import React, { useEffect, useRef, useState } from "react";
import { Alert, Box, Button, Chip, MenuItem, Paper, Stack, TextField, Typography } from "@mui/material";
import DeleteOutlineIcon from "@mui/icons-material/DeleteOutline";
import { api, getApiErrorMessage } from "../../api";
import { useConfirm } from "../../confirm";
import { useI18n } from "../../i18n/I18nProvider";
import { PageSection } from "../../layout/PageLayout";

type Evidence = { id: number; category: string; title: string; statement: string; tags: string[]; sourceReference: string | null };

export default function CareerEvidenceBank() {
  const { t } = useI18n();
  const { confirm } = useConfirm();
  const [items, setItems] = useState<Evidence[]>([]);
  const [title, setTitle] = useState("");
  const [statement, setStatement] = useState("");
  const [category, setCategory] = useState("achievement");
  const [tags, setTags] = useState("");
  const [source, setSource] = useState("");
  const [loading, setLoading] = useState(true);
  const [readAttempt, setReadAttempt] = useState(0);
  const [loadError, setLoadError] = useState<{ cause: unknown } | null>(null);
  const [saveError, setSaveError] = useState<{ cause: unknown } | null>(null);
  const [deleteErrors, setDeleteErrors] = useState<Record<number, { cause: unknown }>>({});
  const [busy, setBusy] = useState(false);
  const [deletingId, setDeletingId] = useState<number | null>(null);
  const writePending = useRef(false);
  const titleInputRef = useRef<HTMLInputElement>(null);
  const focusAfterDelete = useRef(false);

  useEffect(() => {
    let cancelled = false;
    setLoading(true);
    api.get<Evidence[]>("/career/evidence")
      .then((response) => { if (!cancelled) { setItems(response.data); setLoadError(null); } })
      .catch((cause) => { if (!cancelled) setLoadError({ cause }); })
      .finally(() => { if (!cancelled) setLoading(false); });
    return () => { cancelled = true; };
  }, [readAttempt]);

  useEffect(() => {
    if (focusAfterDelete.current) {
      focusAfterDelete.current = false;
      titleInputRef.current?.focus();
    }
  }, [items]);

  const add = async () => {
    if (writePending.current || loading || loadError || !title.trim() || !statement.trim()) return;
    writePending.current = true;
    setBusy(true);
    try {
      const response = await api.post<Evidence>("/career/evidence", { category, title, statement, tags: tags.split(","), sourceType: "manual", sourceReference: source, isVerified: true });
      setItems((previous) => [response.data, ...previous]);
      setTitle(""); setStatement(""); setTags(""); setSource("");
      setSaveError(null);
    } catch (cause) {
      setSaveError({ cause });
    } finally {
      writePending.current = false;
      setBusy(false);
    }
  };

  const remove = async (item: Evidence) => {
    if (writePending.current || loading || loadError) return;
    writePending.current = true;
    try {
      if (!(await confirm({ title: t("careerEvidenceDeleteTitle"), message: t("careerEvidenceDeleteMessage", { title: item.title }), confirmLabel: t("deleteAction"), destructive: true }))) return;
      setDeletingId(item.id);
      await api.delete(`/career/evidence/${item.id}`);
      focusAfterDelete.current = true;
      setItems((previous) => previous.filter((entry) => entry.id !== item.id));
      setDeleteErrors((previous) => { const next = { ...previous }; delete next[item.id]; return next; });
    } catch (cause) {
      setDeleteErrors((previous) => ({ ...previous, [item.id]: { cause } }));
    } finally {
      writePending.current = false;
      setDeletingId(null);
    }
  };
  const categories = ["achievement", "metric", "project", "technology", "responsibility", "example"];
  const categoryLabel = (value: string) => categories.includes(value) ? t(`careerEvidenceCategory_${value}` as "careerEvidenceCategory_achievement") : value;
  return <PageSection title={t("careerEvidenceTitle")} description={t("careerEvidenceSubtitle")}>
    <Stack spacing={2}>
    {loading ? <Typography role="status" color="text.secondary">{t("loading")}</Typography> : loadError ? <Alert severity="error" action={<Button color="inherit" disabled={busy || deletingId !== null} onClick={() => { titleInputRef.current?.focus(); setReadAttempt((attempt) => attempt + 1); }}>{t("retry")}</Button>}>{getApiErrorMessage(loadError.cause, t("careerEvidenceLoadFailed"))}</Alert> : null}
    <PageSection surface title={t("careerEvidenceAdd")} level="h3"><Stack spacing={1.5}>
      {saveError ? <Alert severity="error">{getApiErrorMessage(saveError.cause, t("careerEvidenceSaveFailed"))}</Alert> : null}
      <TextField select size="small" disabled={busy} label={t("careerEvidenceCategory")} value={category} onChange={e => setCategory(e.target.value)}>{categories.map(v => <MenuItem key={v} value={v}>{categoryLabel(v)}</MenuItem>)}</TextField>
      <TextField required disabled={busy} inputRef={titleInputRef} label={t("careerEvidenceItemTitle")} value={title} onChange={e => setTitle(e.target.value)} />
      <TextField required disabled={busy} label={t("careerEvidenceStatement")} value={statement} onChange={e => setStatement(e.target.value)} multiline minRows={3} helperText={t("careerEvidenceTruthHelp")} />
      <TextField disabled={busy} label={t("careerEvidenceTags")} value={tags} onChange={e => setTags(e.target.value)} helperText={t("careerEvidenceTagsHelp")} />
      <TextField disabled={busy} label={t("careerEvidenceSource")} value={source} onChange={e => setSource(e.target.value)} helperText={t("careerEvidenceSourceHelp")} />
      <Button variant="contained" disabled={busy || deletingId !== null || loading || Boolean(loadError) || !title.trim() || !statement.trim()} onClick={() => void add()} sx={{ alignSelf: "flex-start" }}>{t("careerEvidenceSave")}</Button>
    </Stack></PageSection>
    {!loading && !loadError && items.length === 0 ? <Alert severity="info">{t("careerEvidenceEmpty")}</Alert> : null}
    {items.map(item => <Paper key={item.id} component="article" aria-labelledby={`career-evidence-${item.id}-title`} variant="outlined" sx={{ p: "var(--app-card-padding)", borderRadius: 1, minWidth: 0, overflowWrap: "anywhere" }}><Stack spacing={1}>
      <Stack direction="row" justifyContent="space-between" flexWrap="wrap" gap={1}><Box sx={{ minWidth: 0 }}><Typography id={`career-evidence-${item.id}-title`} component="h3" variant="sectionTitle">{item.title}</Typography><Typography variant="caption" color="text.secondary">{categoryLabel(item.category)} · {item.sourceReference || t("careerEvidenceManualSource")}</Typography></Box><Button color="error" size="small" disabled={busy || deletingId !== null || loading || Boolean(loadError)} aria-label={t("careerEvidenceDeleteMessage", { title: item.title })} startIcon={<DeleteOutlineIcon />} onClick={() => void remove(item)}>{t("deleteAction")}</Button></Stack>
      {deleteErrors[item.id] ? <Alert severity="error" action={<Button color="inherit" disabled={busy || deletingId !== null || loading || Boolean(loadError)} onClick={() => void remove(item)}>{t("retry")}</Button>}>{getApiErrorMessage(deleteErrors[item.id].cause, t("careerEvidenceDeleteFailed"))}</Alert> : null}
      <Typography variant="body2">{item.statement}</Typography><Stack direction="row" flexWrap="wrap" gap={0.5}>{item.tags.map(tag => <Chip key={tag} size="small" label={tag} />)}</Stack>
    </Stack></Paper>)}
    </Stack>
  </PageSection>;
}