evidence of anything, so the
  /// delivery is attempted and the server remains the judge. Blocking here
  /// would strand a rider at a door because a GET timed out.
  unknown,
}

/// Reads a consignment's authoritative state and answers what may be done.
///
/// ── Why this needs a network call at all ──
///
/// Nothing the rider's device already holds can answer it. `GET /miler/bookings`
/// carries the *booking* status (terminal at `Converted_To_Consignment`) and no
/// consignment status at all — verified against the live API. The local
/// collected/out-for-delivery sets record what the *rider* did on *this*
/// handset, which is exactly what a reinstall, a second device or a
/// hub-side change makes wrong.
///
/// `GET /miler/consignments/:consignmentid` reports the current state directly
/// — shipped 21 Aug 2026 at this app's request. Before it, the only route that
/// carried consignment state was `…/logs/:id`, and reading a state machine
/// meant pulling its entire history and sorting it. That still works and
/// remains the fallback here, because a rider mid-round on a build that meets
/// an older deployment must not be blocked by a 404.
class ConsignmentGate {
  ConsignmentGate._();

  /// Reads the current state of [consignmentId].
  ///
  /// Returns [ConsignmentState.unknown] on any failure — see [DeliverGate].
  static Future<ConsignmentState> stateOf(Object consignmentId) async {
    final id = consignmentId.toString().trim();
    if (id.isEmpty || id == '0') return ConsignmentState.unknown;

    try {
      final res = await MilerApi.consignment(id);
      if (res.ok) {
        final state = _stateFromDetail(res.data);
        if (state != ConsignmentState.unknown) {
          debugPrint('[CONSIGNMENT] $id is ${state.name}');
          return state;
        }
      } else {
        debugPrint('[CONSIGNMENT] get $id -> ${res.status} ${res.message}');
      }
      // Either the route is not deployed yet, or it answered something this
      // build cannot read. The history still holds the answer.
      return _stateFromLogs(id);
    } catch (e) {
      debugPrint('[CONSIGNMENT] could not read $id: $e');
      return ConsignmentState.unknown;
    }
  }

  /// Reads `GET /miler/consignments/:id`.
  ///
  /// The response carries both a `status` string and the derived booleans
  /// (`collected`, `out_for_delivery`, `delivered`, `can_deliver`…). The
  /// string is preferred: it is the state itself, whereas the flags are the
  /// server's opinion *about* the state and can be extended independently.
  /// The flags are only consulted when the string is a word this build has
  /// never heard of — and there, `delivered` first, because mistaking a
  /// completed delivery for an open one is the failure that makes a rider
  /// re-post work he has already done.
  static ConsignmentState _stateFromDetail(Map<String, dynamic> data) {
    if (data.isEmpty) return ConsignmentState.unknown;

    final raw = data['consignmentstatus'] ?? data['status'] ?? data['state'];
    final named = consignmentStateFromRaw(raw);
    if (named != ConsignmentState.unknown) return named;

    bool flag(String key) => data[key] == true || '${data[key]}' == 'true';

    // State flags first — they describe where the consignment *is*.
    if (flag('delivered')) return ConsignmentState.delivered;
    if (flag('out_for_delivery')) return ConsignmentState.outForDelivery;
    if (flag('collected')) return ConsignmentState.collectedByMiler;

    // Then the permission flags, which describe what may be *done*. A weaker
    // signal — `can_deliver` is the server having already decided the answer
    // this app derives from the state — but a far better one than giving up:
    // `unknown` blocks the Start delivery bar and makes the door guess.
    if (flag('can_deliver')) return ConsignmentState.outForDelivery;
    if (flag('can_start_delivery')) return ConsignmentState.collectedByMiler;
    return ConsignmentState.unknown;
  }

  /// The pre-21-Aug-2026 read: the whole history, newest row wins.
  static Future<ConsignmentState> _stateFromLogs(String id) async {
    final res = await MilerApi.consignmentLogs(id);
    if (!res.ok) {
      debugPrint('[CONSIGNMENT] logs $id -> ${res.status} ${res.message}');
      return ConsignmentState.unknown;
    }

    // Rows arrive oldest-first; the state is whatever happened last. Sorted
    // on `historyid` rather than trusting arrival order, because a state
    // machine read out of order is worse than not read.
    final rows = <Map<String, dynamic>>[
      for (final r in res.list)
        if (r is Map) r.map((k, v) => MapEntry(k.toString(), v)),
    ];
    if (rows.isEmpty) return ConsignmentState.unknown;

    rows.sort((a, b) {
      final ai = int.tryParse('${a['historyid'] ?? 0}') ?? 0;
      final bi = int.tryParse('${b['historyid'] ?? 0}') ?? 0;
      if (ai != bi) return ai.compareTo(bi);
      return (a['createdat'] ?? '').toString().compareTo(
        (b['createdat'] ?? '').toString(),
      );
    });

    final state = consignmentStateFromRaw(
      rows.last['eventstatus'] ?? rows.last['status'],
    );
    debugPrint('[CONSIGNMENT] $id is ${state.name} (from logs)');
    return state;
  }

  /// [_stateFromDetail], reachable from a test.
  ///
  /// The flag-reading path is the one that runs when the backend adds a state
  /// this build has never heard of — the case that cannot be produced by
  /// naming a status, and is exactly the case worth pinning.
  @visibleForTesting
  static ConsignmentState stateFromDetailForTest(Map<String, dynamic> data) =>
      _stateFromDetail(data);

  /// Maps a state to what the delivery flow may do about it.
  static DeliverGate gateFor(ConsignmentState state) {
    if (state.isDeliverable) return DeliverGate.deliverable;
    if (state.isDelivered) return DeliverGate.alreadyDelivered;
    if (state.needsRelease) return DeliverGate.needsRelease;
    if (state.awaitsHub) return DeliverGate.awaitingHub;
    if (state.awaitsHubInward) return DeliverGate.awaitingInward;
    if (state.isClosed) return DeliverGate.closed;
    return DeliverGate.unknown;
  }

  /// Convenience: read and classify in one call.
  static Future<DeliverGate> gateOf(Object consignmentId) async =>
      gateFor(await stateOf(consignmentId));
}