import React, { useEffect, useRef, useState } from "react";

import {
  Box,
  Button,
  Chip,
  Table,
  TableBody,
  TableCell,
  TableContainer,
  TableHead,
  TableRow,
  Typography,
} from "@mui/material";

import { api, getApiErrorMessage } from "../api";
import { useToast } from "../toast";
import { useI18n } from "../i18n/I18nProvider";
import { useViewResource } from "../hooks/useViewResource";
import ViewStateNotice from "../components/ViewStateNotice";
import { PageHeader, PageSection } from "../layout/PageLayout";
import { checkSessionCookie, getSessionContext, isSessionInvalidated } from "../sessionBoundary";

type AuditItem = {
  id: number;
  type: string;
  oldValue?: string | null;
  newValue?: string | null;
  note?: string | null;
  at: string;
  jobApplicationId: number;
  jobTitle?: string | null;
  companyName?: string | null;
  ownerUserId?: string | null;
  ownerEmail?: string | null;
  ownerUserName?: string | null;
};

function canUndo(type: string) {
  return ["StatusChanged", "FollowUpSet", "ResponseUpdated", "Deleted", "Restored"].includes(type);
}

export default function AdminAuditPage() {
  const { toast } = useToast();
  const { language, t } = useI18n();
  const [busyId, setBusyId] = useState<number | null>(null);
  const body=useRef<HTMLDivElement>(null);
  const owner=useRef({ mounted: true, generation: 0, busy: false });
  const currentTranslation=useRef(t);
  const fallback=useRef(t("adminAuditLoadFailed"));
  useEffect(() => { currentTranslation.current=t; }, [t]);
  useEffect(() => { const lifetime=owner.current; lifetime.mounted=true; lifetime.generation+=1; return () => { lifetime.mounted=false; lifetime.generation+=1; }; }, []);

  const auditResource = useViewResource(
    async () => {
      const r = await api.get<AuditItem[]>("/admin/audit?take=200");
      return r.data ?? [];
    },
    { initialData: [], errorMessage: fallback.current },
  );

  const mutate = async (e: AuditItem, action: "undo" | "restore") => {
    if (action === "undo" ? !canUndo(e.type) : e.type !== "Deleted") return;
    checkSessionCookie(); const lifetime=owner.current;
    if (!lifetime.mounted || lifetime.busy || isSessionInvalidated()) return;
    lifetime.busy=true;
    const generation=lifetime.generation; const context=getSessionContext();
    const active=() => { checkSessionCookie(); return lifetime.mounted && lifetime.generation===generation && !isSessionInvalidated() && getSessionContext()===context; };
    if (body.current?.contains(document.activeElement)) body.current.focus();
    setBusyId(e.id);
    try {
      const res=await api.post<{ ok: boolean; message?: string }>(action === "undo" ? `/admin/audit/${e.id}/undo` : `/jobapplications/${e.jobApplicationId}/restore`, {});
      if (!active()) return;
      toast(action === "undo" && res.data?.message || currentTranslation.current(action === "undo" ? "adminAuditUndone" : "adminAuditRestored"), "success");
      await auditResource.reload();
    } catch (error) {
      if (active()) toast(getApiErrorMessage(error, currentTranslation.current(action === "undo" ? "adminAuditUndoFailed" : "adminAuditRestoreFailed")), "error");
    } finally {
      lifetime.busy=false;
      if (active()) setBusyId(null);
    }
  };

  const rows = auditResource.data;
  const error=auditResource.error?.message===fallback.current ? { ...auditResource.error, message: t("adminAuditLoadFailed") } : auditResource.error;

  return (
    <Box sx={{ display: "grid", gap: "var(--app-section-gap)", minWidth: 0 }}>
      <PageHeader level="h2" title={t("adminAuditTitle")} description={t("adminAuditSubtitle")} />
      <PageSection level="h3" surface title={t("adminAuditEvents")}>
      <Box ref={body} role="region" aria-label={t("adminAuditTitle")} tabIndex={0} aria-busy={busyId!==null || auditResource.loading || auditResource.refreshing} sx={{ minWidth: 0, overflow: "auto" }}>

      <ViewStateNotice
        loading={auditResource.loading}
        error={error}
        title={t("adminAuditLoadFailed")}
        description={t("adminAuditLoadFailedBody")}
        onRetry={async () => { body.current?.focus(); await auditResource.reload(); }}
      />

      {!auditResource.error ? <TableContainer sx={{ overflow: "visible" }}>
        <Table size="small" aria-label={t("adminAuditTitle")} sx={{ minWidth: 900, "& th, & td": { overflowWrap: "anywhere" }, "& button": { whiteSpace: "normal", "@media (pointer: coarse)": { minHeight: 44 } } }}>
          <TableHead>
            <TableRow>
              <TableCell sx={{ width: 165 }}>{t("adminAuditAt")}</TableCell>
              <TableCell sx={{ width: 160 }}>{t("adminAuditType")}</TableCell>
              <TableCell sx={{ minWidth: 260 }}>{t("adminAuditJob")}</TableCell>
              <TableCell sx={{ width: 220 }}>{t("adminAuditUser")}</TableCell>
              <TableCell sx={{ minWidth: 220 }}>{t("adminAuditDetails")}</TableCell>
              <TableCell sx={{ width: 170 }}>{t("adminAuditActions")}</TableCell>
            </TableRow>
          </TableHead>
          <TableBody>
            {auditResource.loading ? (
              <TableRow>
                <TableCell colSpan={6}>
                  <Typography sx={{ color: "text.secondary" }}>{t("loading")}</Typography>
                </TableCell>
              </TableRow>
            ) : rows.length === 0 ? (
              <TableRow>
                <TableCell colSpan={6}>
                  <Typography sx={{ color: "text.secondary" }}>{t("adminAuditNoEvents")}</Typography>
                </TableCell>
              </TableRow>
            ) : (
              rows.map((e) => {
                const jobLabel = e.jobTitle || t("adminAuditJobFallback", { id: e.jobApplicationId });
                const ownerLabel = e.ownerEmail || e.ownerUserName || e.ownerUserId || "-";
                const details = e.oldValue || e.newValue ? `${e.oldValue ?? ""} -> ${e.newValue ?? ""}` : "";
                const disabled = busyId !== null;
                const showRestore = e.type === "Deleted";

                return (
                  <TableRow key={e.id} hover>
                    <TableCell>{e.at ? new Date(e.at).toLocaleString(language === "nb" ? "nb-NO" : "en-GB") : ""}</TableCell>
                    <TableCell>
                      <Chip label={e.type} size="small" variant="outlined" />
                    </TableCell>
                    <TableCell>
                      <Typography sx={{ fontWeight: 800, lineHeight: 1.25 }}>
                        {e.companyName ? `${e.companyName} - ` : ""}
                        {jobLabel}
                      </Typography>
                      <Typography variant="caption" sx={{ color: "text.secondary" }}>
                        jobId={e.jobApplicationId}
                      </Typography>
                    </TableCell>
                    <TableCell>
                      <Typography sx={{ fontWeight: 700 }}>{ownerLabel}</Typography>
                    </TableCell>
                    <TableCell>
                      <Typography sx={{ whiteSpace: "pre-wrap", color: "text.secondary" }}>
                        {details}
                        {e.note ? `${details ? "\n" : ""}${e.note}` : ""}
                      </Typography>
                    </TableCell>
                    <TableCell>
                      <Box sx={{ display: "flex", gap: 1, flexWrap: "wrap" }}>
                        {canUndo(e.type) ? (
                          <Button size="small" variant="outlined" disabled={disabled} onClick={() => void mutate(e, "undo")}>
                            {t("adminAuditUndo")}
                          </Button>
                        ) : null}
                        {showRestore ? (
                          <Button size="small" variant="contained" disabled={disabled} onClick={() => void mutate(e, "restore")}>
                            {t("adminAuditRestore")}
                          </Button>
                        ) : null}
                      </Box>
                    </TableCell>
                  </TableRow>
                );
              })
            )}
          </TableBody>
        </Table>
      </TableContainer> : null}
      </Box>
      </PageSection>
    </Box>
  );
}