import "package:flutter/material.dart";
import "package:intl/intl.dart";

import "main.dart";
import "models.dart";
import "theme.dart";

final _numFmt = NumberFormat.decimalPattern();

/// Formats a date per the signed-in user's chosen date format (appSettings),
/// mirroring the web app's format.js.
String formatDate(DateTime? d) {
  if (d == null) return "—";
  final pattern = switch (appSettings.dateFormat) {
    "DMY_NUM" => "dd-MM-yyyy",
    "DMY" => "dd MMM yyyy",
    "MDY" => "MMM dd, yyyy",
    _ => "yyyy-MM-dd", // YMD
  };
  return DateFormat(pattern).format(d);
}

String formatKm(int? km) => (km == null || km == 0) ? "—" : "${_numFmt.format(km)} km";

const int _kmSoon = 1000;

enum StatusKey { unknown, ok, soon, overdue }

class Status {
  final StatusKey key;
  final String label;
  const Status(this.key, this.label);

  /// Soft tint background for the status pill — DriverVault semantic colours,
  /// re-cut for dark surfaces.
  Color bg(bool dark) => switch (key) {
        StatusKey.overdue => dark ? DriverVault.dangerSoftDark : DriverVault.dangerSoft,
        StatusKey.soon => dark ? DriverVault.warningSoftDark : DriverVault.warningSoft,
        StatusKey.ok => dark ? DriverVault.successSoftDark : DriverVault.successSoft,
        StatusKey.unknown => dark ? DriverVault.darkSunken : DriverVault.ink50,
      };
  Color fg(bool dark) => switch (key) {
        StatusKey.overdue => DriverVault.danger,
        StatusKey.soon => DriverVault.warning,
        StatusKey.ok => DriverVault.success,
        StatusKey.unknown => dark ? DriverVault.darkTextMuted : DriverVault.ink500,
      };
}

int _rank(StatusKey k) => switch (k) {
      StatusKey.unknown => 0,
      StatusKey.ok => 1,
      StatusKey.soon => 2,
      StatusKey.overdue => 3,
    };

Status _dateSignal(DateTime? nextDate) {
  if (nextDate == null) return const Status(StatusKey.unknown, "No data");
  final today = DateTime.now();
  final days = DateTime(nextDate.year, nextDate.month, nextDate.day)
      .difference(DateTime(today.year, today.month, today.day))
      .inDays;
  if (days < 0) return Status(StatusKey.overdue, "Service Overdue ${days.abs()}d");
  if (days <= 30) return Status(StatusKey.soon, "Due in ${days}d");
  return Status(StatusKey.ok, "OK · ${days}d");
}

Status _kmSignal(int currentKm, int? nextKm) {
  if (currentKm == 0 || nextKm == null) return const Status(StatusKey.unknown, "No km");
  final remaining = nextKm - currentKm;
  if (remaining < 0) return Status(StatusKey.overdue, "Service Overdue ${_numFmt.format(remaining.abs())} km");
  if (remaining <= _kmSoon) return Status(StatusKey.soon, "In ${_numFmt.format(remaining)} km");
  return Status(StatusKey.ok, "${_numFmt.format(remaining)} km left");
}

/// Combines the date- and km-based signals, returning the worse of the two —
/// the same logic as the web app and the spreadsheet idea.
Status serviceStatus(ServiceRecord? latest, Car car) {
  final date = _dateSignal(latest?.nextServiceDate);
  final km = _kmSignal(car.currentKm, latest?.nextServiceKm);
  final worse = _rank(km.key) > _rank(date.key) ? km : date;
  if (date.key == StatusKey.unknown && km.key != StatusKey.unknown) return km;
  if (km.key == StatusKey.unknown && date.key != StatusKey.unknown) return date;
  return worse;
}