import { useSignal } from '@preact/signals';
import { useEffect, useRef } from 'preact/hooks';
import { Chart } from 'chart.js';

import { formatNumber } from '/lib/utils/misc.ts';
import { Budget, SupportedCurrencySymbol } from '/lib/types.ts';

interface ListBudgetsProps {
  budgets: Budget[];
  month: string;
  currency: SupportedCurrencySymbol;
  onClickEditBudget: (budgetId: string) => void;
}

export default function ListBudgets(
  {
    budgets,
    month,
    currency,
    onClickEditBudget,
  }: ListBudgetsProps,
) {
  const view = useSignal<'list' | 'chart'>('list');
  const chartRef = useRef<HTMLCanvasElement>(null);

  // Calculate a total budget to show before all others
  const totalBudget: Omit<Budget, 'user_id' | 'created_at'> = {
    id: 'total',
    name: 'Total',
    month,
    value: budgets.reduce((accumulatedValue, budget) => accumulatedValue + budget.value, 0),
    extra: {
      usedValue: budgets.reduce((accumulatedValue, budget) => accumulatedValue + budget.extra.usedValue, 0),
      availableValue: budgets.reduce((accumulatedValue, budget) => accumulatedValue + budget.extra.availableValue, 0),
    },
  };

  function swapView(newView: 'list' | 'chart') {
    view.value = view.value === newView ? 'list' : newView;
  }

  useEffect(() => {
    if (view.value === 'chart') {
      const budgetColors = [totalBudget, ...budgets].map((_, index) =>
        index === 0
          ? 'rgba(59, 130, 246, 0.8)'
          : `hsl(${(index - 1) * (360 / budgets.length)}, ${index % 2 ? 85 : 70}%, ${index % 2 ? 55 : 65}%, 0.8)`
      );

      new Chart(chartRef.current as HTMLCanvasElement, {
        type: 'doughnut',
        data: {
          labels: [{ name: 'Available' }, ...budgets].map((budget) => budget.name),
          datasets: [{
            label: '',
            data: [totalBudget, ...budgets].map((budget) =>
              budget.id === 'total' ? budget.extra.availableValue : budget.extra.usedValue
            ),
            backgroundColor: budgetColors,
            borderWidth: 1,
            borderColor: '#222',
          }],
        },
        options: {
          backgroundColor: '#222',
          plugins: {
            legend: {
              position: 'bottom',
              fullSize: true,
              labels: {
                usePointStyle: true,
                pointStyle: 'circle',
                padding: 10,
              },
            },
          },
        },
      });
    }
  }, [view.value]);

  return (
    <section class='mx-auto max-w-7xl my-8'>
      {budgets.length === 0
        ? (
          <article class='px-6 py-4 font-normal text-center w-full'>
            <div class='font-medium text-slate-400 text-md'>No budgets to show for {month}</div>
          </article>
        )
        : (
          <section class='w-full flex flex-wrap gap-4 justify-center items-center'>
            {view.value === 'list'
              ? [totalBudget, ...budgets].map((budget) => {
                let backgroundColorClass = 'bg-green-600';
                let usedValuePercentage = Math.ceil(100 * budget.extra.usedValue / budget.value);

                if (usedValuePercentage >= 100) {
                  usedValuePercentage = 100;
                  backgroundColorClass = 'bg-red-600';
                }

                return (
                  <div
                    onClick={() => budget.id === 'total' ? swapView('chart') : onClickEditBudget(budget.id)}
                    class='flex max-w-sm gap-y-4 gap-x-4 rounded shadow-md bg-slate-700 relative cursor-pointer py-4 px-6 hover:opacity-80'
                  >
                    <article class='order-first tracking-tight flex flex-col text-base mr-4'>
                      <span class='font-bold text-lg' title='Amount used from budgeted amount'>
                        {formatNumber(currency, budget.extra.usedValue)} of {formatNumber(currency, budget.value)}
                      </span>
                      <span
                        class='bg-gray-600 h-1.5 w-full block rounded-full mt-2 mx-0'
                        title={`${usedValuePercentage}% of budget used`}
                      >
                        <span
                          class={`${backgroundColorClass} w-0 block h-1.5 rounded-full`}
                          style={{ width: `${usedValuePercentage}%` }}
                        >
                        </span>
                      </span>
                      <span class='mt-2 font-normal text-gray-400'>{budget.name}</span>
                    </article>
                    <span class='text-lg text-right text-gray-200' title='Amount available from budgeted amount'>
                      {formatNumber(currency, budget.extra.availableValue)}
                    </span>
                  </div>
                );
              })
              : (
                <section class='p-4 rounded-lg shadow-sm cursor-pointer' onClick={() => swapView('list')}>
                  <canvas ref={chartRef}></canvas>
                </section>
              )}
          </section>
        )}
    </section>
  );
}