import { useState } from "react";
import {
  Badge,
  Button,
  Card,
  Collapse,
  Group,
  Stack,
  Text,
  Textarea,
  Tooltip,
} from "@mantine/core";
import type { UseMutationResult } from "@tanstack/react-query";
import { ArrowRight, CheckCircle2, Clock, XCircle } from "lucide-react";

import type { RateChangeRequest } from "@/services/ruleEngine/ruleEngine.service";

/** Field labels for the diff — anything not listed falls back to the raw key. */
const FIELD_LABELS: Record<string, string> = {
  rateValue: "Rate",
  currency: "Currency",
  rateUnit: "Unit",
  appliesTo: "Applies to",
  trigger: "Trigger",
  tradeDirection: "Direction",
  containerTypeId: "Container type",
  cargoTypeId: "Cargo type",
  originYardId: "Origin yard",
  destinationYardId: "Destination yard",
  minKm: "From km",
  maxKm: "To km",
  baseLiters: "Base liters",
  rateType: "Rate type",
};

/**
 * A key the backend diffed but the UI has no label for still names a real
 * change, so turn "baseLiters" into "Base liters" rather than hiding it.
 */
const labelFor = (field: string): string =>
  FIELD_LABELS[field] ??
  field
    .replace(/([A-Z])/g, " $1")
    .replace(/^./, (c) => c.toUpperCase())
    .replace(/\bId\b/, "")
    .trim();

const fmtDateTime = (iso: string) =>
  new Date(iso).toLocaleString("en-GB", {
    day: "numeric",
    month: "short",
    hour: "2-digit",
    minute: "2-digit",
    hour12: false,
  });

const fmtValue = (
  field: string,
  value: unknown,
  labels?: Record<string, string>,
): string => {
  // "Not set" reads as a real before-state; a bare em dash on both sides of the
  // arrow made a newly-set field look like no change at all.
  if (value === null || value === undefined || value === "") return "Not set";
  if (field === "rateValue") {
    const num = Number(value);
    return Number.isNaN(num) ? String(value) : num.toLocaleString();
  }
  // Any id is unreadable — an approver decides on "Perishable → Truck", not on
  // a pair of uuids. Covers yards, cargo types, container types and lines.
  if (field.endsWith("Id")) {
    return labels?.[String(value)] ?? String(value);
  }
  return String(value).replace(/_/g, " ");
};

/** "Ocean freight · 40HC" — what rate this change targets. */
const rateSummary = (r: RateChangeRequest): string => {
  const rate = (r.rate ?? {}) as Record<string, unknown>;
  const parts = [
    rate.rateType ? String(rate.rateType).replace(/_/g, " ") : null,
    rate.appliesTo ? String(rate.appliesTo) : null,
    rate.trigger && rate.trigger !== "ALWAYS" ? String(rate.trigger) : null,
  ].filter(Boolean);
  return parts.join(" · ") || "Rate";
};

/**
 * Every change in the request, as readable before→after pairs. The queue must
 * be scannable without expanding: a cargo or direction change is just as much
 * the point as a repricing, so it gets the same one-line treatment as the rate.
 */
const summaryRows = (
  r: RateChangeRequest,
  labels?: Record<string, string>,
): Array<{ field: string; label: string; before: string; after: string; suffix: string }> => {
  const currency = String(
    r.payload.currency ??
      r.previousValues.currency ??
      (r.rate as Record<string, unknown> | undefined)?.currency ??
      "",
  );
  // Rate first — it is what most changes are about — then the rest in a stable
  // order so the same edit always reads the same way.
  const fields = Object.keys(r.payload).sort((a, b) =>
    a === "rateValue" ? -1 : b === "rateValue" ? 1 : a.localeCompare(b),
  );
  return fields.map((field) => ({
    field,
    label: labelFor(field),
    before: fmtValue(field, r.previousValues[field], labels),
    after: fmtValue(field, r.payload[field], labels),
    suffix: field === "rateValue" && currency ? ` ${currency}` : "",
  }));
};

type Decide = UseMutationResult<
  RateChangeRequest,
  unknown,
  { id: string; decisionNote?: string }
>;

interface RateApprovalsSectionProps {
  requests: RateChangeRequest[];
  /** Whether this user holds the rates approve permission. */
  canDecide: boolean;
  approve: Decide;
  reject: Decide;
  /** id → label for every reference a diff can name (yards, cargo/container
   * types, shipping lines), so a change reads as names, not UUIDs. */
  refLabels?: Record<string, string>;
}

/**
 * Pending edits to LIVE rates. Each row is a before→after diff: the left value
 * is what pricing charges right now and keeps charging until someone approves.
 * Rendered above the rates table.
 */
const RateApprovalsSection = ({
  requests,
  canDecide,
  approve,
  reject,
  refLabels,
}: RateApprovalsSectionProps) => {
  const [openId, setOpenId] = useState<string | null>(null);
  const [notes, setNotes] = useState<Record<string, string>>({});

  if (requests.length === 0) return null;

  const decidingId = approve.variables?.id ?? reject.variables?.id ?? null;

  return (
    <Card withBorder radius="md" padding="md" mb="md">
      <Group gap={8} mb={4}>
        <Clock size={16} />
        <Text fw={700}>Pending rate changes</Text>
        <Badge variant="light" color="yellow">
          {requests.length}
        </Badge>
      </Group>
      <Text size="xs" c="dimmed" mb="sm">
        Each rate below still charges its current value. Nothing changes until approved.
      </Text>

      <Stack gap={8}>
        {requests.map((r) => {
          const isOpen = openId === r.id;
          const fields = Object.keys(r.payload);
          const rows = summaryRows(r, refLabels);
          // Only the row being decided shows a spinner — the mutation's
          // isPending is shared across every row.
          const busy = decidingId === r.id;

          return (
            <Card key={r.id} withBorder radius="md" padding="sm">
              <Group justify="space-between" wrap="nowrap" align="flex-start">
                <Stack gap={4} style={{ minWidth: 0 }}>
                  <Group gap={8} wrap="nowrap">
                    <Badge variant="light" color="blue" radius="sm">
                      update
                    </Badge>
                    <Text size="sm" fw={600} truncate>
                      {rateSummary(r)}
                    </Text>
                  </Group>

                  {rows.map((row) => (
                    <Group key={row.field} gap={6} wrap="wrap" align="center">
                      <Text size="xs" c="dimmed">
                        {row.label}
                      </Text>
                      <Text size="sm" c="dimmed" td="line-through">
                        {row.before}
                      </Text>
                      <ArrowRight size={13} style={{ flexShrink: 0 }} />
                      <Text size="sm" fw={700} c="edr-green">
                        {row.after}
                        {row.suffix}
                      </Text>
                    </Group>
                  ))}

                  <Group gap={6}>
                    <Text size="xs" c="dimmed">
                      Submitted {fmtDateTime(r.createdAt)} · {fields.length}{" "}
                      {fields.length === 1 ? "field" : "fields"} changed
                    </Text>
                    {canDecide ? (
                      <Button
                        size="compact-xs"
                        variant="subtle"
                        onClick={() => setOpenId(isOpen ? null : r.id)}
                      >
                        {isOpen ? "Hide note" : "Add a note"}
                      </Button>
                    ) : null}
                  </Group>
                </Stack>

                {canDecide ? (
                  <Group gap={8} wrap="nowrap">
                    <Button
                      size="compact-sm"
                      variant="subtle"
                      color="red"
                      leftSection={<XCircle size={14} />}
                      loading={busy && reject.isPending}
                      disabled={busy && approve.isPending}
                      onClick={() =>
                        reject.mutate({ id: r.id, decisionNote: notes[r.id] || undefined })
                      }
                    >
                      Reject
                    </Button>
                    <Button
                      size="compact-sm"
                      color="edr-green"
                      leftSection={<CheckCircle2 size={14} />}
                      loading={busy && approve.isPending}
                      disabled={busy && reject.isPending}
                      onClick={() =>
                        approve.mutate({ id: r.id, decisionNote: notes[r.id] || undefined })
                      }
                    >
                      Approve &amp; apply
                    </Button>
                  </Group>
                ) : (
                  <Tooltip label="You need the rates approve permission to decide this">
                    <Badge variant="light" color="gray" radius="sm">
                      Awaiting approver
                    </Badge>
                  </Tooltip>
                )}
              </Group>

              <Collapse in={isOpen}>
                {canDecide ? (
                  <Stack gap={6} mt="sm" pt="sm" style={{ borderTop: "1px solid var(--mantine-color-default-border)" }}>
                    {/* The change itself is always visible above, so this panel
                        carries only what the approver adds. */}
                    <Textarea
                      size="xs"
                      autosize
                      minRows={2}
                      label="Decision note (optional)"
                      placeholder="Shown to the requester with your decision"
                      value={notes[r.id] ?? ""}
                      onChange={(e) =>
                        setNotes((prev) => ({ ...prev, [r.id]: e.currentTarget.value }))
                      }
                    />
                  </Stack>
                ) : null}
              </Collapse>
            </Card>
          );
        })}
      </Stack>
    </Card>
  );
};

export default RateApprovalsSection;