import React, { useMemo, useState, useEffect, useRef } from "react";
import { useParams, useNavigate } from "react-router-dom";
import {
  Box,
  Container,
  Paper,
  Typography,
  Button,
  Chip,
  CircularProgress,
  Alert,
  Divider,
} from "@mui/material";
import ReplayIcon from "@mui/icons-material/Replay";
import CheckCircleIcon from "@mui/icons-material/CheckCircle";
import ErrorIcon from "@mui/icons-material/Error";
import WarningAmberIcon from "@mui/icons-material/WarningAmber";
import PlayArrowIcon from "@mui/icons-material/PlayArrow";
import RemoveCircleOutlineIcon from "@mui/icons-material/RemoveCircleOutline";
import FiberManualRecordIcon from "@mui/icons-material/FiberManualRecord";
import { useResource, useItemSse, useAppContext, DetailFieldRenderer, applyDisplayFormat } from "../../react-openapi";
import { useQuery } from "@tanstack/react-query";
import { RETRY_MAX, formatApiError } from "../features/fetch-requests";
import type { FetchRequestStatus, SSEEvent, ProgressMessage } from "../features/fetch-requests";
import { PipelineStepper } from "./components/PipelineStepper";
import { AmbiguityResolver } from "./components/AmbiguityResolver";
import { PageHeader } from "../ui/PageHeader";
import { useToast } from "../ui/Toast";

const statusColors: Record<FetchRequestStatus, "default" | "primary" | "warning" | "info" | "success" | "error"> = {
  pending: "default",
  processing: "info",
  paused: "warning",
  raw_expenses_done: "primary",
  enriched_done: "warning",
  completed: "success",
  failed: "error",
};

const statusIcons: Record<FetchRequestStatus, React.ReactNode> = {
  pending: <PlayArrowIcon sx={{ fontSize: 16 }} />,
  processing: <CircularProgress size={14} />,
  paused: <WarningAmberIcon sx={{ fontSize: 16 }} />,
  raw_expenses_done: <CheckCircleIcon sx={{ fontSize: 16 }} />,
  enriched_done: <CheckCircleIcon sx={{ fontSize: 16 }} />,
  completed: <CheckCircleIcon sx={{ fontSize: 16 }} />,
  failed: <ErrorIcon sx={{ fontSize: 16 }} />,
};

function formatProgressMessage(msg: ProgressMessage): string {
  if (msg.lines !== undefined) return `${msg.lines} lines`;
  if (msg.blocks !== undefined) return `${msg.blocks} blocks`;
  if (msg.count !== undefined && msg.unit) return `${msg.count} ${msg.unit}`;
  if (msg.count !== undefined) return `${msg.count} items`;
  if (msg.raw_ocr_line) return `"${msg.raw_ocr_line.slice(0, 60)}${msg.raw_ocr_line.length > 60 ? "…" : ""}"`;
  if (msg.error) return msg.error.slice(0, 80);
  return "";
}

function sseIcon(status: SSEEvent["status"]) {
  switch (status) {
    case "started": return <CircularProgress size={14} />;
    case "completed": return <CheckCircleIcon sx={{ fontSize: 16, color: "success.main" }} />;
    case "failed": return <ErrorIcon sx={{ fontSize: 16, color: "error.main" }} />;
    case "skipped": return <RemoveCircleOutlineIcon sx={{ fontSize: 16, color: "text.disabled" }} />;
    case "paused": return <WarningAmberIcon sx={{ fontSize: 16, color: "warning.main" }} />;
    case "progress": return <FiberManualRecordIcon sx={{ fontSize: 14, color: "info.main" }} />;
  }
}

function Section({ title, children, action }: { title: string; children: React.ReactNode; action?: React.ReactNode }) {
  return (
    <Paper sx={{ p: 3, borderRadius: 3, mb: 3 }} variant="outlined">
      <Box sx={{ display: "flex", alignItems: "center", gap: 1, mb: 2 }}>
        <Typography variant="subtitle1" fontWeight={700} sx={{ flex: 1 }}>
          {title}
        </Typography>
        {action}
      </Box>
      {children}
    </Paper>
  );
}

export default function FetchRequestDetail() {
  const { id } = useParams<{ id: string }>();
  const navigate = useNavigate();
  const { get, patch, resource } = useResource("fetch-requests");
  const { resources: allResources } = useAppContext();
  const [stepStats, setStepStats] = useState<Record<string, number>>({});
  const [liveParsedCount, setLiveParsedCount] = useState<number | undefined>(undefined);
  const [retrying, setRetrying] = useState(false);
  const { showToast } = useToast();
  const feedRef = useRef<HTMLDivElement>(null);

  const { data: fetchRequest, isLoading, error: fetchError, refetch: refetchRequest } = useQuery({
    queryKey: ["fetch-requests", "detail", id],
    queryFn: () => get(id!),
    enabled: !!id,
  });

  const sseUrl = id ? `/fetch-requests/${id}/events` : null;
  const { connected: sseConnected, events: sseEvents } = useItemSse(sseUrl, {
    onEvent: (parsed: SSEEvent) => {
      if (parsed.status === "progress" && parsed.message.count !== undefined) {
        if (parsed.step === "txn_dicts") setLiveParsedCount(parsed.message.count);
        if (parsed.step === "enrich") setStepStats((prev) => ({ ...prev, enrich_count: parsed.message.count! }));
        if (parsed.step === "save_expenses") setStepStats((prev) => ({ ...prev, save_count: parsed.message.count! }));
      }

      if (parsed.status === "completed" && parsed.message.count !== undefined) {
        const stats: Record<string, number> = {};
        if (parsed.step === "raw_lines" && parsed.message.lines !== undefined) stats.raw_lines = parsed.message.lines;
        if (parsed.step === "txn_blocks" && parsed.message.blocks !== undefined) stats.txn_blocks = parsed.message.blocks;
        if (parsed.step === "txn_dicts") stats.txn_dicts = parsed.message.count;
        if (parsed.step === "enrich") stats.enrich_count = parsed.message.count;
        if (parsed.step === "save_expenses") stats.save_count = parsed.message.count;
        if (Object.keys(stats).length) {
          setStepStats((prev) => ({ ...prev, ...stats }));
        }
      }

      if (parsed.status === "paused") {
        refetchRequest();
      }
      if (parsed.status === "failed") {
        showToast(parsed.message.error || "Fetch request failed", "error");
        refetchRequest();
      }
      if (parsed.status === "completed" || parsed.step === "resume_extract") {
        refetchRequest();
      }
    },
  });

  useEffect(() => {
    if (feedRef.current) {
      feedRef.current.scrollTop = feedRef.current.scrollHeight;
    }
  }, [sseEvents]);

  const displayEvents = useMemo(() => {
    const progressSteps = new Set(["txn_dicts", "enrich", "save_expenses"]);
    const lastProgressIdx: Record<string, number> = {};
    for (let i = sseEvents.length - 1; i >= 0; i--) {
      const e = sseEvents[i];
      if (progressSteps.has(e.step) && e.status === "progress" && lastProgressIdx[e.step] === undefined) {
        lastProgressIdx[e.step] = i;
      }
    }

    const terminalStatuses = new Set(["completed", "skipped", "paused", "failed"]);
    return sseEvents.filter((e, i) => {
      if (progressSteps.has(e.step) && e.status === "progress") return i === lastProgressIdx[e.step];
      if (e.status === "started") {
        return !sseEvents.slice(i + 1).some(
          (later) => later.step === e.step && terminalStatuses.has(later.status),
        );
      }
      return true;
    });
  }, [sseEvents]);

  const handleRetry = async () => {
    if (!id || !patch || retrying) return;
    setRetrying(true);
    try {
      await patch(id, { status: "pending" });
      refetchRequest();
    } catch (err: any) {
      showToast(formatApiError(err), "error");
    } finally {
      setRetrying(false);
    }
  };

  const req = fetchRequest as any;
  const retryCount = req?.retry_count ?? 0;
  const isRetryExhausted = retryCount >= RETRY_MAX;
  const status = (req?.status ?? "pending") as FetchRequestStatus;
  const detailFields = (resource?.orderedFields ?? []).filter(
    (f) => f.name !== "source",
  );

  const displayTitle = useMemo(() => {
    if (!resource || !req) return "";
    const resolved = Object.fromEntries(
      resource.orderedFields.map((field) => {
        const value = req[field.name];
        if (field.fk && typeof value === "object" && value != null) {
          const target = allResources.find((r) => r.name === field.fk!.resource);
          if (target) return [field.name, applyDisplayFormat(value, target.displayFormat)];
        }
        return [field.name, value];
      }),
    );
    return applyDisplayFormat(resolved, resource.displayFormat);
  }, [resource, req, allResources]);

  if (isLoading) {
    return (
      <Box sx={{ display: "flex", justifyContent: "center", p: 8 }}>
        <CircularProgress />
      </Box>
    );
  }

  if (fetchError || !fetchRequest) {
    return (
      <Container sx={{ mt: 4 }}>
        <PageHeader
          crumbs={[{ label: "Home", path: "/" }, { label: "Fetch Requests", path: "/fetch-requests" }, { label: "Details" }]}
          title="Fetch Request"
        />
        <Alert severity="error">Failed to load fetch request</Alert>
      </Container>
    );
  }

  return (
    <Container maxWidth="lg" sx={{ py: 4 }}>
      <PageHeader
        crumbs={[{ label: "Home", path: "/" }, { label: "Fetch Requests", path: "/fetch-requests" }, { label: displayTitle }]}
        title={displayTitle}
        subtitle="Live pipeline status, progress events, and ambiguity resolution for this import."
      />

      <Section
        title="Overview"
        action={
          <Chip
            icon={statusIcons[status] as any}
            label={status.replace(/_/g, " ")}
            color={statusColors[status]}
            sx={{ textTransform: "capitalize" }}
          />
        }
      >
        <Box sx={{ display: "flex", alignItems: "center", gap: 2, mb: 2, flexWrap: "wrap" }}>
          <Chip
            label={"path" in (req.source ?? {}) ? "File" : "Email"}
            size="small"
            variant="outlined"
            color={"path" in (req.source ?? {}) ? "primary" : "secondary"}
          />
          <Typography variant="caption" color="text.secondary">
            ID: {req.id}
          </Typography>
        </Box>

        <Box sx={{ display: "flex", gap: 4, flexWrap: "wrap", mb: 2 }}>
          {detailFields.map((field) => {
            const value = req[field.name];
            let fmt = resource?.displayFormat;
            if (field.fk && typeof value === "object" && value != null) {
              const target = allResources.find((r) => r.name === field.fk!.resource);
              if (target) fmt = target.displayFormat;
            }
            return (
              <DetailFieldRenderer
                key={field.name}
                field={field}
                value={value}
                displayFormat={fmt}
              />
            );
          })}
        </Box>

        <Divider sx={{ my: 2 }} />

        <Box sx={{ display: "flex", alignItems: "center", gap: 2 }}>
          <Box sx={{ flex: 1, maxWidth: 300 }}>
            <Typography variant="caption" color="text.secondary">
              Retries: {retryCount}/{RETRY_MAX}
            </Typography>
          </Box>
          {status === "failed" && !isRetryExhausted && (
            <Button
              variant="outlined"
              size="small"
              startIcon={<ReplayIcon />}
              onClick={handleRetry}
              disabled={retrying}
            >
              Retry
            </Button>
          )}
        </Box>
      </Section>

      {status === "failed" && req.error_message && (
        <Alert severity="error" sx={{ mb: 3, borderRadius: 2 }}>
          {req.error_message}
        </Alert>
      )}
      {isRetryExhausted && status === "failed" && (
        <Alert severity="info" sx={{ mb: 3, borderRadius: 2 }}>
          Max retries reached — no further retry attempts will be made.
        </Alert>
      )}

      <PipelineStepper
        fetchRequest={req}
        sseEvents={sseEvents}
        stepStats={stepStats}
        liveParsedCount={liveParsedCount ?? 0}
      />

      <Section
        title="Progress Events"
        action={
          <Box sx={{ display: "flex", alignItems: "center", gap: 1 }}>
            <Box
              sx={{
                width: 8,
                height: 8,
                borderRadius: "50%",
                bgcolor: sseConnected ? "success.main" : "error.main",
              }}
            />
            <Typography variant="caption" color="text.secondary">
              {sseConnected ? "Connected" : "Disconnected"}
            </Typography>
          </Box>
        }
      >
        <Box
          ref={feedRef}
          sx={{
            maxHeight: 300,
            overflowY: "auto",
            display: "flex",
            flexDirection: "column",
            gap: 1,
            pr: 0.5,
          }}
        >
          {displayEvents.length === 0 ? (
            <Typography variant="body2" color="text.disabled" sx={{ textAlign: "center", py: 2 }}>
              Waiting for events...
            </Typography>
          ) : (
            displayEvents.map((evt, i) => (
              <Box
                key={i}
                sx={{
                  display: "flex",
                  alignItems: "center",
                  gap: 1.5,
                  p: 1.25,
                  borderRadius: 2,
                  bgcolor: "action.hover",
                }}
              >
                {sseIcon(evt.status)}
                <Box sx={{ flex: 1 }}>
                  <Typography variant="body2" fontWeight={600}>
                    {evt.step.replace(/_/g, " ")}
                  </Typography>
                  {evt.message && formatProgressMessage(evt.message) && (
                    <Typography variant="caption" color="text.secondary">
                      {formatProgressMessage(evt.message)}
                    </Typography>
                  )}
                </Box>
              </Box>
            ))
          )}
        </Box>
      </Section>

      <AmbiguityResolver fetchRequestId={id!} />
    </Container>
  );
}