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

import { Alert, Box, Button, Divider, Typography } from "@mui/material";
import { PageSection } from "../layout/PageLayout";
import { api, getApiErrorMessage } from "../api";
import { clearAuthClientState } from "../auth";
import { useToast } from "../toast";
import { useI18n } from "../i18n/I18nProvider";
import { usePrompt } from "../prompt";
import { checkSessionCookie, getSessionContext, isSessionInvalidated } from "../sessionBoundary";

type AccountLifecycleStatus = {
  deletionEnabled: boolean;
  deletionStatus: string;
  requiredConfirmation: string;
  request?: { status: string; stage: string } | null;
};

export default function BackupCard() {
  const { toast } = useToast();
  const { t } = useI18n();
  const { prompt } = usePrompt();
  const [downloading, setDownloading] = useState(false);
  const [exportingAccount, setExportingAccount] = useState(false);
  const [deletingAccount, setDeletingAccount] = useState(false);
  const [lifecycle, setLifecycle] = useState<AccountLifecycleStatus | null>(null);
  const [lifecycleFailed, setLifecycleFailed] = useState(false);
  const [loadingLifecycle, setLoadingLifecycle] = useState(true);
  const [readAttempt, setReadAttempt] = useState(0);
  const session = useRef({ mounted: true, generation: 0, busy: false });
  const currentTranslation = useRef(t);
  const body = useRef<HTMLDivElement>(null);
  useEffect(() => { currentTranslation.current = t; }, [t]);
  useEffect(() => {
    const owner=session.current; owner.mounted=true; owner.generation += 1;
    return () => { owner.mounted=false; owner.generation += 1; };
  }, []);

  const beginAction = () => {
    checkSessionCookie();
    const owner=session.current;
    if (!owner.mounted || owner.busy || isSessionInvalidated()) return null;
    owner.busy=true;
    if (body.current?.contains(document.activeElement)) body.current.focus();
    const context=getSessionContext(); const generation=owner.generation;
    return () => { checkSessionCookie(); return owner.mounted && owner.generation === generation && !isSessionInvalidated() && getSessionContext() === context; };
  };

  useEffect(() => {
    let active = true;
    const context=getSessionContext();
    api.get<AccountLifecycleStatus>("/account-lifecycle/status")
      .then((response) => { if (active && !isSessionInvalidated() && getSessionContext() === context) setLifecycle(response.data); })
      .catch(() => { if (active && !isSessionInvalidated() && getSessionContext() === context) setLifecycleFailed(true); })
      .finally(() => { if (active && !isSessionInvalidated() && getSessionContext() === context) setLoadingLifecycle(false); });
    return () => { active = false; };
  }, [readAttempt]);

  const downloadBlob = (blob: Blob, contentDisposition: string | undefined, fallbackName: string) => {
    const url = URL.createObjectURL(blob);
    const match = /filename="?([^";]+)"?/i.exec(contentDisposition || "");
    const link = document.createElement("a");
    link.href = url;
    link.download = match?.[1] ?? fallbackName;
    document.body.appendChild(link);
    link.click();
    link.remove();
    window.setTimeout(() => URL.revokeObjectURL(url), 5000);
  };

  const downloadAccountExport = async () => {
    const active=beginAction(); if (!active) return;
    setExportingAccount(true);
    try {
      const res = await api.post("/export/account", null, { responseType: "blob" });
      if (!active()) return;
      downloadBlob(res.data as Blob, res.headers?.["content-disposition"] as string | undefined, `jobjakt-account-export-${new Date().toISOString().slice(0, 10)}.zip`);
      toast(currentTranslation.current("accountExportDownloaded"), "success");
    } catch (error: any) {
      if (active()) toast(getApiErrorMessage(error, currentTranslation.current("accountExportFailed")), "error");
    } finally {
      session.current.busy=false;
      if (active()) setExportingAccount(false);
    }
  };

  const downloadEncrypted = async () => {
    const active=beginAction(); if (!active) return;
    setDownloading(true);
    try {
      const res = await api.post("/backup/encrypted", null, { responseType: "blob" });
      if (!active()) return;
      downloadBlob(res.data as Blob, res.headers?.["content-disposition"] as string | undefined, `jobtracker_backup_${new Date().toISOString().slice(0, 10)}.jtbackup`);
      toast(currentTranslation.current("backupDownloaded"), "success");
    } catch (error: any) {
      if (active()) toast(getApiErrorMessage(error, currentTranslation.current("backupFailed")), "error");
    } finally {
      session.current.busy=false;
      if (active()) setDownloading(false);
    }
  };

  const deleteAccount = async () => {
    if (!lifecycle?.deletionEnabled || lifecycle.deletionStatus !== "active") return;
    const active=beginAction(); if (!active) return;
    setDeletingAccount(true);
    try {
      const confirmation = await prompt({
        title: t("accountDeleteTitle"),
        message: t("accountDeletePrompt", { confirmation: lifecycle.requiredConfirmation }),
        confirmLabel: t("accountDeleteButton"),
        cancelLabel: t("cancel"),
      });
      if (!active() || confirmation === null) return;
      if (confirmation.trim() !== lifecycle.requiredConfirmation) {
        toast(currentTranslation.current("accountDeleteConfirmationMismatch"), "error");
        return;
      }
      const response = await api.post("/account-lifecycle/delete", { confirmation });
      if (!active()) return;
      setLifecycle((current) => current ? { ...current, deletionStatus: "pending", request: response.data } : current);
      clearAuthClientState();
      window.location.assign("/login");
    } catch (error: any) {
      if (active()) toast(getApiErrorMessage(error, currentTranslation.current("accountDeleteFailed")), "error");
    } finally {
      session.current.busy=false;
      if (active()) setDeletingAccount(false);
    }
  };

  return (
    <PageSection surface title={t("backupTitle")}>
      <Box ref={body} role="group" aria-label={t("backupTitle")} tabIndex={-1} aria-busy={downloading || exportingAccount || deletingAccount}>
      <Typography sx={{ color: "text.secondary", mb: 1 }}>
        {t("accountExportBody")}
      </Typography>
      <Box sx={{ display: "flex", gap: 1, flexWrap: "wrap" }}>
        <Button variant="contained" onClick={downloadAccountExport} disabled={exportingAccount || downloading || deletingAccount} aria-busy={exportingAccount}>
          {exportingAccount ? t("accountExportPreparing") : t("accountExportDownload")}
        </Button>
      </Box>
      <Alert severity="info" sx={{ mt: 1.5 }}>{t("accountExportRecentSignIn")}</Alert>
      <Divider sx={{ my: 2 }} />
      <Typography component="h3" variant="sectionTitle">{t("backupEncryptedTitle")}</Typography>
      <Typography sx={{ color: "text.secondary", mb: 1 }}>
        {t("backupBody")}
      </Typography>
      <Box sx={{ display: "flex", gap: 1, flexWrap: "wrap" }}>
        <Button variant="outlined" onClick={downloadEncrypted} disabled={downloading || exportingAccount || deletingAccount} aria-busy={downloading}>
          {downloading ? t("backupPreparing") : t("backupDownload")}
        </Button>
      </Box>
      <Divider sx={{ my: 2 }} />
      <Typography component="h3" variant="sectionTitle">{t("accountDeleteTitle")}</Typography>
      {loadingLifecycle ? <Typography role="status">{t("loading")}</Typography> : lifecycleFailed ? <Alert severity="error" action={<Button color="inherit" onClick={() => { body.current?.focus(); setLifecycleFailed(false); setLoadingLifecycle(true); setReadAttempt(value => value+1); }}>{t("retry")}</Button>}>{t("accountLifecycleUnavailable")}</Alert> : lifecycle?.deletionStatus === "pending" ? (
        <Alert severity="warning">{t("accountDeletePending", { stage: lifecycle.request?.stage ?? "pending" })}</Alert>
      ) : lifecycle?.deletionEnabled ? (
        <Box>
          <Alert severity="error" sx={{ mb: 1.5 }}>{t("accountDeleteWarning")}</Alert>
          <Button color="error" variant="outlined" onClick={() => void deleteAccount()} disabled={deletingAccount || exportingAccount || downloading} aria-busy={deletingAccount}>
            {deletingAccount ? t("accountDeleteStarting") : t("accountDeleteButton")}
          </Button>
        </Box>
      ) : (
        <Alert severity="info">{t("accountDeleteDisabled")}</Alert>
      )}
      </Box>
    </PageSection>
  );
}