import React, { useCallback, useEffect, useMemo, useRef, useState } from "react";
import {
  Box,
  Typography,
  Accordion,
  AccordionSummary,
  AccordionDetails,
  Menu,
  MenuItem,
  ListItemText,
} from "@mui/material";
import { alpha } from "@mui/material/styles";
import ExpandMoreIcon from "@mui/icons-material/ExpandMore";
import KeyboardArrowDownIcon from "@mui/icons-material/KeyboardArrowDown";
import { formatCurrency } from "../../../react-openapi";
import type { ExpenseItem, TxnFieldConfigs } from "../types";
import { groupByDate, groupByMonth } from "../utils/transactions";
import { monthLabel } from "../utils/dates";
import { TransactionRow } from "./TransactionRow";

interface TransactionListProps {
  items: ExpenseItem[];
  fields: TxnFieldConfigs;
}

export function TransactionList({ items, fields }: TransactionListProps) {
  const [activeMonth, setActiveMonth] = useState<string | null>(null);
  const [openMonth, setOpenMonth] = useState<string | null>(null);
  const [menuAnchor, setMenuAnchor] = useState<HTMLElement | null>(null);
  const groups = useMemo(() => groupByMonth(items), [items]);
  const listRef = useRef<HTMLDivElement>(null);
  const pillRef = useRef<HTMLDivElement>(null);
  const didInitOpenMonth = useRef(false);

  useEffect(() => {
    if (!didInitOpenMonth.current && groups.length > 0) {
      didInitOpenMonth.current = true;
      setOpenMonth(groups[0].key);
    }
  }, [groups]);

  const scrollToMonth = useCallback((key: string) => {
    const anchor = listRef.current?.querySelector<HTMLElement>(
      `[data-month-anchor="${key}"]`,
    );
    if (!anchor) return;
    const offset = window.matchMedia("(min-width: 900px)").matches ? 64 : 56;
    const top = anchor.getBoundingClientRect().top + window.scrollY - offset;
    window.scrollTo({ top, behavior: "smooth" });
  }, []);

  const handleSelectMonth = useCallback(
    (key: string) => {
      setMenuAnchor(null);
      setOpenMonth(key);
      scrollToMonth(key);
    },
    [scrollToMonth],
  );

  const handlePillKeyDown = useCallback(
    (event: React.KeyboardEvent) => {
      if (event.key === "Enter" || event.key === " ") {
        event.preventDefault();
        if (pillRef.current) setMenuAnchor(pillRef.current);
      }
    },
    [],
  );

  const selectedMonth = activeMonth ?? openMonth ?? groups[0]?.key ?? null;

  useEffect(() => {
    const root = listRef.current;
    if (!root || groups.length === 0) return;
    let ticking = false;

    const update = () => {
      ticking = false;
      const headers = root.querySelectorAll<HTMLElement>("[data-month-header]");
      let current: string | null = null;
      for (const header of headers) {
        if (header.getBoundingClientRect().top <= 72) {
          current = header.dataset.monthHeader ?? null;
        } else {
          break;
        }
      }
      setActiveMonth(current);
    };

    const onScroll = () => {
      if (!ticking) {
        ticking = true;
        requestAnimationFrame(update);
      }
    };

    update();
    window.addEventListener("scroll", onScroll, { passive: true });
    window.addEventListener("resize", onScroll);
    return () => {
      window.removeEventListener("scroll", onScroll);
      window.removeEventListener("resize", onScroll);
    };
  }, [groups]);

  return (
    <>
      <Box ref={listRef} sx={{ display: "flex", flexDirection: "column", gap: 2.5 }}>
        {groups.map((group) => (
          <Box key={group.key}>
            <span data-month-anchor={group.key} aria-hidden="true" style={{ display: "block", height: 0 }} />
            <Accordion
              disableGutters
              data-month-header={group.key}
              expanded={openMonth === group.key}
              onChange={(_, isExpanded) => setOpenMonth(isExpanded ? group.key : null)}
              TransitionProps={{ unmountOnExit: true }}
              sx={{
                border: "1px solid",
                borderColor: openMonth === group.key ? "primary.main" : "divider",
                borderRadius: 2,
                overflow: "hidden",
                boxShadow: "none",
                backgroundColor: "background.paper",
                "&:before": { display: "none" },
                transition: "border-color 160ms ease, background-color 160ms ease",
                "&:hover": { borderColor: "primary.light" },
              }}
            >
              <AccordionSummary
                expandIcon={<ExpandMoreIcon />}
                sx={{
                  px: 2,
                  py: 1,
                  "& .MuiAccordionSummary-content": {
                    alignItems: "center",
                    gap: 1.5,
                    minWidth: 0,
                  },
                }}
              >
                <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={700} color="error.main">
                  {formatCurrency(group.spent, group.currency)}
                </Typography>
                <Typography variant="body2" color="text.disabled">
                  /
                </Typography>
                <Typography variant="body2" fontWeight={700} color="success.main">
                  {formatCurrency(group.income, group.currency)}
                </Typography>
              </AccordionSummary>
              <AccordionDetails sx={{ p: 1.5, pt: 1 }}>
                <Box sx={{ display: "flex", flexDirection: "column", gap: 1 }}>
                  {groupByDate(group.items).map((dateGroup) => (
                    <Box
                      key={dateGroup.date}
                      sx={{
                        border: "1px solid",
                        borderColor: "divider",
                        borderRadius: 2,
                        backgroundColor: "background.default",
                        p: 1,
                      }}
                    >
                      <Box
                        sx={{
                          display: "flex",
                          alignItems: "center",
                          gap: 1,
                          px: 1,
                          pb: 1,
                          borderBottom: "1px solid",
                          borderColor: "divider",
                          mb: 1,
                        }}
                      >
                        <Typography variant="subtitle2" fontWeight={600} sx={{ letterSpacing: "-0.01em" }}>
                          {dateGroup.label}
                        </Typography>
                        <Box sx={{ flex: 1 }} />
                        <Typography variant="caption" color="text.secondary">
                          {dateGroup.items.length} transaction{dateGroup.items.length === 1 ? "" : "s"}
                        </Typography>
                      </Box>
                      <Box sx={{ display: "flex", flexDirection: "column", gap: 1 }}>
                        {dateGroup.items.map((item) => (
                          <TransactionRow
                            key={item.id}
                            item={item}
                            currency={group.currency}
                            fields={fields}
                          />
                        ))}
                      </Box>
                    </Box>
                  ))}
                </Box>
              </AccordionDetails>
            </Accordion>
          </Box>
        ))}
      </Box>

      <Box
        sx={{
          position: "fixed",
          bottom: 16,
          left: "50%",
          transform: "translateX(-50%)",
          zIndex: 3,
          pointerEvents: activeMonth ? "auto" : "none",
          opacity: activeMonth ? 1 : 0,
          transition: "opacity 160ms ease",
        }}
      >
        <Box
          ref={pillRef}
          role="button"
          tabIndex={0}
          onClick={(e) => setMenuAnchor(e.currentTarget)}
          onKeyDown={handlePillKeyDown}
          aria-haspopup="menu"
          aria-expanded={Boolean(menuAnchor)}
          sx={{
            display: "flex",
            alignItems: "center",
            gap: 0.5,
            px: 1.5,
            py: 0.75,
            borderRadius: "999px",
            cursor: "pointer",
            userSelect: "none",
            backgroundColor: (theme) => alpha(theme.palette.background.default, 0.85),
            backdropFilter: "blur(8px)",
            border: "1px solid",
            borderColor: "divider",
            boxShadow: 1,
            transition: "background-color 160ms ease, transform 160ms ease",
            "&:hover": {
              backgroundColor: (theme) => alpha(theme.palette.background.default, 0.95),
              transform: "translateY(-1px)",
            },
            "&:focus-visible": {
              outline: "2px solid",
              outlineColor: "primary.main",
            },
          }}
        >
          <Typography variant="caption" fontWeight={700} color="text.secondary">
            {activeMonth ? monthLabel(activeMonth) : ""}
          </Typography>
          <KeyboardArrowDownIcon sx={{ fontSize: 14, color: "text.secondary" }} />
        </Box>
      </Box>

      <Menu
        anchorEl={menuAnchor}
        open={Boolean(menuAnchor)}
        onClose={() => setMenuAnchor(null)}
        anchorOrigin={{ vertical: "top", horizontal: "center" }}
        transformOrigin={{ vertical: "bottom", horizontal: "center" }}
      >
        {groups.map((group) => (
          <MenuItem
            key={group.key}
            selected={selectedMonth === group.key}
            onClick={() => handleSelectMonth(group.key)}
          >
            <ListItemText
              primary={monthLabel(group.key)}
              secondary={`${group.items.length} transactions`}
            />
          </MenuItem>
        ))}
      </Menu>
    </>
  );
}