import React, { useEffect, useState } from "react";
import { useNavigate } from "react-router-dom";

import {
  Box,
  Button,
  Checkbox,
  Chip,
  LinearProgress,
  Menu,
  MenuItem,
  Paper,
  Stack,
  Typography,
} from "@mui/material";
import { alpha, useTheme } from "@mui/material/styles";
import TuneIcon from "@mui/icons-material/Tune";
import TrendingUpIcon from "@mui/icons-material/TrendingUp";
import MailOutlineIcon from "@mui/icons-material/MailOutline";
import BusinessOutlinedIcon from "@mui/icons-material/BusinessOutlined";
import AutoGraphIcon from "@mui/icons-material/AutoGraph";

import { api } from "../api";
import { getUserKeyFromToken } from "../themePrefs";
import { useI18n } from "../i18n/I18nProvider";
import { buildWorkflowPath, getWorkflowAction } from "../jobWorkflowSignals";
import { JobApplication } from "../types";

interface JobStats {
  total: number;
  active: number;
  deleted: number;
  byStatus: Record<string, number>;
  appliedLast30Days: number;
  averageDaysSinceApplied: number;
}

type ReminderJob = JobApplication;

type AnalyticsPoint = { month: string; applied: number; responses: number };
type TagPoint = { tag: string; count: number };
type OverviewAnalytics = {
  funnel: { label: string; count: number }[];
  responseRateBySource: { label: string; total: number; responses: number; rate: number }[];
  topCompanies: { companyId: number; company: string; count: number; responses: number; responseRate: number }[];
  medianDaysToFirstResponse?: number | null;
  totalResponses: number;
  totalActive: number;
};
type TagTrendResponse = { months: string[]; series: { tag: string; counts: number[] }[] };

type Prefs = {
  cards: boolean;
  activity: boolean;
  funnel: boolean;
  companies: boolean;
  skills: boolean;
};

function prefsKey() {
  return `dashboardPrefs:${getUserKeyFromToken()}`;
}

function loadPrefs(): Prefs {
  try {
    const raw = window.localStorage.getItem(prefsKey());
    if (!raw) return { cards: true, activity: true, funnel: true, companies: true, skills: true };
    return { cards: true, activity: true, funnel: true, companies: true, skills: true, ...JSON.parse(raw) };
  } catch {
    return { cards: true, activity: true, funnel: true, companies: true, skills: true };
  }
}

function savePrefs(next: Prefs) {
  window.localStorage.setItem(prefsKey(), JSON.stringify(next));
}

function clamp(n: number, a: number, b: number) {
  return Math.max(a, Math.min(b, n));
}

function buildLinePath(values: number[], width: number, height: number) {
  if (!values.length) return "";
  const min = Math.min(...values);
  const max = Math.max(...values);
  const step = width / Math.max(1, values.length - 1);
  const yFor = (value: number) => {
    const t = max === min ? 0.5 : (value - min) / (max - min);
    return height - t * height;
  };

  return values
    .map((value, index) => `${index === 0 ? "M" : "L"} ${Math.round(index * step)} ${Math.round(yFor(value))}`)
    .join(" ");
}

function MiniSpark({ values, color }: { values: number[]; color: string }) {
  const width = 180;
  const height = 52;
  const path = buildLinePath(values, width, height);

  return (
    <svg width={width} height={height} viewBox={`0 0 ${width} ${height}`}>
      <path d={path} fill="none" stroke={color} strokeWidth="3" strokeLinecap="round" />
    </svg>
  );
}

function SectionCard({ children, sx = {} }: { children: React.ReactNode; sx?: any }) {
  return (
    <Paper
      sx={{
        p: 2.25,
        borderRadius: 4,
        border: "1px solid",
        borderColor: "divider",
        background: "background.paper",
        boxShadow: "0 18px 50px rgba(15, 23, 42, 0.06)",
        ...sx,
      }}
    >
      {children}
    </Paper>
  );
}

export default function DashboardView() {
  const theme = useTheme();
  const navigate = useNavigate();
  const { t } = useI18n();
  const [stats, setStats] = useState<JobStats | null>(null);
  const [overview, setOverview] = useState<OverviewAnalytics | null>(null);
  const [tagTrends, setTagTrends] = useState<TagTrendResponse | null>(null);
  const [analytics, setAnalytics] = useState<AnalyticsPoint[]>([]);
  const [tags, setTags] = useState<TagPoint[]>([]);
  const [months, setMonths] = useState<6 | 12 | 24>(12);
  const [reminderJobs, setReminderJobs] = useState<ReminderJob[]>([]);
  const [prefs, setPrefs] = useState<Prefs>(() => loadPrefs());
  const [prefsAnchor, setPrefsAnchor] = useState<HTMLElement | null>(null);

  useEffect(() => {
    api.get<JobStats>("/jobapplications/stats").then((r) => setStats(r.data));
    api.get<OverviewAnalytics>("/jobapplications/analytics-overview").then((r) => setOverview(r.data)).catch(() => setOverview(null));
    api.get<ReminderJob[]>("/jobapplications/reminders", { params: { upcomingDays: 14 } }).then((r) => setReminderJobs(Array.isArray(r.data) ? r.data : [])).catch(() => setReminderJobs([]));
  }, []);

  useEffect(() => {
    const params = { months };
    api.get<AnalyticsPoint[]>("/jobapplications/analytics", { params }).then((r) => setAnalytics(r.data ?? [])).catch(() => setAnalytics([]));
    api.get<TagPoint[]>("/jobapplications/tags", { params: { limit: 10, ...params } }).then((r) => setTags(r.data ?? [])).catch(() => setTags([]));
    api.get<TagTrendResponse>("/jobapplications/tag-trends", { params: { months, limit: 5 } }).then((r) => setTagTrends(r.data)).catch(() => setTagTrends(null));
  }, [months]);

  const appliedValues = analytics.map((x) => x.applied);
  const responseValues = analytics.map((x) => x.responses);
  const chartWidth = 860;
  const chartHeight = 250;
  const appliedPath = buildLinePath(appliedValues, chartWidth, chartHeight);
  const responsePath = buildLinePath(responseValues, chartWidth, chartHeight);
  const tagColors = [theme.palette.primary.main, theme.palette.success.main, theme.palette.warning.main, theme.palette.info.main, theme.palette.error.main];
  const funnelMax = overview?.funnel?.length ? Math.max(...overview.funnel.map((item) => item.count)) : 0;
  const topSource = overview?.responseRateBySource?.[0];
  const missingCvCount = reminderJobs.filter((job) => job.workflowSignal?.hasPackageGap).length;

  const metricCards = [
    {
      label: t("dashboardActiveApplications"),
      value: stats?.active ?? 0,
      sub: t("dashboardCurrentlyInProgress"),
      icon: <TrendingUpIcon fontSize="small" />,
      tone: theme.palette.primary.main,
      spark: appliedValues,
    },
    {
      label: t("dashboardApplied30Days"),
      value: stats?.appliedLast30Days ?? 0,
      sub: t("dashboardNewApplications"),
      icon: <AutoGraphIcon fontSize="small" />,
      tone: theme.palette.success.main,
      spark: appliedValues.slice(-6),
    },
    {
      label: t("dashboardMedianFirstResponse"),
      value: overview?.medianDaysToFirstResponse ?? "—",
      sub: t("dashboardDaysUntilFirstReply"),
      icon: <MailOutlineIcon fontSize="small" />,
      tone: theme.palette.info.main,
      spark: responseValues,
    },
    {
      label: t("dashboardResponsesLogged"),
      value: overview?.totalResponses ?? 0,
      sub: t("dashboardAcrossActiveJobs"),
      icon: <BusinessOutlinedIcon fontSize="small" />,
      tone: theme.palette.warning.main,
      spark: responseValues.slice(-6),
    },
  ];

  const togglePref = (key: keyof Prefs) => {
    const next = { ...prefs, [key]: !prefs[key] };
    setPrefs(next);
    savePrefs(next);
  };

  const totalApplied = appliedValues.reduce((sum, value) => sum + value, 0);
  const totalResponses = responseValues.reduce((sum, value) => sum + value, 0);
  const responseRate = totalApplied > 0 ? Math.round((totalResponses / totalApplied) * 100) : 0;
  const priorityJobs = reminderJobs.slice(0, 5);
  const getReminderAction = (job: ReminderJob) => getWorkflowAction(job, {
    packageWork: t("jobTablePackageWork"),
    followUp: t("jobTableFollowUp"),
    interviewPrep: t("jobTableInterviewStage"),
    readiness: t("jobTableReadiness"),
  });

  const openReminderJob = (job: ReminderJob) => {
    navigate(buildWorkflowPath(job));
  };

  return (
    <Box>
      <SectionCard
        sx={{
          background: theme.palette.mode === "dark"
            ? `radial-gradient(circle at top left, ${alpha(theme.palette.primary.main, 0.26)}, transparent 35%), linear-gradient(135deg, rgba(15,23,42,0.94), rgba(15,23,42,0.78))`
            : `radial-gradient(circle at top left, ${alpha(theme.palette.primary.main, 0.18)}, transparent 35%), linear-gradient(135deg, rgba(255,255,255,0.98), rgba(248,250,252,0.96))`,
          overflow: "hidden",
          position: "relative",
        }}
      >
        <Box sx={{ display: "flex", justifyContent: "space-between", gap: 2, flexWrap: "wrap", alignItems: "flex-start" }}>
          <Box sx={{ maxWidth: 760 }}>
            <Typography variant="overline" sx={{ color: "primary.main", fontWeight: 800 }}>
              {t("dashboardHeroLabel")}
            </Typography>
            <Typography variant="h4" sx={{ fontWeight: 950, mt: 0.5, letterSpacing: -0.6 }}>
              {t("dashboardOverviewTitle")}
            </Typography>
            <Typography variant="body1" sx={{ color: "text.secondary", mt: 1.25, maxWidth: 680 }}>
              {t("dashboardOverviewBody")}
            </Typography>

            <Stack direction={{ xs: "column", md: "row" }} spacing={1.25} sx={{ mt: 2.25, flexWrap: "wrap" }}>
              <Chip color="primary" variant="outlined" label={t("dashboardResponseRate", { rate: responseRate })} />
              <Chip variant="outlined" label={`${missingCvCount} ${t("dashboardMissingTailoredCv").toLowerCase()}`} />
              <Chip variant="outlined" label={topSource ? `${topSource.label}: ${topSource.rate}%` : t("dashboardResponseSources")} />
            </Stack>
          </Box>

          <Box sx={{ display: "flex", gap: 1, flexWrap: "wrap", alignItems: "center" }}>
            {([6, 12, 24] as const).map((m) => (
              <Button key={m} size="small" variant={months === m ? "contained" : "outlined"} onClick={() => setMonths(m)}>
                {t("dashboardMonthsShort", { count: m })}
              </Button>
            ))}
            <Button variant="outlined" startIcon={<TuneIcon />} onClick={(e) => setPrefsAnchor(e.currentTarget)}>
              {t("dashboardCustomize")}
            </Button>
            <Menu anchorEl={prefsAnchor} open={Boolean(prefsAnchor)} onClose={() => setPrefsAnchor(null)}>
              {[
                ["cards", t("dashboardSummaryCards")],
                ["activity", t("dashboardActivityChart")],
                ["funnel", t("dashboardConversionFunnel")],
                ["companies", t("dashboardTopCompanies")],
                ["skills", t("dashboardSkillsInsights")],
              ].map(([key, label]) => (
                <MenuItem key={key} onClick={() => togglePref(key as keyof Prefs)}>
                  <Checkbox checked={prefs[key as keyof Prefs]} />
                  {label}
                </MenuItem>
              ))}
            </Menu>
          </Box>
        </Box>
      </SectionCard>

      {prefs.cards ? (
        <Box sx={{ display: "grid", gridTemplateColumns: { xs: "1fr", md: "repeat(2, 1fr)", xl: "repeat(4, 1fr)" }, gap: 2, mt: 2 }}>
          {metricCards.map((card) => (
            <SectionCard key={card.label}>
              <Box sx={{ display: "flex", justifyContent: "space-between", gap: 2 }}>
                <Box>
                  <Typography variant="overline" sx={{ color: "text.secondary" }}>{card.label}</Typography>
                  <Typography variant="h4" sx={{ fontWeight: 950, mt: 0.5 }}>{card.value}</Typography>
                  <Typography variant="body2" sx={{ color: "text.secondary", mt: 0.75 }}>{card.sub}</Typography>
                </Box>
                <Box sx={{ width: 42, height: 42, borderRadius: 3, display: "grid", placeItems: "center", backgroundColor: alpha(card.tone, 0.12), color: card.tone }}>
                  {card.icon}
                </Box>
              </Box>
              <Box sx={{ mt: 1.5 }}>
                <MiniSpark values={card.spark.length ? card.spark : [0, 0, 0]} color={alpha(card.tone, 0.95)} />
              </Box>
            </SectionCard>
          ))}
        </Box>
      ) : null}

      <Box sx={{ display: "grid", gridTemplateColumns: { xs: "1fr", xl: "minmax(0, 1.8fr) minmax(320px, 0.9fr)" }, gap: 2, mt: 2 }}>
        {prefs.activity ? (
          <SectionCard>
            <Box sx={{ display: "flex", justifyContent: "space-between", gap: 2, flexWrap: "wrap", alignItems: "flex-start" }}>
              <Box>
                <Typography variant="h6" sx={{ fontWeight: 950 }}>{t("dashboardApplicationActivity")}</Typography>
                <Typography variant="body2" sx={{ color: "text.secondary" }}>{t("dashboardMonthlyApplicationsResponses")}</Typography>
              </Box>
              <Stack direction="row" spacing={1} flexWrap="wrap">
                <Chip size="small" label={t("dashboardAppliedCount", { count: totalApplied })} variant="outlined" />
                <Chip size="small" label={t("dashboardResponsesCount", { count: totalResponses })} variant="outlined" />
              </Stack>
            </Box>

            <Box sx={{ mt: 2, overflowX: "auto" }}>
              <Box sx={{ minWidth: chartWidth }}>
                <svg width={chartWidth} height={chartHeight} viewBox={`0 0 ${chartWidth} ${chartHeight}`}>
                  {[0.2, 0.4, 0.6, 0.8].map((tick) => (
                    <line
                      key={tick}
                      x1="0"
                      x2={chartWidth}
                      y1={Math.round(chartHeight * tick)}
                      y2={Math.round(chartHeight * tick)}
                      stroke={alpha(theme.palette.text.primary, 0.08)}
                      strokeDasharray="6 6"
                    />
                  ))}
                  {responsePath ? <path d={responsePath} fill="none" stroke={alpha(theme.palette.info.main, 0.95)} strokeWidth="3" strokeLinecap="round" /> : null}
                  {appliedPath ? <path d={appliedPath} fill="none" stroke={alpha(theme.palette.success.main, 0.95)} strokeWidth="3" strokeLinecap="round" /> : null}
                </svg>
                <Box sx={{ display: "flex", justifyContent: "space-between", mt: 1 }}>
                  {analytics.map((point) => (
                    <Typography key={point.month} variant="caption" sx={{ width: `${100 / Math.max(1, analytics.length)}%`, textAlign: "center", color: "text.secondary" }}>
                      {point.month.slice(5)}
                    </Typography>
                  ))}
                </Box>
              </Box>
            </Box>
          </SectionCard>
        ) : null}

        <SectionCard>
          <Typography variant="h6" sx={{ fontWeight: 950 }}>{t("dashboardConversionFunnelTitle")}</Typography>
          <Typography variant="body2" sx={{ color: "text.secondary", mb: 1.5 }}>{t("dashboardResponseSources")}</Typography>
          <Stack spacing={1.2}>
            {(overview?.funnel ?? []).map((item) => {
              const width = funnelMax ? clamp((item.count / funnelMax) * 100, 0, 100) : 0;
              return (
                <Box key={item.label}>
                  <Box sx={{ display: "flex", justifyContent: "space-between", mb: 0.5 }}>
                    <Typography variant="body2" sx={{ fontWeight: 700 }}>{item.label}</Typography>
                    <Typography variant="body2" sx={{ color: "text.secondary" }}>{item.count}</Typography>
                  </Box>
                  <LinearProgress
                    variant="determinate"
                    value={width}
                    sx={{
                      height: 10,
                      borderRadius: 999,
                      backgroundColor: alpha(theme.palette.primary.main, 0.08),
                      '& .MuiLinearProgress-bar': {
                        borderRadius: 999,
                        background: `linear-gradient(90deg, ${theme.palette.primary.main}, ${alpha(theme.palette.success.main, 0.85)})`,
                      },
                    }}
                  />
                </Box>
              );
            })}
          </Stack>

          <Box sx={{ mt: 2.25, p: 1.5, borderRadius: 3, backgroundColor: alpha(theme.palette.primary.main, 0.05) }}>
            <Typography variant="body2" sx={{ fontWeight: 800 }}>{topSource?.label ?? t("dashboardResponseSources")}</Typography>
            <Typography variant="h5" sx={{ fontWeight: 950, mt: 0.5 }}>{topSource ? `${topSource.rate}%` : "—"}</Typography>
            <Typography variant="body2" sx={{ color: "text.secondary", mt: 0.5 }}>
              {topSource ? t("dashboardResponseConversion", { responses: topSource.responses, total: topSource.total }) : t("dashboardNoSourceData")}
            </Typography>
          </Box>
        </SectionCard>
      </Box>

      <Box sx={{ display: "grid", gridTemplateColumns: { xs: "1fr", xl: "1.15fr 0.85fr" }, gap: 2, mt: 2 }}>
        <SectionCard>
          <Typography variant="h6" sx={{ fontWeight: 950, mb: 1 }}>{t("remindersTitle")}</Typography>
          <Typography variant="body2" sx={{ color: "text.secondary", mb: 1.5 }}>{t("remindersSubtitle")}</Typography>
          {priorityJobs.length === 0 ? (
            <Typography sx={{ color: "text.secondary" }}>{t("remindersNothing")}</Typography>
          ) : (
            <Stack spacing={1.1}>
              {priorityJobs.map((job) => {
                const action = getReminderAction(job);
                return (
                <Box key={job.id} sx={{ p: 1.5, borderRadius: 3, border: "1px solid", borderColor: "divider", backgroundColor: alpha(theme.palette.primary.main, 0.03), display: "flex", justifyContent: "space-between", gap: 2, alignItems: "center", flexWrap: "wrap" }}>
                  <Box>
                    <Typography sx={{ fontWeight: 900 }}>{job.company?.name ?? t("jobTableCompany")} • {job.jobTitle}</Typography>
                    <Typography variant="body2" sx={{ color: "text.secondary" }}>{action?.detail ?? job.workflowSignal?.reason ?? job.followUpReason ?? t("remindersFollowUpLabel")}</Typography>
                  </Box>
                  <Button variant="outlined" onClick={() => openReminderJob(job)}>
                    {action?.label ?? t("remindersOpen")}
                  </Button>
                </Box>
              )})}
            </Stack>
          )}
          <Box sx={{ mt: 1.5 }}>
            <Button variant="text" onClick={() => navigate('/reminders')}>{t("reminders")}</Button>
          </Box>
        </SectionCard>

        {prefs.companies ? (
          <SectionCard>
            <Typography variant="h6" sx={{ fontWeight: 950, mb: 1 }}>{t("dashboardTopCompaniesByActivity")}</Typography>
            <Stack spacing={1.25}>
              {(overview?.topCompanies ?? []).map((item, index) => (
                <Box key={item.companyId} sx={{ p: 1.5, borderRadius: 3, border: "1px solid", borderColor: "divider", backgroundColor: alpha(theme.palette.primary.main, index === 0 ? 0.05 : 0.02) }}>
                  <Box sx={{ display: "flex", justifyContent: "space-between", gap: 2, alignItems: "center", flexWrap: "wrap" }}>
                    <Box>
                      <Typography sx={{ fontWeight: 900 }}>{item.company}</Typography>
                      <Typography variant="body2" sx={{ color: "text.secondary" }}>{t("dashboardCompanyJobsResponses", { jobs: item.count, responses: item.responses })}</Typography>
                    </Box>
                    <Chip label={`${item.responseRate}%`} color={item.responseRate >= 50 ? "success" : item.responseRate >= 25 ? "warning" : "default"} variant="outlined" />
                  </Box>
                </Box>
              ))}
            </Stack>
          </SectionCard>
        ) : null}

        {prefs.skills ? (
          <SectionCard>
            <Typography variant="h6" sx={{ fontWeight: 950, mb: 1 }}>{t("dashboardTopSkills")}</Typography>
            {tags.length === 0 ? (
              <Typography sx={{ color: "text.secondary" }}>{t("dashboardNoTagsYet")}</Typography>
            ) : (
              <Stack spacing={1.15}>
                {tags.slice(0, 8).map((tag, index) => {
                  const max = Math.max(...tags.map((item) => item.count), 1);
                  const width = (tag.count / max) * 100;
                  return (
                    <Box key={tag.tag}>
                      <Box sx={{ display: "flex", justifyContent: "space-between", gap: 1, mb: 0.5 }}>
                        <Typography variant="body2" sx={{ fontWeight: 800 }}>{tag.tag}</Typography>
                        <Typography variant="body2" sx={{ color: "text.secondary" }}>{tag.count}</Typography>
                      </Box>
                      <Box sx={{ height: 10, borderRadius: 999, bgcolor: alpha(theme.palette.text.primary, 0.08), overflow: "hidden" }}>
                        <Box sx={{ width: `${width}%`, height: "100%", borderRadius: 999, bgcolor: tagColors[index % tagColors.length] }} />
                      </Box>
                    </Box>
                  );
                })}
              </Stack>
            )}

            <Typography variant="h6" sx={{ fontWeight: 950, mt: 3, mb: 1 }}>{t("dashboardSkillTrends")}</Typography>
            {!tagTrends || tagTrends.series.length === 0 ? (
              <Typography sx={{ color: "text.secondary" }}>{t("dashboardNoTagTrendData")}</Typography>
            ) : (
              <Stack spacing={1.1}>
                {tagTrends.series.map((series, index) => (
                  <Box key={series.tag}>
                    <Box sx={{ display: "flex", justifyContent: "space-between", mb: 0.5 }}>
                      <Typography variant="body2" sx={{ fontWeight: 800 }}>{series.tag}</Typography>
                      <Typography variant="caption" sx={{ color: "text.secondary" }}>{series.counts.reduce((sum, value) => sum + value, 0)} total</Typography>
                    </Box>
                    <Box sx={{ display: "grid", gridTemplateColumns: `repeat(${series.counts.length}, 1fr)`, gap: 0.5 }}>
                      {series.counts.map((count, i) => (
                        <Box
                          key={`${series.tag}-${i}`}
                          sx={{
                            height: 18,
                            borderRadius: 1.25,
                            backgroundColor: count > 0 ? alpha(tagColors[index % tagColors.length], 0.22 + Math.min(0.6, count / 10)) : alpha(theme.palette.text.primary, 0.05),
                          }}
                          title={`${tagTrends.months[i]}: ${count}`}
                        />
                      ))}
                    </Box>
                  </Box>
                ))}
              </Stack>
            )}
          </SectionCard>
        ) : null}
      </Box>
    </Box>
  );
}