import { useEffect, useState } from "react";
import { Button, Card, Group, NumberInput, Stack, Text, Title } from "@mantine/core";

import { trainSchedulingService } from "@/services/trainScheduling.service";
import { useToast } from "@/hooks/use-toast";
import type { TrainSchedulingGlobalRules } from "@/types/trainScheduling";

export default function TrainSchedulingGlobalRulesPage() {
  const { toast } = useToast();
  const [loading, setLoading] = useState(true);
  const [saving, setSaving] = useState(false);
  const [form, setForm] = useState<Partial<TrainSchedulingGlobalRules>>({});

  useEffect(() => {
    void (async () => {
      try {
        const rules = await trainSchedulingService.getGlobalRules();
        setForm(rules);
      } catch {
        toast({ title: "Failed to load train scheduling rules", variant: "destructive" });
      } finally {
        setLoading(false);
      }
    })();
  }, [toast]);

  const handleSave = async () => {
    setSaving(true);
    try {
      const updated = await trainSchedulingService.updateGlobalRules({
        maxTrainLengthMeters: Number(form.maxTrainLengthMeters),
        maxTrainWeightTons: Number(form.maxTrainWeightTons),
        maxWagonsPerTrain: Number(form.maxWagonsPerTrain),
        max20ftContainerWeightTons: Number(form.max20ftContainerWeightTons),
        max20ftPairWeightDiffTons: Number(form.max20ftPairWeightDiffTons),
      });
      setForm(updated);
      toast({ title: "Train scheduling rules saved" });
    } catch {
      toast({ title: "Failed to save rules", variant: "destructive" });
    } finally {
      setSaving(false);
    }
  };

  return (
    <Stack gap="lg" maw={720}>
      <Stack gap={4}>
        <Title order={3}>Train scheduling rules</Title>
        <Text size="sm" c="dimmed">
          Global limits applied when previewing and assigning bookings to trains.
        </Text>
      </Stack>

      <Card radius="xl" padding="lg" withBorder>
        <Stack gap="md">
          <NumberInput
            label="Max train length (m)"
            description="Sum of all wagon lengths must not exceed this"
            value={form.maxTrainLengthMeters ?? ""}
            onChange={(value) =>
              setForm((current) => ({ ...current, maxTrainLengthMeters: Number(value) }))
            }
            min={1}
            disabled={loading}
          />
          <NumberInput
            label="Max train weight (T)"
            description="Total container and bulk cargo weight must not exceed this"
            value={form.maxTrainWeightTons ?? ""}
            onChange={(value) =>
              setForm((current) => ({ ...current, maxTrainWeightTons: Number(value) }))
            }
            min={1}
            disabled={loading}
          />
          <NumberInput
            label="Max wagons per train"
            value={form.maxWagonsPerTrain ?? ""}
            onChange={(value) =>
              setForm((current) => ({ ...current, maxWagonsPerTrain: Number(value) }))
            }
            min={1}
            disabled={loading}
          />
          <NumberInput
            label="Max 20ft container weight (T)"
            description="Each individual 20ft container gross weight limit"
            value={form.max20ftContainerWeightTons ?? ""}
            onChange={(value) =>
              setForm((current) => ({
                ...current,
                max20ftContainerWeightTons: Number(value),
              }))
            }
            min={0.001}
            disabled={loading}
          />
          <NumberInput
            label="Max 20ft pair weight difference (T)"
            description="When two 20ft containers share a wagon, |weight1 − weight2| must not exceed this"
            value={form.max20ftPairWeightDiffTons ?? ""}
            onChange={(value) =>
              setForm((current) => ({
                ...current,
                max20ftPairWeightDiffTons: Number(value),
              }))
            }
            min={0}
            disabled={loading}
          />
          <Group justify="flex-end">
            <Button color="teal" loading={saving} disabled={loading} onClick={() => void handleSave()}>
              Save rules
            </Button>
          </Group>
        </Stack>
      </Card>
    </Stack>
  );
}
