"use client";

import React, { useCallback, useEffect, useRef, useState } from "react";
import {
  Send,
  Paperclip,
  Bold,
  Italic,
  Underline,
  Strikethrough,
  List,
  ListOrdered,
  Link as LinkIcon,
  Undo2,
  X,
  Sparkles,
  CheckCircle2,
  Flag,
} from "lucide-react";
import { useTranslations } from "../i18n/provider";
import { Button } from "../components/ui/Button";
import { notifyMailStateChanged } from "../lib/useFolders";
import { signatureToHtml } from "../lib/signature";
import { RecipientInput } from "../components/RecipientInput";
import { parseAddress, parseAddressList, prefixSubject } from "../lib/recipients";

/** Entries from a query-string list, which may be several addresses. */
function entriesFrom(value: string | undefined): string[] {
  return value ? parseAddressList(value).map((p) => p.entry) : [];
}

interface AttachedFile {
  id: string;
  name: string;
  size: number;
  type: string;
}

export interface ComposerInitial {
  replyTo?: string;
  cc?: string;
  subject?: string;
  inReplyTo?: string;
  mode?: string;
  draft?: string;
}

interface ComposerProps {
  initial?: ComposerInitial;
  /**
   * "page" is the full compose screen. "inline" is the reply written under the
   * conversation it answers: no title, no subject row (a reply keeps its
   * subject) and a shorter editor, so the messages stay in view above it.
   */
  variant?: "page" | "inline";
  onSent: () => void;
  onDiscarded: () => void;
}

export function Composer({ initial, variant = "page", onSent, onDiscarded }: ComposerProps) {
  const t = useTranslations();
  const inline = variant === "inline";
  const params = initial ?? {};

  // Recipients are lists of entries, not one string to be split later: a
  // reply-all arrives with several people already in To and Cc.
  const [to, setTo] = useState<string[]>(() => entriesFrom(params?.replyTo));
  const [cc, setCc] = useState<string[]>(() => entriesFrom(params?.cc));
  const [bcc, setBcc] = useState<string[]>([]);
  const [showCcBcc, setShowCcBcc] = useState(() => entriesFrom(params?.cc).length > 0);
  const [subject, setSubject] = useState(
    params?.subject ? prefixSubject(params.subject, params.mode === "forward" ? "forward" : "reply") : "",
  );
  // The Message-ID being answered, so the reply threads under it.
  const [inReplyTo, setInReplyTo] = useState(params?.mode === "forward" ? "" : params?.inReplyTo || "");
  const [important, setImportant] = useState(false);
  const [attachments, setAttachments] = useState<AttachedFile[]>([]);
  const [sending, setSending] = useState(false);
  const [undoSeconds, setUndoSeconds] = useState<number | null>(null);
  const [draftStatus, setDraftStatus] = useState<string>("");
  const [discarding, setDiscarding] = useState(false);
  const [sendError, setSendError] = useState<string | null>(null);
  // The UID of the draft already stored for this message. Sent back on each
  // autosave so the server replaces it instead of leaving another copy.
  const draftUidRef = useRef<number>(0);
  // Set once the writer has discarded the message. An autosave already on its
  // way when that happens would otherwise land afterwards and bring the draft
  // back, so every save checks this before and after it talks to the server.
  const discardedRef = useRef(false);
  // The send waiting out its ten seconds, so Undo can stop it and leaving the
  // screen cannot lose it.
  const pendingSend = useRef<{ timer: ReturnType<typeof setInterval>; html: string } | null>(null);
  const sendRef = useRef<(html: string) => Promise<void>>(async () => undefined);
  const unmounted = useRef(false);

  const editorRef = useRef<HTMLDivElement>(null);
  // The body, mirrored into React state.
  //
  // It used to live only inside the contenteditable, read through the ref at
  // save time. Nothing observed it, so the autosave effect - which depends on
  // what it reads - never re-ran when the message itself was typed. The draft
  // was written once, moments after the address was entered, and never again:
  // that is why a draft left behind by a sent message was empty.
  const [body, setBody] = useState("");

  // Leaving with a send still counting down sends it now. Dropping it would lose
  // a message the writer was told was on its way; Undo is the way to cancel.
  useEffect(() => {
    unmounted.current = false;
    return () => {
      unmounted.current = true;
      const pending = pendingSend.current;
      if (pending) {
        clearInterval(pending.timer);
        pendingSend.current = null;
        void sendRef.current(pending.html);
      }
    };
  }, []);

  // An inline reply is opened to be written in, so the cursor starts in it.
  useEffect(() => {
    if (inline) editorRef.current?.focus();
  }, [inline]);

  useEffect(() => {
    const savedSig = localStorage.getItem("lm_user_signature");
    // signatureToHtml, not the raw value: the signature may be the plain text
    // of the old field, whose newlines are whitespace once assigned as HTML -
    // which is why every line break in a signature used to vanish here.
    const signatureHtml = signatureToHtml(savedSig ?? "");
    if (editorRef.current && signatureHtml) {
      const initial = `<br/><br/>--<br/>${signatureHtml}`;
      editorRef.current.innerHTML = initial;
      setBody(initial);
    }
  }, []);

  // Reopening a draft loads what was written into the composer, and adopts its
  // UID so carrying on writing replaces that draft instead of leaving the old
  // copy behind and starting a second one.
  //
  // Opening a draft used to land in the reader, which offered to reply to the
  // half-written message and gave no way to finish it.
  const draftParam = params?.draft;
  useEffect(() => {
    const uid = Number(draftParam);
    if (!Number.isFinite(uid) || uid <= 0) return;

    let cancelled = false;
    void (async () => {
      try {
        const res = await fetch(`/api/v1/mail/message/${uid}?folder=drafts`, { cache: "no-store" });
        if (!res.ok || cancelled) return;
        const message = await res.json();
        if (cancelled) return;

        draftUidRef.current = uid;
        setTo(message.to ?? []);
        setCc(message.cc ?? []);
        setImportant(Boolean(message.important));
        setInReplyTo(message.in_reply_to ?? "");
        if ((message.cc ?? []).length > 0) setShowCcBcc(true);
        setSubject(message.subject ?? "");
        const html = message.html || message.text || "";
        if (editorRef.current) editorRef.current.innerHTML = html;
        setBody(html);
      } catch {
        // A draft that cannot be loaded leaves an empty composer rather than
        // a broken screen; the draft itself is untouched on the server.
      }
    })();
    return () => {
      cancelled = true;
    };
  }, [draftParam]);

  // Removes a stored draft for good. discard_draft is what keeps it out of
  // Trash: an ordinary delete moves it there, and a draft sitting in Trash is
  // not discarded.
  const removeDraft = async (uid: number): Promise<boolean> => {
    try {
      const res = await fetch("/api/v1/mail/delete", {
        method: "POST",
        headers: { "Content-Type": "application/json" },
        body: JSON.stringify({ folder: "drafts", uid, discard_draft: true }),
      });
      return res.ok;
    } catch {
      return false;
    }
  };

  // Saves the draft for real. This used to be a setTimeout that set the words
  // "draft saved automatically" and nothing else - no request, no storage - so
  // closing the tab lost the message while the screen had just said otherwise.
  const saveDraft = useCallback(async () => {
    if (discardedRef.current) return;
    const html = editorRef.current?.innerHTML ?? body;
    if (to.length === 0 && !subject && !body.trim() && !html.trim()) return;
    setDraftStatus(t("mail.draftSaving"));
    try {
      const res = await fetch("/api/v1/mail/draft", {
        method: "POST",
        headers: { "Content-Type": "application/json" },
        body: JSON.stringify({
          to,
          cc,
          bcc,
          subject,
          html,
          important,
          in_reply_to: inReplyTo,
          replace_uid: draftUidRef.current,
        }),
      });
      if (res.ok) {
        const data = await res.json().catch(() => ({}));
        if (typeof data.uid === "number") draftUidRef.current = data.uid;
        // Discarded while this save was in flight: what it just stored is a
        // draft nobody wants, so it goes too.
        if (discardedRef.current && draftUidRef.current > 0) {
          void removeDraft(draftUidRef.current);
          return;
        }
      }
      setDraftStatus(res.ok ? t("mail.draftSaved") : t("mail.draftSaveFailed"));
    } catch {
      setDraftStatus(t("mail.draftSaveFailed"));
    }
  }, [to, cc, bcc, subject, body, important, inReplyTo, t]);

  // Debounced so a draft is written after a pause in typing rather than on
  // every keystroke. Skipped once the message is on its way out.
  useEffect(() => {
    if (sending) return;
    // The body alone is enough: a message typed before its recipient is still
    // worth keeping, and requiring an address here is half of why drafts were
    // being stored with nothing in them.
    if (to.length === 0 && !subject && !body.trim()) return;
    const timer = setTimeout(() => void saveDraft(), 2500);
    return () => clearTimeout(timer);
  }, [to, subject, cc, bcc, body, important, sending, saveDraft]);

  // Throws the message away: stops the autosave, removes the draft already
  // stored for it, and only then leaves. Leaving first was the old behaviour -
  // a link to the inbox - and left the draft in Drafts, as if nothing had
  // been discarded.
  const discardMessage = async () => {
    discardedRef.current = true;
    setDiscarding(true);
    setSendError(null);
    const uid = draftUidRef.current;
    if (uid > 0 && !(await removeDraft(uid))) {
      // Still there, so say so and let the autosave carry on rather than
      // leaving the page with a draft the writer thinks is gone.
      discardedRef.current = false;
      setDiscarding(false);
      setSendError(t("mail.discardFailed"));
      return;
    }
    draftUidRef.current = 0;
    notifyMailStateChanged();
    onDiscarded();
  };

  const executeFormat = (command: string, value: string | undefined = undefined) => {
    document.execCommand(command, false, value);
    editorRef.current?.focus();
    // execCommand edits the DOM directly, so the mirrored body is re-read
    // here rather than relying on an input event that may not be dispatched.
    setBody(editorRef.current?.innerHTML ?? "");
  };

  const handleFileUpload = (e: React.ChangeEvent<HTMLInputElement>) => {
    if (!e.target.files) return;
    const newFiles: AttachedFile[] = Array.from(e.target.files).map((f) => ({
      id: Math.random().toString(36).substring(2, 9),
      name: f.name,
      size: f.size,
      type: f.type || "application/octet-stream",
    }));
    setAttachments((prev) => [...prev, ...newFiles]);
  };

  const removeAttachment = (id: string) => {
    setAttachments((prev) => prev.filter((a) => a.id !== id));
  };

  // Anything in a recipient field that is not an address. These stay on screen
  // as red chips; sending with one would queue mail to a destination that
  // cannot exist and report success.
  const invalidRecipients = [...to, ...cc, ...bcc].filter((entry) => !parseAddress(entry).valid);
  const hasRecipient = to.length + cc.length + bcc.length > 0;

  const handleSend = async (e: React.FormEvent) => {
    e.preventDefault();
    if (!hasRecipient) {
      setSendError(t("mail.noRecipients"));
      return;
    }
    if (invalidRecipients.length > 0) {
      setSendError(t("mail.fixRecipients"));
      setShowCcBcc(true);
      return;
    }
    setSendError(null);
    setSending(true);
    setUndoSeconds(10);

    const bodyHtml = editorRef.current?.innerHTML || body;

    // The countdown is counted here and not inside a state updater. The send
    // used to be a side effect of that updater, which React may run twice (the
    // message went out twice) and which Undo could not stop: Undo only cleared
    // the number, and the next tick - finding it empty - sent the message
    // anyway.
    let remaining = 10;
    const timer = setInterval(() => {
      remaining -= 1;
      if (remaining > 0) {
        setUndoSeconds(remaining);
        return;
      }
      clearInterval(timer);
      pendingSend.current = null;
      setUndoSeconds(null);
      void sendRef.current(bodyHtml);
    }, 1000);
    pendingSend.current = { timer, html: bodyHtml };
  };

  const sendActualMessage = async (htmlBody: string) => {
    try {
      const res = await fetch("/api/v1/mail/send", {
        method: "POST",
        headers: { "Content-Type": "application/json" },
        body: JSON.stringify({
          to,
          cc,
          bcc,
          subject,
          html: htmlBody,
          important,
          in_reply_to: inReplyTo,
          // The draft this message grew out of, so the server can discard it.
          // Without this the draft outlived the message it became and sat in
          // Drafts as a duplicate of mail already sent.
          draft_uid: draftUidRef.current,
        }),
      });
      if (!res.ok) {
        // Reporting success on a refused send is how a message silently
        // disappears: the composer used to navigate away regardless.
        const data = await res.json().catch(() => ({}));
        setSendError(data.message ?? t("errors.serverError"));
        setSending(false);
        return;
      }
      // A flush after leaving must not drag the writer back to Sent.
      if (!unmounted.current) onSent();
    } catch {
      setSendError(t("errors.serverError"));
      setSending(false);
    }
  };

  sendRef.current = sendActualMessage;

  const handleUndo = () => {
    // Stops the timer itself: clearing the number on screen is not enough.
    if (pendingSend.current) {
      clearInterval(pendingSend.current.timer);
      pendingSend.current = null;
    }
    setUndoSeconds(null);
    setSending(false);
  };

  /** One row of the compose sheet: a fixed-width label beside the control. */
  const fieldRow = "flex flex-wrap items-center gap-x-3 gap-y-2 px-4 py-2.5 shadow-[inset_0_-1px_0_0_rgb(var(--ink)/0.07)]";
  const fieldLabel = "w-14 flex-none text-[12.5px] leading-snug text-slate-400";
  const bareInput =
    "min-h-[30px] min-w-[160px] flex-1 border-0 bg-transparent text-sm text-slate-100 placeholder-slate-500 focus:outline-none";
  const toolButton =
    "flex h-8 w-8 items-center justify-center rounded-lg text-slate-300 transition-colors hover:bg-ink/[0.07] hover:text-slate-100";

  return (
    <div className={inline ? "" : "flex-1 overflow-y-auto bg-dark-bg px-5 pb-11 pt-7 sm:px-8"}>
      <form
        onSubmit={handleSend}
        className={inline ? "flex w-full flex-col gap-3" : "mx-auto flex w-full max-w-[860px] flex-col gap-[18px]"}
      >
        <div className="flex flex-wrap items-end justify-between gap-4">
          <div className="min-w-0">
            {!inline && <h1 className="text-[25px] font-medium leading-tight text-slate-100">{t("mail.compose")}</h1>}
            {draftStatus && (
              <div className="mt-1 flex items-center gap-1.5 text-[12.5px] text-slate-400">
                <CheckCircle2 className="h-3.5 w-3.5 flex-none text-indigo-500" />
                {draftStatus}
              </div>
            )}
          </div>
          <div className="flex flex-wrap gap-2">
            <button
              type="button"
              onClick={() => setImportant((v) => !v)}
              aria-pressed={important}
              disabled={sending}
              title={t("mail.highImportanceHint")}
              className={`inline-flex h-10 items-center gap-2 rounded-xl px-3.5 text-sm shadow-edge transition-colors focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-indigo-400 ${
                important ? "bg-rose-900/70 text-rose-100" : "bg-dark-card text-slate-200 hover:bg-ink/[0.07]"
              }`}
            >
              <Flag className="h-4 w-4" fill={important ? "currentColor" : "none"} />
              <span>{t("mail.highImportance")}</span>
            </button>
            <Button
              type="button"
              variant="secondary"
              size="md"
              disabled={sending || discarding}
              onClick={() => void discardMessage()}
            >
              {t("mail.discard")}
            </Button>
            <Button type="submit" variant="primary" size="md" disabled={sending}>
              <Send className="h-4 w-4" />
              <span>{sending ? t("mail.sending") : t("mail.sendMessage")}</span>
            </Button>
          </div>
        </div>

        {sendError && (
          <div className="rounded-xl bg-rose-900/60 px-4 py-3 text-xs leading-relaxed text-rose-200 shadow-edge">
            {sendError}
          </div>
        )}

        {undoSeconds !== null && (
          <div className="flex flex-wrap items-center justify-between gap-3 rounded-xl bg-dark-card px-4 py-3 text-xs text-slate-200 shadow-edge">
            <div className="flex items-center gap-2">
              <Sparkles className="h-4 w-4 flex-none animate-spin text-indigo-500" />
              {/* The countdown is a placeholder inside the message, not text
                  bolted on after it. It used to be both: the bundle's own
                  "{seconds}" was never substituted and a second, hardcoded
                  count was appended, so this read "Undo Send ({seconds}s
                  remaining) (9s remaining)". */}
              <span>{t("mail.undoSend", { seconds: undoSeconds })}</span>
            </div>
            {/* type="button": inside this form a button submits it, so Undo used to
                stop the countdown and then send the message again. */}
            <Button type="button" variant="primary" size="sm" onClick={handleUndo}>
              <Undo2 className="h-3.5 w-3.5" />
              {t("mail.undoSendAction")}
            </Button>
          </div>
        )}

        {/* One sheet, the fields stacked as rows inside it, rather than a stack
            of separately outlined inputs: the message is one object. */}
        <div className="overflow-hidden rounded-2xl bg-dark-panel shadow-edge">
          <div className={fieldRow}>
            <label htmlFor="compose-to" className={fieldLabel}>
              {t("ui.toRecipients")}
            </label>
            <RecipientInput
              id="compose-to"
              value={to}
              onChange={setTo}
              placeholder="recipient@example.com"
              disabled={sending}
              invalid={to.some((e) => !parseAddress(e).valid)}
            />
            <button
              type="button"
              onClick={() => setShowCcBcc(!showCcBcc)}
              className="flex-none rounded-lg px-2 py-1 text-[12.5px] text-indigo-500 transition-colors hover:bg-indigo-500/10"
            >
              {showCcBcc ? t("mail.hideCcBcc") : t("mail.showCcBcc")}
            </button>
          </div>

          {showCcBcc && (
            <>
              <div className={fieldRow}>
                <label htmlFor="compose-cc" className={fieldLabel}>
                  {t("mail.ccLabel")}
                </label>
                <RecipientInput
                  id="compose-cc"
                  value={cc}
                  onChange={setCc}
                  placeholder="cc@domain.com"
                  disabled={sending}
                  invalid={cc.some((e) => !parseAddress(e).valid)}
                />
              </div>
              <div className={fieldRow}>
                <label htmlFor="compose-bcc" className={fieldLabel}>
                  {t("mail.bccLabel")}
                </label>
                <RecipientInput
                  id="compose-bcc"
                  value={bcc}
                  onChange={setBcc}
                  placeholder="bcc@domain.com"
                  disabled={sending}
                  invalid={bcc.some((e) => !parseAddress(e).valid)}
                />
              </div>
            </>
          )}

          {!inline && (
            <div className={fieldRow}>
              <label htmlFor="compose-subject" className={fieldLabel}>
                {t("ui.subject")}
              </label>
              <input
                id="compose-subject"
                type="text"
                value={subject}
                onChange={(e) => setSubject(e.target.value)}
                placeholder={t("ui.subject")}
                required
                disabled={sending}
                className={bareInput}
              />
            </div>
          )}

          {/* Formatting Toolbar */}
          <div className="flex flex-wrap items-center gap-0.5 px-3 py-2 shadow-[inset_0_-1px_0_0_rgb(var(--ink)/0.07)]">
            <button type="button" onClick={() => executeFormat("bold")} className={toolButton} title={t("mail.bold")}>
              <Bold className="h-4 w-4" />
            </button>
            <button type="button" onClick={() => executeFormat("italic")} className={toolButton} title={t("mail.italic")}>
              <Italic className="h-4 w-4" />
            </button>
            <button
              type="button"
              onClick={() => executeFormat("underline")}
              className={toolButton}
              title={t("mail.underline")}
            >
              <Underline className="h-4 w-4" />
            </button>
            <button
              type="button"
              onClick={() => executeFormat("strikeThrough")}
              className={toolButton}
              title={t("mail.strikethrough")}
            >
              <Strikethrough className="h-4 w-4" />
            </button>
            <span className="mx-1.5 h-[18px] w-px bg-ink/[0.14]" />
            <button
              type="button"
              onClick={() => executeFormat("insertUnorderedList")}
              className={toolButton}
              title={t("mail.bulletList")}
            >
              <List className="h-4 w-4" />
            </button>
            <button
              type="button"
              onClick={() => executeFormat("insertOrderedList")}
              className={toolButton}
              title={t("mail.numberedList")}
            >
              <ListOrdered className="h-4 w-4" />
            </button>
            <span className="mx-1.5 h-[18px] w-px bg-ink/[0.14]" />
            <button
              type="button"
              onClick={() => {
                const url = prompt(t("mail.insertUrl"));
                if (url) executeFormat("createLink", url);
              }}
              className={`${toolButton} text-indigo-500`}
              title={t("mail.insertLink")}
            >
              <LinkIcon className="h-4 w-4" />
            </button>
          </div>

          <div
            ref={editorRef}
            contentEditable
            suppressContentEditableWarning
            onInput={(e) => setBody((e.target as HTMLDivElement).innerHTML)}
            onBlur={(e) => setBody((e.target as HTMLDivElement).innerHTML)}
            aria-label={t("ui.messageBody")}
            role="textbox"
            aria-multiline="true"
            className={`${inline ? "min-h-[150px]" : "min-h-[280px]"} px-[22px] py-5 font-sans text-[14.5px] leading-relaxed text-slate-200 focus:outline-none`}
          />

          {/* Attachment Selector & Display */}
          <div className="flex flex-wrap items-center gap-2.5 px-4 py-3.5 shadow-[inset_0_1px_0_0_rgb(var(--ink)/0.07)]">
            <label className="flex flex-none cursor-pointer items-center gap-2 rounded-[10px] border border-ink/[0.14] px-3 py-2 text-[13px] text-slate-200 transition-colors hover:bg-ink/[0.07]">
              <Paperclip className="h-[15px] w-[15px]" />
              <span>{t("mail.addFiles")}</span>
              <input type="file" multiple onChange={handleFileUpload} className="hidden" />
            </label>

            {attachments.map((file) => (
              <div
                key={file.id}
                className="flex items-center gap-2 rounded-[10px] bg-dark-card px-3 py-2 text-[12.5px] text-slate-200 shadow-edge"
              >
                <Paperclip className="h-[15px] w-[15px] flex-none text-indigo-400" />
                <span className="max-w-[160px] truncate">{file.name}</span>
                <span className="text-[11px] text-slate-500">{(file.size / 1024).toFixed(1)} KB</span>
                <button
                  type="button"
                  onClick={() => removeAttachment(file.id)}
                  className="text-slate-400 transition-colors hover:text-rose-400"
                  aria-label={t("common.delete")}
                >
                  <X className="h-3.5 w-3.5" />
                </button>
              </div>
            ))}

            {/* Says so plainly rather than letting someone attach a contract
                and watch it silently not arrive: /mail/send is handed the file
                names only, because there is no upload endpoint behind this
                picker yet. */}
            {attachments.length > 0 && (
              <span className="ml-auto text-[11.5px] leading-relaxed text-slate-400">
                {t("mail.attachmentsUnsupported")}
              </span>
            )}
          </div>
        </div>
      </form>
    </div>
  );
}