import React, { useCallback, useEffect, useMemo, useState } from "react";
import { useNavigate } from "react-router-dom";
import {
  Box,
  Chip,
  CircularProgress,
  FormControl,
  InputLabel,
  MenuItem,
  Paper,
  Select,
  Stack,
  TextField,
  Typography,
  Button,
} from "@mui/material";
import MailOutlineIcon from "@mui/icons-material/MailOutline";
import { api, getApiErrorMessage } from "../api";
import { useToast } from "../toast";

export type CorrespondenceInboxItem = {
  id: number;
  jobApplicationId: number;
  companyName?: string | null;
  jobTitle?: string | null;
  from: string;
  direction?: string | null;
  subject?: string | null;
  channel?: string | null;
  date: string;
  contentPreview: string;
  externalThreadId?: string | null;
  externalFrom?: string | null;
  externalTo?: string | null;
  labelCount: number;
  attachmentCount: number;
};

export default function CorrespondenceInboxPage() {
  const navigate = useNavigate();
  const { toast } = useToast();
  const [items, setItems] = useState<CorrespondenceInboxItem[]>([]);
  const [loading, setLoading] = useState(false);
  const [query, setQuery] = useState("");
  const [direction, setDirection] = useState<string>("all");
  const [linkState, setLinkState] = useState<string>("all");

  const load = useCallback(async () => {
    setLoading(true);
    try {
      const res = await api.get<CorrespondenceInboxItem[]>("/correspondence", {
        params: {
          q: query.trim() || undefined,
          direction: direction === "all" ? undefined : direction,
          linkState: linkState === "all" ? undefined : linkState,
        },
      });
      setItems(res.data ?? []);
    } catch (error) {
      toast(getApiErrorMessage(error, "Failed to load correspondence inbox."), "error");
    } finally {
      setLoading(false);
    }
  }, [direction, linkState, query, toast]);

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

  const filteredSummary = useMemo(() => {
    const linked = items.filter((item) => item.externalThreadId).length;
    const inbound = items.filter((item) => item.direction === "inbound").length;
    return { linked, inbound };
  }, [items]);

  return (
    <Paper sx={{ mt: 0, p: 2 }}>
      <Box sx={{ display: "flex", justifyContent: "space-between", gap: 2, alignItems: "center", flexWrap: "wrap", mb: 2 }}>
        <Box>
          <Typography variant="h5" sx={{ fontWeight: 900 }}>Correspondence inbox</Typography>
          <Typography variant="body2" sx={{ color: "text.secondary" }}>
            Cross-job view of imported correspondence and Gmail-linked history.
          </Typography>
        </Box>
        <Box sx={{ display: "flex", gap: 1, flexWrap: "wrap" }}>
          <Chip icon={<MailOutlineIcon />} label={`${items.length} items`} variant="outlined" />
          <Chip label={`${filteredSummary.linked} linked`} variant="outlined" color={filteredSummary.linked > 0 ? "success" : "default"} />
          <Chip label={`${filteredSummary.inbound} inbound`} variant="outlined" />
        </Box>
      </Box>

      <Box sx={{ display: "grid", gridTemplateColumns: { xs: "1fr", md: "2fr 1fr 1fr auto" }, gap: 1.25, mb: 2 }}>
        <TextField label="Search" value={query} onChange={(e) => setQuery(e.target.value)} placeholder="Company, role, recruiter, subject" />
        <FormControl fullWidth>
          <InputLabel>Direction</InputLabel>
          <Select value={direction} label="Direction" onChange={(e) => setDirection(String(e.target.value))}>
            <MenuItem value="all">All</MenuItem>
            <MenuItem value="inbound">Inbound</MenuItem>
            <MenuItem value="outbound">Outbound</MenuItem>
            <MenuItem value="internal">Internal</MenuItem>
          </Select>
        </FormControl>
        <FormControl fullWidth>
          <InputLabel>Link state</InputLabel>
          <Select value={linkState} label="Link state" onChange={(e) => setLinkState(String(e.target.value))}>
            <MenuItem value="all">All</MenuItem>
            <MenuItem value="linked">Linked threads</MenuItem>
            <MenuItem value="manual">Manual/internal only</MenuItem>
          </Select>
        </FormControl>
        <Button variant="contained" onClick={() => void load()} disabled={loading}>{loading ? "Loading..." : "Refresh"}</Button>
      </Box>

      {loading ? <Box sx={{ py: 6, display: "flex", justifyContent: "center" }}><CircularProgress size={28} /></Box> : null}

      {!loading && items.length === 0 ? (
        <Typography sx={{ color: "text.secondary", py: 4, textAlign: "center" }}>No correspondence matches the current filters.</Typography>
      ) : null}

      <Stack spacing={1.25}>
        {items.map((item) => (
          <Paper key={item.id} variant="outlined" sx={{ p: 1.5, borderRadius: 3 }}>
            <Box sx={{ display: "flex", justifyContent: "space-between", gap: 2, flexWrap: "wrap", alignItems: "flex-start" }}>
              <Box sx={{ minWidth: 0 }}>
                <Typography sx={{ fontWeight: 800, overflowWrap: "anywhere" }}>{item.companyName || "Unknown company"} • {item.jobTitle || "Unknown role"}</Typography>
                <Typography variant="body2" sx={{ color: "text.secondary", overflowWrap: "anywhere" }}>{item.subject || item.contentPreview}</Typography>
                <Typography variant="caption" sx={{ color: "text.secondary", display: "block", mt: 0.5 }}>
                  {item.externalFrom || item.from} {item.externalTo ? `→ ${item.externalTo}` : ""} · {new Date(item.date).toLocaleString()}
                </Typography>
              </Box>
              <Box sx={{ display: "flex", gap: 0.75, flexWrap: "wrap", justifyContent: "flex-end" }}>
                {item.direction ? <Chip size="small" label={item.direction} variant="outlined" /> : null}
                {item.externalThreadId ? <Chip size="small" label={`Thread ${item.externalThreadId}`} color="success" variant="outlined" /> : <Chip size="small" label="Manual/internal" variant="outlined" />}
                {item.labelCount > 0 ? <Chip size="small" label={`${item.labelCount} labels`} variant="outlined" /> : null}
                {item.attachmentCount > 0 ? <Chip size="small" label={`${item.attachmentCount} attachments`} variant="outlined" /> : null}
                <Button size="small" variant="text" onClick={() => navigate(`/jobs?open=${item.jobApplicationId}`)}>Open job</Button>
              </Box>
            </Box>
          </Paper>
        ))}
      </Stack>
    </Paper>
  );
}