import React, { useCallback, useMemo, useState } from "react";
import {
  Box,
  Typography,
  Accordion,
  AccordionSummary,
  AccordionDetails,
} from "@mui/material";
import ExpandMoreIcon from "@mui/icons-material/ExpandMore";
import { ListCellRenderer, CurrencyField, applyDisplayFormat, formatCurrency } from "../../react-openapi";
import type { ExpenseItem, ExpenseFieldConfigs } from "./types";
import { monthKey, monthLabel } from "./types";
import { ExpenseDetail } from "./ExpenseDetail";

interface GroupedMonth {
  key: string;
  items: ExpenseItem[];
  total: number;
  currency: string;
}

function groupByMonth(items: ExpenseItem[]): GroupedMonth[] {
  const map = new Map<string, ExpenseItem[]>();
  for (const item of items) {
    const key = monthKey(item.occurred_at);
    const list = map.get(key) ?? [];
    list.push(item);
    map.set(key, list);
  }
  return [...map.entries()]
    .map(([key, list]) => {
      const sorted = [...list].sort(
        (a, b) => new Date(b.occurred_at ?? 0).getTime() - new Date(a.occurred_at ?? 0).getTime(),
      );
      const currency = sorted.find((it) => it.account?.currency)?.account?.currency ?? "INR";
      const total = sorted.reduce((sum, it) => sum + (it.amount ?? 0), 0);
      return { key, items: sorted, total, currency };
    })
    .sort((a, b) => b.key.localeCompare(a.key));
}

interface ExpenseCardProps {
  item: ExpenseItem;
  expanded: boolean;
  currency: string;
  fields: ExpenseFieldConfigs;
  onToggle: (id: string) => void;
}

const ExpenseCard = React.memo(function ExpenseCard({ item, expanded, currency, fields, onToggle }: ExpenseCardProps) {
  const itemCurrency = item.account?.currency ?? currency;

  return (
    <Accordion
      disableGutters
      expanded={expanded}
      onChange={(_, isExpanded) => onToggle(isExpanded ? item.id : "")}
      TransitionProps={{ unmountOnExit: true }}
      sx={{
        border: "1px solid",
        borderColor: expanded ? "primary.main" : "divider",
        borderRadius: 2,
        overflow: "hidden",
        boxShadow: "none",
        "&:before": { display: "none" },
        transition: "border-color 160ms ease, background-color 160ms ease",
        "&:hover": { borderColor: "primary.light" },
      }}
    >
      <AccordionSummary
        expandIcon={<ExpandMoreIcon />}
        sx={{
          "& .MuiAccordionSummary-content": {
            alignItems: "center",
            gap: 2,
            minWidth: 0,
            py: 0.5,
          },
        }}
      >
        <Box
          sx={{
            width: 40,
            flexShrink: 0,
            display: "flex",
            alignItems: "center",
            justifyContent: "center",
          }}
        >
          {item.entity?.logo ? (
            <ListCellRenderer field={fields.logo} value={item.entity.logo} />
          ) : (
            <Box sx={{ width: 40, height: 40, borderRadius: 2, bgcolor: "action.hover" }} />
          )}
        </Box>
        <Box sx={{ flex: 1, minWidth: 0 }}>
          <Typography
            variant="body1"
            fontWeight={600}
            noWrap
            sx={{ fontSize: "0.9375rem", lineHeight: 1.3 }}
          >
            {item.entity ? applyDisplayFormat(item.entity, fields.formats.entity) : "Unknown"}
          </Typography>
          <Box sx={{ display: "flex", alignItems: "center", gap: 1, mt: 0.25, flexWrap: "wrap" }}>
            <ListCellRenderer field={fields.occurredAt} value={item.occurred_at} />
            {item.account?.name && (
              <ListCellRenderer
                field={fields.account}
                value={item.account}
                displayFormat={fields.formats.account}
              />
            )}
          </Box>
        </Box>
        <CurrencyField value={item.amount} currency={itemCurrency} large />
      </AccordionSummary>
      <AccordionDetails sx={{ pt: 0 }}>
        <ExpenseDetail item={item} fields={fields} />
      </AccordionDetails>
    </Accordion>
  );
});

interface ExpenseListProps {
  items: ExpenseItem[];
  fields: ExpenseFieldConfigs;
}

export function ExpenseList({ items, fields }: ExpenseListProps) {
  const [expandedId, setExpandedId] = useState<string | null>(null);
  const groups = useMemo(() => groupByMonth(items), [items]);
  const handleToggle = useCallback((id: string) => {
    setExpandedId((prev) => (prev === id ? null : id));
  }, []);

  return (
    <Box sx={{ display: "flex", flexDirection: "column", gap: 4 }}>
      {groups.map((group) => (
        <Box key={group.key}>
          <Box sx={{ display: "flex", alignItems: "baseline", gap: 1.5, mb: 1.5 }}>
            <Typography variant="h6" fontWeight={700} sx={{ letterSpacing: "-0.01em" }}>
              {monthLabel(group.key)}
            </Typography>
            <Typography variant="caption" color="text.secondary">
              {group.items.length} transaction{group.items.length === 1 ? "" : "s"}
            </Typography>
            <Box sx={{ flex: 1 }} />
            <Typography variant="body2" fontWeight={600}>
              {formatCurrency(group.total, group.currency)}
            </Typography>
          </Box>

          <Box sx={{ display: "flex", flexDirection: "column", gap: 1 }}>
            {group.items.map((item) => (
              <ExpenseCard
                key={item.id}
                item={item}
                expanded={expandedId === item.id}
                currency={group.currency}
                fields={fields}
                onToggle={handleToggle}
              />
            ))}
          </Box>
        </Box>
      ))}
    </Box>
  );
}

export { groupByMonth };