import React, { useCallback, useEffect, useMemo, useState } from "react";
import {
  Container,
  Box,
  Paper,
  Typography,
  Alert,
  Accordion,
  AccordionSummary,
  AccordionDetails,
} from "@mui/material";
import ExpandMoreIcon from "@mui/icons-material/ExpandMore";
import AssessmentIcon from "@mui/icons-material/Assessment";
import { useResource, useAppContext } from "../../react-openapi";
import { useToast } from "../ui/Toast";
import { PageHeader } from "../ui/PageHeader";
import { EmptyState } from "../ui/EmptyState";
import { StatCard } from "../common/components/StatCard";
import { buildTxnFieldConfigs } from "../common/utils/fieldConfigs";
import { GenerateReportPanel } from "./GenerateReportPanel";
import { ReportList } from "./ReportList";
import { ReportViewer } from "./ReportViewer";
import { apiErrorMessage, buildReportFieldConfigs } from "./types";

export default function Report() {
  const { resources } = useAppContext();
  const { showToast } = useToast();
  const { list, loading, error } = useResource("reports");
  const { create, remove } = useResource("reports");

  const [reports, setReports] = useState<any[] | null>(null);
  const [selectedId, setSelectedId] = useState<string | null>(null);
  const [viewerVersion, setViewerVersion] = useState(0);

  const reportFields = useMemo(() => buildReportFieldConfigs(resources), [resources]);
  const txnFields = useMemo(() => buildTxnFieldConfigs(resources), [resources]);

  const load = useCallback(async () => {
    const res = await list({ limit: 200 });
    setReports(res.items ?? []);
  }, [list]);

  useEffect(() => {
    load();
  }, [load]);

  const handleGenerated = useCallback(
    (created: any) => {
      load();
      if (created?.id) setSelectedId(created.id);
    },
    [load],
  );

  const handleRegenerate = useCallback(
    async (report: any) => {
      try {
        const created = await create(report.query ?? {});
        showToast("Report regenerated");
        setSelectedId(created?.id ?? report.id);
        setViewerVersion((v) => v + 1);
        load();
      } catch (e: any) {
        showToast(apiErrorMessage(e), "error");
      }
    },
    [create, load, showToast],
  );

  const handleDelete = useCallback(
    async (id: string) => {
      try {
        await remove(id);
        showToast("Report deleted");
        if (selectedId === id) setSelectedId(null);
        load();
      } catch (e: any) {
        showToast(apiErrorMessage(e), "error");
      }
    },
    [remove, load, selectedId, showToast],
  );

  const summary = useMemo(() => {
    const rows = reports ?? [];
    const granularities = new Set<string>();
    for (const r of rows) for (const g of r.query?.granularities ?? []) granularities.add(g);
    return { count: rows.length, granularities: [...granularities].join(", ") };
  }, [reports]);

  return (
    <Container maxWidth="lg" sx={{ py: 4 }}>
      <PageHeader
        crumbs={[{ label: "Home", path: "/" }, { label: "Reports" }]}
        title="Reports"
        subtitle="Build an immutable snapshot cube once, then slice by granularity, period, payee and tag at view time."
      />

      {error && (
        <Alert severity="error" sx={{ mb: 3, borderRadius: 2 }}>
          Failed to load reports: {error}
        </Alert>
      )}

      <Box sx={{ display: "flex", gap: 2, flexWrap: "wrap", mb: 4 }}>
        <StatCard label="Reports" value={summary.count.toLocaleString("en-IN")} />
        <StatCard label="Granularities covered" value={summary.granularities || "—"} />
      </Box>

      <GenerateReportPanel onGenerated={handleGenerated} />

      <Accordion
        disableGutters
        defaultExpanded
        sx={{
          border: "1px solid",
          borderColor: "divider",
          borderRadius: 2,
          overflow: "hidden",
          boxShadow: "none",
          backgroundColor: "background.paper",
          "&:before": { display: "none" },
          mb: 4,
        }}
      >
        <AccordionSummary
          expandIcon={<ExpandMoreIcon />}
          sx={{
            px: 2.5,
            py: 1,
            "& .MuiAccordionSummary-content": {
              alignItems: "center",
              gap: 1.5,
              minWidth: 0,
            },
          }}
        >
          <Typography variant="h6" fontWeight={700} sx={{ letterSpacing: "-0.01em" }}>
            Saved reports
          </Typography>
          {reports !== null && (
            <Typography variant="caption" color="text.secondary">
              {reports.length} report{reports.length === 1 ? "" : "s"}
            </Typography>
          )}
        </AccordionSummary>
        <AccordionDetails sx={{ px: 2.5, pb: 2.5, pt: 0 }}>
          {reports !== null && reports.length === 0 ? (
            <Paper variant="outlined" sx={{ borderRadius: 3 }}>
              <EmptyState
                icon={<AssessmentIcon />}
                title="No reports yet"
                description="Generate your first snapshot above — choose granularities and grouping dimensions, then slice the cached cube by period, payee and tag."
              />
            </Paper>
          ) : (
            <Box sx={{ display: "flex", flexDirection: "column", gap: 2.5 }}>
              <ReportList
                reports={reports ?? []}
                loading={loading}
                fields={reportFields}
                selectedId={selectedId}
                onView={(id) => setSelectedId(id)}
                onRegenerate={handleRegenerate}
                onDelete={handleDelete}
              />
            </Box>
          )}
        </AccordionDetails>
      </Accordion>

      {selectedId && (
        <ReportViewer
          key={selectedId}
          id={selectedId}
          version={viewerVersion}
          fields={txnFields}
          onClose={() => setSelectedId(null)}
          onRegenerated={handleRegenerate}
        />
      )}
    </Container>
  );
}