import React, { useEffect, useMemo, useRef, useState } from "react";
import ReactMarkdown from "react-markdown";
import remarkGfm from "remark-gfm";
import { ButtonPrimary, ButtonSoft } from "./ui";
import { apiFetch } from "../api/client";
import { parseResponseBody, resolveApiErrorInfo } from "../utils/responseShell";
import { useAppCommandListener } from "../utils/appCommands";
import { confirmDestructiveAction } from "../utils/confirmAction";

type HelperMessage = {
  id: string;
  role: "assistant" | "user";
  text: string;
  tone?: "slate" | "green" | "amber" | "red" | "blue";
};

type UtilityTab = "assist" | "support";

const ROUTER_HELPER_CONTEXT_SESSION_KEY = "masters_toolkit_router_helper_context_v1";
const HELPER_INTRO = "I can answer router selection and FAQ questions from internal sources.";
const HELPER_PROMPTS: string[] = [
  "Recommend 2 routers for a small branch using primary 5G.",
  "Compare selected routers by device details.",
  "What is network slicing?",
];
const HELPER_DETAILS_THRESHOLD = 540;
const TABLE_ROW_RE = /^\s*\|.*\|\s*$/;
const TABLE_DELIM_RE = /^\s*\|?(?:\s*:?-{3,}:?\s*\|)+\s*:?-{3,}:?\s*\|?\s*$/;
const SUPPORT_EMAIL = "support@masterstelecom.com";
const SUPPORT_PHONE_DISPLAY = "561-531-0462";
const SUPPORT_PHONE_TEL = "+15615310462";
const SUPPORT_PHONE_EXTENSION = "Option 6";
const SUPPORT_SLACK_URL = "https://verizon.enterprise.slack.com/archives/C035HSFT7MZ";

function safeUrlTransform(url: string) {
  try {
    const base = typeof window !== "undefined" ? window.location.origin : "http://localhost";
    const parsed = new URL(url, base);
    if (parsed.protocol === "http:" || parsed.protocol === "https:") return parsed.toString();
    return "";
  } catch {
    return "";
  }
}

function HelperMarkdownTable(props: any) {
  const [readerOpen, setReaderOpen] = useState(false);
  const inlineTableRef = useRef<HTMLTableElement | null>(null);
  const modalTableRef = useRef<HTMLTableElement | null>(null);

  useEffect(() => {
    if (!readerOpen) return;
    const onKey = (event: KeyboardEvent) => {
      if (event.key === "Escape") setReaderOpen(false);
    };
    window.addEventListener("keydown", onKey);
    return () => window.removeEventListener("keydown", onKey);
  }, [readerOpen]);

  return (
    <>
      <div className="my-3 overflow-hidden rounded-[16px] border border-slate-200 bg-white/95 shadow-sm">
        <div className="space-y-2 border-b border-slate-200 px-3 py-3">
          <div className="mt-section-subtle">Comparison ready</div>
          <button
            type="button"
            className="mt-button-primary w-full rounded-xl border-2 px-4 py-2.5 text-base"
            onClick={() => setReaderOpen(true)}
          >
            Click here for comparison table
          </button>
        </div>
        <div className="max-h-[20rem] overflow-auto bg-white [&_tbody_tr:nth-child(even)]:bg-slate-50/55">
          <table
            ref={inlineTableRef}
            className="min-w-[64rem] w-max text-sm text-slate-800 [border-collapse:separate] [border-spacing:0]"
            {...props}
          />
        </div>
      </div>

      {readerOpen ? (
        <div
          className="fixed inset-0 z-[100] flex items-center justify-center bg-slate-900/50 p-2 backdrop-blur-[1px]"
          onMouseDown={(e) => {
            if (e.target === e.currentTarget) setReaderOpen(false);
          }}
        >
          <div className="flex h-[94vh] w-full max-w-[96vw] flex-col overflow-hidden rounded-[20px] border border-slate-200 bg-white shadow-2xl">
            <div className="flex items-center justify-between gap-3 border-b border-slate-200 px-4 py-3">
              <div>
                <div className="text-sm font-semibold text-slate-900">Comparison table reader</div>
                <div className="text-xs text-slate-600">Full-table view with sticky headers for easier model comparison.</div>
              </div>
              <button
                type="button"
                className="rounded-full border border-slate-200 bg-white px-2.5 py-1 text-xs font-semibold text-slate-700 hover:bg-slate-50"
                onClick={() => setReaderOpen(false)}
              >
                Close
              </button>
            </div>
            <div className="flex-1 overflow-auto bg-white px-3 py-3 [scrollbar-gutter:stable]">
              <table
                ref={modalTableRef}
                className="min-w-[92rem] w-max text-sm text-slate-900 [border-collapse:separate] [border-spacing:0] [&_tbody_tr:nth-child(even)]:bg-slate-50/50"
                {...props}
              />
            </div>
          </div>
        </div>
      ) : null}
    </>
  );
}

function findMarkdownTableRange(lines: string[]): [number, number] | null {
  for (let i = 0; i < lines.length - 1; i++) {
    if (!TABLE_ROW_RE.test(lines[i]) || !TABLE_DELIM_RE.test(lines[i + 1])) continue;
    let end = i + 2;
    while (end < lines.length && TABLE_ROW_RE.test(lines[end])) end += 1;
    return [i, end];
  }
  return null;
}

function hasMarkdownTable(markdown: string): boolean {
  const lines = String(markdown || "").split(/\r?\n/);
  return findMarkdownTableRange(lines) !== null;
}

function simplifyComparisonTableAnswer(markdown: string): string {
  const raw = String(markdown || "").trim();
  if (!raw) return raw;
  const lines = raw.split(/\r?\n/);
  const tableRange = findMarkdownTableRange(lines);
  if (!tableRange) return raw;
  const [start, end] = tableRange;
  const tableOnly = lines.slice(start, end).join("\n").trim();
  if (!tableOnly) return raw;
  return `Click here for comparison table.\n\n${tableOnly}`;
}

function buildMessageWithContext(message: string): string {
  const trimmed = String(message || "").trim();
  if (!trimmed) return "";
  try {
    const context = String(window.sessionStorage.getItem(ROUTER_HELPER_CONTEXT_SESSION_KEY) || "").trim();
    if (!context) return trimmed;
    return `${trimmed}\n\nContext from Rapid Router form:\n${context}`;
  } catch {
    return trimmed;
  }
}

function helperPreviewText(markdown: string): string {
  const flattened = String(markdown || "")
    .replace(/```[\s\S]*?```/g, " ")
    .replace(/\|[^|\n]*(\|[^|\n]*)+\|?/g, " ")
    .replace(/[#>*_`~]/g, " ")
    .replace(/\s+/g, " ")
    .trim();
  if (!flattened) return "Answer generated.";
  if (flattened.length <= 180) return flattened;
  return `${flattened.slice(0, 177).trimEnd()}...`;
}

function UtilityTabButton({
  label,
  active,
  onClick,
}: {
  label: string;
  active: boolean;
  onClick: () => void;
}) {
  return (
    <button
      type="button"
      role="tab"
      aria-selected={active}
      onClick={onClick}
      className={[
        "mt-focus rounded-full border px-3 py-2 text-sm font-semibold transition",
        active
          ? "text-white shadow-sm"
          : "border-slate-200 bg-white text-slate-700 hover:bg-slate-50",
      ].join(" ")}
      style={active ? { borderColor: "var(--mt-primary)", backgroundColor: "var(--mt-primary)" } : undefined}
    >
      {label}
    </button>
  );
}

export default function FloatingRouterHelper() {
  const [open, setOpen] = useState(false);
  const [activeTab, setActiveTab] = useState<UtilityTab>("assist");
  const [input, setInput] = useState("");
  const [busy, setBusy] = useState(false);
  const [state, setState] = useState<Record<string, any>>({});
  const [messages, setMessages] = useState<HelperMessage[]>([
    { id: "global-router-helper-intro", role: "assistant", text: HELPER_INTRO, tone: "blue" },
  ]);

  const helperMdComponents = useMemo(
    () => ({
      h1: (p: any) => <h1 className="mb-1 mt-2 text-base font-semibold text-slate-900" {...p} />,
      h2: (p: any) => <h2 className="mb-1 mt-2 text-base font-semibold text-slate-900" {...p} />,
      h3: (p: any) => <h3 className="mb-1 mt-2 text-sm font-semibold text-slate-900" {...p} />,
      p: (p: any) => <p className="my-1.5 leading-relaxed text-[15px] text-slate-800" {...p} />,
      ul: (p: any) => <ul className="my-1.5 list-disc space-y-1 pl-5 text-[15px] text-slate-800" {...p} />,
      ol: (p: any) => <ol className="my-1.5 list-decimal space-y-1 pl-5 text-[15px] text-slate-800" {...p} />,
      li: (p: any) => <li className="my-1" {...p} />,
      table: (p: any) => <HelperMarkdownTable {...p} />,
      th: (p: any) => (
        <th
          className="sticky top-0 z-[2] border-b border-slate-200 bg-slate-50 p-3 text-left text-[13px] font-semibold leading-snug text-slate-700 first:sticky first:left-0 first:z-[3] first:border-r first:border-slate-200"
          {...p}
        />
      ),
      td: (p: any) => (
        <td
          className="max-w-[28rem] border-b border-slate-100 p-3 align-top text-[13px] leading-relaxed text-slate-800 first:sticky first:left-0 first:z-[1] first:border-r first:border-slate-100 first:bg-white whitespace-pre-wrap break-words"
          {...p}
        />
      ),
      a: (p: any) => <a {...p} target="_blank" rel="noreferrer" className="underline" />,
      code: (p: any) => <code className="rounded bg-slate-100 px-1 py-0.5 text-[12px] text-slate-800" {...p} />,
    }),
    []
  );

  const resetChat = () => {
    if (!confirmDestructiveAction("Reset the assist conversation?")) return false;
    setBusy(false);
    setInput("");
    setState({});
    setMessages([{ id: `global-router-helper-intro-${Date.now()}`, role: "assistant", text: HELPER_INTRO, tone: "blue" }]);
    return true;
  };

  const openLauncher = (tab: UtilityTab) => {
    setActiveTab(tab);
    setOpen(true);
  };

  useAppCommandListener((command) => {
    if (command === "router_helper:open") {
      openLauncher("assist");
      return;
    }
    if (command === "support:open") {
      openLauncher("support");
      return;
    }
    if (command === "router_helper:close" || command === "support:close") {
      setOpen(false);
    }
  });

  const sendMessage = async (overrideMessage?: string) => {
    if (busy) return;
    const raw = typeof overrideMessage === "string" ? overrideMessage : input;
    const userMessage = String(raw || "").trim();
    if (!userMessage) return;

    setMessages((prev) => [...prev, { id: `global-router-helper-user-${Date.now()}`, role: "user", text: userMessage }]);
    if (typeof overrideMessage !== "string") setInput("");
    setBusy(true);

    try {
      const enriched = buildMessageWithContext(userMessage);
      const res = await apiFetch("/api/knowledgebase/message", {
        method: "POST",
        headers: { "Content-Type": "application/json" },
        body: JSON.stringify({
          message: enriched,
          state,
          mode: "router_docs",
          audience: "auto",
          show_citations: false,
        }),
      });

      const data = (await parseResponseBody(res)) as any;
      if (!res.ok) {
        const info = resolveApiErrorInfo(data, `Assist request failed (${res.status}).`);
        const errorText = info.shell?.result || info.text || "Assist request failed.";
        setMessages((prev) => [
          ...prev,
          { id: `global-router-helper-assistant-error-${Date.now()}`, role: "assistant", text: errorText, tone: "red" },
        ]);
        return;
      }

      const assistantRaw = String(data?.assistant || "").trim() || "I could not generate an answer for that request. Please rephrase.";
      const assistantText = simplifyComparisonTableAnswer(assistantRaw);
      const nextState = data?.state && typeof data.state === "object" ? (data.state as Record<string, any>) : {};
      setState(nextState);
      setMessages((prev) => [
        ...prev,
        { id: `global-router-helper-assistant-${Date.now()}`, role: "assistant", text: assistantText, tone: "blue" },
      ]);
    } catch (e: any) {
      setMessages((prev) => [
        ...prev,
        {
          id: `global-router-helper-assistant-catch-${Date.now()}`,
          role: "assistant",
          text: e?.message || "Assist request failed.",
          tone: "red",
        },
      ]);
    } finally {
      setBusy(false);
    }
  };

  return (
    <>
      {!open ? (
        <button
          type="button"
          className="mt-button-primary fixed bottom-5 right-5 z-[82] rounded-full border-2 px-4 py-2 text-sm shadow-lg"
          onClick={() => setOpen(true)}
          aria-label="Open help and assist launcher"
        >
          Help
        </button>
      ) : null}

      {open ? (
        <div className="fixed inset-x-2 bottom-2 z-[82] flex max-h-[86vh] flex-col overflow-hidden rounded-[20px] border border-slate-200 bg-white shadow-2xl sm:inset-x-auto sm:bottom-5 sm:right-5 sm:w-[min(92vw,560px)]">
          <div className="flex items-center justify-between gap-2 border-b border-slate-200 px-4 py-3">
            <div>
              <div className="text-lg font-semibold text-slate-900">Help + assist</div>
              <div className="text-xs text-slate-600">
                {activeTab === "assist"
                  ? busy
                    ? "Assist is working on your question."
                    : "Ask router questions here, or switch to Support for a person."
                  : "Support is available by phone, email, or Slack. Switch back to Assist for router questions."}
              </div>
            </div>
            <button
              type="button"
              className="rounded-full border border-slate-200 bg-white px-2.5 py-1 text-xs font-semibold text-slate-700 hover:bg-slate-50"
              onClick={() => setOpen(false)}
            >
              Close
            </button>
          </div>

          <div className="border-b border-slate-200 px-4 py-3">
            <div role="tablist" aria-label="Help launcher sections" className="flex flex-wrap gap-2">
              <UtilityTabButton label="Assist" active={activeTab === "assist"} onClick={() => setActiveTab("assist")} />
              <UtilityTabButton label="Support" active={activeTab === "support"} onClick={() => setActiveTab("support")} />
            </div>
          </div>

          {activeTab === "assist" ? (
            <div role="tabpanel" aria-label="Assist tab" className="flex min-h-0 flex-1 flex-col overflow-hidden">
              <div role="log" aria-live="polite" aria-relevant="additions text" className="max-h-[42vh] min-h-0 space-y-3 overflow-y-auto px-4 py-3 sm:max-h-[46vh]">
                {messages.map((msg) => {
                  const isAssistant = msg.role === "assistant";
                  const tone = msg.tone || "slate";
                  const isTableAnswer = isAssistant && hasMarkdownTable(msg.text);
                  const hasLongAnswer = isAssistant && !isTableAnswer && msg.text.length > HELPER_DETAILS_THRESHOLD;
                  const bubbleClass =
                    tone === "red"
                      ? "mt-panel-danger"
                      : tone === "amber"
                        ? "mt-panel-warning"
                        : tone === "blue"
                          ? "mt-panel-primary"
                          : "border-slate-200 bg-slate-50 text-slate-900";
                  const bubbleWidthClass = isAssistant ? "w-full max-w-full" : "max-w-[95%]";

                  return (
                    <div key={msg.id} className={["flex", isAssistant ? "justify-start" : "justify-end"].join(" ")}>
                      <div className={[bubbleWidthClass, "rounded-[16px] border px-3 py-2.5 text-sm leading-relaxed", bubbleClass].join(" ")}>
                        {isAssistant ? (
                          isTableAnswer ? (
                            <ReactMarkdown urlTransform={safeUrlTransform} remarkPlugins={[remarkGfm]} components={helperMdComponents}>
                              {msg.text}
                            </ReactMarkdown>
                          ) : hasLongAnswer ? (
                            <div className="space-y-2">
                              <div className="mt-section-subtle text-slate-700">Answer</div>
                              <div className="text-sm text-slate-800">{helperPreviewText(msg.text)}</div>
                              <details className="rounded-[12px] border border-slate-200 bg-white/80 px-3 py-2">
                                <summary className="cursor-pointer text-xs font-semibold text-slate-700">View details</summary>
                                <div className="mt-2">
                                  <ReactMarkdown urlTransform={safeUrlTransform} remarkPlugins={[remarkGfm]} components={helperMdComponents}>
                                    {msg.text}
                                  </ReactMarkdown>
                                </div>
                              </details>
                            </div>
                          ) : (
                            <ReactMarkdown urlTransform={safeUrlTransform} remarkPlugins={[remarkGfm]} components={helperMdComponents}>
                              {msg.text}
                            </ReactMarkdown>
                          )
                        ) : (
                          <div className="whitespace-pre-wrap">{msg.text}</div>
                        )}
                      </div>
                    </div>
                  );
                })}
              </div>

              <div className="space-y-3 border-t border-slate-200 px-4 py-3">
                <div className="flex flex-wrap gap-2">
                  {HELPER_PROMPTS.map((prompt) => (
                    <button
                      key={prompt}
                      type="button"
                      className="rounded-full border border-slate-200 bg-white px-3 py-1.5 text-sm text-slate-700 hover:bg-slate-50"
                      onClick={() => setInput(prompt)}
                      disabled={busy}
                    >
                      {prompt}
                    </button>
                  ))}
                </div>

                <textarea
                  className="min-h-[96px] w-full rounded-xl border border-slate-200 bg-white px-3 py-2 text-sm"
                  placeholder="Ask for router picks, model comparisons, or FAQ guidance."
                  value={input}
                  onChange={(e) => setInput(e.target.value)}
                  onKeyDown={(e) => {
                    if (e.key === "Enter" && !e.shiftKey) {
                      e.preventDefault();
                      void sendMessage();
                    }
                  }}
                  disabled={busy}
                />

                <div className="flex items-center justify-between gap-2">
                  <ButtonSoft onClick={resetChat} disabled={busy}>
                    Reset assist
                  </ButtonSoft>
                  <ButtonPrimary
                    onClick={() => void sendMessage()}
                    disabled={busy || !input.trim()}
                  >
                    {busy ? "Thinking..." : "Ask assist"}
                  </ButtonPrimary>
                </div>
              </div>
            </div>
          ) : (
            <div role="tabpanel" aria-label="Support tab" className="space-y-3 px-4 py-4">
              <div className="rounded-[16px] border border-slate-200 bg-slate-50 px-4 py-3 text-sm text-slate-700">
                For a fast answer, use Slack first. If you need human follow-up, email or phone is available here.
              </div>

              <a
                href={SUPPORT_SLACK_URL}
                target="_blank"
                rel="noreferrer"
                className="mt-button-success block w-full rounded-xl border-2 px-4 py-3 text-center text-sm"
              >
                Open Slack support
              </a>

              <a
                href={`mailto:${SUPPORT_EMAIL}?subject=Masters%20Toolkit%20Support%20Request`}
                className="block w-full rounded-xl border border-slate-200 bg-white px-4 py-2.5 text-center text-sm font-semibold text-slate-800 hover:bg-slate-50"
              >
                Email {SUPPORT_EMAIL}
              </a>

              <a
                href={`tel:${SUPPORT_PHONE_TEL}`}
                className="block w-full rounded-xl border border-slate-200 bg-white px-4 py-2.5 text-center text-sm font-semibold text-slate-800 hover:bg-slate-50"
              >
                Call {SUPPORT_PHONE_DISPLAY} ({SUPPORT_PHONE_EXTENSION})
              </a>

              <div className="rounded-[12px] border border-slate-200 bg-white px-4 py-3 text-xs text-slate-600">
                Need router questions answered first? Switch to <span className="font-semibold">Assist</span> for internal-source guidance and model comparison help.
              </div>
            </div>
          )}
        </div>
      ) : null}
    </>
  );
}